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why do you make EVs with such high voltage? Why not 48V?

33743 Views 24 Replies 12 Participants Last post by  floydr
Why are DIY's electric vehicles made to work on such high voltages, like 96V, 144V and over 200V? Wouldn't it be better to run everything on something around 48V, so its safe to touch?

I know the wires would need to be 3-4 times thicker to get the same resistance (voltage drop) and current handling, but so what? Wire is expensive, but not so extremely expensive not to afford to spend 3-4 times as much on wire (which are not so long in a car anyway) in the name of significant safety.

We are not ever running more then 20kW though the wires, no?
So at 50V that would be 400A. About 200 mm^2 would do, no? Or about ten AWG4 wires in parallel for US guys. That would be about 150 EUR or 200 USD per meter, right? So how many meters of 20kW capable wire do you need in total in an EV?

OK, if you use a few meters, it's quite an amount of money, but still cheaper then getting a new life after touching 200V. And you can design the car to place batteries close to the motor to save on wire. At least I could imagine placing them withing 1 meter.

So are there any other reasons to use anything significantly over 48V, then saving money on copper wire?

If I can afford the wire, should I build a EV out of my 2035 kg van on 48V for safety (only 16 LiFePO4 cells in series, instead of 48 or 64 - what I spend on wires I can save on having a simpler 16S BMS, instead of trying to balance 64 cells...)?
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Wouldn't it be better to run everything on something around 48V, so its safe to touch?
Safe to touch isn't as fun to drive! ;)

Safe is a relative term though, 'high voltage' in the 120-144V range isn't really that high. Most of the world uses 220-240V in home sockets, so although accidents happen, it's apparently safe enough for unruly peasants to use.

Defibrilators run in the 300-1000V range, with 1000V most typical, so that's where I'd be worried about safety. While I wouldn't lick a 120V battery (though I grew up licking the 9V ones) an occasional zap is unlikely to cause any real harm. Just a reminder to be more careful.
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