Battery Cycles

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AirAg
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Post by AirAg »

I have just started a project on an 88 Toyota Corolla. I am trying to work out battery packs and it seems that the LiPo batteries are the go.
I have been working out costs of batteries per km and have come up with a bit of a shock at the high cost of battery replacement.
This is how I did it.
45 x 3.2v x 90Ahr Thundersky x 70% DOD x 1500 cycles = 13608Kw of power
If a battery pack costs $8000 that is a cost of $0.60 per Kwh
If my car gets 200wh/km that is a cost of 12c per km.
Add that to the electricity costs for a total of 15c per km. My old commodore ute sucks fuel to the rate of about 16c per km. Hardly a huge saving seeing as the cost of the project is going to be about $16,000
However I am wondering at the number of cycles that thundersky batteries can do. ZEVA website and forum members seem to think about 1000 to 1500 cycles. The datasheet from thundersky states 2000 for 80% DOD and 3000+cycles for 70% DOD. If you put these figures into the above calculations you get your cost of battery replacement back to 6c per km which is a lot more interesting.
Incidently the lead acid batteries came out at 22c up to 30c per km for replacement.
Does anyone have real world experience of the life of these batteries? Are my calculations correct?
Peter
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antiscab
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Post by antiscab »

Hiya Peter,

Have a look at the spreadsheets here (theyre getting updated today, so they may change):
http://www.waeva.asn.au/batrun_tutorial.htm
a few things you might want to consider:
1. the on going maintenence cost of a petrol vehcile (servicing?) for my car it comes up to as much as i spend on fuel.
2. the end of service life value (or cost) of the batteries. lead has become fairly valuable. currently you need to pay of recycle lithium (adds about $700 to battery change over cost once every 5yrs)
3. to calculate electricity cost, you need to factor in the efficiency of the chemistry. Lithium is very efficient, you get back about 90% of what you put in. There are no secondary reactions, so coulomb efficiency is 99%+, the only losses are resistance based.
Lead acids, however, do have side reactions which means the coulomb efficiency is only about 75%. on top of this, you lose some to resistance so total efficiency is around 60%. depending on how expensive electricity is for you, this will have a bearing.

There are a couple of people who have done cycle life testing on the thundersky cells on the thundersky yahoo group. if you intend to use it, id suggest joining so you can look through at other peoples setups.

Matt
antiscab
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Post by antiscab »

oh, i just realised youve come from the other forums:
http://www.zeva.com.au/forum.php?category=2&thread=83

welcome to the other side:)

a few more things now that im thinking about it:
th $8k for the thundersky would include bms? if it does, you normally wouldnt change the bms when replacing batteries, on the other hand something beter may come out in 5 years and u might. something else to think about.

Matt
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Post by Richo »

Hmmm....
200Wh/km is about 130km/hr for a '88 Toyota corolla.
That's a lot of speeding fines - Don't forget to add that to the cost!
Specs-> Cd=0.31, fA=2.25m^2, m=1000kg, Cr=0.015
150Wh/km would be a bit more realistic.

The 1000-1500 cycles was a conservative figure to start - no point saying they will get 5000 cycles then they find out they only get 3000 as it might make people angry. Image
No-one (that I've heard of) has needed to replace them yet so the actual amount is still unknown. Image
I think as long as you treat the batteries good they should be better than the quoted conservative figure.

I doubt the $8k Peter has quoted includes the BMS.
Taking into account a group buy price with BMS it would be about $9k.

Lead is heavy - Don't do it!

Agreed hopefully in 5 years time batteries would be cheaper or a new battery would have better life or something in ultracaps would be available/affordable etc..

And don't forget that the money you save or don't save is still saving the environment.(I'm hugging a tree right now for you!)
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AirAg
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Post by AirAg »

Thanks for that information Richo. I have also got a quote back on my batteries...$6000 (plus BMS $1000) so plugged in 150whr/km and 3000 cycles and came up with a battery cost of 19c/Kwh and an overall running cost of 5c per km. Much better. Makes lead look pretty sick!
Thanks for that link Matt..still digesting it.
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Post by Hartmut »

http://www.baseportal.de/cgi-bin/basepo ... nge=200,20
For anybody interested in battery cycles. The german site shows
practical experience with actual cars on the road. In total 22o entries. I am sure you can figure out what it all means.
Saft batteries ( French company) has in test 100 000 km. Not bad at all. They are building new factories in the south ready for the coming
boom.
everything electric from solar
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Post by antiscab »

yeh, saft used to manufacture flooded ni-cd batteries. indestructible is how i would characterise those.
theyre a bit hard to get hold of now, from what ive heard.

Matt
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Post by acmotor »

I know those flooded NiCads, I worked on an emergency lighting system in a performing arts centre not long back and it had its original (1978) floodeds. They still pass load test. They do require watering regularly. They do not suffer the paste NiCad memory effect.

Power to weight is a bit off current expectations though.
iMiEV MY12     110,230km in pure Electric and loving it !
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Thalass
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Post by Thalass »

What sort of range are you expecting, Peter? 90km?
I'll drive an electric vehicle one day.
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AirAg
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Post by AirAg »

My calculations for range:

45 x 90Ahr x 3.2v x .7 DOD / 200whr/km = 45km

If Richo is correct and I get 150whr/km then that will be 60km

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Post by roddilkes »

Range really depends on your driving style and speed.
I regularly do 60km commute using 45 x LFP90AHA (144V).
However I am a careful driver, others might get much less.
As a general rule, work on 150-180 Wh/km for a light EV.
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AirAg
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Post by AirAg »

Rod,
my commute all highway travel so I want to be able to keep up with traffic at 100kph.
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Post by Rattrap »

Thats my concern also. 95% of our driving is highway travel so i would need a top speed of probably 140kph with peak economy of driving at around 110kph & with a range of 60klm minimum, 200 would cover us almost completly.
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Post by woody »

Rod, you really should mention your EV is mighty boy which gives you a fair range advantage :-)
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