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mattW

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I was curious about the practical relationship between voltage and top speed but I didn't know how to test it, everyone usually says voltage = top speed but can you draw something more concrete than that? Then I realised that the EV album has the voltage and speed data for a whole bunch of vehicles, why not just take a sampling and see if there is a correlation. So here are the results of a sampling of 40 normal sized cars and pick-ups using flooded lead acid batteries and DC motors:

As you can see there is a pretty linear upward trend. My conclusion based on a line of best fit with an accuracy of plus or minus 20% (with the variation probably due to vehicle size) is this: Your top speed will be a third of your voltage plus 30mph.
i.e.Top Speed = (Voltage)/3 +30

Grant_NZ

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you sure? I worked out a 200V 400 Ah pack will give me 155kph (96MPH)!! awesome of course I must add thats using an AC motor and lithium batteries... haha

mattW

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Yeah as I said I worked it out with Flooded LA and DC, but there was 1 144V EV that peaked at 96mph... It wouldn't be impossible

elevatorguy

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This might be good information for the wiki..
I see that if I use 132v vs 120v I only will see 4 mph difference, would it be an advantage to run the higher voltage if the top speed (4mph) is not a factor?

mattW

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Well higher voltages also mean more efficiency (less heat losses in the resistive loads eg. wires), more power capabilities and as long as you don't also reduce the Ah rating it usually means more energy which means more range. It will also cost more and be slightly more dangerous.

I don't know if its wiki material seeing as the accuracy is way out its +-10mph at the lower end and +-15 at the top end, maybe if I just followed one vehicle size it would be a closer grouping...

rbgrn

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Oops, you just reminded me that I forgot to add top speed to the cars in the diy ev garage.

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