Somebody did a higher-voltage DIY EV, in Australia!
Tuarn Brown's 1982 Suzuki Sierra SJ40
It's a 576VDC direct-to-transfercase AC Suzuki 4x4. Can do ~50mph at 4000RPM, which is apparently the limit for that motor/controller/voltage combination.
Built using industrial drive and motor. 6x 96V packs, tied together in a junction box by the drive to keep any single wire's potential as low as possible. Apparently has contactors in each 96V box to separate into a total of 12 48V modules. Can charge with 48V.
Started out as a 600VDC pack nominal, in two 300VDC strings, to keep the max voltage potentials outside the junction box basically the same as 240VAC mains (max peak of AC vs the DC). Dropped it to 576VDC due to not being able to use all the regen the drive was capable of. Voltage chosen to match the most common/least expensive industrial VFD's. I can't seem to find the thread where they went into the drive to get at the DC bus.
Huh, seems this person also at some point used a 240VAC-500VAC multitap transformer, plus a rectifier and some other bits, to feed voltage to the motor-side of the controller, and used it as a charger for the full 600VDC pack. Dropped it as being less efficient and more dangerous than charging at lower DC voltages to separate strings.
Red Suzi - The Australian Electric Vehicle Asn - Page 1
Very nice buildup - and exactly what I was thinking in terms of separating the pack, keeping the potential voltage across any given points as low as possible, etc. though the builder used common industrial boxes and conduits and such, rather than repurposed OEM bits.
576VDC at stock current levels ought to push a Leaf motor to ~118kw output without increasing heating overmuch. Now going to 200kw doesn't seem that much of an over-current push for short-term acceleration.
redpoint5 - as for build and test and rebuild and retest, well, I won't want to spend forever working on it. I will try to engineer it all up front. This Suzuki example - which passed Australia's somewhat stricter vehicle modification laws - seems to be as clean a setup as I can find. I can probably figure out how to start at a single pack voltage, then go to double pack voltage later, so long as I have two packs of similar condition so they work well in series.