For safety and the ability to continue active activities in the dark, a person needs artificial lighting. Primitive people pushed back the darkness by setting fire to tree branches, then they came up with a torch and a kerosene stove. And only after the invention of the prototype of a modern battery by the French inventor Georges Leclanche in 1866, and the incandescent lamp in 1879 by Thomson Edison, did David Mizell have the opportunity to patent the first electric flashlight in 1896.
Since then, nothing has changed in the electrical circuit of new flashlight samples, until in 1923, Russian scientist Oleg Vladimirovich Losev found a connection between luminescence in silicon carbide and the p-n junction, and in 1990, scientists managed to create an LED with greater luminous efficiency, allowing them to replace a light bulb incandescent The use of LEDs instead of incandescent lamps, due to the low energy consumption of LEDs, has made it possible to repeatedly increase the operating time of flashlights with the same capacity of batteries and accumulators, increase the reliability of flashlights and practically remove all restrictions on the area of their use.
The LED rechargeable flashlight that you see in the photograph came to me for repair with a complaint that the Chinese Lentel GL01 flashlight I bought the other day for $3 does not light, although the battery charge indicator is on.
The external inspection of the lantern made a positive impression. High-quality casting of the case, comfortable handle and switch. The plug rods for connecting to a household network for charging the battery are made retractable, eliminating the need to store the power cord.
Attention! When disassembling and repairing the flashlight, if it is connected to the network, you should be careful. Touching unprotected parts of your body to uninsulated wires and parts may result in electric shock.
How to disassemble the Lentel GL01 LED rechargeable flashlight
Although the flashlight was subject to warranty repair, remembering my experiences during the warranty repair of a faulty electric kettle (the kettle was expensive and the heating element in it burned out, so it was not possible to repair it with my own hands), I decided to do the repair myself.
It was easy to disassemble the lantern. It is enough to turn the ring that secures the protective glass a small angle counterclockwise and pull it off, then unscrew several screws. It turned out that the ring is fixed to the body using a bayonet connection.
After removing one of the halves of the flashlight body, access to all its components appeared. On the left in the photo you can see a printed circuit board with LEDs, to which a reflector (light reflector) is attached using three screws. In the center there is a black battery with unknown parameters; there is only a marking of the polarity of the terminals. To the right of the battery there is a printed circuit board for the charger and indication. On the right is a power plug with retractable rods.
Upon closer examination of the LEDs, it turned out that there were black spots or dots on the emitting surfaces of the crystals of all LEDs. It became clear even without checking the LEDs with a multimeter that the flashlight did not light due to their burnout.
There were also blackened areas on the crystals of two LEDs installed as backlight on the battery charging indication board. In LED lamps and strips, one LED usually fails, and acting as a fuse, it protects the others from burning out. And all nine LEDs in the flashlight failed at the same time. The voltage on the battery could not increase to a value that could damage the LEDs. To find out the reason, I had to draw an electrical circuit diagram.
Finding the cause of the flashlight failure
The electrical circuit of the flashlight consists of two functionally complete parts. The part of the circuit located to the left of switch SA1 acts as a charger. And the part of the circuit shown to the right of the switch provides the glow.
The charger works as follows. The voltage from the 220 V household network is supplied to the current-limiting capacitor C1, then to a bridge rectifier assembled on diodes VD1-VD4. From the rectifier, voltage is supplied to the battery terminals. Resistor R1 serves to discharge the capacitor after removing the flashlight plug from the network. This prevents electric shock from capacitor discharge in the event of your hand accidentally touching two pins of the plug at the same time.
LED HL1, connected in series with current-limiting resistor R2 in the opposite direction with the upper right diode of the bridge, as it turns out, always lights up when the plug is inserted into the network, even if the battery is faulty or disconnected from the circuit.
The operating mode switch SA1 is used to connect separate groups of LEDs to the battery. As you can see from the diagram, it turns out that if the flashlight is connected to the network for charging and the switch slide is in position 3 or 4, then the voltage from the battery charger also goes to the LEDs.
If a person turns on the flashlight and discovers that it does not work, and, not knowing that the switch slide must be set to the “off” position, about which nothing is said in the flashlight’s operating instructions, connects the flashlight to the network for charging, then at the expense If there is a voltage surge at the output of the charger, the LEDs will receive a voltage significantly higher than the calculated one. A current that exceeds the permissible current will flow through the LEDs and they will burn out. As an acid battery ages due to sulfation of the lead plates, the battery charge voltage increases, which also leads to LED burnout.
Another circuit solution that surprised me was the parallel connection of seven LEDs, which is unacceptable, since the current-voltage characteristics of even LEDs of the same type are different and therefore the current passing through the LEDs will also not be the same. For this reason, when choosing the value of resistor R4 based on the maximum permissible current flowing through the LEDs, one of them may overload and fail, and this will lead to an overcurrent of parallel-connected LEDs, and they will also burn out.
Rework (modernization) of the electrical circuit of the flashlight
It became obvious that the failure of the flashlight was due to errors made by the developers of its electrical circuit diagram. To repair the flashlight and prevent it from breaking again, you need to redo it, replacing the LEDs and making minor changes to the electrical circuit.
In order for the battery charge indicator to actually signal that it is charging, the HL1 LED must be connected in series with the battery. To light an LED, a current of several milliamps is required, and the current supplied by the charger should be about 100 mA.
To ensure these conditions, it is enough to disconnect the HL1-R2 chain from the circuit in the places indicated by red crosses and install an additional resistor Rd with a nominal value of 47 Ohms and a power of at least 0.5 W in parallel with it. The charge current flowing through Rd will create a voltage drop of about 3 V across it, which will provide the necessary current for the HL1 indicator to light. At the same time, the connection point between HL1 and Rd must be connected to pin 1 of switch SA1. In this simple way, it will be impossible to supply voltage from the charger to the LEDs EL1-EL10 while charging the battery.
To equalize the magnitude of the currents flowing through the LEDs EL3-EL10, it is necessary to exclude resistor R4 from the circuit and connect a separate resistor with a nominal value of 47-56 Ohms in series with each LED.
