My first thought was that your YTs are simply worn out, after all they are 3 years old. But then I started adding up the numbers you posted.
20Ah from 3 yr old YTs is still fairly respectable, getting only 9 miles from 20Ah on a 192V pack is not. That's about 400 watt hour per mile, about twice what it should be. Normally this would indicate that either you are driving with a lead foot, driving way too fast, or that you have a mechanical problem. Then I noticed the 750ft elevation change. The rule of thumb is that every 100ft of elevation change is roughly the same as driving 1 extra mile at 55mph. However I can't tell from your post if you mean 9 miles range on flat ground or 9 miles while climbing 750'. Even if it is, that's still to much energy. 20Ah from your pack is about 3400-3500 watt hours. I drive about 9.5 miles to work with approx 600-700 ft of elevation change. I only use about 2900 whs and that's in a pickup. I don't know how fast you are driving but if it's more than 55mph, try slowing down. The energy needed to overcome air resistance goes up as the square of your speed. It takes almost 50% more power to go 65 than it does to go 55. Accelerate slowly and watch the stop lights way before you get to them. If you are a 1/2 mile away and it turns red, slow down so that it will turn green before you get to it. That way you can carry some speed through the light rather than wasting energy stoping and starting. Depending on how you drive, 3 years sounds about right for battery life. If you drive 5 days a week, that's 250+ cycles a year for a total of 750 cycles. Getting 750 cycles from YTs is pretty good. Unless you are willing to spring $20,000 for NiMH you aren't going to do any better, and there isn't enough data yet to say whether the NiMH will last significantly longer. NiCads will last for 25 years or more, but they need to be watered frequently. You can, however, buy watering systems for them. Still it's an expensive option (probably $10-15,000 with the watering system) at least in the short term. Long term, the nicads will be cheaper than YTs but who can say what kind of batteries will be available in 10 years? Short term, I'd try replacing the three batteries that are giving you the most problems and try the tips above. One other thing, if the batteries aren't insulated, add some. If you keep the packs temperature up around 80-100 degrees(f) you'll get much better performance out of them. If they get down to 60-70 degrees expect to see much less useable capacity, below 60 your capacity might only be 1/2. FWIW, Lead-Acid batteries are probably the most recycled product on the planet. Even with all the ones dumped in odd places (inside cars) 97% of them get recycled. So while generating a pallet of dead batteries every few years is expensive, it's not hurting the enviroment anywhere near as bad as burning dead dinosaurs. > I'm an experienced electronics tech, but new to EVs. > Recently I bought a 1991 MR2 conversion with a 196V > system. The batteries are Optima YTs of 1999 vintage. > My controller is a Griz and the motor is an Advanced > DC. The charger is a Manzanita with a home-brew > regulator box set to bypass current around any battery > showing more than 14.8 volts. The previous owner > claimed a 45 mile max range, I'd be happy if it could > make 25 miles. Sadly, the batteries in their present > state are pretty much dead at 9 miles. My experience > has been that the car cannot even get me to work (~10 > miles freeway 750' higher elevation than my home). > This is NOT what I had in mind, nor even plausibly > related to what the previous owner claimed. The pack > is only capable of providing 20-22 Ah or so before > getting really soft. At that time, if I put a 2A load > on the bank, three of them dip to about 5-8V while the > others are around 10.5V. In a 5A static load test, > similar voltages appear at the 4.5 hour mark. Is this > typical aging YT behavior, or is my pack limp for some > other (possibly correctable) reason? If it really is > dying this soon, what would I have to do to get the > range I want out of a longer lived battery technology > (Evercel, etc)? My whole point in driving an EV is to > be less polluting. Generating a pallet of dead > batteries every 3 years is out of the question! BTW, > there are batteries in the tunnel, so sealed > technology is a requirement. At least conventional LA > is out. > > Thanks, > > Andrew > > __________________________________________________ > Do you Yahoo!? > Faith Hill - Exclusive Performances, Videos & More > http://faith.yahoo.com > >
