[willo]

TLR:
Looking for good options to build out a ~96v (up to 115) pack to drive about 25Kw of output. (AKA 250A @ 96v)
I'm thinking of upping the voltage just a hair to keep amps a bit lower since I'm already at high DC voltages.
For safety, I think I want to build this to be able to break the system into 48v packs when not in use. I'm sure that'll make the bms super happy.
Target is 20-40Kwh of storage. I need to support 250A of sustained drive current.

I see three possible solutions here.
1) LFP/LifePO4 cells.
32cells*3.2v = 102.4v
102.4*100Ah = 10.24Kwh
So, if I use say, 2 to 4 100ah cells in parallel to deliver the amperage I need, this gets pretty approachable. I can add a cell or two to the series config to up the voltage and reduce my amp load just a bit - and allow for puling a cells out of service if I have a failure. Cost: Around 2-4k depending on config/seller/shipping/etc.

2) EV traction pack reconfigure. An interesting pack to me is the BMW i3 pack. It uses something like 48v modules that are easy to remove and reconfigure into a 96v pack. It would be harder to up the voltage if I wanted to. In addition, It looks like about $3k for a likely degraded 22kwh on the open market for these.

3) Custom 18650/26650 cell packs.
This is interesting as I could build custom packs into waterproof pelican style cases. It would be a crap ton of cell welding. After poking around a bit, I've found a similar cost per Kwh unless I absolutely score some epic recycling deals. Seems like similar pricing otherwise and just a ton more fabrication work for me.

Have I missed anything I should seriously consider?

 

[willo]

Tesla modules would come down to cost. I think I'd have to run 5s to get the voltage/amp ratio I want.
I have one I used in my RV previously, but would want some in excellent shape for the boat.

 

[willo]

I found one spec that rated Tesla modules for 225a continuous. I'm wondering if I'll have to go with double packs later but I could live with 22kw of output to start I think.
I found a good deal on a few modules locally so I'm tempted. I kinda like the idea of water cooling the packs anyhow.

 

[willo]

I'm waiting to hear back from Thunderstruck to validate what I'm doing, I'm thinking 4 or 5 packs. The controller is good for up to 125v but I want to make sure that's reasonable.
Max charge voltage is 25.2, but I think it's better to be a bit conservative and stay a volt or so away from min/max charge levels.
On the one pack I used (which is actually a crappy one) It seemed that the tesla packs like to sag a bit in voltage as they discharge and I'm thinking 5 would keep the voltage over 100 for most of my usage, and give me a little more headroom to avoid driving the cells quite as hard.

 

[willo]

Meh, I'm half awake. It's been an... interesting day so far