I'm about to hit the 3000 mile mark with my NiCad-powered Geo Prizm. Each trip I log the miles driven and the KWH used (as determined by the E-Meter). The first 84 trips I was logging AH instead of KWH.
Since April 23, 2002, I've driven 2990 miles in 128 trips, for an average of 23 miles/trip. The first 84 trips averaged 2.36 AH/mile, and the remaining trips averaged 293 WH/mile. Most of my trips are 25 mile commutes to work and back on I-5, going over the hill between Portland, Oregon and Lake Oswego. This includes a fairly steep incline going south in the morning, and then having to accelerate uphill to merge with freeway traffic on the way home. I can easily keep up with or pass traffic on the morning commute (typically 65-70mph), but when I crest the hill in the evening the car will barely go 60mph. This is not a problem since there are usually other cars going about the same speed. My pack has 20 Saft STM5-100 MR NiCad modules (air cooled), rated at 100ah. The deepest discharge was 8.76kwh (about 80ah). At this point, the pack sags to 80v or below with current draws of 100-200 amps. The SAFT spec says the modules are considered "empty" when the module sags to 4v at 100 amps. The pack starts feeling fairly "soft" between 7 and 8kwh but the voltage will stay above 90v or so, so driving anywhere except up steep hills or on the freeway is acceptable and safe. Once the pack is down over 8kwh, I need to be on level roads and then find a plug ASAP. The longest trip I've taken was 34 miles, mostly all freeway miles at speeds between 60-65mph, using 8kwh. I actually did this twice in one day when I drove out to Woodburn and (thanks to Manzanita Micro's PFC-50), back again. I had to water the pack once so far, at 2694 miles. This would have been a 15 minute operation except for the trip to the store when I ran out of water. (Note to self - remember to have three gallons of distilled water on hand next time.) (Note to Ford Motor Company - what the heck do you do that requires you to keep the Th!nks for two days for this operation? Do you use a solar still to manually distill the water as required?) The Saft modules get fairly warm when they're pushed hard. The Saft spec says that charging is not allowed when the modules are over 40 degrees C. My battery boxes have variable speed cooling fans that come on when the modules reach 20C and reach full-speed at 40C. I used to have the fans setup so they only came on while charging, but during our recent hot spells the charger wouldn't start for several hours after I got home. Now I have the fans setup to run while driving or while charging and the packs seem to be running cooler. Overall, these are great batteries. I bought them used with about 1900 miles on them (probably about 100 cycles). They sat idle for a couple of years with only occasional charging as I was testing something in the car. After I ran the INIT charge (9 amps for 15 hours, then add water) they were ready for daily use. They are rated at 2500 cycles, so if things continue as they have so far, the pack should last quite a long time. Ralph
