[Kevin Sharpe]

Cheers, I have a feeling the controller will be an expensive part of this build along with batteries of course

I suspect this will be expensive and difficult... an alternative approach for the T4 would be a 'small' Tesla drivetrain which contains the motor, inverter, and transmission in a single package weighing just ~90kg.

One is available in The Netherlands (here) that is slightly damaged and I suspect could be purchased for ~2000 Euros

 

[Kevin Sharpe]

if you could get your hands on reasonably priced battery packs that would be the best option.

A quick look on eBay has Tesla 5.3kWh Modules at $1199 (here) which equates to $2.70 for each 3400mAh cell. I don't know what current prices are for complete 85kWh Tesla packs in the US but in Europe we can typically buy them for 11,000 Euros (~13,000 Dollars) which equates to 1.55 Euros ($1.86) per cell.

It's hard to imagine that you can build a lower cost battery pack if you factor in the hardware required for the case, cell fuses, BMS, etc. I also doubt you can produce something as compact as the Tesla design if you include cell heating/cooling (IMO a critical safety requirement).

 

[Kevin Sharpe]

Since sdb's intent is to convert a camper or van, it should not be necessary to custom-build a pack to suit some oddly shaped cavity; reconfiguring the modules of a production EV pack (whether those modules contain pouch cells or cylindrical cells) seems like the most practical approach.

If we're talking about a VW camper then it would be trivial to fit Nissan Modules beneath the floor and above the motor without cutting the bus. Indeed it's possible to fit 14 Tesla modules with only minor cuts