Published Friday November 29, 2013: Updated 8/12/2014 (controller duct)
Geo Metro EV Summer Performance
It’s been almost 1 year since I started exclusively driving the Geo Metro EV to work and back every day. While in the pickup truck, I used to charge up at work every day, but in the Geo, it’s battery pack is more than sufficient to go 40 miles a day so I only charge up at home. Typically after driving 20 miles to work and 20 miles back, at the end of the day, the State-Of-Charge meter reads 55%.
A typical charge only draws 7 kWh from the wall. On an equivalent energy perspective, that is like getting 200 mpg. That’s almost double what the electric pick-up truck was getting.
While the Geo EV is plenty peppy below 40 mph, at freeway speeds, it has very limited acceleration. That’s the nature of PM DC brushed motors. In hindsight, I should have gone with an AC induction motor/controller and benefited from the mind-blowing torque and regenerative breaking they provide. Oh well. The motor and controller were dirt cheap and are super easy to maintain. No engine lift necessary.
Once the outdoor temperature got above 85 °F, the motor started running a little hot. To remedy this, I cut some vent holes in the undercarriage aeromods.
This, in conjunction with the air duct I installed earlier in the year, allowed the Geo EV to maintain sufficiently cool motor temperatures even when it is 105 °F outside. Keep in mind my daily commute is largely on flat ground and mostly freeway.
There was one hot day in August when after work, I drove from Salt Lake to Ogden to pick up some fence materials. On the way to the freeway, there was a lot of start stop traffic. Following that, the on-ramp leading to the interstate is kind of steep and the freeway is also heading up a hill. With the high amp-draw pulling the hill plus accelerating to freeway speeds, the motor was fine but the controller started over-heating and limited current to the motor. This prevented me from getting up to freeway speed until several hundred meters after the on-ramp. It was slightly annoying but that was the extent of problems while diving in the Geo this summer.
I didn’t opt to install an
air-conditioner in the Geo either. If this were my wife’s car and
she was driving around town with the kids, and getting stuck in
traffic, well then yes, A/C would have been installed. But as my
daily commuter car, where half of my traveling is done early in the
morning when it’s still cooler outside, I didn’t really see the
need for it.
If you want air-conditioning in your converted EV then spend the extra money for an air-conditioner that will run off of the DC traction pack voltage. You can get them for as little as $450.
Update August 12, 2014: This past summer, I pushed the car a lot more than usual and found the controller was now the weak link when it comes to overheating problems. This is especially apparent when it is more than 90 °F outside and you romp on the throttle for more a casual on-ramp acceleration. Using some dryer hose that I had on hand, I ran a duct from under the car to the intake vent of the speed controller.
This cools the controller sufficiently well.
In anticipation for this winter, I bought a heated seat cover. It plugs into the 12V outlet in the car and only draws 3-5 Amps. It makes a huge difference with how cold it feels in the cab.
1/23/2015: Throughout the first winter, the heated seat cover kept shifting around on the seat and bunching up. So I glued it directly to the seat. Now it stays put.
I am still on the fence weather I want to install a real cabin heater. There are several options to choose from.