More Zombie Street Driving

I’m enjoying getting used to the Zombie’s increased range that the compact 22.7 kWh Dow Kokam pack provides. I’ve had the occasion to play around with tire pressure, and having had a special low friction process done to the ring and pinion gears, and am happy to report the Zombie’s Wh per mile has improved as a result. With the rear tires now set to 40 psi for street driving and in mostly freeway type driving at 60-65 mph speeds, the Zombie is in the 190-195 Wh per mile area. It’s still not as good as Blue Meanie, but considering the big footprint in back, a sub-200 Wh per mile is pretty good.

Two runs from the Wayland home downhill to the airport, then back uphill to home again at 14 miles round trip have given me some good data. Both times, at 27 amps charge current -r amping down to 25 amps, then to a one minute finish rate much lower, it took about 17 minutes to recharge the pack to where the regs were all lit up with all cells very well equalized…call it 27 amps for 15 minutes. This represents ~7 ah put back into the pack. Usually, one uses the nominal pack voltage to figure watt hours consumed, but to be as accurate as possible I used the actual voltage of the pack for the run. That started out as 391V under light loads and going downhill at freeway speeds, and it was in the 385V range returning uphill at 65 mph – call it 390 pack volts to be on the conservative side of things. 7 ah X 390V = 2730 watt hours. 2730 /14 = 195 Who per mile. The 355V pack can easily give 55 ah while not fully draining it (it’s rated at 60 ah @ C5 and 64 ah @ C2). 55ah / 7ah comes to 7.85. If the car uses 7 ah to travel 14 miles, then the math is 7.85 x 14 = 110 miles.

It seems my early estimates of 90-100 miles of mixed regular driving, and 110-120 miles at steady state highway cruising is still reasonable. I’ve got an 85 mile run from Portland to Corvallis planned in about two weeks for a Wayland/Otmar test session where he and I will take data and investigate the high voltage – parallel bucking problem we had, so it’s good to explore the capabilities of this pack in these incremental ways before taking on a longer range run. I think a few 60-70 mile runs are in order, too. The Zombie is rock’n pretty hard in straight series mode, so I have no plans to go back to the series/parallel shift for now…in fact, after Otmar and I have had our weekend session, I will be simplifying-rewiring the motor loop circuits removing the series/parallel contactors completely.

See Ya…John Wayland

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