I’ve spoken to that guy and he’s done an amazing job. You can go down the route of buying a new kit but it can be very expensive. However, you are guaranteed that everything is plug and play. Using parts from wrecked cars can be a lot cheaper but you have to work harder at the systems integration. There has been a lot of Nissan Leafs, Toyota Prius/Auris/Yaris, Lexus, BMW etc made and wrecked. The motors, inverters and even batteries are usually fine. Did I mention cheap? I got my motor and inverter for €700. Add another €500 for the vehicle control unit from Damian Maguire. A new kit can easily cost €4500.
Batteries too can be expensive if you buy new. I have Tesla modules (25V each) which varied in price from €1000-1300. They are considered the best technology but they are large. Fitting them into a Lotus is hard! You can pick up a bmw hybrid battery from €1000-€1500. The beauty of those is they are at full system voltage (400v) and granular in size and shape compared to to Tesla modules. They are designed to fit in the space for the old fuel tank. There are drawbacks, as always! The battery chemistry is hotter and they do require some form of management system. LiFePo4 cells, although less energy dense are very safe and once PROPERLY bottom balanced at the start, require minimal management. More monitoring really.
High or low voltage systems? Back to school. P=IV. To produce a high amount of Power during acceleration you will need a lot of current from a low voltage system. Meaning thicker cables and a lot of heat. Typically you need to use 70mm2 or 2/0 cable. Raise the voltage and the current goes down which means lighter cabling. There is a reason why OEMs have settled on 300-400VDC as their battery pack voltage. The VRMS is around the 220-240VAC range. Typical single phase domestic supply.
There are some very good resources on YouTube. Ev4u (Richard Van Wyhe did a great series on converting a Porsche 912), EVTV (although Jack’s moved into solar storage now) and EVBMW (That’s Damien Maguire here in Ireland).
It makes no financial sense whatsoever. I did it because I enjoyed the engineering challenge. Rather like owning a Lotus in general. On the Elan forum the same guy who criticized me about adding weight (which I didn’t) said I should have butchered a crappy city runabout and not a museum piece like the Elan. Firstly, my Elan isn’t a museum piece. It’s there to be used and enjoyed. Secondly, after you’ve converted a crappy city runabout you still have a crappy city runabout. Why not convert something interesting?