Originally Posted by AndyH
What level of performance do you need? When will you need the cells?
There is a range of price/performance between A123-systems and Thunder Sky, some of which are covered in Dimitri's post, some not.
Actually I am very intersted in a larger spiral battery that has threaded studs and use interlocking plastic blocks to allow packs of different configuratuion to be built.
Right now I am starting my projects out at a lower level to prove the concept without breaking too many things.
What I am doing is converting one of my ultralight pulling tractors from ICE to Electric (to 72 volt 450 amp controller). I am also doing a conversion of a older Cub Cadet Garden tractor (to 48 volt 450 amps) which I will use as a utility vehicle at the track and on the farm. I will also pull with it. Both will have basically off the shelf motors.
I am currently going to be using AGM batteries in both tractors becaise of the available 10-15C or so discharge rate (also, although they are used but were also free
). I have three strings of six 16ah Hawker Odysseys for the ultrlight and one string of 4 High Rate 41ah UPS batteries for the garden tractor.
Eventually I want to go to higher voltages and amprages for both and more watt hours for the garden tractor. The AGMs have me pretty much maxed me out for weight so I will need to go to LiFePO4 to get the performance I want.
I was planing, per my question, on trying to collect he necessary cells to eventually double the voltage on the ultra light and go to 72 volts on the garden tractor over the next year. I would most probably try to duplicate the existing battery packs with LiFePO4 to close out this year if I could afford the cost of a total changeover (chargers, BMS etc) otherwise I would go for next season with a ramp up of voltage till things start to break.
Enough rambling. It looks like the general feeling is . . . I'm better off waiting, not so much because of battery storage problems but for cost advantages of a single large purchase.
I would still like to get an answer about buying over an extended period. Storing them untill suffucient batteries are procured to build the packs needed.