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View Full Version : How low can you sag? 144v sag to 19.4 volts



Tony Coiro
10 February 2011, 2234
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So, two of my partners in crime in the EV club converted a Porsche 924 to electric. To quote my friend's quote on DIY, "We don't usually try to do this on purpose, but we weren't going to make it home and just had to see how low it would go. We have 12 marine deep cycle flooded cells in series. They are the cheapest and worst battery anyone can put in an EV. We plan to replace them someday, but we college students lack the funds." For the record, I was the one in the passenger seat laughing my ass off. Also, as your EV's get older (the Porsche conversion is almost 3 years old with original lead pack), you begin to notice they develop a bit of a personality. My favorite quirk about the Porsche is the accessory battery is total **** (I think it was actually free) and due to the terrible DC-DC converter, the accessory battery is dead all the time. I have found myself helping more than once to jump start the car by tapping off one of the traction batteries.

Nuts & Volts
10 February 2011, 2306
Well I guess lead acids batts have a sense of humor at least.

I think you found the one way in which Lead are better than Lipo.

chef
11 February 2011, 2316
12 cells @ 19.4v... avg of 1.6v per cell :O Impressive. Those cells must have some serious plate damage.


I think you found the one way in which Lead are better than Lipo.
True, altho if they had a lithium based pack, they would still have plenty of juice at that point ;)

Richard230
12 February 2011, 0839
12 cells @ 19.4v... avg of 1.6v per cell :O Impressive. Those cells must have some serious plate damage.


True, altho if they had a lithium based pack, they would still have plenty of juice at that point ;)

But I'll bet they would have a really fat battery pack if they had LiFePo4 cells. The pack would probably look like a blimp. :D

NonPolluter
24 March 2011, 0837
Our experience with LIFEPO4 agrees with Richard's post.

What we found is that when LIFEPO4 batteries sag a lot, there is little, or no charge left, even though the battery voltage may rise back to 3.2 - 3.3 V after usage.