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In terms of batteries, this is a little tricky. Nearly everyone on here these days uses junkyard batteries (usually Tesla, Volt or Leaf). They are cheaper than anything else available.

But your application is not that well suited for those. You have a small vehicle, and you don't need a lot of range, so you're looking for a pretty small pack, probably on the order of 10 kWh. But on the other hand you need a lot of power.

There are two challenges with using salvage OEM batteries. First of all, with OEM batteries the capacity (Ah) is what it is, and typically it is a larger number than you would want for a small battery, and if you use just a subset you don't get the voltage you need. Going with a very low system voltage, like you would do if you used a brushed DC motor, helps in this regard a little. But it still limits you somewhat. For example, the Tesla Model S batteries have an Ah capacity of about 260 Ah. So even if you went all the way down to 144V nominal, your pack would be 37 kWh. Way too big for your application. Probably the only OEM batteries that would have a chance would be Volt batteries, as they have a relatively small size while still being at 400V. But they are much lower density so it's not a complete slam dunk. You'd just have to see if you could fit enough in to get to the voltage you need.

The other challenge is power. You want your pack to be small but still pretty powerful. But most OEM packs use low power cells and get their power by making the pack very big. The cells in a Tesla pack actually aren't very powerful, but they put 100 kWh of them in and that's how they can make their car powerful. If you took just 10 kWh of Tesla cells, you would not have much power at all. Again, probably Volt cells would be your best bet. Like before, since they have a small pack they have to use higher power cells. For sure Leaf cells would be out of the question, as they aren't very powerful at all.

If Volt cells wouldn't work for you, you may have to look past the salvage market. But that's going to cost more.
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