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

33744 Views 24 Replies 12 Participants Last post by floydr, Feb 21, 2022

miernik

Discussion Starter · Apr 7, 2011

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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cobratom

· #21 · Feb 20, 2022

brian_ said:
Well, that completely changes the meaning of your later posts. You could have just said that when you realized the error.

I edited the post but you had already replied.

I am not sure how else you would like me to word this so it makes sense to you? I wrote OR not AND
..
Original unless you have redundant connections or fuse links (like the way Tesla packs are designed) ...

1. Unless they have redundant connections. They make also have fuse links (like the way Tesla packs are designed).

2. Unless they have fuse links (like the way Tesla packs are designed). Or they may have redundant connections.

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remy_martian

· #22 · Feb 20, 2022

@cobratom Bigger brains, and an entire industry, has decided what's optimal for them, so I don't understand what point you're trying to make in all this. Why were you even replying to an ELEVEN year old thread, posted before the Model S was released?

You're not going to outgenius the industry and their experts, nor several people on here, even.

Changing your story to cover obvious ignorance doesn't work here. You just keep burying yourself into a hole of deeper asshattery. Especially to talk about matches when rubbing two sticks together was to be revealed in a year.

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cobratom

· #23 · Feb 20, 2022

remy_martian said:
@cobratom Bigger brains, and an entire industry, has decided what's optimal for them, so I don't understand what point you're trying to make in all this. Why were you even replying to an ELEVEN year old thread, posted before the Model S was released?

You're not going to outgenius the industry and their experts, nor several people on here, even.

Changing your story to cover obvious ignorance doesn't work here. You just keep burying yourself into a hole of deeper asshattery. Especially to talk about matches when rubbing two sticks together was to be revealed in a year.

1. Get your shit together, and maybe read the thread first before you make assumptions.
2. I did not bring this up from the dead. I did not even realize this was an old thread as it showed up in the recent threads list on the forum. Username oaiken brought it up from the dead.
3. I did not change my story. There was 1 incident where I replied to Brian where I accidentally said series instead of parallel, but had you read what I said it would have been blatantly obvious to you.
4. I am 100% on the team of high voltage batteries, and everything I typed was AGAINST running a low voltage high amperage setup. I have a model 3, a model S and a Polaris Ranger EV that I bumped up to the max voltage capability of the sevcon controller with Lifepo4 cells.

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remy_martian

· #24 · Feb 20, 2022

Again with the deflection.

You responded to 2011 content with showing off that you now know so much about things that were emerging at that time, not this 2022 content:

"How about fresh water electrocution risk ? How bad is it when an EV crashes in a flood ?"

What on earth did your response to that 2022 post have to do with electrocution?

NOTHING

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floydr

· #25 · Feb 21, 2022

oaiken said:
How about fresh water electrocution risk ? How bad is it when an EV crashes in a flood ?

car makers have thought of this and built in a failsafe mechanism that cuts power to the batteries and stops the spread of electricity in a split second. resettable inertia switches ?
Another method when the airbags go off a 'pyrofuse' triggers a series of small explosions in the car's electrics, severing the link with the battery and isolating the dangerous current. This prevents the risk of electrocution or fire. It's the same technology that's been used for decades to set off your car's airbags. The pyrofuse can even be retrofitted into existing electric cars fairly easily.

Later floyd

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