rewire 48v as 36V pack.

[e-lmer]

My 48V battery has one triplet of bad cells.
I have removed them.

Prior to the operation the pack was 3P13S.
48V/13=3.6V per set.

I have a 750W 36V Pi. (Old School)
Should I take 6 more cells out to make this 36V?

Can I rewire the inputs to the 48V balancer to ignore the missing 3 sets or do I need to get a different balancer?

Thanks for any advice.

[Bikemad]

Hi e-lmer,

If you change it to a 36V pack (10S3P instead of 13S3P) you will probably need to replace the balancer (BMS) and the charger.
Some BMS can be rewired to work with fewer cells but some can't.

A 10S 36V pack would also require a maximum charging voltage of 42V instead of the 54.6V that your current charger puts out, therefore it is probably easier for you to simply replace the three cells with some suitable 18650 cells instead.

If you have and old laptop battery you may be able to reuse the best three cells from there.

The best option would be to replace all of the cells in your battery with new ones, considering that the remaining cells are just as old as the ones that have already died.

Alan
 

[e-lmer]

Thanks for your answer Alan. 

I looked at the GM 48V balancer and it does not look simple to rewire.
(I would not want to try removing that daughter board).

The only reason I was thinking about going 36V is that I have a GM 36V kit on a bike already.
I have a 3 battery SLA pack that is just way too heavy, so I hoped to be able to use that
charger with the 36V Li pack.

Do you know if GM sells the 36V balancer separately?

[Bikemad]

You can try emailing sales@goldenmotor.com and ask if they have a suitable BMS available separately, but I wouldn't be surprised if they say no.

If your 36V charger is designed for use with lead acid batteries, it is unlikely to be suitable for use with a 36V lithium pack. 

Alan