Leaderboard

The answer to this thread's title is NO. I wouldn't think of trying this even though (sorry to say all this) I'm a professionally licensed engineer with a Masters Degree in EE and decades of engineering work experience including years with VFDs operating at twice the voltage and many times the power. These hybrid car systems are nothing like working with a couple of 12V lead-acid batteries in series or parallel. Theoretically, most anything is "possible" but this one isn't feasible - too many unknowns, too much complexity and too great a danger to both you and the car. Much simpler, safer, and likely cheaper to get a used Leaf or Volt.

I doubt this will work out as you want it to. There's a LOT of electronics and programming involved that expect a given battery capacity and voltage. Also charging is an issue with cell balancing involved. The vehicle would need to be made aware of the second pack that it needs to manage. Even moreso, expecting to push more 'voltage' into the drive motor is out as that is all on the inverters and vehicle programming. Short of being able to reverse engineer and reprogram that (and likely replacing some electrical components in the inverter), you aren't getting anywhere on this one. Not to say I'm dissuading you from trying, but these systems are a LOT more complex than you're implying.