+1 for this. There’s actually an uglier but better version this. The purple one above is analog controls with digital display. You twiddle the knobs until the displayed numbers are what you like. The ugly one below is digital controls. You set the numbers and hit ON.
And apparently there are knockoffs lol.
http://www.360customs.de/en/2017/01/150w-constant-current-load-60v-10a-battery-capacity-tester/
It’s worth it, you can set the current you want to drain at, and when to stop. 60v 10a up to 150w. 4 wire sense (compensates for voltage drop across the power wires due to resistance+current). Really useful tool.
I linked the top one earlier but I guess the OP wants to go a different route. I totally agree though.
Edit: just realized that was a “quote” 
still dusting off the cobb webs from a late night in the battery lab.
Lipos then all bets are off. I have seen some very interesting behaviour with those. Quite funny you mention that because I charged up my Revo for the first time in about 18 months and 1 battery puffed before my eyes yesterday. Other one was fine. My 2 max amps took a charge no drama but they are good quality cells.
It would be good to have some definitive data to back up experience.
Hey so that second one is basically the same as far as the load it can handle(about 3A at 12s full)? But it is programmable. Think I might have to give one a try! Super cheap comparatively as well. Good recommendation
Yeah I got lured by the pretty colors, then found that youtube video. Ended up with both. Pretty one stayed in the drawer until I fried the ugly one. Tried the pretty one, I was like, wtf? Ordered another ugly one.
It’s seriously useful. For balancing p-groups, testing buck converters and power supplies, questionable batteries, storage charge, fusing current of fuse wire, etc etc etc.
Hey @DerelictRobot do you think putting a few in parallel to increase current would work? I’ve wanted to try some nickel strip current handling tests but the 10A max makes things annoying.
Did you happen to check the voltage on it prior? Was it within norm? If so, that’s the exact behavior I’ve observed dozens of times. We discovered this the hard way when… I shit you not: we received an entire batch of lipos that had been fully charged at the factory for some fuckodd reason. Only about 200 packs in that batch, but they had already sat on a boat across the lake then sat in our warehouse for another 2 months before we noticed.
I’ve got some 4s lipos chilling in a box hooked up to an led “lipo killer”
It’s been 2 weeks and that light is still on lol. Starting to think it was meant for smaller batteries like for quadcopters.
Probably not a great idea without knowing exactly how it’s generating load. Purely resistive, sure it could work. But without looking at a schematic it’s all guess work.
Higher end load generators will have load balancing between multiple units, but that’s way beyond a $50 units features.
I think it’s using the linear region thing in a mosfet. And it’s $25, but it should at least have overcurrent protection (I think).
Hairdryers take a lot of power. Best thing I found around the house.
I haven’t looked into it but nichrome wire maybe would be ideal. If it has high enough resistance and doesn’t transfer heat to the cell
I didn’t but the other one was at 75% so I assume they were both somewhere near there.
I have 6 others that I shall check later on.
Ahh. Poor man’s load balancing. Hah.
I’m kidding. Mostly. Please don’t set anything on fire.
I found schematics.
https://www.eevblog.com/forum/repair/part-identification-150w-constant-current-electronic-load-60v-10a/?action=dlattach;attach=378940;PHPSESSID=0qchk46haqpvb7bk1ub5fanfk1 from https://www.eevblog.com/forum/repair/part-identification-150w-constant-current-electronic-load-60v-10a/
It appears to be some kind of electronic device.
For sure leaving batteries laying round at full charge is detrimental
They recently changed the voltage cells should be at when shipped a bit lower. Slightly related
Are you a fuckin wizard? Last thing I expected to just be available online. Haha
Nowadays all the cool shit seems to be open source or derived, or some nerd reverse engineered it. Great times.
Okay, I know almost nothing, but I’ve pieced some non-facts together from various youtube videos and some circuits courses from decades ago.
schematics have IRFP250N
https://www.infineon.com/cms/en/product/power/mosfet/12v-300v-n-channel-power-mosfet/irfp250n/
Ptot max 214.0 W
So yeah I think it’s what I said before.
I’m ignoring everything else in the schematic because I don’t understand it so it’s invisible to me lol.
No doubt. Great time to be of the learning inclination.
Looking at that schematic, it’s actually more advanced than I’d given it credit for.
At a glance it doesn’t look like you’ll blow anything up by using two in parallel but it’s definitely not designed for that. There is reverse current protection built into the input and before the shunt.
Oh sweet, you’re awesome man. This is worth ordering 2 more I guess, so if I blow 2 up I’ll still have 1.
2 units will let me get to 20A, which is what 30Qs can do, so nice.
Thanks again @DerelictRobot for taking the time to look at the schematics.