Watts per mile.

[Boyntonstu]

After a 6 mile ride at 13 MPH, the recharge current was 2250 mA.

The motor speed was set via a servo tester to propel the bike at 7 mph.

I pedal assisted up to 13 mph and I had a fine sweaty workout.

The 2250 mA charged into 36 18650 cells at 22.7 volts or 50.5 Watts.

Therefore my bike is using less than 10 Watts/mile.

How many Watts per mile does your bike consume?

 

[gogo]

If you had the servo set to 7 MPH, were you charging your batteries by pedal effort when going 13 MPH? If so, 10 Watt hours per mile isn't very good.

There's a stickied thread for this:

http://endless-sphere.com/forums/viewtopic.php?f=3&t=6615

 

[Boyntonstu]

If you had the servo set to 7 MPH, were you charging your batteries by pedal effort when going 13 MPH? If so, 10 Watt hours per mile isn't very good.

There's a stickied thread for this:

http://endless-sphere.com/forums/viewtopic.php?f=3&t=6615

There is no charging while pedaling.

As can be seen here, the current at no load is very low: https://endless-sphere.com/forums/viewtopic.

 

[d8veh]

Al these discussions about watt-hours per mile are pretty meaningless, especially at speeds below 20 mph. On my road bike, I can do 40 miles at an average speed of about 13mph, which works out at zero watt-hours per mile. When I've done the same journey at the same speed on my electric bike, I've had anything from 4 wh/m to 15wh/m depending on how hard I pedal and how hard the wind blows. One thing I did find out, though, is that road bikes slip through the air much more easily than a MTB ( pretty obvious). The effort to pedal my road bike is about the same as my electric MTB on the lowest level of assist (80w), but when it comes to down-hills, it's much faster.

Extra Energy have just issued their latest magazine. They use all sorts of sophisticated equipment and methods to compare different OEM electric bikes objectively. The results don't show any significant difference between different types of motors. Some really good reading in this magazine, all 230 pages:

http://issuu.com/extraenergy/docs/extraenergy-pedelec-e-bike-magazin-

 

[Boyntonstu]

My bike is a 20" mountain bike that is probably twice as hard to pedal as a 27" road bike.

That being said, I use the bike for exercise riding around a 1.7 mile loop inside of a gated community. Almost zero traffic.

At my max cadence I can barely pedal it to about 15 mph. (I am almost 77)

The 5 speed gearing and the small tire diameter combination, does not allow for higher pedaling speeds.

With electric at 18 mph it feels very fast.

Also, a 20" bike is very twitchy and highly maneuverable, but I cannot ride it hands off.

I can pedal a 26" adult sized bike backwards when sitting on the handlebars.

I am satisfied riding it at 13 mph using pedal assist to increase the powered speed up from 7 mph.

The result is smooth exercise workout that I do every day.

I intend to ride a 16 mile round trip to an electric bicycle shop to demonstrate the bike to the owner.

That will be interesting.

 

[gogo]

That's great! I believe one of the best features of electric bikes is the ability to launch from standstill without the awkward stress that puts on my body. Its much smoother, too, so there's that added safety advantage.

 

[Drunkskunk]

At ~12mph I use 10 watts per mile on my Monster bike, with zero human input. My bike is not very efficient, so I suspect you may have problems with yours if you're getting similar results while pedaling.

 

[Boyntonstu]

At ~12mph I use 10 watts per mile on my Monster bike, with zero human input. My bike is not very efficient, so I suspect you may have problems with yours if you're getting similar results while pedaling.

After a 6 mile run with the speed set to 8-9 and me pedaling to 12 it takes 2250 mA to recharge the battery.

(I use a 12V 900 mA wall adapter to power the Skyrc balance charger)

At 90% efficiency I have used 22V and 2A or 44 Watts for 6 miles.

About 7 Watts per mile.

I will repeat without pedaling at 12 mph and I will post my results.

All of this on recycled laptop batteries.

 

[rsilvers]

7 Wh per mile. Not watts.

 

[Boyntonstu]

7 Wh per mile. Not watts.

I need some explaining.

A single 18650 cell is rated at 2,000 mA hr. If it discharged 2 A into a load it would be completely discharged in 1 hr.

2 Amps at an average of 3.5 V in 1 hr would be 7 Watt-hrs. Correct?

How much power does the charger put back into the cell if the meter indicates 2,000mA however long it takes?

I would estimate 2,000 mA-hr.

My bike has a 6S battery at 22.7 Volts.

Therefore 2 Amps at 22.7 V = 45.4 Watt hrs are available when recharged.

If I go for a 6 mile ride and it takes 1/2 hr, the power in an hour would be 90.8 Watt-hrs.

12 miles and 90.8 Watt hrs of power consumed.

7.55 Watt hrs per mile.

Please correct my errors.

 

[rsilvers]

7 Wh per mile. Not watts.

I need some explaining.