Electrical diagram after modification
Minor changes made to the circuit increased the information content of the charge indicator of an inexpensive Chinese LED flashlight and greatly increased its reliability. I hope that LED flashlight manufacturers will make changes to the electrical circuits of their products after reading this article.
After modernization, the electrical circuit diagram took the form as in the drawing above. If you need to illuminate the flashlight for a long time and do not require high brightness of its glow, you can additionally install a current-limiting resistor R5, thanks to which the operating time of the flashlight without recharging will double.
LED battery flashlight repair
After disassembly, the first thing you need to do is restore the functionality of the flashlight, and then start upgrading it.
Checking the LEDs with a multimeter confirmed that they were faulty. Therefore, all the LEDs had to be desoldered and the holes freed from solder to install new diodes.
Judging by its appearance, the board was equipped with tube LEDs from the HL-508H series with a diameter of 5 mm. LEDs of type HK5H4U from a linear LED lamp with similar technical characteristics were available. They came in handy for repairing the lantern. When soldering LEDs to the board, you must remember to observe polarity; the anode must be connected to the positive terminal of the battery or battery.
After replacing the LEDs, the PCB was connected to the circuit. The brightness of some LEDs was slightly different from others due to the common current-limiting resistor. To eliminate this drawback, it is necessary to remove resistor R4 and replace it with seven resistors, connected in series with each LED.
To select a resistor that ensures optimal operation of the LED, the dependence of the current flowing through the LED on the value of the series-connected resistance was measured at a voltage of 3.6 V, equal to the voltage of the flashlight battery.
Based on the conditions for using the flashlight (in case of interruptions in the power supply to the apartment), high brightness and illumination range were not required, so the resistor was chosen with a nominal value of 56 Ohms. With such a current-limiting resistor, the LED will operate in light mode, and energy consumption will be economical. If you need to squeeze out maximum brightness from the flashlight, then you should use a resistor, as can be seen from the table, with a nominal value of 33 Ohms and make two modes of operation of the flashlight by turning on another common current-limiting resistor (in the diagram R5) with a nominal value of 5.6 Ohms.
To connect a resistor in series with each LED, you must first prepare the printed circuit board. To do this, you need to cut any one current-carrying path on it, suitable for each LED, and make additional contact pads. The current-carrying paths on the board are protected by a layer of varnish, which must be scraped off with a knife blade to the copper, as in the photograph. Then tin the bare contact pads with solder.
It is better and more convenient to prepare a printed circuit board for mounting resistors and soldering them if the board is mounted on a standard reflector. In this case, the surface of the LED lenses will not be scratched, and it will be more convenient to work.
Connecting the diode board after repair and modernization to the flashlight battery showed that the brightness of all LEDs was sufficient for illumination and the same brightness.
Before I had time to repair the previous lamp, a second one was repaired, with the same fault. I didn’t find any information about the manufacturer or technical specifications on the flashlight body, but judging by the manufacturing style and the cause of the breakdown, the manufacturer is the same, Chinese Lentel.
Based on the date on the flashlight body and on the battery, it was possible to establish that the flashlight was already four years old and, according to its owner, the flashlight worked flawlessly. It is obvious that the flashlight lasted a long time thanks to the warning sign “Do not turn on while charging!” on a hinged lid covering a compartment in which a plug is hidden for connecting the flashlight to the mains for charging the battery.
In this flashlight model, the LEDs are included in the circuit according to the rules; a 33 Ohm resistor is installed in series with each one. The resistor value can be easily recognized by color coding using an online calculator. A check with a multimeter showed that all the LEDs were faulty, and the resistors were also broken.
An analysis of the cause of the failure of the LEDs showed that due to sulfation of the acid battery plates, its internal resistance increased and, as a result, its charging voltage increased several times. During charging, the flashlight was turned on, the current through the LEDs and resistors exceeded the limit, which led to their failure. I had to replace not only the LEDs, but also all the resistors. Based on the above-mentioned operating conditions of the flashlight, resistors with a nominal value of 47 Ohms were chosen for replacement. The resistor value for any type of LED can be calculated using an online calculator.
Redesign of the battery charging mode indication circuit
The flashlight has been repaired, and you can begin making changes to the battery charging indication circuit. To do this, it is necessary to cut the track on the printed circuit board of the charger and indication in such a way that the HL1-R2 chain on the LED side is disconnected from the circuit.
The lead-acid AGM battery was deeply discharged, and an attempt to charge it with a standard charger was unsuccessful. I had to charge the battery using a stationary power supply with a load current limiting function. A voltage of 30 V was applied to the battery, while at the first moment it consumed only a few mA of current. Over time, the current began to increase and after a few hours increased to 100 mA. After fully charging, the battery was installed in the flashlight.
Charging deeply discharged lead-acid AGM batteries with increased voltage as a result of long-term storage allows you to restore their functionality. I have tested the method on AGM batteries more than a dozen times. New batteries that do not want to be charged from standard chargers are restored to almost their original capacity when charged from a constant source at a voltage of 30 V.
The battery was discharged several times by turning on the flashlight in operating mode and charged using a standard charger. The measured charge current was 123 mA, with a voltage at the battery terminals of 6.9 V. Unfortunately, the battery was worn out and was enough to operate the flashlight for 2 hours. That is, the battery capacity was about 0.2 Ah and for long-term operation of the flashlight it is necessary to replace it.
The HL1-R2 chain on the printed circuit board was successfully placed, and it was necessary to cut only one current-carrying path at an angle, as in the photograph. The cutting width must be at least 1 mm. Calculation of the resistor value and testing in practice showed that for stable operation of the battery charging indicator, a 47 Ohm resistor with a power of at least 0.5 W is required.
The photo shows a printed circuit board with a soldered current-limiting resistor. After this modification, the battery charge indicator lights up only if the battery is actually charging.
Modernization of the operating mode switch
To complete the repair and modernization of the lights, it is necessary to resolder the wires at the switch terminals.
