Jumping in with both feet - replacing electronics in Olight M31 SST50

Okay guys, my Olight M31 is dead. I'm calling it. The modes don't work. Very dim output. Nobody from Olight has gotten back to me.



Now... I disassembled it and isolated the beautiful SST-50 that still works. I tried it for a split-second on 2 CR123's and it lights up fine but I don't want to fry it...



What sort of driver/resistor... thing can I put between the batteries and LED to give me a nice single-mode, I'm hoping in the 400-lumen range.

Any ideas, comments, please let me know.

My SST-50 mag @ 2.8A does about 540 lumens OTF, so if you wanted less than that you would want lower drive current. Take a look at the sst-50 data sheet on the luminus website. I assume you are going the multi-cell route so you would need a buck driver. If you can get the stcok driver out take some measurements of the diameter and height you have to work with.

LilKevin715 said:

My SST-50 mag @ 2.8A does about 540 lumens OTF, so if you wanted less than that you would want lower drive current. Take a look at the sst-50 data sheet on the luminus website. I assume you are going the multi-cell route so you would need a buck driver. If you can get the stcok driver out take some measurements of the diameter and height you have to work with.

Click to expand...

Thanks! I'd be okay with around 500 lumens as long as I don't overdrive the LED and get somewhat decent battery life. The boards inside are a round one that's held in place by the head being screwed together and a vertical one soldered... used to be... soldered to it at a 90 degree angle. Yes, I'll retain the original cell configuration of 3 CR123's so I'm guessing that will put out more than 2.8A so I'll need a buck driver.

Thanks for the info dude, that at least gives me a place to start.

Follow-up Question: What is the difference between a buck driver, and figuring out what resistor(s) I need to limit the current to around 3 amps? What does a buck driver do that the resistor(s) (assuming they are the proper resistance) won't? I realize that may be a sophmoric question, but I want to learn. To be clear, I have a very elementary understanding of the electronics and how they all play together.

sween1911 said:

Follow-up Question: What is the difference between a buck driver, and figuring out what resistor(s) I need to limit the current to around 3 amps? What does a buck driver do that the resistor(s) (assuming they are the proper resistance) won't? I realize that may be a sophmoric question, but I want to learn. To be clear, I have a very elementary understanding of the electronics and how they all play together.

Click to expand...

A resistor will often have much higher loss than a buck driver.
The buck driver converts power from one voltage to a lower voltage, the current will increase.
A resistor waste power while reducing the voltage, the current will be the same.

A buck driver cannot have 100% efficiency, but it is usual above 80% (Can be 95% in some cases), this means that with very small voltage drops, the resistor can have higher efficiency.

HKJ said:

A resistor will often have much higher loss than a buck driver.
The buck driver converts power from one voltage to a lower voltage, the current will increase.
A resistor waste power while reducing the voltage, the current will be the same.

A buck driver cannot have 100% efficiency, but it is usual above 80% (Can be 95% in some cases), this means that with very small voltage drops, the resistor can have higher efficiency.

Click to expand...

Ah, thanks. Where does one source a buck driver? If I'm using a 9 volt power supply (3 CR123's or 2 17500's), and I want to get around 2.8A, is that a specific "recipe" I need to look up? I'll get the measurement across. The circular board, oriented perpendicular to the stack of batteries, was held in place by the body screwed to an adaptor between the body and bezel. That board was also the positive battery terminal with spring. That board has a few components on it, I'm thinking that would be reused as just the battery terminal, remove the other components and solder whatever I get to the back of it, if that makes sense.

sween1911 said:

Ah, thanks. Where does one source a buck driver? If I'm using a 9 volt power supply (3 CR123's or 2 17500's), and I want to get around 2.8A, is that a specific "recipe" I need to look up? I'll get the measurement across. The circular board, oriented perpendicular to the stack of batteries, was held in place by the body screwed to an adaptor between the body and bezel. That board was also the positive battery terminal with spring. That board has a few components on it, I'm thinking that would be reused as just the battery terminal, remove the other components and solder whatever I get to the back of it, if that makes sense.