A single 18650 cell is rated at 2,000 mA hr. If it discharged 2 A into a load it would be completely discharged in 1 hr.

2 Amps at an average of 3.5 V in 1 hr would be 7 Watt-hrs. Correct?

Yes. 2Ah at 3.5v is 7Wh.

How much power does the charger put back into the cell if the meter indicates 2,000mA however long it takes?

I would estimate 2,000 mA-hr.

It is 2000Mah or 2Ah if the cell makes it rating. Some premium cells do. Someone tested all of the 18650s on eBay under $3 and *none* of them made even 70% of their claimed capacity. It is very common for a maker to lie about Mah ratings.

My battery pack makes 86.5% of what the maker claimed, which is semi-legit (typical inflated misrepresentation rather than a total scam).

http://www.ebay.com/gds/18650-Battery-Buying-Guide-test-on-all-from-eBay-below-3-/10000000178020340/g.html

My bike has a 6S battery at 22.7 Volts.

Therefore 2 Amps at 22.7 V = 45.4 Watt hrs are available when recharged.

That is a 272.4Wh pack if you have 36 cells. But what you say is true if you have one cell or only put in that much power.

 

[Boyntonstu]

Therefore 2 Amps at 22.7 V = 45.4 Watt hrs are available when recharged.[/quote]

There are more than six total cells in your pack. You said 36 cells. That is a 272.4Wh pack.

I disagree: TThere could be 6 huge single cells in series or 6 cells in parallel to make a single huge cell.

When you pump 2 amps into any 22.7 V battery go put in 45.4 Watts. No more and no less.

If I go for a 6 mile ride and it takes 1/2 hr, the power in an hour would be 90.8 Watt-hrs.

Since you have 6P, then you are really using 22.7 watt-hours per mile. That is within the range of normal but on the high side. With that much power I can average over 20mph.

I disagree: In an hour the bike going 12 mph would travel 2 x 6 = 12 miles.

Cell capacity of 2000Mah is not your battery capacity. A cell is one 18650. You have 36 of them. Combine them, and they become a battery. You have 6S, but you also have 6 in parallel. Your battery is really a 12Ah pack.

I agree with your last sentence.

 

[rsilvers]

I disagree: TThere could be 6 huge single cells in series or 6 cells in parallel to make a single huge cell.

You said you had 36 cells. But yes, if you only input 2A at 22.7v, into the pack, then 45.4 Wh would be available (minus charging losses).

I disagree: In an hour the bike going 12 mph would travel 2 x 6 = 12 miles.

You didn't specify that the pack was empty after 30 minutes, you just said that you rode for 30 minutes. I was assuming the pack was depleted after an hour since all of your previous examples were in one hour and you didn't say otherwise in this example.

If I go for a 6 mile ride and it takes 1/2 hr, the power in an hour would be 90.8 Watt-hrs.

If you depleted the battery in 30 minutes, then that would be 7.57Wh per mile, which seems reasonable.

 

[Boyntonstu]

I disagree: TThere could be 6 huge single cells in series or 6 cells in parallel to make a single huge cell.

You said you had 36 cells. But yes, if you only input 2A at 22.7v, into the pack, then 45.4 Wh would be available (minus charging losses).

I disagree: In an hour the bike going 12 mph would travel 2 x 6 = 12 miles.

You didn't specify that the pack was empty after 30 minutes, you just said that you rode for 30 minutes. I was assuming the pack was depleted after an hour since all of your previous examples were in one hour and you didn't say otherwise in this example.

If I go for a 6 mile ride and it takes 1/2 hr, the power in an hour would be 90.8 Watt-hrs.

If you depleted the battery in 30 minutes, then that would be 7.57Wh per mile, which seems reasonable.

Sorry if I misinformed you. I do not recall using the term "depleted". I go for a 6 mile ride and the battery is not depleted. I just top off every night with a Wall Wart powering my balance charger. I will use the battery until it is depleted and see how far it takes me without pedaling.

Thanks for you input.

 

[rsilvers]

I see. You rode your bike 6 miles to Walmart (30 minute ride) and then topped off the battery when you got home, which ends up as adding 45.4Wh. Yes, that is 45.4 / 6 = 7.6Wh per mile.

 

[Boyntonstu]

I see. You rode your bike 6 miles to Walmart (30 minute ride) and then topped off the battery when you got home, which ends up as adding 45.4Wh. Yes, that is 45.4 / 6 = 7.6Wh per mile.

Great! We agree 100%. I am quite pleased that my six pack battery on a stick salvaged from laptops is competitive with new batteries.

I thought of an analogy: When you want to measure your auto MPG, you record the mileage on your odometer and you fill up the gas tank.

You drive some distance to use at least 5 gallons of fuel.

You go to a gas station, record the distance traveled, and the number of gallons to refill the tank.

It is the same with electric bicycles.

The SkyRC balance charger indicates the mAhr recharge total. The mAhr x V will allow you to calculate Watt-hours per mile.