[brian_]

4. Also, anyone know of a good resource to find 12V batteries for EVs?

What do you mean by "12V batteries"? Are you thinking of using lead-acid batteries?

Very few people would use lead-acid for a car now; they're just used for low-speed vehicles, because they don't store much energy for their weight compared to lithium batteries. People are even ripping out lead-acid batteries from previously converted cars and rebuilding them with newer technology.

 

[brian_]

3. Can I couple two warp 11 HVs or just the regular warp 11s?

According to Netgain, both the regular and HV versions of the WarP 11 have double-ended shafts; that's what allows them to be coupled end-to-end.

 

[brian_]

1. If use a Warp 11 HV single, what advantages in terms of power output does it have over the Warp 11 regular?

These two variants of Netgain's 11" motor have similar maximum power output and apparently similar maximum operating speed, but the speed for peak power is different. There are performance charts (in a very annoying form resulting from their crude test method) on the Netgain motor page. I suggest looking at those, but be prepared to spend some time to understand them.