Off-topic: solar LED flashlight repair question

[Yurtdweller]

My solar flashlight quit working, and I have determined that the driver is bad. The power source is dual 18650 batteries at 7.2v nom. The bulb is cree xm-l (C1). Bulb powers up on 4v from the bench top supply, but power applied to the driver does nothing. Can someone advise me on how to buy a new driver? I cannot seem to find the appropriate part, or I do not know what specifications are appropriate. This is a very nice light. Tactical, aluminum, and also charges off USB. Paid a bunch for it. The company no longer exists. Thanks.

 

[justgary]

My solar flashlight quit working, and I have determined that the driver is bad. The power source is dual 18650 batteries at 7.2v nom. The bulb is cree xm-l (C1). Bulb powers up on 4v from the bench top supply, but power applied to the driver does nothing. Can someone advise me on how to buy a new driver? I cannot seem to find the appropriate part, or I do not know what specifications are appropriate. This is a very nice light. Tactical, aluminum, and also charges off USB. Paid a bunch for it. The company no longer exists. Thanks.

Please post a photo of the board and driver IC.

 

[Yurtdweller]

Tia.

 

[justgary]

Unsolder the LED star and lift it out. The driver should be underneath, and may just lift out also. If it is a standard size, you should be able to buy a new one for a few bucks. If the whole board and heatsink are the driver, try resoldering all of the connections on it. Lots of good flux is your friend when resoldering small ICs.

 

[Yurtdweller]

Thank you for the advice. My original question was in regards to how to buy a replacement driver. I can manage the process of replacement, but do not know what specs I need to look for in the replacement part. I have found driver's listing 4v input. Can I use such a driver with a 7.2v battery, or must I find a driver that takes 7.2v input? I know that LEDs can handle a wide range of inputs, but I am not really that clear on what the function of the driver is, or what are acceptable voltage ranges for drivers. Thanks.

 

[justgary]

Thank you for the advice. My original question was in regards to how to buy a replacement driver. I can manage the process of replacement, but do not know what specs I need to look for in the replacement part. I have found driver's listing 4v input. Can I use such a driver with a 7.2v battery, or must I find a driver that takes 7.2v input? I know that LEDs can handle a wide range of inputs, but I am not really that clear on what the function of the driver is, or what are acceptable voltage ranges for drivers. Thanks.

It is hard to help you find a driver when you didn't mention the brand of flashlight.... A few measurements would help also. I found a bunch of drivers available that handle more than 7 volts, but I don't know the size you need to match. Most of the drivers I found are on/off rather than flash, etc. What functions did yours have?

The advice was mostly to allow you to liberate the actual driver board so we could see it. Does that heat sink come off? More information is good.

 

[Yurtdweller]

Unfortunately, it is a no-brand from Walmart otherwise, I would have contacted the maker. But I paid 50 bucks for it. Here's some better pics of the driver. It was on/off/sos, I think. I don't care about sos, though. I'd be happy with just on/off. The bottom board is 1.25 inches wide. I'm not sure what you are referring to as a heat sink?

 

[A.Justice]

Mountain Electronics

MTN Electronics

www.mtnelectronics.com

This guy has a ton of drivers and DTP stars (a Direct Thermal Path star is what the LED chip itself is mounted on). I don't know if he has what you're looking for specifically, but you should be able to find something that'll fit with some modifications. If not, grab a Convoy C8+, or S2+, they run around $20 or less, and you won't regret it

 

[Yurtdweller]

Thanks. I'll try him I found an LED bulb that works with wide voltage range, no driver needed. If the flashlight guts will still charge the battery, I may just mod it to use the new bulb. I don't really understand why the driver is even necessary. Thx.

 

[A.Justice]

Thanks. I'll try him I found an LED bulb that works with wide voltage range, no driver needed. If the flashlight guts will still charge the battery, I may just mod it to use the new bulb. I don't really understand why the driver is even necessary. Thx.

The driver is there to buck or boost the voltage down (or up) to what the LED needs to run. A lot of them also have PWM controllers for the lower modes. If you don't care about brightness modes, and your LED roughly matches your batteries voltage, you can just drive it directly off the battery.

I have a light that uses a MOSFET direct drive coupled with a PWM controller for low modes; and another one that uses a PWM controller only. The one with the FET has an LED (SFT-40) that matches the voltage of an 18650 almost perfectly, the other one (Osram CLSNM1.23) needs a lower voltage, and without a driver, the full voltage of the battery would be applied to the LED, and would either burn it out very quickly, or you'll end up with issues in the long run.

Probably an overshare, but I do love flashlights.

 

[Yurtdweller]

No. I never did. I could not figure out what parts to buy. I travel and do shows all summer. Perhaps when I get home in a couple weeks I will take up this pursuit again.

 

[justgary]

The driver is there to buck or boost the voltage down (or up) to what the LED needs to run. A lot of them also have PWM controllers for the lower modes. If you don't care about brightness modes, and your LED roughly matches your batteries voltage, you can just drive it directly off the battery.

I have a light that uses a MOSFET direct drive coupled with a PWM controller for low modes; and another one that uses a PWM controller only. The one with the FET has an LED (SFT-40) that matches the voltage of an 18650 almost perfectly, the other one (Osram CLSNM1.23) needs a lower voltage, and without a driver, the full voltage of the battery would be applied to the LED, and would either burn it out very quickly, or you'll end up with issues in the long run.

Probably an overshare, but I do love flashlights.

A more precise explanation is that the driver is there to limit the current provided to the LED. LEDs are current devices, not voltage devices. As long as the the voltage exceeds their bias voltage, they will light up. Most regular LEDs cannot take more than about 20 mA of current. The high power CREE-style LEDs take more power because they are designed to manage heat in the chip.

A white LED has a bias voltage somewhere around 3 to 4 volts (it depends on the brand). You can test the LED with a current-controlled power supply. Set it to 15 mA and slowly raise the voltage until the LED lights. That is your bias voltage. If you know the power capability of the LED, you can then raise the current limit until you reach that power. Example: You have a 1 W LED, and find that it has a 3.2 V bias. You can bring it to full brightness with 1W / 3.2V = 0.31 A current. Do not exceed the maximum power capacity of the LED or you will blow it.

LED drivers achieve brightness control and even extra brightness through pulse modulation. It is possible to get higher brightness by carefully controlling the average power going to the LED. For example, it should be possible to provide 10W to a 1W LED, but only for 1/10 of the total time a 10% duty cycle modulation). Cheaper units tend to try to push this to the limit to sell crazy bright lights, but that also stresses the cheap parts they use until something burns out.

The CREE XM-L shown in your photo is a 10W LED that should have a driver rated at no more than 3A maximum average output.

 

[deeuubee]

If you go to "budgetlightforum_dot_com" and introduce yourself, you'll get more help than you know what to do with.

 

[Yurtdweller]

Thanks guys. I may get back to this project this winter, but I may just get a new one. It's taking far too much effort.

 

[deeuubee]

Thanks guys. I may get back to this project this winter, but I may just get a new one. It's taking far too much effort.

All of those HD, Lowes, Walmart LED lights are throwaways.
You can get brighter, smaller, cheaper.
Look for Convoy, Sofrin, Astrolux.

 

[A.Justice]

All of those HD, Lowes, Walmart LED lights are throwaways.
You can get brighter, smaller, cheaper.
Look for Convoy, Sofrin, Astrolux.

I love my Sofirn and Convoy lights. I got a Convoy S2+ for about $25, and an extra driver, switch, glass, spring, and led chip for like $10 more. There's nothing in it that can break that I don't have now.