an honest approach for testing of cells, matching banks etc.

[DIGITALKEN]

I recently built a 13s4p battery for a 1200w ebike.. I had a shitload of 16550s from various teardowns.... laptops, milwaukee,dewalt etc and bought a 40 amazon 9900 bullshit batteries. How do you guys test your cells?? I bought some usb lipo battery tester on amazon also a joke..

Im thinking to make a batch tester... start withfully charged cell(s).. pic micro etc, start timer, dicharge across contant current sink 1A, eliminating variables. time dicharge to 2.7v. serialize cells and match... or the weak link breaks chain

 

[amberwolf]

There are a lot of cell testing threads here in this subforum, and a few in others.

I'd start with those.

 

[docw009]

OK, you bought cells marked as 9900 mah on amazon for around $3/cell. What did your tester say about their capacity? The best cells in the world are only promising 3500 mah,

Next time, go to 18650batterystore,com. You could have bought Eve 35V's, a real 3500 mah cell suitable for ebikes for $2,85.cell, and they don't need a tester as they will test out at 3500 mah, They're also quality cells. I recently bought Panasonic 35E's on sale there for about the same price.

I use a Liittokala 500S tester, around $30 on amazon. It only tests 4 at a time and is slow. It takes about a day to cycle 4 cells thru a full test using a 500 ma charge/discharge rate. That means it takes 13 days to do a complete test on all the cells for a 13S-4P. have used recycled cells in the past. Now I prefer to buy new ones on sale now and not spend time testing them,

Another tool you might need is an AC IR tester like the YR1035. When the IR resistance gets over 30 milliohms, the cells start to sag under higher current. You can go thru your box of collected cells quickly and find out if any are suited for an ebike battery. New cells will range between 12 and 24 milliohms. I paid about $30 for mine from China several years ago, and they're asking $75 on amazon? Too high.