In models of flashlights being repaired, a four-position slide-type switch is used to turn on. The middle pin in the photo shown is general. When the switch slide is in the extreme left position, the common terminal is connected to the left terminal of the switch. When moving the switch slide from the extreme left position to one position to the right, its common pin is connected to the second pin and, with further movement of the slide, sequentially to pins 4 and 5.
To the middle common terminal (see photo above) you need to solder a wire coming from the positive terminal of the battery. Thus, it will be possible to connect the battery to a charger or LEDs. To the first pin you can solder the wire coming from the main board with LEDs, to the second you can solder a current-limiting resistor R5 of 5.6 Ohms to be able to switch the flashlight to an energy-saving operating mode. Solder the conductor coming from the charger to the rightmost pin. This will prevent you from turning on the flashlight while the battery is charging.
Repair and modernization
LED rechargeable spotlight "Foton PB-0303"
I received another copy of a series of Chinese-made LED flashlights called the Photon PB-0303 LED spotlight for repair. The flashlight did not respond when the power button was pressed; an attempt to charge the flashlight battery using a charger was unsuccessful.
The flashlight is powerful, expensive, costs about $20. According to the manufacturer, the luminous flux of the flashlight reaches 200 meters, the body is made of impact-resistant ABS plastic, and the kit includes a separate charger and a shoulder strap.
The Photon LED flashlight has good maintainability. To gain access to the electrical circuit, simply unscrew the plastic ring holding the protective glass, rotating the ring counterclockwise when looking at the LEDs.
When repairing any electrical appliances, troubleshooting always starts with the power source. Therefore, the first step was to measure the voltage at the terminals of the acid battery using a multimeter turned on in mode. It was 2.3 V, instead of the required 4.4 V. The battery was completely discharged.
When connecting the charger, the voltage at the battery terminals did not change, it became obvious that the charger was not working. The flashlight was used until the battery was completely discharged, and then it was not used for a long time, which led to a deep discharge of the battery.
It remains to check the serviceability of the LEDs and other elements. To do this, the reflector was removed, for which six screws were unscrewed. On the printed circuit board there were only three LEDs, a chip (chip) in the form of a droplet, a transistor and a diode.
Five wires went from the board and battery into the handle. In order to understand their connection, it was necessary to disassemble it. To do this, use a Phillips screwdriver to unscrew the two screws inside the flashlight, which were located next to the hole into which the wires went.
To detach the flashlight handle from its body, it must be moved away from the mounting screws. This must be done carefully so as not to tear the wires off the board.
As it turned out, there were no radio-electronic elements in the pen. Two white wires were soldered to the terminals of the flashlight on/off button, and the rest to the connector for connecting the charger. A red wire was soldered to pin 1 of the connector (the numbering is conditional), the other end of which was soldered to the positive input of the printed circuit board. A blue-white conductor was soldered to the second contact, the other end of which was soldered to the negative pad of the printed circuit board. A green wire was soldered to pin 3, the second end of which was soldered to the negative terminal of the battery.
Electrical circuit diagram
Having dealt with the wires hidden in the handle, you can draw an electrical circuit diagram of the Photon flashlight.
From the negative terminal of the battery GB1, voltage is supplied to pin 3 of connector X1 and then from its pin 2 through a blue-white conductor it is supplied to the printed circuit board.
Connector X1 is designed in such a way that when the charger plug is not inserted into it, pins 2 and 3 are connected to each other. When the plug is inserted, pins 2 and 3 are disconnected. This ensures automatic disconnection of the electronic part of the circuit from the charger, eliminating the possibility of accidentally turning on the flashlight while charging the battery.
From the positive terminal of battery GB1, voltage is supplied to D1 (microcircuit-chip) and the emitter of a bipolar transistor type S8550. The CHIP performs only the function of a trigger, allowing a button to turn on or off the glow of EL LEDs (⌀8 mm, glow color - white, power 0.5 W, current consumption 100 mA, voltage drop 3 V.). When you first press the S1 button from the D1 chip, a positive voltage is applied to the base of the transistor Q1, it opens and the supply voltage is supplied to the LEDs EL1-EL3, the flashlight turns on. When you press button S1 again, the transistor closes and the flashlight turns off.
From a technical point of view, such a circuit solution is illiterate, since it increases the cost of the flashlight, reduces its reliability, and in addition, due to the voltage drop at the junction of transistor Q1, up to 20% of the battery capacity is lost. Such a circuit solution is justified if it is possible to adjust the brightness of the light beam. In this model, instead of a button, it was enough to install a mechanical switch.
It was surprising that in the circuit, LEDs EL1-EL3 are connected in parallel to the battery like incandescent light bulbs, without current-limiting elements. As a result, when turned on, a current passes through the LEDs, the magnitude of which is limited only by the internal resistance of the battery and when it is fully charged, the current may exceed the permissible value for the LEDs, which will lead to their failure.
Checking the functionality of the electrical circuit
To check the serviceability of the microcircuit, transistor and LEDs, a 4.4 V DC voltage was applied from an external power source with a current limiting function, maintaining polarity, directly to the power pins of the printed circuit board. The current limit value was set to 0.5 A.
After pressing the power button, the LEDs lit up. After pressing again, they went out. The LEDs and the microcircuit with the transistor turned out to be serviceable. All that remains is to figure out the battery and charger.
Acid battery recovery
Since the 1.7 A acid battery was completely discharged, and the standard charger was faulty, I decided to charge it from a stationary power supply. When connecting the battery for charging to a power supply with a set voltage of 9 V, the charging current was less than 1 mA. The voltage was increased to 30 V - the current increased to 5 mA, and after an hour at this voltage it was already 44 mA. Next, the voltage was reduced to 12 V, the current dropped to 7 mA. After 12 hours of charging the battery at a voltage of 12 V, the current rose to 100 mA, and the battery was charged with this current for 15 hours.
The temperature of the battery case was within normal limits, which indicated that the charging current was not used to generate heat, but to accumulate energy. After charging the battery and finalizing the circuit, which will be discussed below, tests were carried out. The flashlight with a restored battery illuminated continuously for 16 hours, after which the brightness of the beam began to decrease and therefore it was turned off.
