Calculate amps through each bus bar?

[wholybee]

Sounds great! We went Hawaii—>Seattle—>Mexico last year and this, i
and plan to continue on this fall, aiming to go “the wrong way” to Europe by 2023.

We will probably pass each other as I head through the canal and up the coast back to SF. If I see you I will wave

Can you elaborate? And link to resources/discussions? I’ve seen so many people’s packs with multiple connections. Multiple links allows me to build a perfectly balanced pack, and reduce wire size, which is important because I’m designing for a 400 amp constant load and using tinned wire as interconnects)

Most of the information speaks of ground loops, but it is the same principle. It is huge problem in signaling, so that is what is written about. Honestly it probably isn't a huge deal in this application, but there will be current loops formed, and they might contribute to cell imbalance.

Yup, decided not to go with braid for those reasons.


If I were to use bus bars, and not have multiple links, as you recommend, some bus bars would be carrying 400 amps. Seems like something to avoid.

A buss bar can carry a whole lot of current. I don't remember the math, but others here do. Do the math either way and I don't think current will be an issue however you do it. Just size the conductor appropriately whatever you choose. I would favor the rigid bus bars from concern of the bolts/screws backing out from the wire/lug vibrating. 400A? May I ask what loads you have? Are you doing electric propulsion? Induction cooking? (I hope to add that soon)

I’m using EVE 280ah grade A lfrom Amy, who has an excellent reputation. And I think they require some extra coddling as far as fixturing since they are not as physically robust as Calb/Winston/etc. That’s why I am spending so much time effort on low strain interconnects, and a very supportive battery box with spring compression.

They should be fine. I would test them thoroughly before putting them 4p4s, but I doubt there will be any issues. What I would do is build four 4s packs(one at a time is fine), give them a couple cycles and capacity test them, and if they all work as expected then build the 4p4s pack. I just setup a friend who had bought 4 200Ah cells off Amazon. In a basic wood frame with threaded rod it was very solid.

 

[ohthetrees]

We will probably pass each other as I head through the canal and up the coast back to SF. If I see you I will wave

My boat's name is Sauvage, if you see us, say hello.

A buss bar can carry a whole lot of current. I don't remember the math, but others here do. Do the math either way and I don't think current will be an issue however you do it. Just size the conductor appropriately whatever you choose. I would favor the rigid bus bars from concern of the bolts/screws backing out from the wire/lug vibrating. 400A? May I ask what loads you have? Are you doing electric propulsion? Induction cooking? (I hope to add that soon)

I'm committed a flexible link because I'm worried about stress on the delicate terminals (more so than your more robust Calb) as they contract and expand through charge/discharge cycles. You can see a lot more on this topic on my other thread: https://diysolarforum.com/threads/cell-terminal-strain-relief-bus-bars-and-compression.27439
A solid home-made busbar can easily be made that can handle 400a but I haven't seen high capacity off-the-shelf flexible ones to purchase like (I think you mentioned some, but I think they are around 100a) and I don't want to stack up 4 of those. So wire it is for me. I'm confident I can make a good gas tight crimp to the lug, they are flexible enough, I can get them in high capacity sizes. I'll just be careful to inspect annually for corrosion and heat build up under load.

I'm designing for 400 amp loads because I have a 3000VA inverter, two electric winches, electric windless, and a few other high loads. I would have liked to build a 24v battery bank, but the cost of converting winches, windless, etc is prohibitive, and I haven't found DC-DC 24v-->12v converters that can handle that load. The inverter can run for up to 30 minutes at 1.3x load, so that works out to something like 325 amps. If I were to use a winch or something when the inverter is working hard, I don't want my fuses to blow, so I built in some margin. I don't think I'll be pulling that current very often, but I don't want to under-design. The inverter will be used, when we have excess power, for induction cooking, running a washer, and if we have big surplusses (which I project will will in sunny Baja Mexico), we might have enough making some water, or for an hour or two of aircon to cool the boat at bedtime.

They should be fine. I would test them thoroughly before putting them 4p4s, but I doubt there will be any issues. What I would do is build four 4s packs(one at a time is fine), give them a couple cycles and capacity test them, and if they all work as expected then build the 4p4s pack. I just setup a friend who had bought 4 200Ah cells off Amazon. In a basic wood frame with threaded rod it was very solid.

Thanks, I think properly fixtured, with shock absorbing silcone mat underneath, and flexible bus-bars, the cells should hold up to the marine environment.