Hi
I cannot say for the MP4, but I guess the same limits of MP3 is still valid for the MP4: The internal FETs have a 60V (D-S) limit, quite like the condensators with 63V at max. Going over that range can kill the controller (FETs) in a few microseconds and warranty is lost that way as well.
What ist 52V in what chemistry? LiIon have a 3,6 or 3,7V nominal voltag, which varies from 3,2 up to 4,2V (working range). LiFePO4 can do 2,8 to 3,6V or liPo from 3,4 to 4,2V. So the "how many cells are in series" is important to give an advice.
Important is the max voltage of the pack at any charging. Using recuperation might be very dangerous as lots of internal controllers were killed with a full battery and then using the regen brake.
Why that high voltage? Do you use such small rims to need such a high rotation rate?
Cheers
Sam