[rscohy]

I have a 72 volts Zap. I want to add an extra battery for a 84volt car. What do I need to do for the charge and motor controller?

 

[rscohy]

No one has ever done this? I just want a little more speed here. ANYONE?

 

[electro wrks]

This was done years ago: 84V Upgrade to my ZAP Truck - Endless Sphere
It was also done somewhat later with this result:

The burned vehicle, AIR, had a switched-in extra boost battery. I think it had a switching system not rated for the voltage(a real no-no), problems with a dead short from a bad switching sequence, or a combo of all of the above- probably exacerbated by poor fusing.

You'll probably be ahead of the game by just buying a beater Leaf. These ZAP vehicles were, AIR, pulled by NHTSA because of poor braking performance. I ended up with the burned one. I kick myself for passing on a set of Lancair wings that I would have attached to the burned carcass . Not to ever fly, but to mess with pilots and drones flying over my bone yard!

 

[rscohy]

Ouch. Did you convert the charger to 84 volts or kept the 72 hopping for the best?