ebike calories - new calculation?

[IanA]

Can anyone check my calcs below to see if I’ve made any glaringly obvious errors?

I’ve always wanted to know how much effort I’m putting in compared to the battery and I’ve come up with a calculation which I think works. I’ve looked through the forum but I can’t find anything like it.

I found the following table of kcals burned per hour for non-assisted cycling at Calories Burned During Exercise - NutriStrategy :

Kcals burned per hour for a person weighing 205lb:-
Cycling, <10mph, leisure bicycling ____372
Cycling, 10-11.9mph, light __________558
Cycling, 12-13.9mph, moderate ______745
Cycling, 14-15.9mph, vigorous _______931
Cycling, 16-19mph, very fast, racing _1117
Cycling, >20mph, racing ___________1489

Obviously a very rough guide to say 9.9 m.p.h is 372 and 10 m.p.h. is 558 – but I will do some work on that.

In March I cycled 13.3 miles home in exactly 1 hour after dropping my car off at the scrap yard

So, according to the table, the energy used (by myself and my battery combined) was about 745 kcals.

When I charge the battery I use an energy monitor sneakily rigged to show how much energy is supplied down to 1/10,000[SUP]th[/SUP] kWh i.e. in Watt hours (Wh) to 1 decimal place.

After scrapping my car the energy used to recharge the battery was 144.2 Wh which I have converted to kcals. 144.2 Wh x 0.86 = 124 kcals.

This should mean that the most the battery could have assisted me was 124 kcals. I presume this is likely to be much less due to inefficiencies of charging and energy delivery to the motor – but could it be similarly inefficient as the human body processing calories from food?

I therefore burned 745 (total) -124 (battery) = 621 kcals

I reckon I normally burn about 140 kcals per hr so the extra for cycling is 621-140 = 481 kcals.

So I contributed 481 kcals and the battery contributed 124 kcals.

Approx. 80% : 20%

The biggest issue is hills (always!) – If your ride is uphill you will obviously go slower and the calorie table then says that you are burning fewer calories per hour (don't think so) but perhaps that evens out if there are equivalent ups and downs?

I think I should be adding the extra weight (in excess of typical bike weight) to my own weight when calculating kcals burned. What do you reckon? (If you follow the link to the calorie table the kcals for each weight shown are simply pro rata so it's easy to work out kcals for other weights. The more you weigh and the more you carry, the more work you have to do.)

btw if anyone’s interested in rigging an energy monitor to show Wh then simply enter the price per unit (kWh) as 999.9 and then read the total price for the energy supplied as Wh.

 

[Scimitar]

Hmmm.... how about contacting the nearest bio-human research lab and suggesting they might like to do a study of human energy expenditure while leccy biking? I can see you now - bipping along the road, with a snorkel and demand meter attached

 

[flecc]

That's a very low ratio of motor contribution you've arrived at, it seems very unlikely. Crank drive units like the Panasonic one are usually arranged so that 50% of wattage is from each in standard power mode, and they are considered harder work than hub motor e-bikes in flat conditions. I'd say that on the flat your figures could be reversed for most throttle controlled e-bikes, and only on steep climbs will most owners contribution be much larger than the motor's.

 

[IanA]

Hmmm.... how about contacting the nearest bio-human research lab and suggesting they might like to do a study of human energy expenditure while leccy biking? I can see you now - bipping along the road, with a snorkel and demand meter attached

Wish someone would, then there'd be no need for these crazy calcs.

I'm not volunteering though

 

[IanA]

That's a very low ratio of motor contribution you've arrived at, it seems very unlikely. Crank drive units like the Panasonic one are usually arranged so that 50% of wattage is from each in standard power mode, and they are considered harder work than hub motor e-bikes in flat conditions. I'd say that on the flat your figures could be reversed for most throttle controlled e-bikes, and only on steep climbs will most owners contribution be much larger than the motor's.

Yes, I was initially surprised at the ratio too. But it varies a lot from ride to ride. That example worked out at 80/20, others are 70/30. Worth noting that I don't have a throttle so I only use a pedelec crank sensor. With a throttle it must be possible to have anything up to 0/100.

A lot of the time I'm doing 11-15 mph or more and the motor starts to cut out at 12 and is completely absent at 15 so will hardly be using it except on hills. So for my style of riding I would say it's probably 95/5 on the flat and probably 60/40 or 50/50 on the hills. So my contribution will be the opposite of 'most owners' if your view is correct.

I've just this minute returned from a 25 mile ride and I'm knackered! So it's hard to believe that I'm putting in less than the battery which will only need about 240 Watt hrs - 206 kcal. Thats one large banana for 2 hrs moderate to hard cycling - that too seems unlikely.

And if I think back to pre motor days when I used to go cycle touring with a heavy load it didn't half feel easy on days when I left the load at the campsite! I suspect that was 20% of the total weight removed, so probably a similar 80/20 effect and that makes me feel like it could be true.

 

[flecc]

I can see what you mean now Ian, its that early 12 mph cutout since that makes a huge difference in the ratio. If it powered to 15 mph you'd see a big difference. This was the range secret with the early Panasonic unit equipped bikes, the power phasing down from 9.4 mph on.

 

[IanA]

I can see what you mean now Ian, its that early 12 mph cutout since that makes a huge difference in the ratio. If it powered to 15 mph you'd see a big difference. This was the range secret with the early Panasonic unit equipped bikes, the power phasing down from 9.4 mph on.

I've done some more research and have revised my calcs (see below). It results in a ratio of 60:40 (much more in keeping with both our initial gut instincts). And the 70:30 that I mentioned in another post obviously becomes 40:60. So this is my best guess and I'll gladly leave this subject for now - there's far too much conflicting info about!

Here's the revised text...

After scrapping my car the energy used to recharge the battery was 144.2 Wh which I have converted to kcals. 144.2 Wh x 0.86 x 2 = 248 kcals. (Now multiplied by 2 because I believe that the battery charger/battery/motor efficiencies are about 50% overall whereas the human body is only about 25% efficient, so the energy used to charge the battery is approx. equivalent to twice the kcals needed by a human being to deliver the same power output)

This should mean that the most the battery could have assisted me was 124 kcals. I presume this is likely to be much less due to inefficiencies of charging and energy delivery to the motor – but could it be similarly inefficient as the human body processing calories from food?

I therefore burned 745 (total) -248 (battery) = 497 kcals

I reckon I normally burn about 140 kcals per hr so the extra for cycling is 497-140 = 357 kcals.

So I contributed 357 kcals and the battery contributed 248 kcals.

Approx. 60% : 40%

 

[gar32]

Very old post I know but I could not find any other like it online.

So too make thing more unsure here. What about the different settings on the ebike. I have Sport, Normal & Eco. I went 60km on Eco yesterday which was my 1st long trip. My wife said it's an e bike why are you tired. Is your 60% :40% on the normal setting ?

 

[trex]

your estimates will need to take into account the type of bike. If you ride a Chinese bike, you will likely to put in less than someone riding a European made bike. Other factors that also need to take into account: air temperature, wind speed, wind direction, clothing, terrain gradients.
A more accurate way to estimate calories is to compare heart beat rate against the same at rest.