Discharging battery modules

Hi guys,

So eventually the prius is back and working. For now at least.

A few notes in case anyone ever has problems and crosses this thread...

After putting the battery back together i got a number of weak module errors over different batteries. I can't be sure of the exact cause of this but here's what I did to rectify it:

1) cleaned all the copper plates in vinegar

2) tightened the nuts more (i read 5nm is the correct level but i was in a rush and just tightened them to the highest clutch setting on my drill driver, probably about 3nm)

3) discharged all the batteries at 1.4ah down to 6.5v. Charged them all to 5000ma in the hope they'd be better balanced. I suspect that fully charging them meant that some modules had a much better capacity than others and this caused problems. Additionally there was probably some self discharge between the first modules I did and the last modules as it took so long to do them all.

Also worth noting:

1) be careful of the sheet steel. I cut my finger bad undoing the rack bolts.

2) the nuts that connect to the leads are very similar to the ones that connect to the battery terminals, don't get them confused

3) you won't get the bottom nuts in or out easily if the rack bolts are loose or undone. The batteries expand and push them out of alignment

4) if you charge any batteries outside the rack, in a clamp for example, give the battery ample time to cool down before removing it from the clamp. I did this too soon after and the battery turned in to a balloon

Anyway... I now have a question i hope one of you could answer for me...

The other threads on rebuilding and reconditioning a battery suggest a discharge rate of 0.7ah down to 6v. Is there a reason for this slow discharge?

I understand the 5ah charge is to ensure the delta peak voltage drop is detected at full charge but can't work out why the discharge needs to be so slow and as this is what takes the longest amount of time it would be handy to raise this (my charger will go up to 2ah for discharge).

Cheers

Dan

 

Thanks TMR-JWAP

So from that, is it safe for me to assume if I was to have to do this again in the future i could discharge at a higher rate without any negative effects? (assuming my charger allows this)