Click to expand...

You can find boards with drives (Buck, boost and linear) on a couple of Chinese websites, look for flashlights parts.
On example is SKU 1143104 from fasttech.

HKJ said:

You can find boards with drives (Buck, boost and linear) on a couple of Chinese websites, look for flashlights parts.
On example is SKU 1143104 from fasttech.

Click to expand...

Dude! You're awesome. Wow, that particular part looks like a drop-in. In fact, the circular parts of the board make it look like it's made for that application.

Just dropped by Radio Shack on my way around and picked up a tube of arctic silver 5. HOLY MOLY THAT STUFF IS EXPENSIVE! A co-worker had a bit left over so he gave me a mostly-depleted tube, but I figured I'd get another tube anyway. $12 from Radio Shack. If I'd known I was going to be doing this, I'd have gotten a better price online.

I also bought a little finned heatsink that I intended to mount on the backside of the LED plate. But the more I think about it, it's going to be inside the head of the light, so a finned heat sink in a mostly air-tight space won't do that much (correct me if I'm wrong). I have a piece of 1/2" aluminum rod at home and I plan to cut a few pieces and screw them to the back of the plate for better heat dissipation. Not direly necessary as there was no additional heat sinking in stock form, but it may help a bit. Not sure how much space I'll have in the head to work with (I don't have the replacement board yet) so I'll have to play with it.

You will get much higher output if you switch to an XM-L2 mounted on a sinkpad. Since you are modding the light anyways I would do this. The SST-50 is seriously outdated when looking at the efficiancy.

The Driver, thanks for your input. The stock LED is fine with me, I just want to get it running again. The SST-50 was plenty bright. I ordered that driver from Fasttech, so we'll see how this modding project goes. If I can hook this up without any problems, maybe I'll give an XM-L2 a shot on another project. Always wanted to do a Magmod with a crazy bright LED.



Edit: Thanks to Norm for putting the thread back.

The OLIGHT IS BACK! Working like a champ. That board that HKJ recommended works perfectly. 3-modes with memory. Not as tactical as original configuration, but I kinda like the ability to change modes with one hand. The completely substandard threading on the body did not support the stock mode changing method of constant unscrewing and retightening. I removed the battery-terminal piece that came with the board and used the original battery contacts from the Olight and soldered it in place. For a bit of protection, I put a foam sleeve from a Mag spare bulb around the board before connecting it up.

Thanks to everyone for the recommendations, I realize this might be a newbie build, but it's my first intro to any sort of buck/boost fiddling. Scarier still, I have a thirst for more! I'd love to hook up a Mag body with that XM-L2 and some 18650 goodness.

Glad to hear you brought your Olight back to life.

Thanks, it's working fine.

Anybody know if it's an issue to run it on 2 17500's? (protected AW) So far I've run it on high for 3 minutes solid, the batteries were NOT hot to the touch. The head got a bit warm. I know the extender that came with the light allows you to run it on 2 18650's, but I do not have any of those (yet).

Its the same voltage as 2 x 18650, the only difference would be the reduced runtime.

I've since gotten ahold of 18650's. LOVING IT! Used it going out with the kids on Halloween.

Revisiting my M31. It's been sitting idle. It works, but it takes painfully long to switch modes and there's too much time between modes, so it tends to switch modes when I don't want to.

In my research to upgrade my Novatac, I just stumbled onto a driver module from mtnelectronics that seems to match up to exactly what I want... it's made for 2- LiIon setups and has 3 mode groups, one of the groups being high-only, which is perfect for tactical use, but I can switch over to a 3-mode when I want flexibility. It's also current controlled, not PWM. It's on the way right now, will follow up when it's installed.

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Update: Works perfectly. If anyone's interested, it's part# LD-2C from Mountain Electronics. Optimized for 1 or 2 Li-Ions. Currently sitting with 2 18650's. Runs the SST-50 perfectly, and there's no mode-change lag. The mode-change bounce time is very short, so it's easy to use without switching modes unintentionally.