How do I calculate how many calories I’ve burned?

[mr_ed]

My brain hurts…

I cycled 50 miles in 6 hours. Strava says 2,600 calories.

My 52v battery lost 5.75Ah.

I was keeping the power down very low to maximise range and get a bit of exercise too.

How can I calculate how many calories of the above the motor is responsible for?

 

[saneagle]

Average voltage was about 50v, depending on the size of the battery, and assuming that it was fully charged when you started, so 5.75 Ah means you used 287.5 wh, which equates to 247 Calories, but your motor is only about 70% efficient, which means it helped you with about 200 Calories.

50 miles with 287 whs doesn't sound right unless you had it switched off most of the time. It equates to around 5wh/mile. When you're that low, you'd probably be better off using a non-electric roadbike because 5wh/mile is about the power needed to overcome the additional weight of the motor and battery.

 

[mr_ed]

Battery started at 58v and was 54v at the end, so probably 325 watt hours.

How did you convert from watt hours to calories? 200 sounds too low to me. If Strava said 2600 calories I’d expect at least half of that to come from the motor?

I was using power level 3 of ten which is a max of 100W I think and using the gears… wasn’t bothered about crawling up the hills and it was mostly flat. Battery was full to start with and I used the BMS to tell me the Ah used. It’s a BBSHD with a 11 speed cassette and a 17.5ah 52v battery.

 

[Peter.Bridge]

I think these calorie calculations are fraught with error - different fitness bands give very different estimates. Some do an estimate purely on heart rate not on distance/speed. If you looked at it in purely heart rate in 6 hours of cycling, you would struggle to burn less than 400 calories per hour, so I think 2400 calories is a reasonable estimate.

 

[saneagle]

Battery started at 58v and was 54v at the end, so probably 325 watt hours.

How did you convert from watt hours to calories? 200 sounds too low to me. If Strava said 2600 calories I’d expect at least half of that to come from the motor?

I was using power level 3 of ten which is a max of 100W I think and using the gears… wasn’t bothered about crawling up the hills and it was mostly flat. Battery was full to start with and I used the BMS to tell me the Ah used. It’s a BBSHD with a 11 speed cassette and a 17.5ah 52v battery.

1wh = 0.86 Calories
OK, so it's now 6.5 wh/mile. When I got that low, I switched to a roadbike and found it to be better. It's much faster on downhills and flat roads. You feel the difference on hills at first, but your body soon adjusts, then you can do anything.

When people talk about burning calories, what do they mean - food burnt or energy output? Your body is only about 20% efficient, so 2600 Calories eaten means 520 Calories output. In that case 2/3 of the energy for the ride came from you.

 

[mr_ed]

Aha, that starts to make a bit more sense. So the 2600 calories that Strava quotes probably means equivalent to me eating 2600 calories and outputting 520.

And of that the motor is giving 280 calories so just over half. This feels realistic to me.

I've never tried a road bike...just mountain bikes and hybrids. But I know what you're saying. I would quite like to build another super light e-bike... a bit like the Orbeau £10K carbon ebikes that have a minimal motor and battery just to take the edge off the hills.