how Fuced are these batteries? (0.7V Nimh)

[monster]

hi

i want to build a solar ebike charger with a battery bank made from defunked old ebike batteries. i have a load of old Nimh and NiCd cells all in different states of decay. they have been well abused. short circuited, over-charged, fast charged and left to self-discharge for over a year. they were from when i was experimenting with DIY battery chargers and didn't know about battery padding and insulation. i've checked the cell voltages and about half of them are above 1.0V the rest were around 0.7V. i realize i can probably get the first lot to work but should i even bother with the 0.7V cells? lots of them have white crystals around them and heat damaged insulation.

 

[jag]

NiCd/NiMH aren't damaged from low cell voltage (only voltage reversal).
However your other indications, leakage, abuse etc, don;t sound promising.

Yet only way to know is to charge up the batteries, see if they take charge. Discharge (ideally individually) and measure capacity. Nickel chemistries may additionally have to be cycled a fre charge/discharges before reaching full capacity after being unused for some time.

 

[mwkeefer]

Just a note of caution.... slow charge the crap out of it... ie C/10 or even C/15 just until they reach nominal then... you can speed the process back up to 1C.
The leakage is not a good sign but if it's only a few cells... you could still recover most and just replace the few "bad" cells (leakers).

What kind of charger are you going to use on them? Just don't forget to set the charge current to an appropriatly small level (if cells are 3300 mah, charge at 330ma rate until nominal is reached)

-Mike

 

[monster]

What kind of charger are you going to use on them? Just don't forget to set the charge current to an appropriatly small level (if cells are 3300 mah, charge at 330ma rate until nominal is reached)
-Mike

a solar panel no wory about too fast charge there, only worry is self-discharge may trash my efficiency.