Balancing 24 volt system

[tucsonjwt]

I have been individually charging my 4 Battle Born batteries which I had set up in 2 strings of 2 batteries in series for my 24 volt Growatt AIO. It took a few days to get all 4 batteries charged up to 14.2 volts (where the Victron IP65 said it was "storage" state) but now the first 2 batteries charged have dropped down to 13.77 and 13.92 volts. So, I am thinking I need a balancer and am wondering how to hook up a balancer to the 4 batteries. I could get 2 balancers (one for each 2 battery series bank), but I don't know how to balance the two 24 volt banks. I saw the attached drawing for an Amazon balancer which looks like one balancer could balance all 4 batteries. Do you think it would work? I am looking at the image on the top right. Thanks.

 

[timselectric]

Yes, the single balancer will work for a 2p2s configuration.

 

[tucsonjwt]

Yes, the single balancer will work for a 2p2s configuration.

Thanks, timselectric. Do you agree with the 4 battery 2s2p configuration shown in the top right drawing? When I talked to Ian at Watts 24/7 he said I would need two balancers, one for each series string, but when I asked him how I would balance the 2 separate 24 volt battery banks he just said I was "overthinking" the issue. I currently have both primary cables from the 2 separate 24 volt battery banks going to positive and negative buss bars.
Would I have to jumper the positive and negative battery bank cables from one 24 volt bank to the other 24 volt bank, then run a cable from the positive and negative terminals from one of the daisy chained 24 volt banks as shown in the drawing? Would you use one Victron balancer or go with a cheaper balancer? Victron would require a lot more DIY wiring since it does not come with any wiring.

Also, fusing is recommended for the balancer. Should a fuse be on just one of the legs (positive, negative, white common) or should all wires get a fuse? DC systems seem to have the fuses on the positive wires, but if there is a short circuit internally could there be a backfeed through the negative and white wire momentarily before the positive fuse blew? I am reading 4 amp fuse and 10 amp fuse for this purpose - which size do you recommend? Thanks.

 

[timselectric]

2s3p would require 2 balancers.
2p2s would require 1 balancer. (Shown in the top right picture)

I would fuse the midpoint and most positive wire.
Fuse size should be what is recommended by the balancer manufacturer.