Making a 3 or 4 bank 12v battery system for sailboat

[Matt1376]

I am about to order either 12 or 16 3.2v 280 ah cells to replace my current lead acid system (2x 8ds and a starter battery). My plan was to make 4 separate 12v packs with their own 200 amp jbd bms. Then run these parallel into a busbar to power my system. I was about to order from Amy wan and she tells me I shouldn’t do this. I should run one bms and have one 12v bank. I like the redundancy of have multiple banks. I figure at this point the max power I am going to pull at once is 3000 watts. Planning a Victron 3000w charger inverter. Does anyone have any suggestions? Can I do it this way or is there a better way?My plan is to over build the system so I can add things to it later and have lots of redundancy. I have a wind generator and a couple solar panels but will be adding as many solar panels as I can fit.


Thanks in advance
Matt

 

[svsagres]

I would agree with Amy on this one. I’m running a 2p4s diy battery to give me 460AHr. If you go with a contactor based BMS, you can always override the BMS if absolutely necessary. IMHO, this is more reliable than FET based BMSs. I’m using a Blue Sea 7713 ML-RBS as my high-side contactor; it has a knob that lets me either manually force it, or manually lock it out (so I can do proper Lockout/tagout on it.

The other thing to consider is a BMS that will integrate into the victron ecosystem. The win here is that most conditions that would cause the BMS to drop the connection are avoided as the system will soft-command it to stop either charging or discharging.

 

[mikefitz]

Go for redundancy with 4 off 12v batteries each with its own bms.

You will be able to engineer a secure containment case for 4 cells, trying to build a case for 16 cells would be almost impossible where you need to tollerate the motion and environment of a sea going vessel.

The most likely part to fail is the BMS.

There are also possible issues having multiple cells in parallel , the risk increases with the number of cells.

Mike

 

[svsagres]

Go for redundancy with 4 off 12v batteries each with its own bms.

You will be able to engineer a secure containment case for 4 cells, trying to build a case for 16 cells would be almost impossible where you need to tollerate the motion and environment of a sea going vessel.

The most likely part to fail is the BMS.

There are also possible issues having multiple cells in parallel , the risk increases with the number of cells.

Mike

I would agree that FET based BMSs can have reliability issues, but the bigger issue they have is the potential for a cascade failure when they're paralleled. Lets say you're running fairly high current, and one of the BMSs popps its fets (or maybe just drops the load for whatever reason). Suddenly, all that load is transferred over to the other BMSs. This transient can be problematic.

This is why I like Contactor based BMSs for larger capacities. Contactors are stupidly reliable, and designed right (where the BMS is controlling the loads/charging sources) won't be switching that often. In my situation, I'm also using a Blue Sea ML-RBS which gives me the ability do mechanically override the BMS, both ways. I can either manually force the contactor on, or lock it out so the BMS can't turn it on automatically. IMHO that safety mechanism is huge.

There are possible issues with cells in parallel, but if you do the mechanical layout well, so that the resistance between the cells is low enough, it can be mitigated.

 

[Blizzard]

I am about to order either 12 or 16 3.2v 280 ah cells to replace my current lead acid system (2x 8ds and a starter battery). My plan was to make 4 separate 12v packs with their own 200 amp jbd bms. Then run these parallel into a busbar to power my system. I was about to order from Amy wan and she tells me I shouldn’t do this. I should run one bms and have one 12v bank. I like the redundancy of have multiple banks. I figure at this point the max power I am going to pull at once is 3000 watts. Planning a Victron 3000w charger inverter. Does anyone have any suggestions? Can I do it this way or is there a better way?My plan is to over build the system so I can add things to it later and have lots of redundancy. I have a wind generator and a couple solar panels but will be adding as many solar panels as I can fit.


Thanks in advance
Matt

Here is some very good reading:

https://www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf

https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

 

[Matt1376]

Thanks for that. lots of information to take in