eTrixie — A DIY EV in the Real World
Trixie has now been on the road for a few months. In this time we have used the car for short trips around town, and a couple of longer trips which have used more than 50% of charge in one trip.
Real World Economy
On average with real world driving I’m getting about 120kms range on a charge.
One trip from Wellington to Featherston, was 40 miles (64km) and used 9.8 kWh. This translates to 4.08 miles per kWh, which appears to be similar to a Nissan Leaf, and a little better than a Tesla (which is a much bigger and heavier car).
It is tricky to compare the electric vs petrol cost performance, but if I compare on the basis of energy cost, based on 1 litre of 91 octane fuel in Wellington, I am effectively getting 83km per litre or 233 miles to the gallon. This figures will drop a bit in the future as currently EVs are not subject to ‘road user charges’ — yay!
Charging Trixie “Free of Charge” — Thanks Hutt City!
Battery Capacity and Balance
I have set my battery capacity on the battery monitor to 155Ah, which provides 25Ah buffer on stated capacity of 180Ah. When my battery monitor reaches 0% capacity when driving around after a full charge I should have a 25Ah buffer and at 0% the overall battery voltage is comfortably above 100V, or 2.70V per cell.
In part 11 of the eTrixie story I discussed bottom balancing. As well as balancing the battery voltage at the bottom, it is good to keep an eye on voltage at the top, when the battery is fully charged. Poor balance at the top can lead to overcharging a cell. I did my first top balance check last weekend, about 4 months after my initial bottom balance and I have found that at the top all of the 37 cells are measuring an identical 3.34V. I am very happy with this consistency, and pleased that the decision not to use a per cell BMS is an ok decision for the moment.
Wellington Constructors Car Club
I was given the opportunity to take Trixie along to the Constructors Car Club as the ‘guest car’ for their recent club night. It was great fun to talk with so many car enthusiasts. Trixie was well received by the group and I was very thankful for the opportunity to show her off.
Trixie meeting with the Constructors!
Read more about the conversion:
Electric certification in part one
Power and brakes in part two
Removal of petrol components in part three
Flywheel and clutch upgrades in part four
The AC induction motor in part five
New Fuel in part six
High Currents in part seven
The Loom in part eight
Keeping it cool in part nine
Putting it all together in part 10 (including a video of the first drive!)
Bottom balancing and battery management systems in part 11
Getting the certification examination in part 12
eTrixie the Movie! Video walk through