# Range calculation....am I doing this correctly .



## JW1980 (12 Aug 2015)

Hi everyone. 

I recently wrote a post asking for some help with a newly purchased second hand E bike. 

It turned out one of the three batteries was no good so I have replaced that one like for like. 

All seems ok but I am trying to wirk out the correct range of the bike. 

Just wondered if someone could confirm I am doing it right or could correct me if not? 

So here is what I have done. 

1/ Take the power of the motor and devide that by the battery voltage to give me the current consumed by the motor.

2/ Take the Ah rating of the batteries and divide the current cosumed by it. This should give me the total running time. 

3/ Take this running time and multiply it by the running speed to give me the maximum distance. 

I have assumed a couple of things here.

a) the throttle is fully open to running at max speed / motor power.

b) there is no pedalling so running purly on the batteries. 

I guess, if I have done this correctly then the real figure will be slighly less due to efficiency of the motor and other external influences etc.. 

Thanks in advance everyone. 

Best regards

Jonathan


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## ColinJ (12 Aug 2015)

It sounds about right, but why don't you just ride it and see how far you can go on a full charge?


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## JW1980 (12 Aug 2015)

Hi ColinJ,

Thanks for responding. 

My reasin is to check that everthing is working Correctly and I am getting what I should out of it. 

My problem is there does not seem to be a whole lot of information about this model on the net and it did not come with any


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## fossyant (12 Aug 2015)

Add in variances for hills, traffic light stops, wind, weight and you'll be bob on.

PS if you decide to ride it to see, do it in a circular route, just incase you've got a walk back home.


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## ColinJ (12 Aug 2015)

JW1980 said:


> Hi ColinJ,
> 
> Thanks for responding.
> 
> ...


Ah, ok.

As fossy suggests, even if all is well, the range will probably be a bit less than you expect, but at least you have a reasonable idea from your calculations.


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## DaveReading (12 Aug 2015)

fossyant said:


> if you decide to ride it to see, do it in a circular route, just incase you've got a walk back home.



And try to plan your route so that it's all downhill.


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## JW1980 (12 Aug 2015)

Thanks fossyant,

Thats a good idea


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## JW1980 (12 Aug 2015)

Thanks ColinJ


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## JW1980 (12 Aug 2015)

Thanks DaveReading

I will try that too.


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## JW1980 (12 Aug 2015)

Hi everyone, 

I have just thought of another question but not sure if there is a simple answer to it.

I wanted to ask. Is there a way to estimate how much the distance travelled will be increased by pedalling as well?


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## ColinJ (12 Aug 2015)

Ah, well that is one thing that you _CAN_ find out by just doing it! 

Without a powermeter to measure how much work you are putting in, I can't see how you could calculate how much difference it would make.

Actually, if you know what kind of speed you can do on a conventional bike then you could get an idea of your power output. If you could put in about half as much power as the motor, then you would extend the bike's range by about 50%.

Play around with THIS BIKE CALCULATOR to come up with a power figure for yourself.


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## snorri (12 Aug 2015)

JW1980 said:


> All seems ok but I am trying to wirk out the correct range of the bike.


I do wonder if it is worthwhile spending much time trying to estimate the range by calculation, there are so many variables as to make the calculation little more than a guesstimate. e.g. gradients, surface rolling resistance, load carried on bike, undulations on different routes, battery ageing, wind speeds and direction.
Even the cycle manufacturers claimed range could be considerably different to the actual on the road range. I'm thinking of some car manufacturers claimed fuel consumption figures which have been proved to be rather misleading.


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## JW1980 (13 Aug 2015)

Thanks ColinJ. 

I will gove that a go.


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## JW1980 (13 Aug 2015)

Hi Snorri,

My car certainly does not to what is says in paper.

I am really just trying to work out if the bike is working as it should because I don't have any paperwork or manuals with it and finding anyting on like is proving to be difficult


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## fossyant (13 Aug 2015)

It will go as far as you can pedal it if you don't press the go button.


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## jonny jeez (13 Aug 2015)

JW1980 said:


> Hi everyone.
> 
> I recently wrote a post asking for some help with a newly purchased second hand E bike.
> 
> ...


I would have thought it impossible to calculate an exact expectation of range as the eventual range will be effected by wind, terrain, heat, stopping and starting (traffic) and even the rain.

Not to mention any potential modifications to chainring or sprockets (to gain more speed)

Don't the manufacturers suggest a range that you can check by just riding.


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## jonny jeez (13 Aug 2015)

snorri said:


> I do wonder if it is worthwhile spending much time trying to estimate the range by calculation, there are so many variables as to make the calculation little more than a guesstimate. e.g. gradients, surface rolling resistance, load carried on bike, undulations on different routes, battery ageing, wind speeds and direction.
> Even the cycle manufacturers claimed range could be considerably different to the actual on the road range. I'm thinking of some car manufacturers claimed fuel consumption figures which have been proved to be rather misleading.


You beat me to it!


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## fossyant (13 Aug 2015)

Don't forget to add into the equation if you had a dump this morning as it may affect the weight calculation especially if you had curry the night before.


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## JW1980 (13 Aug 2015)

LoL fossyant


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## steveindenmark (13 Aug 2015)

This is the site I would ask this question on. It is a dedicated site for Electric bikes. The guys know all there is to know about Electric bikes.

http://www.pedelecs.co.uk/


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## JW1980 (17 Aug 2015)

Thanks steveindenmark


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## snailracer (27 Aug 2015)

JW1980 said:


> ...All seems ok but I am trying to wirk out the correct range of the bike...


You can estimate how much energy (in kCalories) your journey takes by using http://www.cyclestreets.net/. The energy is calculated at a certain default speed, which is typically slower than average for an electric bike, so recalculate how much energy any of the 3 suggested routes takes by hitting the "change" button and increasing the speed to 15mph - note that this will increase the amount of energy required. Also, the energy required will be different for outward and return journeys, due to elevation differences and one-way roads.

You can then estimate the amount of energy in your battery according to the following formulae:

Usable Battery Energy (in kCalories) = Voltage X Ah X 0.35​
To be clear, the amp-hour rating of, say, four 18Ah batteries in series, is still only 18Ah.

The "0.35" is a combined Joules-to-kCalories conversion and fudge factor that, hopefully, accounts for controller, motor and battery inefficiencies.

If the battery energy exceeds that required for both outward and return journeys, then you have a sporting chance of making the round-trip without running out of batteries. If there is a strong wind, or lots of stop-starts, old battery, etc. then allow extra margin.


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## voyager (15 Sep 2015)

Just picked up on this thread 

I can only assume that you are using SLA batteries ( assuming its 36v and one battery is u/s )

If you are using SLA batteries then the rating at the 1 hour rate is about 55% that of the marked rating on the battery ie 12 ah is at the one hour rate about 7 ah where as Lipo , Lifepo4 and lithium have a longer life being able to use about 90% of the charge before the BMS cuts in and isolates the power.

hope this might clarify the situation more 

regards emma ( twinkle on pedelec site )


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## raleighnut (16 Sep 2015)

I'd also be aware that temperature has a big effect on batteries, the range on my trike is about 2/3 on a cold day compared to a warm one.


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