The saga continues: I didn't measure the wheelbase, but I'm sure enough that I'm going to have to rip the components out and convert a small body. I did finally get around to overvolting the system. The first attempt was fruitless - the "potato boilers" evidently have one maximum output in mind, and doubling the pack voltage did nothing. That was several weeks ago. I made it back up again to the rents' house where the cart is being stored this last friday (6/19 for a note-to-self tick on the timeline of this project). I circumvented the potato boilers and hooked the pack and motor directly up to the "forward, neutral, reverse" lever, which is really a sort of contactor that switches which field poles on the motor to run the voltage through. This also circumvented the "key" system, which was connected to the array of potato boilers. I didn't take photos of this, because it's very straightforward. I effectively made a "GO" switch out of the FWD/REV lever. I hooked 3 12v batteries in series with the rest of the pack of 6v batteries. I read extensively on this before doing it to ensure that there was no danger - if different voltages are added in series, the pack assumes the amperage of the "weakest" battery, and just drains it a little quicker than normal.
The first attempt yielded a much faster cart - I drove it up the short road my parents live on, and couldn't make the turn to return, so I used reverse. This immediately made one of the old EXIDE batteries pop a cell and steam and bubble a little. I took it out of the pack, leaving me with ~60v. This actually made it go even FASTER and I nearly fell off when I popped it into FWD. 0-60 (volts) in a millisecond. This put a smile on my face and concluded the test. Given the results, I think maybe even a 96 or 108 volt setup would be sufficient. Even a light car chassis would be much heavier than the cart, but that thing TOOK OFF at 60v. The motor wasn't even a little warm after the short test - I think it could take the punishment I give it with a bit of cooling. I'm still wondering if mixing voltages will be feasible in the actual working conversion. It seems like 96 or 108v worth of 6v batteries would be too heavy for the gvwr of a little metro or similar light bodied shell, but I haven't crunched any numbers yet.
Here's what the setup looked like after I took away the jumper cables. I was too excited to take "progress" pictures, and I didn't want to touch my camera with greasy hands. The exide in the middle was the one that blew. You can kind of see the wetness from the acid on the side of the battery closest to the camera.