Using the method described above, I had to repeatedly restore the functionality of deeply discharged small-sized acid batteries. As practice has shown, only serviceable batteries that have been forgotten for some time can be restored. Acid batteries that have exhausted their service life cannot be restored.
Charger repair
Measuring the voltage value with a multimeter at the contacts of the output connector of the charger showed its absence.
Judging by the sticker pasted on the adapter body, it was a power supply that outputs an unstabilized DC voltage of 12 V with a maximum load current of 0.5 A. There were no elements in the electrical circuit that limited the amount of charging current, so the question arose, why in the quality charger, did you use a regular power supply?
When the adapter was opened, a characteristic smell of burnt electrical wiring appeared, which indicated that the transformer winding had burned out.
A continuity test of the primary winding of the transformer showed that it was broken. After cutting the first layer of tape insulating the primary winding of the transformer, a thermal fuse was discovered, designed for an operating temperature of 130°C. Testing showed that both the primary winding and the thermal fuse were faulty.
Repairing the adapter was not economically feasible, since it was necessary to rewind the primary winding of the transformer and install a new thermal fuse. I replaced it with a similar one that was on hand, with a DC voltage of 9 V. The flexible cord with a connector had to be resoldered from a burnt adapter.
The photo shows a drawing of the electrical circuit of a burnt-out power supply (adapter) of the Photon LED flashlight. The replacement adapter was assembled according to the same scheme, only with an output voltage of 9 V. This voltage is quite sufficient to provide the required battery charging current with a voltage of 4.4 V.
Just for fun, I connected the flashlight to a new power supply and measured the charging current. Its value was 620 mA, and this was at a voltage of 9 V. At a voltage of 12 V, the current was about 900 mA, significantly exceeding the load capacity of the adapter and the recommended battery charging current. For this reason, the primary winding of the transformer burned out due to overheating.
Finalization of the electrical circuit diagram
LED rechargeable flashlight "Photon"
To eliminate circuit violations in order to ensure reliable and long-term operation, changes were made to the flashlight circuit and the printed circuit board was modified.
The photo shows the electrical circuit diagram of the converted Photon LED flashlight. Additional installed radio elements are shown in blue. Resistor R2 limits the battery charging current to 120 mA. To increase the charging current, you need to reduce the resistor value. Resistors R3-R5 limit and equalize the current flowing through the LEDs EL1-EL3 when the flashlight is illuminated. The EL4 LED with a series-connected current-limiting resistor R1 is installed to indicate the battery charging process, since the developers of the flashlight did not take care of this.
To install current-limiting resistors on the board, the printed traces were cut, as shown in the photo. The charge current-limiting resistor R2 was soldered at one end to the contact pad, to which the positive wire coming from the charger had previously been soldered, and the soldered wire was soldered to the second terminal of the resistor. An additional wire (yellow in the photo) was soldered to the same contact pad, intended to connect the battery charging indicator.
Resistor R1 and indicator LED EL4 were placed in the flashlight handle, next to the connector for connecting the charger X1. The LED anode pin was soldered to pin 1 of connector X1, and a current-limiting resistor R1 was soldered to the second pin, the cathode of the LED. A wire (yellow in the photo) was soldered to the second terminal of the resistor, connecting it to the terminal of resistor R2, soldered to the printed circuit board. Resistor R2, for ease of installation, could have been placed in the flashlight handle, but since it heats up when charging, I decided to place it in a freer space.
When finalizing the circuit, MLT type resistors with a power of 0.25 W were used, except for R2, which is designed for 0.5 W. The EL4 LED is suitable for any type and color of light.
This photo shows the charging indicator while the battery is charging. Installing an indicator made it possible not only to monitor the battery charging process, but also to monitor the presence of voltage in the network, the health of the power supply and the reliability of its connection.
How to replace a burnt out CHIP
If suddenly a CHIP - a specialized unmarked microcircuit in a Photon LED flashlight, or a similar one assembled according to a similar circuit - fails, then to restore the flashlight's functionality it can be successfully replaced with a mechanical switch.
To do this, you need to remove the D1 chip from the board, and instead of the Q1 transistor switch, connect an ordinary mechanical switch, as shown in the above electrical diagram. The switch on the flashlight body can be installed instead of the S1 button or in any other suitable place.
Repair and alteration of LED flashlight
14Led Smartbuy Colorado
The Smartbuy Colorado LED flashlight stopped turning on, although three new AAA batteries were installed.
The waterproof body was made of anodized aluminum alloy and had a length of 12 cm. The flashlight looked stylish and was easy to use.
How to check batteries for suitability in an LED flashlight
Repair of any electrical device begins with checking the power source, therefore, despite the fact that new batteries were installed in the flashlight, repairs should begin with checking them. In the Smartbuy flashlight, the batteries are installed in a special container, in which they are connected in series using jumpers. In order to gain access to the flashlight batteries, you need to disassemble it by rotating the back cover counterclockwise.
Batteries must be installed in the container, observing the polarity indicated on it. The polarity is also indicated on the container, so it must be inserted into the flashlight body with the side on which the “+” sign is marked.
First of all, it is necessary to visually check all contacts of the container. If there are traces of oxides on them, then the contacts must be cleaned to a shine using sandpaper or the oxide must be scraped off with a knife blade. To prevent re-oxidation of the contacts, they can be lubricated with a thin layer of any machine oil.
Next you need to check the suitability of the batteries. To do this, touching the probes of a multimeter turned on in DC voltage measurement mode, you need to measure the voltage at the contacts of the container. Three batteries are connected in series and each of them should produce a voltage of 1.5 V, therefore the voltage at the terminals of the container should be 4.5 V.
If the voltage is less than specified, then it is necessary to check the correct polarity of the batteries in the container and measure the voltage of each of them individually. Perhaps only one of them sat down.
If everything is in order with the batteries, then you need to insert the container into the flashlight body, observing the polarity, screw on the cap and check its functionality. In this case, you need to pay attention to the spring in the cover, through which the supply voltage is transmitted to the flashlight body and from it directly to the LEDs. There should be no traces of corrosion on its end.
