EV Math: Electric Porsche 914 Range

by Kimura Kellen
(Salt Lake City, UT, USA)



I have just been doing a little bit of math, and I am missing something.

I was viewing a manufacturers website that does conversions for Porsche 914s, and it said, "Heavy cars use 288 Wh per mile" and then later on it said, "Use about 16-24 6v batteries." for your conversion. Now, the typical range I see on the converted 914s is 40-50 miles, but a 24 cell pack (6v * 240 Ah * 24cells/288 Wh) equals 118 miles. Where is all that range going? Why doesn't it add up?

Hi, Kimura -
Well, I can't speak for the website you visited, but I'm wondering if they weren't considering the Porsche 914 a heavy car, maybe.

Here's what I'm looking at: 6 volt batteries are almost always used in DC systems. The voltage range you described (96-144) would not move a heavy car much at all; the 96 volt DC system might power a fair VW bug or Geo Metro, and the 144v system might work pretty nicely for your Porsche.

As for the math, I suspect the 288 wh applies to something bigger than the 96-144v systems.

Regards,
Lynne

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by: Ken

How much does ur car weigh?
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starstarstarstarstar 		RE: Electric Porsche 914 Range
by: RayRay

Hi Kimura,
The 118 miles represents 100% of the pack. With lead acid you only want to discharge about 30% to 40% of the total pack, so that you can make them last for a few years.. So, if you take 40% of the 118 - that puts right at the 40 to 50 miles...
-ray

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