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MetroMPG 01-10-2008 01:38 PM

Test: 200w electric bicycle efficiency = 1512 MPG equivalent
The best efficiency I've been able to squeeze from the ForkenSwift so far this winter is 107.7 equivalent MPG (US), or 311.5 Watt hours / mile if you speak EV.

bennelson says an efficient run on his electric Kawasaki motorcycle is 15 miles and about 1 kWh to recharge. That works out to 67 Wh/mi, or 503 eMPG, by my formula.

I've been wondering how an electric bicycle compares to these. So I went for an 8.7 km spin on the 200 Watt electric Schwinn. No pedalling. Top speed seen was about 28 km/h (17 mph) - but it's more like 22 km/h (14 mph) on the level.;d=1311600456

It's recharging now. I'll post back later with the results.

Daox 01-10-2008 02:19 PM


Originally Posted by MetroMPG (Post 4811)
It's recharging now. I'll post back later with the results.

You big tease. :p

BTW, what is your formula for calculating equivalent mpg?

MetroMPG 01-10-2008 02:22 PM


1 kWh = 3412 BTU
1 gal (US) gasoline = 114,500 BTU

EDIT: and the electric efficiency figures quoted are energy use "at the wall" (including charging inefficiencies), not just energy drained from the pack.

Who 01-10-2008 02:34 PM

How are you measuring the "at the wall" number and how efficient do you think your charger is?

MetroMPG 01-10-2008 02:40 PM

At the wall measurement is from a Kill-a-watt meter.

I'm not really sure how efficient the charger is because I don't have on-board instrumentation to tell me how much I've fed into or drawn from the pack.

EDIT: but I have seen references of 70-80% charger efficiency chucked around.

MetroMPG 01-10-2008 03:17 PM

Oh my...

8.7 km (5.4 miles)
0.12 kWh to recharge

= 22.2 watt-hours/mile

= 1512 MPG (US) equivalent

MetroMPG 01-10-2008 03:26 PM

Note: obviously it's not a direct comparison. The car & motorcycle are faster than the e-bike. So their efficiency is calculated at a higher average speed.

But the imbalance is countered somewhat by the fact that we're comparing the best case efficiencies of the car & motorcycle, vs. a flat-out worst case run on the e-bike.

Yes, I avoided using the brakes as much as possible, but I did not drive for load or accelerate gently to minimize resistance & Peukert losses, as I try to do in the car. No, I pretty much had the twist grip pinned on "GO!!!" for the full 8.7 km.

Also worth noting: if I'd pedalled some, maybe I could have doubled the electric efficiency. Not an option (yet! :p) in the ForkenSwift or on the motorbike.

Who 01-10-2008 03:33 PM

Call some charger mfr.s and ask them if they'd like to provide you with models to test for your EV web site. Then just accidentally lose the best one. ;)

1512? Nice... with lights on or would that have cost 100 MPG?

AndrewJ 01-10-2008 04:52 PM

Nice, I'm gonna try to get the wife a little e-scooter sometime. I think I can handle a 500-700mpg equivalent. Much better than her Cavalier is doing...

bennelson 01-10-2008 05:52 PM

E-bikes really are insanely efficient!

One thing you do have to watch is what charger you use.

I did some tests on my cycle using a cheapo 1.5A 36V trickle charger that came with my electric bike hub wheel kit. Man does it charger the cycle slow!

However, I also tried charging my batteries with a couple big old "charge your car batter" 12v chargers which were higher amp. They were about HALF as efficient as the little solid-state trickle charger!

A Killawatt is a great device for measuring electric use. I have slain phantom power in my house down to a $30 a month electric bill.
I think measuring power use at the wall is the only fair way to do it, because it builds in charger efficiency into all the equations. This encourages people to use better chargers!

I saw an E-bike that ran off a couple of DeWalt Lion batteries - that was pretty cool too!

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