Paul G wrote: > In the world of lead acid batteries I don't think anyone (at least in > modern times) had managed to get a pack in an on-road vehicle (car or > Pickup) to last much more than about 30k miles.
It all depends on the batteries you choose. Let's say we have a long-range EV with about half its weight in batteries, like the Red Beastie pickup, which can go 100 miles on a charge: Consider AGMs, like Hawkers or Optimas. Life at a 1C discharge rate is generally around 250 cycles at 80% depth of discharge, or 400 cycles at 50% DOD. Cycles x DOD is the same for both, so the pack will last 250 cycles x 80% x 100 miles = 20,000 miles. Now consider 6v golf cart batteries. Using the data Martin Jackson just posted, the greatest total mileage occurs at 560 cycles and 40% depth of discharge. The pack will last 1400 cycles x 40% DOD x 100 miles = 56,000 miles. Then there are *really* long life lead-acids, as used in forklifts and other industrial vehicles. Oldham tubular plate flooded lead-acid cells are rated at 6500 cycles to 10% DOD, 2400 cycles to 50%, and 1350 cycles to 75% DOD. Best life is at 50% DOD, where the pack will last 2400 cycles x 50% x 100 miles = 120,000 miles! (To satisfy the skeptics, Eric Sandell of Sweden put a set of *used* Oldhams in his Nissan Micra EV conversion. Last I heard, he has over 50,000 miles on them and they are still going!) But the drawback is that maximizing life also increases internal resistance and Peukert effects. Thsi means the lower the battery life, the less peak power you can get out of it. The AGMs give you fast accelleration and high top speed, but short life. The Oldhams give you great life, but sluggish accelleration and low top speed. What I think is an interesting concept is to combine the two types into a single "hybrid" battery pack. Use the AGMs for fast accelleration, then recharge them from the floodeds. The AGMs depth of discharge is very low, for long life. Conversely, the AGMs shield the floodeds from the high peak currents; they can deliver power smoothly and continuously to minimize losses from internal resistance and Peukert effects. -- Lee A. Hart Ring the bells that still can ring 814 8th Ave. N. Forget your perfect offering Sartell, MN 56377 USA There is a crack in everything leeahart_at_earthlink.net That's how the light gets in - Leonard Cohen
