S - P question

[Stucco]

So I am thinking about designing my custom batteries. And bouncing between packing my own with repacked LION vs LiFePo4. Found these packs from Battery Hookup, I am using these same cells for my electric cycle project.

36v 48ah 1.78kWh POWER Module - 60x SPIM08HP

These batteries come with a steel enclosure which can also be mounted. This product must ship freight which is calculated. The more you buy the cheaper it gets per battery for freight. We include residential and lift gate service. Or you can pick up for free from our Bensalem, PA location. 60...

batteryhookup.com

So if I did their 7 pack recommendation that would be a 14s30p if I did a single 12 kwh design.

Or would it be better if I broke that down to a few batteries with separate BMSes and parallel those.

 

[MisterSandals]

a 14s30p if I did a single 12 kwh design.

This would require 30x 14S BMSs.

Backing up a step, what is your target voltage and max load?

 

[Stucco]

This will be my home ups. Planning on doing dedicated drops from my solar design to specific house locations to run them off of solar/keep them running when we lose power from storms/hurricanes.

Target Voltage is 48v to power 2 mpp 4xxx inverters.

Probably wouldn't do 30 separate batteries, but wondering if it would be better to break this out to 14s15px2 or 14s10px3 or 14s5px6

 

[MisterSandals]

break this out to 14s15px2 or 14s10px3 or 14s5px6

Assuming you are putting cells in parallel first?
15P14S x2 or 10P14S x3 or 5P14S x6

Would require 2x BMSs, 3x BMSs, 6x BMSs

LIFePO4 = 3.2V
Packs 14S = 44.8V (standard is 16S 51.2V)

Is there a reason for your desire to make undervoltage batteries?
Are 14S BMSs readily available? Same or other equipment to charge 14S?

 

[Stucco]

Im just spitballing at this point. I meant 16, but it is early.

Just wondering if there is any benefit to doing a single big battery, or splitting it up to a few smaller batteries.

I know I will need more bms, but looking more about 1 vs many.

 

[MisterSandals]

I know I will need more bms, but looking more about 1 vs many.

I suspect the biggest consideration is finding/buying BMSs that can be connected in series in large numbers. And with that being able to handle your anticipated loads.

Otherwise it’s largely a form factor.

 

[Stucco]

Ok, so no benefit breaking them out for maintenance, scaling, load, etc.

Cool. Thanks. Again, this is all grey matter space right now, but I need to start solidifying this when I start purchasing stuff in the next month or so.

 

[MisterSandals]

There have been a bunch of folks here doing what you are thinking but my overall impression is that it is a LOT of work and in the end is not any cheaper than big LiFePO4 prismatic cells.

 

[Stucco]

Well, using recycled panels and recycled cells. if I get 8 or these modules that would be over 12 kwh for about 2k so that's a lot more dense than new lifepo4. True no warranty, but my time is free and I get to learn more. And I am a big proponent of keeping stuff out of landfills and getting the full mile.

Getting a nice BMS for this. I used JBD for my bike. The solar inverter/charger I am going new. Planning on single unit to start to feed a dedicated panel. Then adding a second unit to do the dual phase down the road to get some larger amp breakers.

 

[Bvillebob]

Nobody here has had problems with anything from Battery Hookup, right? I suggest you a little search around here for the actual results of what people have purchased verses the advertising.

 

[Stucco]

Have people had issues with them? So far my cells have all been good.