battery giving up the ghost?

[wheelchairer]

These have been damaged for a while. It looks like they are starting to fail now, would you agree?

I was hoping they would last a little longer. I have some 230Ah battery cells lined up to replace the ones in my BM, and the ones in the BM are going in my other wheelchair.

[Burgerman]

Looks like cell 6 (at least) has a bad connection.

[Burgerman]

Take it out. Check the tightness of EVERY connection on the cells TWICE. Then chck again. Every time I do this I find one I missed no matter how certain I was!

Recharge and wait for it to balance and complete properly. And do it again.


Now discharge by say 40Ah. Leave it a day. Then see what a subsequent recharge looks like. I would bet that it will be pretty good as long as all connections are good/deoxit used etc. And no crimps.

UNLESS you have some bad cells. How did they get bad? Over discharge? BMS? Over charge? Stored full? Bought used, or fakes?

Headways are very robust. I still have some as good as new from a decade ago working as normal.

[Burgerman]

Why are crimps an issue. Many reasons. Not least in the case of BALANCING they are very problematic. We are looking to balance to a few mV. When you bolt or push (crimp) connectors on, you have two different metals most of the time. That is a battery in itself! Any humidity in the join between two metals and you get a difference of anything up to a couple of volts trying to happen! So SOLDER everything and be sure all plug in connectors use the same metals.

Take a voltmeter and connect a zinc plated terminal, and a stainless steel screw or copper wire. Touch them together and watch your volt meter read say half a volt. Completely burying the actual mV readings we are balancing to.

Be careful what you use. Copper bus bars on alloy terminals with stainless bolts as used on prismatic cells are a great example of a bad idea!