How to check if the switch is working properly
If the batteries are good and the contacts are clean, but the LEDs do not light, then you need to check the switch.
The Smartbuy Colorado flashlight has a sealed push-button switch with two fixed positions, closing the wire coming from the positive terminal of the battery container. When you press the switch button for the first time, its contacts close, and when you press it again, they open.
Since the flashlight contains batteries, you can also check the switch using a multimeter turned on in voltmeter mode. To do this, you need to rotate it counterclockwise, if you look at the LEDs, unscrew its front part and put it aside. Next, touch the body of the flashlight with one multimeter probe, and with the second touch the contact, which is located deep in the center of the plastic part shown in the photo.
The voltmeter should show a voltage of 4.5 V. If there is no voltage, press the switch button. If it is working properly, then voltage will appear. Otherwise, the switch needs to be repaired.
Checking the health of the LEDs
If the previous search steps failed to detect a fault, then at the next stage you need to check the reliability of the contacts supplying the supply voltage to the board with LEDs, the reliability of their soldering and serviceability.
A printed circuit board with LEDs sealed into it is fixed in the head of the flashlight using a steel spring-loaded ring, through which the supply voltage from the negative terminal of the battery container is simultaneously supplied to the LEDs along the flashlight body. The photo shows the ring from the side it presses against the printed circuit board.
The retaining ring is fixed quite tightly, and it was only possible to remove it using the device shown in the photo. You can bend such a hook from a steel strip with your own hands.
After removing the retaining ring, the printed circuit board with LEDs, which is shown in the photo, was easily removed from the head of the flashlight. The absence of current-limiting resistors immediately caught my eye; all 14 LEDs were connected in parallel and directly to the batteries via a switch. Connecting LEDs directly to a battery is unacceptable, since the amount of current flowing through the LEDs is limited only by the internal resistance of the batteries and can damage the LEDs. At best, it will greatly reduce their service life.
Since all the LEDs in the flashlight were connected in parallel, it was not possible to check them with a multimeter turned on in resistance measurement mode. Therefore, the printed circuit board was supplied with a DC supply voltage from an external source of 4.5 V with a current limit of 200 mA. All LEDs lit up. It became obvious that the problem with the flashlight was poor contact between the printed circuit board and the retaining ring.
Current consumption of LED flashlight
For fun, I measured the current consumption of LEDs from batteries when they were turned on without a current-limiting resistor.
The current was more than 627 mA. The flashlight is equipped with LEDs of type HL-508H, the operating current of which should not exceed 20 mA. 14 LEDs are connected in parallel, therefore, the total current consumption should not exceed 280 mA. Thus, the current flowing through the LEDs more than doubled the rated current.
Such a forced mode of LED operation is unacceptable, as it leads to overheating of the crystal, and as a result, premature failure of the LEDs. An additional disadvantage is that the batteries drain quickly. They will be enough, if the LEDs do not burn out first, for no more than an hour of operation.
The design of the flashlight did not allow soldering current-limiting resistors in series with each LED, so we had to install one common one for all LEDs. The resistor value had to be determined experimentally. To do this, the flashlight was powered by pants batteries and an ammeter was connected to the gap in the positive wire in series with a 5.1 Ohm resistor. The current was about 200 mA. When installing an 8.2 Ohm resistor, the current consumption was 160 mA, which, as tests showed, is quite sufficient for good lighting at a distance of at least 5 meters. The resistor did not get hot to the touch, so any power will do.
Redesign of the structure
After the study, it became obvious that for reliable and durable operation of the flashlight, it is necessary to additionally install a current-limiting resistor and duplicate the connection of the printed circuit board with the LEDs and the fixing ring with an additional conductor.
If previously it was necessary for the negative bus of the printed circuit board to touch the body of the flashlight, then due to the installation of the resistor, it was necessary to eliminate the contact. To do this, a corner was ground off from the printed circuit board along its entire circumference, from the side of the current-carrying paths, using a needle file.
To prevent the clamping ring from touching the current-carrying tracks when fixing the printed circuit board, four rubber insulators about two millimeters thick were glued onto it with Moment glue, as shown in the photograph. Insulators can be made from any dielectric material, such as plastic or thick cardboard.
The resistor was pre-soldered to the clamping ring, and a piece of wire was soldered to the outermost track of the printed circuit board. An insulating tube was placed over the conductor, and then the wire was soldered to the second terminal of the resistor.
After simply upgrading the flashlight with your own hands, it began to turn on stably and the light beam illuminated objects well at a distance of more than eight meters. Additionally, the battery life has more than tripled, and the reliability of the LEDs has increased many times over.
An analysis of the causes of failure of repaired Chinese LED lights showed that they all failed due to poorly designed electrical circuits. It remains only to find out whether this was done intentionally in order to save on components and shorten the life of the flashlights (so that more people would buy new ones), or as a result of the illiteracy of the developers. I am inclined to the first assumption.
Repair of LED flashlight RED 110
A flashlight with a built-in acid battery from the Chinese manufacturer RED brand was repaired. The flashlight had two emitters: one with a beam in the form of a narrow beam and one emitting diffused light.
The photo shows the appearance of the RED 110 flashlight. I immediately liked the flashlight. Convenient body shape, two operating modes, a loop for hanging around the neck, a retractable plug for connecting to the mains for charging. In the flashlight, the diffused light LED section was shining, but the narrow beam was not.
To make the repair, we first unscrewed the black ring securing the reflector, and then unscrewed one self-tapping screw in the hinge area. The case easily separated into two halves. All parts were secured with self-tapping screws and were easily removed.
The charger circuit was made according to the classical scheme. From the network, through a current-limiting capacitor with a capacity of 1 μF, voltage was supplied to a rectifier bridge of four diodes and then to the battery terminals. The voltage from the battery to the narrow beam LED was supplied through a 460 Ohm current-limiting resistor.
All parts were mounted on a single-sided printed circuit board. The wires were soldered directly to the contact pads. The appearance of the printed circuit board is shown in the photograph.
