How do I compare / calculate range between 2 packs?

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Alan2000   100 mW

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How do I compare / calculate range between 2 packs?

Post by Alan2000 » Sep 08 2016 3:04pm

I have a 36V 15,500mAh, 561wh pack. I use about 600mAh per mile mountain biking. So I figure my max range is about 26 miles. A friend has the same motor on his bike and all he knows about his battery pack is that it is a 48v 672wh pack. We're trying to figure out what his range should be with all other variables held constant as in if I put his pack on my bike. If I'm doing the math right, I think his pack would be a 14,000mAh pack (672wh/48v=14A). Would it be accurate to simply divide 14,000 by 600 to get 23 miles? I'm not sure how the higher V of his pack plays into calculating range. I know that normally a higher V allows you to spin the motor faster. I'm guessing with a higher V you need less A to go the same distance. So I think my simplistic calculation of 23 miles may be wrong.

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MadRhino   100 GW

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Re: How do I compare / calculate range between 2 packs?

Post by MadRhino » Sep 08 2016 3:24pm

Alan2000 wrote:... all other variables held constant
A watt is a watt, no matter where it comes from.
Then, all other variable does include weight. If you put extra battery capacity on your bike, and still weight the same, and not affecting any other variables, the increase of range will be proportional to the increase of w/h. :D

You see that, when changing one variable, it is not so easy to keep all other variables constant. :wink:
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fesanand   10 W

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Re: How do I compare / calculate range between 2 packs?

Post by fesanand » Sep 08 2016 3:31pm

You have to calculate your consumption in wh/mile, which is 36v*0.6A= 21.6wh/m
Your pack is 561wh divided by 21.6wh/m results in 26miles your're right.


Now, if you ride in the same conditions (avg speed and acceleration) with your friends battery, your consumption should be barely the same 21.6wh/m

672wh / 21wh/m = 32 miles.

For more info use the searcher, there's several threads talking about consumption wh/m and wh/km.

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Drunkskunk   100 GW

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Re: How do I compare / calculate range between 2 packs?

Post by Drunkskunk » Sep 08 2016 3:43pm

It will be a lot easier for you, if you figure your power use per mile in terms of watt hours.
You know, but just to be clear for anyone who finds this post on a google search, Volts X Amp hours = Watt hours. So your 600mAh (0.6Ah) at 36 volts would be 21.6 watt hours per mile. That means your 36v 15500mAh battery (15.5Ah) would have 558 Ah, and if you drain it, you could get 25.8 miles

Since the other battery is 48 volts, 14000mAh (14Ah) it will have 672 watt hours. if you ride at the same speed and don't take advantage of the extra power you could get from the higher voltage pack (Epic levels of self discipline I don't have) you would get the same performance, 21.6 watt hours per mile. That would be 31.1 miles range if totally drained.

Increasing the voltage not only makes the motor faster, but since the V x A = W, and you're increasing the V from 36 to 48, the W is increased as well, meaning you can put more watts, more power through the motor at the same amp limit. It's a 25% increase in power over the 36v battery
So the 48 volt battery has around 20% more range potential, but it will also make your bike 25% more powerful. So you might get that 20% extra range, but there's one more variable to consider. The YEE-HAAA factor. if the bike is more powerful it will be more fun. When it's more fun, it's much harder to stay off the throttle, and not use the extra power so that you can maintain your former efficiency rating. So in reality your actual range may not go up 20%, but your grin may be 25% wider. :mrgreen:
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Alan2000   100 mW

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Re: How do I compare / calculate range between 2 packs?

Post by Alan2000 » Sep 08 2016 4:57pm

Super! Thanks everyone for all the great info. I thought the 48v pack should have a higher range than what I miscalculated. It sounds like he probably will run out sooner unless disciplined to not have fun with the extra power! To avoid the "YEE-HAAA" factor in reducing my range, and giving me a little more of a workout, I have re-programmed my 25A controller to only put out 18A. :D Sounds like with me at 26mi and him at 31mi we probably will both have about the same range which is what we were trying to figure out. His bike is still programmed to use up to 25A.

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dogman dan   100 GW

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Re: How do I compare / calculate range between 2 packs?

Post by dogman dan » Sep 09 2016 6:50am

Yeah,, chances are,, you will use that power riding off road and possibly have less range.

Myself,, I get about 1 ah per mile, or less riding off road, 48v. I don't pedal hard, often riding fast enough for the trail conditions to be just standing the pedals and concentrating on not doing an over the bars as I leave the trail. So my wh/mi is very high compared to yours. Trail conditions make the most difference off road. Some I can get 3 miles per ah,, but around here, the trails are pretty rugged, and my use is much higher than yours.

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