Li-pos, the new wonder cell for electric cars. You have them in mobile phones, laptops, ipods, everywhere, but in most cases they are on single cell use.
When Li-pos are used in series which they are in cars they have a little problem that no one is telling you about.
When charging over discharging multi cells some of them become unbalanced, that is they develop a different capacity and voltage to its neighbour. If Lipos are over discharged they will never regain the original capacity. Now when you come to recharge it wil get hot,,, and catch fire.
Evwn in use, if one cell becomes over discharged its neighbours then have to make up for the loss of voltage and current, these other cells become hot and.... catch fire.
Its no use using water as Lithium releases its own oxygen when burning, these things bvurn under water.
In the Uk last year there were 3 house fires caused by Li-Po cells, plus of course we had the lap top fires from a few years ago, the ipod failures etc.
And li-pos do NOT like being used below about 5degs c. They must not be allowed to freeze and if they do, they must not be used as the internal structure will have failed and they will catch fire. At 5deg and below they lose upto 60% of their performance.
They must not be recharged at temps below 5 degs c as this will result in an over charge which will once again damage the internal structure.
Also with lipo.s the car manufacturers do not actually know how many charge / dishcharge cycles they are going to get, some believe it may be as low as 300, others believe it may get 600. So potentially thats £3k plus every 300 trips, and not to forget that over time the capacity of the lipos will fall, so over time the vehilce will only be able to make it to the end of the road.
I ise multi cell li-pos as p;art of my hobby, and i have had a 3 cell 100% balanced pack overheat and explode. Yes it exploded and the resulting fire is very intense. I know store all my cells outside in sealed tins.eus
Befor buying an electric car that uses li-pos wait a few more years for the new A123 cells and Li-Fe cells to be developed as these are much less susceptible to the charge/dischrge/temp issues that Li-Po suffer from.
http://www.electric-cars-are-for-girls.com/lithium-polymer-batteries.html
im taking bets on the next poster being......