10 side light LEDs were connected in parallel. The supply voltage was supplied to them through a common current-limiting resistor 3R3 (3.3 Ohms), although according to the rules, a separate resistor must be installed for each LED.
During an external inspection of the narrow beam LED, no defects were found. When power was supplied through the flashlight switch from the battery, voltage was present at the LED terminals, and it heated up. It became obvious that the crystal was broken, and this was confirmed by a continuity test with a multimeter. The resistance was 46 ohms for any connection of the probes to the LED terminals. The LED was faulty and needed to be replaced.
For ease of operation, the wires were unsoldered from the LED board. After freeing the LED leads from the solder, it turned out that the LED was tightly held by the entire plane of the reverse side on the printed circuit board. To separate it, we had to fix the board in the desktop temples. Next, place the sharp end of the knife at the junction of the LED and the board and lightly hit the knife handle with a hammer. The LED bounced off.
As usual, there were no markings on the LED housing. Therefore, it was necessary to determine its parameters and select a suitable replacement. Based on the overall dimensions of the LED, the battery voltage and the size of the current-limiting resistor, it was determined that a 1 W LED (current 350 mA, voltage drop 3 V) would be suitable for replacement. From the “Reference Table of Parameters of Popular SMD LEDs,” a white LED6000Am1W-A120 LED was selected for repair.
The printed circuit board on which the LED is installed is made of aluminum and at the same time serves to remove heat from the LED. Therefore, when installing it, it is necessary to ensure good thermal contact due to the tight fit of the rear plane of the LED to the printed circuit board. To do this, before sealing, thermal paste was applied to the contact areas of the surfaces, which is used when installing a radiator on a computer processor.
In order to ensure a tight fit of the LED plane to the board, you must first place it on the plane and slightly bend the leads upward so that they deviate from the plane by 0.5 mm. Next, tin the terminals with solder, apply thermal paste and install the LED on the board. Next, press it to the board (it’s convenient to do this with a screwdriver with the bit removed) and warm up the leads with a soldering iron. Next, remove the screwdriver, press it with a knife at the bend of the lead to the board and heat it with a soldering iron. After the solder has hardened, remove the knife. Due to the spring properties of the leads, the LED will be pressed tightly to the board.
When installing the LED, polarity must be observed. True, in this case, if a mistake is made, it will be possible to swap the voltage supply wires. The LED is soldered and you can check its operation and measure the current consumption and voltage drop.
The current flowing through the LED was 250 mA, the voltage drop was 3.2 V. Hence the power consumption (you need to multiply the current by the voltage) was 0.8 W. It was possible to increase the operating current of the LED by decreasing the resistance to 460 Ohms, but I did not do this, since the brightness of the glow was sufficient. But the LED will operate in a lighter mode, heat up less, and the flashlight’s operating time on a single charge will increase.
Checking the heating of the LED after operating for an hour showed effective heat dissipation. It heated up to a temperature of no more than 45°C. Sea trials showed a sufficient illumination range in the dark, more than 30 meters.
Replacing a lead acid battery in an LED flashlight
A failed acid battery in an LED flashlight can be replaced with either a similar acid battery or a lithium-ion (Li-ion) or nickel-metal hydride (Ni-MH) AA or AAA battery.
The Chinese lanterns being repaired were equipped with lead-acid AGM batteries of various sizes without markings with a voltage of 3.6 V. According to calculations, the capacity of these batteries ranges from 1.2 to 2 A×hours.
On sale you can find a similar acid battery from a Russian manufacturer for the 4V 1Ah Delta DT 401 UPS, which has an output voltage of 4 V with a capacity of 1 Ah, costing a couple of dollars. To replace it, simply re-solder the two wires, observing the polarity.
Nowadays, more and more equipment uses lithium-ion batteries as batteries. They do not have a “memory effect”, unlike Ni-Cd. They can deliver high current.
I decided to convert two old flashlights to use 18650 lithium-ion batteries, since I have a large number of them. And it’s not difficult to get them from repair companies that repair laptops.
For the conversion we will need a number of components:
- actual flashlights;
- ;
- ;
- plexiglass;
- a piece of thin plastic;
- ;
- wires, hot glue, tools.
The flashlights are a convenient size for installing two 18650 batteries. In principle, we can describe the modification of one flashlight.
My charge controller boards are different. On one Mini-USB, on the second Micro-USB.
These boards can be purchased in China for 15-20 rubles per unit. They are also sold in radio stores and radio markets. I have boards without protection (BMS), but we can handle it.
We disassemble the flashlights and take out all of them, except for the switches and LEDs.
Now we take thin plastic, I have ABS from an old battery. It turned out that it was black, but it’s not scary, it will also look great on a blue flashlight.
We cut the windows so that they fit tightly into the place where the charging plug used to extend.
We cut out the required size for the window and holes for the connectors of our charge boards. It is not necessary to glue them, they should fit tightly and I will strengthen them later.
Since our boards do not have discharge protection, boards made from mobile phone batteries are used in this situation. You can buy one with protection, but I don’t have those in stock right now. Therefore, I resort to a slightly labor-intensive solution.
We solder the wires from our BMS to the batteries. We put the charge controller boards in place and support them. I used pieces of wine cork as spacers. We strengthen everything with hot glue, but you can do it without it.
We solder the switches, my switches break the plus. The black flashlight has a circuit board with an LED. The switch has two on positions, one of which I set to a single LED, and the second position turns on the main LEDs. The blue flashlight has one switch position.
We assemble the flashlights and solder the reflectors and move on to the next stage.
The next step is to cut out two records from transparent plastic, for me it is plastic from a CD box. We sand it with sandpaper until the surface is matte, this makes the light from the LED more pleasant.
We glue it to the place where the slide used to pull out the power plug used to be. You need to glue it on one half of the flashlight. Suddenly you will need to disassemble the flashlight.
Review of 18650 batteries for different devices, converting the battery to a screwdriver, the best batteries from AliExpress
TEST:
To see if you have enough information about your lithium-ion battery:- When purchasing 18650 batteries for a security flashlight, which manufacturer is preferable?
