Right now I only have two Efest IMR18500 handy. This is all jury rigged with different wires, alligator clips and magnets, but I got a reading of 5.9A.
Okay wight, I tested the voltage across the resistors while running the MTG at 13.45A and got a reading of .049v. I tested each resistor, and got that reading. What it means, I don’t have any clue. Hope I did it correctly.
Ouch! I went to take another reading before I disassembled everything, and smoke was coming out of both resistors. I sure am glad I checked this driver before it went into a light.
Do you see anything different in the components between the 13amp driver and the other 2 drivers. Any bad solder joints or solder bridging components?
I looked it all over with a jewelers loop and didn’t see anything different from the other ones. No burned or charred spots. I even tested a few solder spots with my DMM. Then again, my eyes aren’t that good.
Swap in new sense resistors please.
I’ll have to poke around to see if I can find some.
I swapped in some R086 resistors I scavenged from other drivers. Over 14A and started smoking. All the resistors have holes burned through the center.
Maybe the buck converter is oriented the wrong direction. Unfortunately they grind the label off of them. So I don't know how you could tell.
Thanks for testing this. You definitely got .049 and not 0.49? 13A across a total of 0.034 ohms should give about that much drop (1/2 volt). Sounds a lot like you are getting DD or as close as this driver will come (with the FET and inductor in the mix).
Could be I suppose. With QX5241 that just gives you a dead driver, but the pinout for QX9920 is different enough that it might give you DD; I’m not sure.
I think that it could also simply be a defective controller chip.
My DMM said .049v. I just set it to voltage, it’s got auto ranging. That’s all I know.
Seems like something is going on with the buck converter. Your driver is acting like mine did when I tied the PWM from an Attiny13a to the output pin of the buck converter. Wight pointed out to me then that I had basically turned the driver into a DD.
Later, I accidentally tore a leg off of that buck converter. I purchased a replacement that wight suggested may work. I will hopefully swap it tomorrow night. I'll let you know how it goes. The buck converters are fairly cheap.
wight,
Good call on the QX9920 buck converter. It works. Current to the emitter was as follows:
2S cells 4.5 amps (dropped fast to 4.4)
3S cells 7.15 amps
Thank you 
Ouchyfoot,
Sorry it took me so long to get around to trying out the new buck converter. Here is a data sheet that wight linked me to. Here is where I bought mine from (link from this wight post).
EDIT: My chips were labled LEDA 1402. There was no indicator mark I could find for Pin 1. One of the short sides had a slight nub. I oriented the chip with the nub facing away from the inductor coil.
I added a couple R20 resistors to the above driver (using QX9920 buck converter). Pulls 9.65 amps with both 3S and 4S King Kong cells driving an MT-G2. Piggy backed an Attiny13a with JonnyC's STAR momentary modified by Tom E to include strobe. Wow, what a fun driver. I know exactly what light it's going in. Actually, I know 4 other lights that will be getting the similar setups.
EDIT: I just realized. I heard no PWM whine last night. The only things I did different was the FW just mentioned above and I completely air wired the MCU. In the past, I soldered the PWM leg of the MCU directly to the buck converter. Here is a pic (sorry, it's a bit blurry.)
Very interesting indeed!
Was hoping to find a spot on this driver to use for voltage monitoring. I poked and prodded with a volt meter using 2S and 3S cells, but could not find much of a drop in voltage anywhere on the driver. With 3S, most points read 5.27V. With 2S cells (resting at 7.92V) the same places measured 5.15 With such a small difference, I don't think it would do any good to install a voltage divider. I'm sure one would probably for for 2S, but not for 3S and 4S.
EDIT: Driver was under no load in the above measuring (no MCU or emitters connected).
It’s been a while since I thought about this driver (and I still don’t have one myself). Glancing over your pics again, maybe it does not have a voltage divider. That shouldn’t be showstopper though, airwiring a voltage divider should be an easy thing. I think I’ve covered the component selection (two resistors) pretty well over here (#917). For such a large driver I’d probably just use standard 1/8w or 1/4w through-hole resistors, you probably have the room for them. Higher values are better, less power draw.
Excellent. Great post you linked to there. I will be giving that a shot. I have a 4S build in progress. I should be trying it soon. I'll report back.
Let us know how the 4S goes. The big unknown for me on some of these Chinese boards is what the individual components, especially the capacitors and MOSFETs is voltage rated at. When you take into account the ringing that occurs I would hope to see a 25V rated input capacitor for 16V input use, but who knows? At least ceramics don't explode like electrolytics but I would definitely remove that little yellow tantalum cap. since you're probably not using it anymore, those can burn.
I've already used the driver in free air with 4S driving an MT-G2 at about 10 amps (9.65 per the DMM). Same reading I get with 3S cells. Set up on the driver was
- Two R20 resistors added
- QX9920 buck converter swapped in because I broke a leg on the stock buck converter.
- MCU swappped - Attiny13a with JonnyC's STAR momentary modified by Tom E to include strobe.
Used the stock FET. I did not run it for very long (just a few minutes because it was late), but it showed no signs of distress and worked great. Didn't even get any whine from the MCU.