-Resistor- mod for- olight sr51 driver now running my 2D Magmod

You're lucky it wasn't one that (mis)behaved like this one: https://budgetlightforum.com/t/-/20635 xD

I just received my SR51 yesterday. Really like the beam pattern, but the UI and modes suck. Really high low and not much mode spacing between High and Low. After reading this, I may just going to swap out the whole driver.

Nice to know how to resister mod the stock driver though. Thanks for this thread.

comfychair wrote:

What's the battery config on this light? I checked the Olight site and can't figure how you get a light that uses either six CR123s or two 18650s.

The 18650 holder is 2S. The CR123 holder is 3P2S.

EDIT: Unfortunately, the battery tube can't take 3 18650's and it's too thin walled to bore out. What a shame, there is plenty of vertical room to rig up a 3S carrier in there.

Don’t overlook the stock MCPCB, while it’s really nice looking all copper clad and huge it’s not direct bond, after getting it all back together and measuring lux it didn’t even make it threw the 10sec reading lol. Beam started out nice and neutral and almost instantly there was a major blue shift followed by instant death.

Would it be possible to get any gains from leaving the big bar sense resistor but swapping in a better FET so it would retain factory modes?

Now that I’ve got a new U2 1A dedomed on a XM20 it’s doing 134kcd, I’m happy now and gonna leave it alone but I’m still wondering about the question above.

Yes, that was what I was suggesting earlier. With the high resistance FET and very low sense resistor, it was already running near wide open in stock form. Swapping that around, a low resistance FET and maybe even a higher sense resistor would net you more output while leaving more safety margin.

Dang it C_K… now you make me want to purchase one too :weary:

Man that driver looks complicated. I like the idea of swapping out the FET and also replacing the MCU. Won't be touching the light until after I finish my scratch build though.

If you get a chance, it would be nice to see some beam shots. I think your the first to install dedomed emitter in this light.

So it turns out there is a low still, its just barely dimmer than high lol, its not useful at all and its such a small difference out in the open I couldnt even tell, only when I went into a tunnel was I able to notice.

Beamshots here-

There's what looks like another FET opposite the AO4468, can you get the number off that one, or a pic with the big cap more out of the way?

Maybe 3*17650?

I just tried and 3 17650’s do fit but 17650’s suck. It wouldn’t be worth it to do 3p 17650’s over 2p 18650’s. The only possible reason I can imagine to use 3x 17650 is if it was 3s.

3p 1600mAh 17650’s is >30% less WH than 2p 3400mAh 18650’s, even using high drain 2500mAh 18650’s 3x 17650 is still ~25% less than that.

No argument from this corner. 3s is the only reason you’d do that.

I knew I'd seen some higher capacity skinny cells recently. It turns out they weren't 17650. They were 16650. HKJ has reviews of 3 different ones on his site, here are Keeppower's protected Sanyo cells. They still only make sense when in series, but I thought I'd throw that out there while we were on the topic.

I’d not seen those yet, thanks for posting them, now I have to get some for my quark.

Dissapointing news, the driver has been out of the light (replaced with a 17DD) for awhile now but I’m looking at using it for my 2D to 6AA maglight mod since the input voltage off 6sAA will be right so I finally got around to swapping out that FET (and swapping back to the stock sense resistor) and it runs at the exact same 3.4A to the emitter.

Bummer. For shits and giggles, you should take those DMM leads with the alligator clips out of the equation. Just jam the emitter and driver leads directly into the DMM. You could use wood skewers or dowels to wedge the wires in tight. May not make a difference in this case, but it's the best way to roll. Well, maybe the best, but the easiest best I know of.

Add a 10 ohm pot in parallel with the existing flat-bar sense resistor, see how far it'll go now before losing the modes?

I originally tested with my external shunt resistor DMM but switched to this setup for further [easier] testing. This DMM’s leads are 14AWG wires soldered to the banana connectors inside the body of the DMM and the emitter / battery wires are 20AWG.

I ended up putting the driver at stock drive currents (and with stock modes) into my first 2D maglight build, that took a ton of work to make it fit, it’s not coming back out lol.

I choose it cause it’ll run on either my 6sAA battery carrier or 2 io-ions end to end.

Well here’s where the driver is now, best part is in a few weeks I’m doing another SR51 so I’ll have another one of these drivers to use in something, maybe a cool white 2D mag.

anyway it took some work to get it to fit, I had to grind down the main PCB so much I actually had to run a wire to replace the outer trace, I also had to remove two large sections of the H22A heatsink. That blob on the heatsink is a piece of large copper wire I swaged in a hold I drilled for a good path to ground.

The mechanical clicky was replaced with an e-switch for the olight driver, its a sparkfun tact switch on a BLF 12.2mm oshpark board. The emitter is an L2 S6 7D3 on a 14mm copper board that I converted to direct bond, the MCPCB is the same size as the pedistal and fits right up in the head so the beam is adjustable just like stock.

Cool Mag mod.