# Pb versus Li battery pack ?



## david85 (Nov 12, 2007)

Are you planning a 144v system?

I am a lithium nut myself, and while I am excited at the possibility of cheap LiFePo4 cells from china, I really don't think you need them if all you are looking for is 25 miles of range.

Thindersky's first generation cells got poor reviews, but I have heard good things about their new LiFePo4 cells from others that have made the upgrade. LionEV.com is another potential source for affordable lithium cells, or even "turn key" battery systems. They are a little more expensive than TS, but back their product with up to a lifetime warranty, depending on the setup.


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## dtbaker (Jan 5, 2008)

yes, a 144 volt system is what I am thinking... plenty of zip for a small Swift, within specs for 8"DC motor, controller and zivan3 charger....

I am looking into Li because I like the idea of less size, weight, more cycles, and no maintenance.... any info you can provide to help me evaluate the financial comparison to a similar Pb pack would be helpful.

If you have a handle on good sources for 60AH rated Li batteries, please post!


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## Dan Frederiksen (Jul 26, 2007)

if you are up to connecting some cells together there is Headway from china who make high power medium size cells for a good price. I got a few samples that will be tested but I haven't seen any in practical use. they look like this:
http://www.zev.dk/misc/headway.jpg the big blue ones. the two most interesting models are the 38120P 8Ah cell shown in the picture and the 38120 10Ah of same size. I've been quoted 12euro (17.5$) a piece for either.

with high power lithium you only need mayb 60% of lead capacity because lead has a peukert effect that means it will go flat well before it's capacity at typical EV power levels. their rating is if you discharge it very slowly over 20hours. an EV will drink it in 30-60 minutes. so compare 40Ah power-lithium to 65Ah lead (that's what I hear, don't have personal experience)
here's the specs and prices I was quoted: http://www.zev.dk/misc/HeadwayLiFeO4.htm
they recently changed some of the parameters of the cells so don't rely too heavily on the specs. the 38120 cell for instance weighs 321g and not 300. the 38120P cell does weigh 300 though. for your range you'll need maybe 200 of the 10Ah cells.
we'll test the cells soon to see if they live up to their specs but I think so. we've already tested another LiFePO4 cells from china and it did better than A123's M1 cell. same power, 7-8% higher capacity. 5$ a piece (3.2V 2.5Ah DLG battery, known as K2 in USA)


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## dtbaker (Jan 5, 2008)

I doubt I am up to designing/creating a battery pack unless there are some explicit instructions.... I am not wanting to blaze the way, just to pick the current 'best' tried and true solution. 

I have gotten a few offline emails regarding questionable reliability, and unknown longterm results with the TS units. Can anyone post more firsthand experience on them? Perhaps a better Li alternative?


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## dtbaker (Jan 5, 2008)

After more poking around last night it looks like there are at least two Li options that 'some' people have used... although details are scarce. It appears that a number have used the ThunderSky Li batteries, but it is unclear what is required to add as far as 'battery management system' and how to best recharge them. A second option that popped up was custom packs from LionEV... but there were also some mixed reviews on contact and support from them delivering.

so..... anyone have first-hand details on either of these? Or, help make a reasonable attempt to compare the cost per average cycle?


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## kkjensen (Apr 25, 2008)

I would recommend signing up on the yahoo tech group "thundersky". It was formed after that bad batch of TS cells was purchased in the US and, in spite of this history, seems to be full of a lot of people with positive things to say and actual proof to back it up. The quality of TS cells seems to be on the rise and their popularity is growing. Hunt back through the message archives and you'll find a lot of the info you need.

http://tech.groups.yahoo.com/group/ThunderSky/ 

They've helped dispel my fears and I'm going to make a purchase myself and perhaps help organize a group buy. We're going to try and support local resellers though so we're going to make our list and go to them for support with the import and guarantee.


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## dtbaker (Jan 5, 2008)

http://tech.groups.yahoo.com/group/ThunderSky/ 


Thanks for info, I will lurk a little.... I sure would LIKE to go Li, but am committed to my first project with Pb as I have purchased the batteries already. I'll look at replacing with Li when the Pb dies maybe!

The biggest issue I was seeing was that the charging controllers BMS system are not really available' off the shelf', and I just didn't want to combne that unknown with a first time conversion....

I have actually started, and just pulled the gas motor today! see http://www.envirokarma.org/ev for work-in-progress

D


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## Dan Frederiksen (Jul 26, 2007)

nice. keep up the good work


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