Using batteries in parallel

Hello, All
I know this has come up before but not in at least a few years, so I thought I’d check with the community to see what the current advice is re: connecting BR batteries in parallel. Apparently the BlueBoat setup includes a simple harness with connections for 8 batteries in parallel. Does anyone have any recommendations as to maximum voltage differences between batteries before hooking them up in this way? Or how long to let them sit after being charged before evaluating their voltage?

I used to connect large 4S and 5S packs in parallel with no issue, but i would always make sure they were all within a few hundred millivolts before connecting them, and I had a fuse protecting each pack.

I never had any issues, but I do know that things can go very bad if a pack fails, or if you accidentally put the wrong pack in the mix.

I started using the SeaView Ideal Diode on one system and it worked really good. When I needed more and could no longer get them from SeaView I started making my own.

I make one that is a simple Ideal Diode very similar to the old SeaView one, and I make one that is a Load Switch and Ideal Diode. The load switch just gives you a way to switch the battery power On/Off with a BR Switch or remotely.

Ideal Diodes are the way to go if your connecting packs in Parallel.

Hi @rperkins,

Per the technical details on our BlueBoat product page we’re using 60A fuses on each battery.

I’m not sure on a maximum voltage difference or post-charging rest time recommendation, so I’ve asked internally and will get back to you - that seems valuable for us to provide information about (likely within a more general parallel battery management guide).

Thanks for the replies, y’all. @nperry I’ve been using the SeaView ideal diode setups, too. I guess I run things pretty hard because I’ve burned up a few! I guess I’ll keep running with the ones I have left for the time being. I don’t suppose you have any of your own setups for sale/borrow?

You can find them here: https://www.pacsubsea.com/product-page/ID-227-01