- What indicators should chargers for 18650 provide?
a) The output is 5 Volts and the current is from 0.5 to 1 from the nominal capacity of the battery itself.
b) The output is 10 Volts and the current is from 1 to 3 of the nominal capacity of the battery itself.
- In what temperature range is it desirable to store the battery?
a) + 10 – + 25 – ideal indicators. The battery does not tolerate extremely cold or hot rooms. b) At a temperature of +20 - +45 degrees.
- How many stages does a lithium battery take to charge?
a) Two.
b) Four.
- How many charging stages does a lithium battery have that charges in less than an hour?
Answers:
- b) It is advisable to take Chinese KEEPPOWER batteries. Samsung does not produce models with protection.
- a) The correct output indicators are 5 Volts and the current is from 0.5 to 1 of the nominal capacity of the battery itself.
- a) + 10 – + 25 – ideal indicators. Do not place the battery in other conditions.
- a) Two stages - first with a voltage of 0.2-1A, and then with a high constant.
- a) Only one. High voltage is immediately applied to the element. The remaining stages are missing.
Nickel-cadmium problem battery, installed in the screwdriver, is that it must be used constantly. If the battery is completely discharged or is not used for a long time, the crystallization process will begin in it, and the battery will soon fail completely.
To replace battery you will have to spend a lot of money, since batteries suitable for a screwdriver are not cheap.
For these reasons, screwdriver owners modify the battery slightly to accommodate lithium cells. But before starting such work, you need to think about whether such a modification is necessary and whether it is advisable at all.
Definition: Battery The 18650 is a battery that produces 3.7V power.
3 pros and 5 cons of conversion for a screwdriver
Advantages of remodeling:
- The energy density of the elements will be better than nickel-cadmium. It means that screwdriver will retain its original weight, even be somewhat lighter, while the output voltage will remain within normal limits.
- Lithium batteries Charge much faster than others. It only takes one hour to charge them safely.
- In lithium-ion batteries no memory effect. From this we can conclude that there is no need to completely discharge them before installing them on the charger.
Flaws:
- If you install lithium battery, you will have to carefully monitor it: when charging, it cannot be charged above 4.2 Volts, and discharged by less than 2.7 Volts. Otherwise, the battery will simply fail.
- 18650 cans are used as lithium cells. They are different in size from nickel-cadmium ones. In addition, you will have to find a place for the charge-discharge controller of the wires. And all this should somehow fit into the body of the screwdriver.
- Chargers for cadmium batteries may not be suitable for conversion. You may have to additionally look for a universal charger.
- It will not be possible to work outside in winter, since lithium battery Does not tolerate negative temperatures well.
- Lithium-ion battery costs more than cadmium.
It is also important to know 3 nuances before starting work
- First you need to decide on the number of elements in battery. It is best to use 4 elements, since three will only give 12.6 Volts.
- Assembling the battery 18650, It is necessary to pay attention to the capacity and discharge current. When the battery is running, the current consumed is in the range of 5 or 10 amperes, but if you sharply press the power button, it can jump to 25. This suggests that the maximum discharge current value should be approximately 30 amperes on the battery 18650.
- You should also pay attention to the controller. Its characteristics must be equal to the rated voltage and current discharge. For a 14.4 V battery, the controller is the optimal voltage. The operating current should be several times less than the maximum permissible.
How to avoid 4 mistakes when assembling a 18650 charger
To properly connect to battery lithium cells, you will need to follow the instructions exactly:
Chargers for 18650 batteries
For battery 18650 will have to use the correct charger. At the output it will produce 5 Volts and a current from 0.5 to 1 of the rated capacity of the battery itself. If lithium cells support 2600 mAh, then a current of 1.3-2.6 amperes should be used to charge it.
Device for lithium batteries The battery is charged in several stages:
- First on battery a voltage of 0.2-1A is supplied.
- Further charger already takes place at constant voltage.
If the charger has pulse mode, this will significantly speed up the charging time.
In the event that the battery has graphite, then the voltage should not exceed 4.3 Volts per element. If you exceed this figure, the energy density will increase and the oxidation process will begin.
There are lithium batteries, charging in less than an hour. They do not provide for the second stage - the current is immediately supplied to 80% and after that it is put into operation. This is normal for a lithium battery.
Answers to 5 frequently asked questions about choosing an e-cigarette battery
Battery
Look at the picture battery 18650 for an electronic cigarette. It is quite difficult to choose the right battery for an electronic cigarette, since there are many varieties with different degrees of power. Eg, long-term workers but they cannot be turned on at full power. Others won't get hot even at 40 amps, but they require frequent charging. When selecting a battery for an electric cigarette, people wonder about the criteria.
There are five main criteria: Large energy intensity, rated current indicator, voltage when used, temperature when used, cost. There is no point in paying attention to other nuances, like the color of a cigarette. All this is secondary. To choose a good unit, you should study all the criteria in detail. As a result, the buyer will receive all the necessary information for a good purchase.
Energy intensity Electronic Cigarette
Energy intensity expressed in milliamps per hour. Accordingly, the higher this indicator, the better the model will be. Safety depends on the rated current. The conclusion suggests itself that it is advisable to buy batteries with the highest current supply. For example, the LG hb6 battery has 30 A, which means it is suitable for 40 A. But having made such a purchase, a person will prefer high voltage and sacrifice energy intensity. The energy capacity of the above battery is only 1500 mAh. Therefore, it will hold less charge than options with 3000 mAh.
It is necessary to select indicators rated current, which will not overheat the device, but do not sacrifice battery life. It is better to purchase the LG HD2 model, which has a rating of 25 A and microamps per hour. This will be the average. As for the voltage, you should not rely on this nuance when choosing - if the cigarette has two previous indicators that are good, then the voltage will be sufficient.
Which battery is better for a led flashlight? flashlight charging tests.
You also need to choose devices, having a low degree of heating. Overheating an electric cigarette will soon damage the entire mechanism. That is why you need to take a battery that will work at the lowest temperatures. Price cigarettes approximately the same and this is not the most important criterion. It is advisable to start from the indicators first.
