Readymade lithium iron phosphate packs

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MalcolmB
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Readymade lithium iron phosphate packs

Postby MalcolmB » Mon Aug 20, 2007 3:39 pm

http://www.lifebatt.com/LiFeBATT%20Web_4.html

A US company is offering 'plug and play' LiFePO4 battery packs for ebikes, including BMS, charger and three-year warranty. These are lithium ion batteries, but with a much higher continuous discharge/charge rate and cycle life than other lithium chemistries. They are also reported to be safer and less likely to suffer thermal runaway. They are very expensive, but could potentially make a very fast/long range ebike.

I'm not endorsing these batteries in any way – just thought it was interesting to see how the range of choice is increasing and the technology is gradually becoming more available to a wider market.

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qdos
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Postby qdos » Mon Aug 20, 2007 8:11 pm

Ouch yes they are not cheap. Just as well the pound is strong

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qdlaty
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Postby qdlaty » Wed Aug 29, 2007 1:17 pm

Unfortunately, the LifeBatt company don't reveal their cells efficiency.
So we can assume that cells are not designed to be discharged with high currents without much capacity drop. Unfortunately, that's common for most of LFP type cells produced by third party.

For plain users good thing is the way how you can connect them together. I spent a lot of effort with spot welding small capacity cells in big blocks so I can appreciate that but then comes problem of corrosion and increase of resistance.

So, my advice is to ask LifeBatt for data specs and wait if someone will be able to confirm that or deny.

MalcolmB
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Postby MalcolmB » Wed Aug 29, 2007 2:29 pm

Hi Marcin,

You may have missed it, but there's a downloadable Word file with more detailed specs at the bottom of the home page: http://www.lifebatt.com/index.html
Continuous 10C charge/discharge
85% capacity after 1500 cycles
They use large format 40138 cells

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qdlaty
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Postby qdlaty » Wed Aug 29, 2007 3:06 pm

Hi,
thanks for pointing that but I didn't missed it.
I've quite large experience with such "characteristics" mentioned just by chance in general document.

To confirm the 10C continuous company should provide charts with comparison of different current loads and comparison of capacity loss during discharging with current higher than the one used for capacity grading (which is usually 0.2C !!).
Uppon request company should provide raw data of this tests for any interested (and NDA signed) party.

So far I didn't hear any answer for my two e-mails. So I'm not even concerning buying initial samples from them.

If you are looking for LFP technology try PHET (www.phet.com.tw), Aleees (www.aleees.com) or ThunderSky. Of course, no guarantee is given by any of them but I was able to get fast and reliable answer after first attempt.

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EVguru
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Postby EVguru » Wed Aug 29, 2007 3:32 pm

Someone on the EV discussion list has been testing PHET cells and they haven't been looking that good.

Some original Thundersky cells performed well (100 & 200Ah) whilst others were fairly poor. They rather ruined their reputation in the US with a large batch of cells thay were simply junk. The latest cells in both Cobalt and Iron phosphate chemistries seem to be good.

Cedric reports a 10 fold improvement in internal resistance at 0C on the newer cells.

I'd like to build another motorcycle and I'd probably go with a set of Thundersky cells. I can probably get cells for US$1.25 per Ah through an old EV racing friend in the US.
Paul

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

MalcolmB
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Postby MalcolmB » Wed Aug 29, 2007 3:34 pm

Yes, I agree, the data is not very detailed and I would at least expect to see life cycle plots for different discharge rates.

I didn't realise that you had already tried to contact this company. It seems to be a big problem getting any decent information out of the battery suppliers that are springing up at the moment. It doesn't do the industry any favours.

Thanks for the addresses! I'll check them out.

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qdlaty
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Postby qdlaty » Wed Aug 29, 2007 4:36 pm

EVguru
I know about tests made by Ian Hooper. BUt please note that in later posts he had doubts about the results.

I always wonder why people are looking for cells that are able to give 10-20C continuous discharge. Where is the point of driving at that rate? Where can you go in 10 minutes?

Look at the Tesla ESS - it's build to always be near 1C.
Of course that excludes acceleration but for how long you want to accelerate, 20 sec? It's long enough to get you at top speed and maintaining it should not discharge batteries over 1-1.5 C.

So, I'm always trying to reach a compromise between capacity and currents, and that's why my 42 PHETs in parallel are doing fine with 3C max continuous discharge rate.

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EVguru
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Postby EVguru » Wed Aug 29, 2007 5:19 pm

I only skim the EV list these days, so I hadn't read the test results very closely.
Paul

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

MalcolmB
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Postby MalcolmB » Wed Aug 29, 2007 8:53 pm

I'm always trying to reach a compromise between capacity and currents

Good point, but if you have a battery that can deliver 10C comfortably doesn't it usually also imply robustness and long cycle life? I understand you have a lot of hands-on experience and know what you're talking about, but are you saying that lithium phosphate aren't necessarily the best choice for EV applications or just that we shouldn't over-specify battery packs?


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