[AlexanderB]

Originally Posted by oil pan 4

I don't think any one is cheaper than I am and I have build 2 LiFePO4 packs.

Ah, yeah.

I wonder though, is spending all that money really worth it? because I think $350 worth of cells and whatever worth of extra materials just to replace a $100 starter battery is kinda.. pricy.
And thats just for a little battery, not a full EV pack.

Originally Posted by Cobb

Im not sure you can combine those 2? Not all batteries are created equal and the "cheap" ones usually have a manufacturing defect.

So thats why I don't buy those. I buy OEM packs, usually those have sanyo or sony or some other brand name cells.

Originally Posted by Cobb

You really need to buy 10% more than needed and test them for capacity, then rack and stack em.

Since I'm buying used, I'm under the assumption of a worst-case scenario, 50% of the cells are useable at about 75% of their original ratings, 25% is useable for low-power stuff and has poor capacity, and 25% is just broken or has only a few % of its original capacity left.
We'll see how close I was to this estimate.

Originally Posted by Cobb

Once you got the voltage and amps you need, then depending on the chemistry you need a bms and charger.

Indeed.

Originally Posted by Cobb

I see a lot of lifepo deals on ebay, but I think I rather stick with a prius pack as they dont need a bms, just a grid charge to balance them out.

Eh, I don't like the NiMH cells that much. LiFEPO4 would be nice though, but is still pretty pricy compared to how low I need the price to be to make it work on my 'beer'-budget. (as I don't drink, I have an excuse to spend some money each month on other things.)

In fact, talking about cheap, electric driving is really not cheap.
Electricity here is €0.20 ($0.25) per kWh at home, €0.25 to 0.30 ($0.31 to $0.37) at a public charging station. (theres no free stations)
Using 200 wh/mile as a worst-case scenario, that would work out to $0.05/mile to $0.06/mile.
I pay $0.14/mile in diesel, and another $0.12 or so per mile in vehicle tax. (with my current amount of driving a month).

So battery writeoff will have to be covered by the difference in tax and 'fuel' cost, not a whole lot of room to play with.

Assuming 15000 mile/year, divided by 365 is 41 miles a day. Lets round up by a bunch because I don't spend every day behind the wheel doing the same exact trip, and say I want at least a 100 miles of range. At 200wh/mile, that would mean a 20 kwh pack. This pack would do 150 full cycles a year, or perhaps a ton of part-cycles adding up to 150 full cycles.

Assuming a cheap lithium pack can do an optimistic 1000 cycles, that would write off in 6,6 year. At 15k miles a year, that would be 100k miles. (yay, back to round numbers.)

Lets assume you manage to find some very cheap lithium packs for $500/kwh, so a 20kwh pack would be $10k. $10k divided by 100k miles is $0.10 a mile. Not bad at all, considering our fuel prices in Europe, that would save me actual money in the long run.

As long as the pack doesn't blow up after 250 cycles.
Or I have to loan the 10k with so much interest it doubles the total price.
Or it turns out you can't actually buy any new lithium packs for that slightly optimistic price.
Etc..

Interestingly enough, a 24 kWh Nissan Leaf pack would only be about $6.5k from the dealer? Also not a bad deal, if it holds up to 1k cycles or more.

So thats why I bought "5kwh" of li-ion cells for $120, even if a large portion of the cells are bust or have less than original capacity, thats a very very good deal. Now lets hope I can find more near the same price, that would mean I might be able to trade in my diesel for an electric.

Originally Posted by planetaire

I use peter perkins bms

Thanks. A whole forum about EV's and a subforum full of BMS, thats very cool.

Originally Posted by Xist

How is the plug-in-Prius different?

Its got li-ion cells.

Originally Posted by RedDevil

I do have a small welding kit, unused as of yet, and I would be happy to let you use it for this project.
PM me if you feel like dropping by in Nieuwegein

That would be very nice I'll let you know when the time comes.