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Re: Recommendations for a 'dry' lead acid battery for EV use

Posted: Thu Apr 26, 2012 2:51 pm
by dillond666
GregsGarage wrote: for lithium prismatic cells you should aim for less than 1C average discharge (so less than 100amps for a 100ah pack) to get long life from the cells.

Thanks for the advice Greg, I was a little worried about the current delivering capability of lithium. I have the battery current on my controller limited to 450A max. The sinopoly cells I was looking at has 3C (300a) as the max continuous current with 5c (500a) permissible for 10 sec bursts. I'm not sure how long they'd actually last in my vehicle. If only we could all have 300v AC systems with tiny current requirements :roll:

My wife is dead against the idea of buying new batteries, even though I bought her a (secondhand) Toyota Prius last week. She just doesn't understand :cry: Batteries are eyewateringly expensive though. The price of one battery pack could get you a really good used car and that's how most people look at it.

Edit: Looking (mournfully) at the datasheet for my 160aH Sec Red Tops

Stopping at a cell voltage of 1.8V :

20hr rate (8a) 160aH
1hr rate (89a) 89aH
30min rate (141a) 70aH

So I guess from my pack at the moment I probably can't get much more than 70aH thanks to Peukerts effect. The red tops weigh 611KG the 100aH Sinopoly would weigh 156KG very big difference! Anyone want to buy one of my kidneys?


Re: Recommendations for a 'dry' lead acid battery for EV use

Posted: Thu Apr 26, 2012 5:07 pm
by GregsGarage
It looks like we have hijacked this thread, oh well. :twisted:

Another option is the Headway cells. They do a range of large cylindrical cells, for example the 40160S 16ah. A guy near Dublin has been using a pack of these configured as 4P48S, so about 64ah capacity in a BMW 3 series with a 1000 amp controller and a 10kw charger. Despite this abuse the cells are holding up fine. have a look at his website Also they are being use in the Tango electric car with a Zilla Z2k They are at a slight price premium to the prismatics, but even so you may be able to save money on a smaller pack. The A123 pouch cells are another option but the headways are much easier to work with due to the screw connections and cell holders that they also sell.

Re: Recommendations for a 'dry' lead acid battery for EV use

Posted: Wed Jun 06, 2012 2:03 am
by Beemer
Damien MacGuire (evbmw) is now experimenting with A123 20AH cells. He said they scare him witless. Playing with one 20A cell took out his load at 450A. Stacked up tight these have the highest power density of all LiFePo4 cells. Doing so with any such pack lowers the C rating. Temperature safety is paramount. The Voltage fade under load with these is extraordinarily low. I paid around a Euro/AH for 180 virgin cells from China to my doorstep.

Lead can deliver sorta but they quickly get wrecked as the plates heat & buckle. Voltage drop under load is horrendous. The power/C rate is poor with lead. Not to speak of double the mass per density and only 1/3 the charge. 1/6 as good.

However, there is a lead battery that is said to last.. I think its called a PbC cell. Some US lawyer who runs an investment blog keeps banging on about them at the same time gives lots of bad propaganda on EV's. They'll be unobtainium and he's getting burned. I think his site is "seekingalpha"?

LiFePo4's are the game changer for home builders. Non-Li cells never worked as well and never will. If you must... obtain Nim-H packs off old Prius'.