Wiring more then 4 batteries in parallel?

ollyomm

Hi guys, I've been staring at this picture for an hour now and I cant figure out how this could be applied to 6, 8 or 12 batteries, I know the ideal is a splitter bar but am looking for alternatives.
Thanks in advance

Photowhit

Are you getting the batteries free? Higher system voltage or larger capacity batteries may save you money in the long run.

It's just a pain to get equal resistance across so many batteries in parallel. 

If you must a bus bar can be had pretty cheap. from Lowes/ Home depot;

Something like this from Home Depot, if you are using some small batteries. I think the small are 4 gauge and the large 2/0
Perhaps you could devise your own insulator for this;


https://www.homedepot.com/p/Eaton-14-Terminal-Ground-Bar-Kit-GBK1420CS/100199885?MERCH=REC-_-PIPHorizontal1_rr-_-302610360-_-100199885-_-N

Estragon

It looks like it's a pair of pairs (2^2=4). With 8, it would be a pair of pair of pairs (2^3=8). Each balanced group is iterated as a single battery in the next parallel connection, which is itself cross-connected to maintain balance. 2^4 would be 16 batteries, and so on.

If I'm understanding the idea properly, it needs to be even powers of two, so 6 or 12 wouldn't work. I may well be misunderstanding the idea though.

Although this might theoretically give equal resistance, in real world field wiring I suspect it would be difficult to avoid differences. With more batteries in parallel, the odds of differences would increase, as would the likely range between high and low resistance wire/connections.

IMHO, the ideal would be a single series string, or at most two series strings in parallel.

mcgivor

Method 3 from the Smartgauge website where the image was taken from, could be used for any number of batteries even odd using a bus bar, as suggested by Photowhit, much simpler. The method 4 you refer to seems over complicated for no gain, which ever method is chosen it would be advisable that each battery is fused to prevent a failure of one being fed by all the others, as well as constant monitoring of current of each battery during charging and dischargeing to ensure ballance.

mike95490

Even using identical lengths of cables, well crimped, does not always work, as there is variation and even bolting lugs onto terminals is another variable.   At some point, even busbar won't solve the problem, because of internal variations in the batteries themselves.

ollyomm

Thanks for your help guys, batteries are close to free, 6$ for 39ah gel batteries that appear healthy, most with resting voltage of 12.9 after a few months. So just seeing what can be done and how long they might last as a bank. Also have access to heavy duty scrap wire from a friend. Almost tempted to solder to the battery terminals but will try soldered ring terminals first. Will go a splitter bar. I just liked the theory of the image

mike95490

Please don't solder to battery terminals, you will ruin the seals and then have junk