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Is there such a thing as too many breakers?
Hello I have been collecting Li-Ion cells for a while planing to build some sort of power storage system. Recently I have upped my collection rate and am now looking at putting the cells into a pack. I have decided to go with a 24v 7s battery design, and I have chosen to use the DiyBMS4 by Stuart. At first this will be wired to a grid tie inverter to provide backup power to my home lab, but when I buy my own home I am going to expand this system into a whole home backup / home solar storage system. But I have a few questions I need some help with before I go ham building packs. First a little background on the problem.

A while back I was looking online at batteries that I could salvage and bought a few Kwh of hover board batteries planing to harvest the cells and adding them to my collection. Turns out they were not 18650 cells but pouch cells. It was my fault, if I read the description I would have seen that these were not the cells I was looking for. Oh well, I can find some use for them. A little while latter I picked up some SPIM08HP cells, this time knowing full well they were pouch cells. So my question is, can I use these two types of pouch cells and the 18650's in a a power wall application? I do not plan on mixing the cell form factors, so I would have several 7s batteries hooked in parallel, each with its own set of BMS boards.

Another question I have is related to the wiring fusing and breaking. Below I have two figures. Figure one I have one fuse on the negative side and one shunt trip breaker on the positive side. If any one of the batteries drops into a fault condition, under or over voltage, the whole system would shut down. The second figure has each separate battery pack with its own shunt trip breaker and fuse. Each pack can be turned off individually if it shows a fault condition. Both systems would be expandable as I built more batteries

Figure one would be the more economical solution since shunt trip breakers that can handle 100+ amps cost hundreds of dollars, and each of the battery packs I am planning to build can easily output that much amperage. Figure two would allow me to isolate each battery if I needed to service, replace, or add a battery. What would be better figure one, two or is there a better figure three that I should explore?

Am I missing any crucial parts to my setup? I welcome any parts recommendations when it comes to shunt trips, fuses, breakers, etc that are good to use.

Rock on!


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Is there such a thing as too many breakers? - by nighthawk28 - 05-16-2020, 06:35 PM

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