Building my fourth bike, range vs motor question

[mattb]

Hi All,

Probably a silly question here but as I am simple-minded about these things I thought I'd double check with the experts. I'm on my third eBike, a Pashley Roadster with a Bafang BBS01B 36V with 13ah Samsung battery (below). Now it's time for the fourth bike. I've just bought a GT Zasker Expert with the aim of long distance touring on dirt roads. I may fit my current kit to it, and two 36V 20ah batteries, which based on current experience will give me upwards of 200km range. Range is the priority, and the current motor generally serves me given that I'm not frightened to sweat, however my anticipated adventures will involve much more hill-climbing (mountains!) than I've ever done. So I'm considering buying a new BBS02B 36V 500W. Now my question:

I've set my current 250W bike to provide 4 levels of power (1-2-3-4) and often ride at 2 or 3 out of 4, only going to 4 on inclines. If I get a 500W and set it to 8 levels, and ride at 4, will I be draining the same amount of battery, roughly, as I am when riding at 4 on my 250W?

If that is the case then I will probably buy a 500W for those mountainous days, while still getting great range on the flat. If not, then I will stick with the 250W and sweat (but it seems to be the BBS02B may also be less likely to burn out with the uphill demands I may place on it, and reliability/longevity is an equal priority alongside range....)

Thanks for your help,

Matt

 

[dogman dan]

The only real way to answer your question is to get a watt meter. Which, really, you need anyway if you are going on long range rides. Mountains can vary your range too much for guessing.

So once you get a watt meter, preferably a cycleanalyst, then you can see what your actual watts is on level whatever, and then when you change something, use the watt meter to find the setting that matches what you wanted.

Once you are monitoring watts, you can calculate watt hours per mile, and know your expected range. The watt meter will also allow you to know what your real world battery capacity is. And,, it does vary. At high discharge rates your battery is smaller. So expect a bit shorter range, the more you are running at max rates up the steeper mountains. With experience, you can find the best setting to use on various grades, to max out your efficiency. Or at least, get the most return from your sweat, making the combination of pedaling and motor dish up the most range.

 

[d8veh]

Hi All,

Probably a silly question here but as I am simple-minded about these things I thought I'd double check with the experts. I'm on my third eBike, a Pashley Roadster with a Bafang BBS01B 36V with 13ah Samsung battery (below). Now it's time for the fourth bike. I've just bought a GT Zasker Expert with the aim of long distance touring on dirt roads. I may fit my current kit to it, and two 36V 20ah batteries, which based on current experience will give me upwards of 200km range. Range is the priority, and the current motor generally serves me given that I'm not frightened to sweat, however my anticipated adventures will involve much more hill-climbing (mountains!) than I've ever done. So I'm considering buying a new BBS02B 36V 500W. Now my question:

I've set my current 250W bike to provide 4 levels of power (1-2-3-4) and often ride at 2 or 3 out of 4, only going to 4 on inclines. If I get a 500W and set it to 8 levels, and ride at 4, will I be draining the same amount of battery, roughly, as I am when riding at 4 on my 250W?

If that is the case then I will probably buy a 500W for those mountainous days, while still getting great range on the flat. If not, then I will stick with the 250W and sweat (but it seems to be the BBS02B may also be less likely to burn out with the uphill demands I may place on it, and reliability/longevity is an equal priority alongside range....)

Thanks for your help,

Matt

You have completed your profile properly. You're supposed to enter where you live so that people can give appropriate advice.

 

[docw009]

Viewing this from the point of view of a first year physics student, I think that the energy needed to run a 500W motor and a 250W motor on a bike up a mountain should in theory be about the same if the bikes/rider weigh the same, and go the same speed, and rider puts in similar effort. Then again, fizzicks was 50 years ago. Maybe I flunk the exam.

Last year, I looked at my small 350W motor running on 48V and 36V, and at the same speeds/distance, I used about the same watt-hours per my trusty wattmeter. I thought it would differ but I think physics say no.

 

[mattb]

Thanks guys, much appreciated.

 

[d8veh]

In Australia, you have to comply with EN14194. That means a 250w motor max. Luckily, there's a "250w" version of the motor you suggested. You used to be able to get them from Em3ev.com, but I think heard that they're out of stock. Maybe ask them about it. There's a guy in UK with them and I think the guy in Norway, who first invented them, probably still has them. It might be worth checking your local forums to see if there's an Australian supplier. What you're looking for is a 25A 36v 250w BBS02.

If you don't care about the law or you won't get caught, none of that matters.