# EV Voltage question

1401 Views 7 Replies 5 Participants Last post by  EVfun
Hi all, the more I read the more and I can see volts = less amps/hour consumed on the battery right?

If so, I know im exagerating, why dont we use 10,000volts systems?
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Using a higher voltage will, for the same power, reduce the current.

The reason for not using very high voltage is the ability, or lack of, to switch high voltages in DC without arcing.
Among other things. You also need more individual cells making wiring more complex as well as you BMS.
Using a higher voltage will, for the same power, reduce the current.

The reason for not using very high voltage is the ability, or lack of, to switch high voltages in DC without arcing.
Why not work on that instead of trying / waitting for better batteries?
Why not work on that instead of trying / waitting for better batteries?
Ummm, maybe I should add the term 'affordable' into my previous post and then includ JRP3's post.

It becomes very expensive with high voltages.

Those who run AC motors may be running 300+V but still have to be able to switch the 300+v at DC.

At high voltages the current will be able to arc across a larger gap and maintain the arc burning away the contact material. Even with better contacts the gap will need to increase to break the arc. Magnets can be added around the gap to pull the arc away and even on contactors as low as 48V that is already included.

When you get onto 1000 or 10,000v then the gap that the arc can span is huge. Look at lightning.
Even the relatively low voltages in a spark igniter on a lighter can jump quite large gaps, albeit with little current.

All that makes breaking a high DC voltage difficult as the contacts would need to be able to snap open and form a very large gap and withstand the arcing and cool and defuse the arc very quickly indeed.
And as if that isn't difficult enough, DC also causes contacts to want to stick together so the force required to break the contacts needs to be higher still.

AC is easy.
Open the piddly little contacts a little way at 10,000V and as the cycle swings through zero any arcing stops. If the contacts stick then they won't after each half a cycle.
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Ummm, maybe I should add the term 'affordable' into my previous post and then includ JRP3's post.

It becomes very expensive with high voltages.

Those who run AC motors may be running 300+V but still have to be able to switch the 300+v at DC.

At high voltages the current will be able to arc across a larger gap and maintain the arc burning away the contact material. Even with better contacts the gap will need to increase to break the arc. Magnets can be added around the gap to pull the arc away and even on contactors as low as 48V that is already included.

When you get onto 1000 or 10,000v then the gap that the arc can span is huge. Look at lightning.
Even the relatively low voltages in a spark igniter on a lighter can jump quite large gaps, albeit with little current.

All that makes breaking a high DC voltage difficult as the contacts would need to be able to snap open and form a very large gap and withstand the arcing and cool and defuse the arc very quickly indeed.
And as if that isn't difficult enough, DC also causes contacts to want to stick together so the force required to break the contacts needs to be higher still.

AC is easy.
Open the piddly little contacts a little way at 10,000V and as the cycle swings through zero any arcing stops. If the contacts stick then they won't after each half a cycle.
And this leads to my other noob question

in short terms, what is the main different between AC and DC?

one is blue one is red? they are both electrical currents?
IMPORTANT:
Read through the Wiki for a while, most of the info is there already: