People find ways to rationalize what they do. So it is with battery selection, how they are configured and BMS approach.
I powered my boat for 10 years with golf cart batteries and saw little reason to change from that. Then in 2012 I found myself owning and commuting in a 2011 THINK City electric EV. After months of happy motoring with the car and having regular paychecks with work, I rationalized going with Lithium on my boat by saying I was buying a couple spare battery modules for the car…well, I've never needed a module replaced in the car (now at 50k miles) and I have since purchased 2 complete THINK Enerdel 23kwh lithium packs to power my boat. Actually, mine has 30kwh total and Dan's "Ginger" has been running with about 17kwh of lithium. We've not had any issues with these and have not actively balanced the cells in the pack on any regular basis. I do have a balancer that I built that can handle my 240 pairs of lithium cells, but as I only charge my pack but about 4 times per year and usually only to 46v, there's not a lot of incentive to actively manage the cells. It is getting to be time though.
We have no regrets in going with lithium on our boats. As for paralleling batteries, mine is configured as 20P(12S(2P)) for just under 30kwh of energy. The 20 "modules" are each connected to the central line via 10amp fuses. If any one cell pair should somehow become shorted, the most that can flow into that defective module is 10amps before blowing the fuse.. This has worked well. We do need to balance these cells, but very very infrequently given the very low self discharge rate of the batteries and the small number of charges done annually.
I wouldn't have gone this direction without having a THINK City EV and having a regular income at the time. It is extremely nice not having to worry about periodically doing equalization charges, watering and other care and feeding of lead acid.
Your mileage may vary-
-Myles Twete, Portland, Or.
Posted by: "Myles Twete" <matwete@comcast.net>
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