Tuesday, April 28, 2009

New EV project looming for the summer: E-Bike!

I am interested in eventually replacing my lead-acid battery pack with a LiFePO4 pack, which will decrease weight, increase range and speed, all that good stuff. But since LiFePO4 batteries are much more pricey and are managed differently, I thought I'd start with a smaller EV project that uses them, to better understand how they perform.

Enter the E-Bike project!

I bought a donor bike off of craigslist, and have just ordered a DIY E-Bike conversion kit from goldenmotor.com in China. The kit contains a 36V/750W hub motor, 36V10Ah LiFePO4 battery pack, motor controller, throttle, wiring, etc. Should be here in about three weeks. Can't wait!

Sunday, April 19, 2009

Lessons learned #347: LRR Tires

OK, EV fans. If anyone ever tells you that Low Rolling Resistance (LRR) tires are one of the key pieces to your vehicles energy efficiency, LISTEN TO THEM.

I recently bought a used set of low profile tires off of craigslist that made Electro look supercool and be very energy inefficient. Let me explain.

The stock tires for Electro were 185/60/14, which translates into tires that are 185mm wide and go on 14in wheels.

The new "supercool" wheels/tires I bought were 205/40/16s, which means they were 205mm wide, low profile, and had extra big wheels (16in).

Driving the same distance with the wider tires made a HUGE difference in the amount of energy I was using, which is extremely important in an EV. For a trip where I would normally use 7.1 KWh, I ended up using 9.3 KWh. That's 30% more energy - to look cool.

I am going back to stock wheels/tires for now until I can go the other way and find a narrower set of LRR wheels and tires. Hopefully I will find some that will get me significant range increases!