Price for converting my own smart car

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Jeremy
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Postby Jeremy » Thu Aug 07, 2008 6:24 am

If the cells are lithium technology (which seems highly likely) then they will have a terminal voltage of either 3.2V (for LiFePO4) or 3.7V (for LiCoO2 or LiMnO4), rather than the 2V that is typical for lead acid batteries.

It is this higher terminal voltage that is largely responsible for the greater energy/power density for lithium cells, together with the fact that lithium is much lighter than lead.

Typical cycle life for the best lithium technology currently available in an EV application is around 1000 to 3000 charge/discharge cycles, although this can be significantly improved by not fully discharging or charging the cells. Limiting charge to 95% (using a smart charger) will, on it's own, give a significant cycle life improvement.

Calendar life of lithium cells remains a slight problem, as lithium cells start to degrade from the date of manufacture. However, early indications are that LiFePO4 cells degrade more slowly with age than older lithium technologies. 5 years for a 30% degradation in capacity seems likely for the best cells around at the moment. 10 years seems to be stretching things a bit, as I suspect that cell capacity would be massively reduced after this period of time.


Jeremy

Nigel P.A. Smith
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Location: Bath

Postby Nigel P.A. Smith » Sat Aug 09, 2008 11:54 am

Grumpy B said;

"If you do a bit of calculation 18.5kwh of stored power at 72 volts =
a significant 256 AH of storage. Thats a serious battery cell (s) ."

What about the Trojan T145 6volt batteries that are 244Ah each x 12 to
make 72volts? Has anyone tried these yet? I think I will replace my T105's
with the T145's and they are only 138 dollars on the google spreadsheet,
about £70 each, £840 for a new pack! :)

Nigel


Electric Rover EV in disguise

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EVguru
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Postby EVguru » Sat Aug 09, 2008 10:47 pm

The T145 is not best liked. It uses the same case as the smaller versions but has very little sludge space in the bottom and little spare electrolyte.

It was produced in response to demand from the golf car builders in order to upgrade existing models, but it's a comprimise.
Paul

http://www.compton.vispa.com/scirocco/
http://www.morini-mania.co.uk
http://www.compton.vispa.com/the_named

Nigel P.A. Smith
Posts: 63
Joined: Thu Apr 24, 2008 5:23 pm
Location: Bath

Postby Nigel P.A. Smith » Sun Aug 10, 2008 10:49 am

EVguru wrote:"The T145 is not best liked. It uses the same case as the smaller versions
but has very little sludge space in the bottom and little spare electrolyte."


Hi Paul,

What would you recommend for going up hills at a reasonable speed?
They must be the same size; 7"x10" by 10" high.

Still wondering about the Duo-Regen Reserex pulse system, all my
batteries say 6.5volts, even the one's that get hot! Maybe they are savable!
I would like to see what they have done for Chris B's batteries that he sent
them?

Thanks, Nigel

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EVguru
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Postby EVguru » Sun Aug 10, 2008 1:07 pm

Really, it's just never going to happen at 72 volt.

The Rover is too big and too heavy.
Paul

http://www.compton.vispa.com/scirocco/
http://www.morini-mania.co.uk
http://www.compton.vispa.com/the_named

Nigel P.A. Smith
Posts: 63
Joined: Thu Apr 24, 2008 5:23 pm
Location: Bath

Postby Nigel P.A. Smith » Mon Aug 11, 2008 7:23 pm

Hi EVguru,

What about the Elcat, from Andy Ellis "In connection with your
speed question, a 72V Elcat can do 55 mph. This uses 12 x 6V in series."

The Elcat can't be much lighter than a Rover is it?

I suppose it has a different motor though, I don't mind if I can only get to
35mph but would like to get there a bit quicker and get uphills at 25?

Regards, Nigel


Electric Rover Maybe slow, but I'm not fuming :x
Fuming MX3 for distance
Kawasaki GT550 for peace of mind 8)


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