The Toecutter |
11-01-2006 07:46 PM |
Quote:
Lead acid batteries don't take deep cycling very well. Deep cycling causes PBSO4 (which is created on discharge, and is needed to regenerate PBO2 and Pb at the anode and cathode on charging) to fall out of the plates, reducing capacity over time. Lithium electrodes are not immersed in liquid and don't have this problem, so they theoretically last much longer. Some lithium manufacturers are claiming over 2000 cycles at 80% depth of discharge.
Lithium battery technology and production capacity is advancing so fast that we should see lithiums in EVs and HEVs and PHEVs very soon. Toyota is looking at lithiums for the PHEV they promised.
|
With a pack sized for sufficient range, a lead acid EV won't see many deep discharges, perhaps once every month or two. But you are correct in their intolerance to deep discharges. Sealed lead acid batteries only have about 150-200 80-100% deep discharge cycles or so.
Lithium batteries see their capacity degrade about 2-4% per year if they are properly managed during charge and if they are kept from being able to overheat. In extreme cases, this can be 20% per month if left unchecked. The Li Ions used in the Tesla roadster should have about 500 deep discharge cycles of 80-100%. A Li Ion pack in an EV would last about 7 years or 100,000 miles, whichever comes first.
Ovonic NiMH last 1,750 cycles to 100% discharge according to UC Davis. Cobasys provides a more conservative 1,200 cycles to 80% discharge. Nickel-based batteries last for ****ing ever!
I suspect a VX converted to battery power and aeromodded to hell may be able to do 120-150 miles oer charge on 1,300 pounds of lead acid batteries. This would be a great platform for an EV. It has battery room, is low weight, has decent GVWR, plenty of aftermarket body parts for weight reduction, and is a relatively simple platform.
If I had a VX, I'd consider running a diesel in it. Gasoline to fuel a car like this is an injustice. Either way, the VX trumps the Metro, hands down. krousedb getting 70 mpg with one, without ignition off, is damn impressive.
|