Well, can't guarantee that it's being done correctly. But it seems to. Has the multi wire charge connector to supposedly balance the cells. The 3 LEDs - one for each cell - went red to green roughly about 10 minutes apart after about an hour of starting. So I assume it's working correctly. But, yes, I get a bit skeptical over cheap, too good to be true products.
Hans.
Still, that combo that Hans (
@4regt4) suggested looks like one that will work well. I was serious about checking out that $12 charger...I like to be able to recommend stuff from personal experience and I've done quite a bit of charger testing in the past — I even used to have a "column" on RC Groups years ago called "Recurring Charge" where I did that sort of thing and wrote it up....but rockets came back into my life about 12 years ago and I've not done much RC airplane-related equipment testing since. Instead I've been obsessing over testing altimeters....
I very much look forward to you testing this charger. To see if I screwed up......
Hans.
If it burns your house down, I'm changing my username and going into hiding...
Hans.
Well, it didn't burn down my house on the first instrumented charge.
I charged a 3s Zippy 1300 mAh pack that I'd been using to drive a charger that can charge up to 5 1s cells....cells I use in my night flyers (flown at Sod Blaster a couple of weeks ago) and some other auxiliary cells, specifically the ones I'm using with Eggtimer ION altimeters. The battery was down to 3.67v per cell (slightly imbalanced) when I started. I put the sensing unit for a Hyperion eMeter II (a neat gadget developed to test electric power systems for model airplanes and such) in line with the two outer leads, then let it go until the little charger gave me three green lights. The center one lit first then a small number of minutes later the other two went green simultaneously.
In the end it charged at a maximum of 700 mA, but spent most of the time charging at around 500 mA. It very slightly overcharged all three cells, taking them to 4.21V each, ending up with all three of them with 0.02V of one another. As you can see on the graph below, this is not quite the typical constant current then constant voltage charge regime normally used for LiPoly batteries.
So....I'm still not worried it will burn the house down, based on this first result. I may discharge that same pack a ways, and maybe run the same test again while monitoring just one cell, to see if anything is markedly different. That will have to wait until at least tomorrow....and tomorrow I get a new iPhone (for the first time in a along time — my current one is a 7+) and I'll probably be spending a good chunk of time moving data and such.
The eMeter II is intended for testing electric power systems for models, so its current resolution is lousy (apparently 0.1A or 100 mA). That's obvious on the graph. That small a current delta is negligible when you're talking about power systems pulling hundreds of Watts.
I was recording at the eMeter II's maximum data rate, which is 8 Hz, and the test took over 100 minutes (so over an hour and a half). Consequently there are over 62,000 data points.
I clearly need to learn more about curve smoothing or some kind of approximations in Magic Plot...
Oh - the charger put a little less than 400 mAh into the pack over this time.