Range on a New 500mAh Bosch

[Gubbins]

I was slightly reluctant to reply to Gubbins queery about how I manage to achieve around a 20mph average speed on my road ride home due to the way many threads have previously got derailed by the legal bike/non legal bike polarising argument, and how certain members who are entirely rational when discussing any other issue seem to lose the plot completely on this topic. I can almost feel Colin rushing to his keyboard as I write.

So I will whisper ever so quietly that my bike keeps helping me above the legal cut off point.

One of the better threads I contributed to on the commute to work/ de restricted bike argument that is also mercifully short and full of humour was by pedalec member Wolfie70 in his thread Terry Scott gets Badasse! Made back on May 11th 2016 in the electric buke reviews section. Well worth a read just for the humour.

One myth for me at least and pertinent to a thread about battery range is that a de restricted bike will wear your battery out quicker, as mine is now in its fourth year with 9146 miles since I bought the bike in 2015 and no sign of a loss in capacity at all (My display shows that it uses the same amount of my batteries capacity for my journeys as it always has), although there must be some obviously.

To be honest I do not take a note my average speed for my 10 mile road trip home very often but just enjoy my ride home, and know that it varies according to weather conditions, my effort etc, but when I did take a note of it one night I had averaged just over 20mph after taking 29 minutes to cover the 10 mile undulating B road return from work. Weather conditions were very good on that night and I was obviously in the mood to add lots of effort as well.

I do agree that bike shops do mis-lead new buyers with their very optimistic range figures.

The figures I posted in my Beautiful Symetry post just amused me as the potential range of my longer off road journey at 56 miles for my 400Wh battery was exactly twice as far as the potential range of my shorter road trip home.

As I only use my bike to commute to work and back the total range of my bike is never an issue. I am also lucky enough to be able to charge my battery back up at work ready for the journey home.

Ah. This explains a great deal and thankyou for the extra detail, you won't get any agro from me regarding such devices as my view has always been that of a fence sitter, it was just the average figure that I found intesting.
In find that high average speeds over relatively short distances are one thing but as the distance increases all the small low speed instances soon mount up to drag the average down. The other point is that using a speedup device puts any battery usage comments in a totally separate arena.

 

[anotherkiwi]

The energy required to cover a set distance will be similar with or without restriction:

- going faster unrestricted will mean more energy per km used to defeat air resistance
- going slower will mean using less energy per km but for a longer period of time
- in both cases rolling resistance and other forces remain equal.

The laws of physics are pretty well written and give measurable results...

 

[Gubbins]

The energy required to cover a set distance will be similar with or without restriction:

- going faster unrestricted will mean more energy per km used to defeat air resistance
- going slower will mean using less energy per km but for a longer period of time
- in both cases rolling resistance and other forces remain equal.

The laws of physics are pretty well written and give measurable results...

You are forgetting one small thing.. you are more likely to travel with no assistance on a restricted bike whereas an derestricred bike will be using power constantly.

 

[anotherkiwi]

You are forgetting one small thing.. you are more likely to travel with no assistance on a restricted bike whereas an derestricred bike will be using power constantly.

True if you are in the wrong gear.

When you are in the right gear and working yourself it is amazing how few W are shown on the LCD - in the low to mid 30's (km/h) I often see less than 100 W power draw, typically between 60 and 90 W. At 45 km/h on the flat about 230-280 W which means I am providing about 160 W myself.

 

[Gubbins]

Rules seem to be different for you. If I were to ride at 30kph i would be using zero power from the bike.

True if you are in the wrong gear.

When you are in the right gear and working yourself it is amazing how few W are shown on the LCD - in the low to mid 30's (km/h) I often see less than 100 W power draw, typically between 60 and 90 W. At 45 km/h on the flat about 230-280 W which means I am providing about 160 W myself.

 

[anotherkiwi]

I also ride restricted - 27 km set = about 25 km/h real because of big tyres. In town I am rarely over the cut off.

 

[Deleted member 4366]

The energy required to cover a set distance will be similar with or without restriction:

- going faster unrestricted will mean more energy per km used to defeat air resistance
- going slower will mean using less energy per km but for a longer period of time
- in both cases rolling resistance and other forces remain equal.

The laws of physics are pretty well written and give measurable results...

Hang on, I think you must be a bit sleep deprived today. You normally talk sense, but that's twice today I have to disagree with you. You're going to start hating me soon.

The losses are not the same in those too scenarios. Air resistance varies a lot with speed, and it's not linear. It's a cube function, so resistance is eight times as much if you double the speed. On an electric bike, that means that you use a lot more wh/m to go fast as you do when you go slow.

Remember this?

Aside from this, there's so much misinformation about range. It's dead simple. You and your bike have weight, rolling resistance, drive train resistance and air resistance. No clever engineering by Bosch or anybody other motor manufacturer can change that. All motors have approximately the same efficiency. you get the max efficiency when it's spinning at about 75% of its max rpm. Constant changes in rpm spoil the efficiency. After that are the biggest factors which affect how much battery you use, and that's firstly how hard you pedal. I can get a range from 15 miles to 160 miles on the same bike on the same rides depending on how hard I pedal. The next important factor is the type of terrain over which you ride, i.e. hills, roughness and wetness. This is where weight comes into it. It takes twice as much power to drag a 130 kg of bike and rider up a slope compared with 65kg. On my road bike, when the path changes from cinder to tarmac, I can immediately change up two gears, which is a difference of around 20% speed for the same effort.

Lastly, too many people are predicting their range incorrectly with statements like, "I did 50 miles and used two bars on my battery display out of four, therefore I can do 100 miles". I say try it! You'll be lucky to get 75 miles. Likewise, I doubt that you can trust any predictions that your LCD makes when your battery is more than half-way down because it's based on previous events. As the battery goes down, so does the voltage and the power, which means that you'd have to pedal harder to compensate, but actually, you will be tired, so making less contribution.

 

[anotherkiwi]

I agree with everything you say in the above if you read me again (you know we can agree to disagree, I doubt if you can tip my anger level beyond that ).

My favorite graph which you used above (did I say you can use that? ) in the text that goes with it states "on flat ground with no wind". At legal speed losses from rolling resistance and drive train losses are still significant. A pedelec has to add in pedelec specific losses such as motor efficiency and extra weight so at that speed a pedelec will have closer to 50% loss due to aero and 50% due to other factors.

I was replying to someone who was talking about 32 km/h average and there aerodynamics has the upper hand - losses from aero becoming much more important than other losses. It is the air which will be eating most of your battery Wh at those speeds and above.

Over a given distance all other conditions being equal a de-restricted bike and a restricted bike will use roughly the same energy. One will use more energy in less time than the other to go the same distance. I am talking about removing the 25 km/h speed limit, not playing around with volts and Amps and whatnot.

P.S. a de-restricted bike and a legal pedelec will use the same amount of Watts at 32 km/h in one cas the battery will be supplying a bit and the rider a bit and in the other case the rider will be supplying the whole lot.