Top 3 best battery chargers
Nightcore digicharger D4
Charger device Can power four batteries. This is an already proven brand, loved by many owners of lithium batteries.
Device It is equipped with a convenient display - you can study various data, including charging speed and time, voltage on each element. It is very convenient to monitor the battery status on this display.
This is universal charger, Designed not only for the 18650 model. D4 should be used by people who have a large number of mobile devices that fit several types of batteries.
Beginners will quickly master the work, since charging occurs automatically mode.
Efest luc Blu6 oled Bluetooth intelligent Charger
This is also a very good charger model devices, designed for 6 batteries. To safely charge, the device is equipped with special protection against high current, voltage, and so on.
The user gets the opportunity to connect his mobile phone to charging via Bluetooth- You can remotely monitor the battery charge level. The only drawback of charging is the high price.
Nightcore i2 intellicharger
Charger went on sale recently. This is a modern type of device, equipped with interesting features and improved design.
Users don't need to worry about speed and time charging, since the device detects everything automatically. The person only needs to install the battery in its proper place.
The device only has room for two batteries, but the charger is very compact and can be taken with you when traveling.
Li-ion battery 18650 for flashlight
- Lithium-ion batteries operate in the range of 4.35 - 4.2 Volts. They are often used to make LED lights work.
- You need to make sure that battery did not discharge below the set level - 2 volts. In order not to constantly monitor the required voltage, you need to use battery for flashlight with protection. They store elements from overcharging or deep vacuum.
Companies Samsung, Panasonic, LG and Sony do not produce such equipment. For this purpose, it is better to purchase a Chinese KEEPPOWER device.
The best 18650 batteries on AliExpress according to reviews
- Rechargeable Battery
- Samsung icr18650
- Rechargeable flat Top Battery
Ideal conditions for batteries– temperature +10 – +25 degrees.
Literally, the flashlight was disassembled on the knee, the network connector was removed (the charge was from 220 in the original) and the “interfering wires” - You really shouldn't have touched them :)
Instead of the original battery, I used a power bank with a 2600 can, removed the original case from the power bank (there is no use for metal next to the printed circuit board), and secured it with electrical tape so that the structure would not fall apart due to vibrations or possible falls of the phone.
In fact, everything can be done MUCH more accurately, but I was interested in the simplicity and speed of the solution at the time of remodeling.
This is approximately how it turned out (the wiring could not have been pulled out through the power bank, but at first there was an idea for a slightly different arrangement, I did not redo it).
The power bank itself was secured by inserting it into the former network connector, even without additional ones. the mount sits quite firmly
Main advantages:
The lantern is alive!
Quite easy and inexpensive!
It is easy to change the battery (in case of failure) - they are common and inexpensive.
You can charge from any USB (including in a car), and also, if necessary, use the flashlight itself as a power bank. There is a flashlight charge control.
The flashlight shines normally. I didn’t try to time it, but it shines for a VERY long time, several hours for sure, I didn’t try to discharge it at once.
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Price: $2.06
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The new flashlight... sat for a year and its battery died (as it turned out, this happens to all similar flashlights, the same thing happened to 4 friends) - it’s a shame to throw it away (used it once), a new battery. very difficult to find and the cost of the battery is equal to the cost of a new flashlight...
I found a simple solution to the problem literally “on my knees”... perhaps someone will find the idea useful :)
The link to the seller where I bought the “filling” for the conversion is already dead, so I found exactly the same one in the header. It was chosen according to two criteria - as inexpensive, and also “tested” in reviews, i.e. more or less decent. The power bank cost me even less, only 60 rubles.
It is clear that you may ALREADY have a working power bank that can be used for something like this without damaging it - the main idea is :)
It is curious that the lanterns had different operating conditions (by February 23 they were presented to employees) - but all died “in one hour.” Naturally it’s a shame, you just needed a “new” flashlight :(
Having tried to search by special. stores and markets for similar batteries came to the conclusion that it is not at all advisable to buy such a NEW battery for the cost of a flashlight. I couldn’t find a cheap alternative, and besides, the battery characteristics were confusing... On the battery itself, the indicated 5V was strained for conversion to a different type of battery, differing in voltage. 
There was no desire to radically redo the charging and the flashlight, although at first there was an idea to plug in 18650 - but the voltage is one volt lower (how the flashlight will burn is unknown - again, alterations... + disassemble/assemble for charging... in short, some complications that do not make sense :(
The solution was found to be very simple - buy an external cheap power bank, which already produces 5V output, has a built-in charging system CHEAP AND TASTY :) 18650 batteries (like many) were “lying around” in the house. You can also find them inexpensively from old laptops. 
Well, that is. use “ready-made” 5V power banks to charge the flashlight.
In fact, the “native” battery had 2Ah. I used an idle 18650 at 2600. It is clear that in our case there will be all sorts of losses and in the end the result may even be below 2000 - but the price justifies the means + some advantages appear :)
Literally, the flashlight was disassembled on the knee, the network connector was removed (the charge was from 220 in the original) and the “interfering wires” - they could not really be touched :)
Instead of the original battery, I used a power bank with a 2600 can, removed the original cover from the power bank (there is no use for metal next to the printed circuit board), and secured it with electrical tape so that the structure would not fall apart due to vibrations or possible falls of the flashlight.
In fact, everything can be done MUCH more accurately, but at the time of remodeling I was interested in the simplicity and speed of the solution. 
That's pretty much how it turned out. It was possible not to pull the wiring through the power bank, but at first there was an idea for a slightly different arrangement and later I didn’t bother to redo it - it doesn’t bother me.
The power bank itself was secured by inserting it into the former network connector, even without additional fastening it “sits” quite firmly. 
Main advantages:
The lantern is alive!
Quite easy, fast and inexpensive!
It is easy to change the battery (in case of failure) - they are common and inexpensive.
You can charge from any USB (including in a car), and also, if necessary, use the flashlight itself as a power bank. There is a flashlight charge control.
The flashlight shines normally. I didn’t try to time it, but it shines for a VERY long time, several hours for sure, I didn’t try to discharge it at once.
