How do you calculate lipo capacity for commute miles?

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VoKuS

100 W
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My commute to work is 1.8 miles one way... ( I know, I should just pedal but someday you just dont wana, and some times you cant pedal fast enough... when running late haha )...

So how much capacity would I need?

Wishful Bike Spec's

Trek 26" Mountain Bike
Maxxis Hookworms 26" ( with disk brakes :p )
5403 Motor ( with cnc torque arm by meh )
20S Lipo NanoTech from KH ( two 10s in series )
One of Ly's Fancy Controllers...
A couple of 10S Chargers...

Would 5000mah do it? or 10,000mah?
 
I was getting about 10 miles out of my 250w setup on 5AH; that's with a 14a controller... and some hills.

A lot of things factor in though:
1. what kind of tires.
2. how heavy is the rider
3. any hills?
4. how many amps are you running?
5. how fast will you be going?

Safe guess: If you stay below 30mph, you should be able to pull that off a ~3.6 mile round-trip easily on 5ah.
 
It all depends on lots of things (how heavy you and the bike is, how fast you drive, hills etc).

As a VERY general rule of thumb you need 10-20 watt hours per kilometer which would equal 16-32 Wh per mile.
Now watts is voltage * amps. Your voltage for 20S is 3.7 volts per cell times 20 = 74V.
A 20S 5000mAh pack would be 5 * 74 = 370Wh which would last about 11 to 23 miles.

(I am new at this so please correct me if I did get this wrong).
 
pelle242 said:
It all depends on lots of things (how heavy you and the bike is, how fast you drive, hills etc).

As a VERY general rule of thumb you need 10-20 watt hours per kilometer which would equal 16-32 Wh per mile.
Now watts is voltage * amps. Your voltage for 20S is 3.7 volts per cell times 20 = 74V.
A 20S 5000mAh pack would be 5 * 74 = 370Wh which would last about 11 to 23 miles.

(I am new at this so please correct me if I did get this wrong).
Click to expand...

Yeah, you kinda are..
Aerodynamic drag is a big factor. i believe that on a bicycle, it doubles the amount of power you need for every 10mph after 20mph..

And hills are a big variable. Much like in a car, it takes multiples of the same power to get up a hill.

Range is way hard to calculate from a blank slate.
I say have more capacity than you need. You wouldn't buy a car that can only go 3.6 miles, right? :)
 
neptronix said:
Yeah, you kinda are..
Aerodynamic drag is a big factor. i believe that on a bicycle, it doubles the amount of power you need for every 10mph after 20mph..

And hills are a big variable. Much like in a car, it takes multiples of the same power to get up a hill.

Range is way hard to calculate from a blank slate.
I say have more capacity than you need. You wouldn't buy a car that can only go 3.6 miles, right? :)
Click to expand...

Well I was more thinking if the use of numbers was wrong. That a bent lowracer with racewheels and a fairing will get better range than a MTB with big tires is kind of obvious.
What you can get is a ballpark number that tells you if you are close or way of. In this case the OP will most likely be fine since it looks like he will have an order of magnitude more range than he needs....
 
A 5403 will put you in electric motorcycle territory, we're talking about amusement park ride fun if you feed it the amps it wants. Budget for at least 40-50wh/mile, or you're just wasting the potential of the motor and should get a lesser one. If you are a large person and have big hills to contend with, you'll want a different turn count motor, because the '03's will be harder on controllers.

Sure that's enough battery for that short commute, and to experience what this high power ebike thing is about. Count on wanting more battery capacity within a week for more joy riding, so don't even worry about how to mount the 2 packs. Just duct tape them on for those first rides. You'll have to figure out how to fit at least 4 or 6 soon enough. If you're concerned about the look, call it an experiment.

Make sure you get the full programmable rig from Lyen so you can tune it to your tastes. The motor will want to suck some serious juice under acceleration and up hills, so a 200lb and under person wants an 18 fet controller and a larger person a 24 or 36. The 18 is easy to fit, but the big bricks need a seat post mount. You'll want regen braking even if you don't activate it at first. You will get tired of fiddling with the brakes, since bike brakes on an electric motorcycle require lots of upkeep.

Dual suspension, yes definitely. Look for the longest wheelbase you can find. If it's for trail riding, then that's the wrong motor and you need an '04. If you can find a bike with a steel swingarm, buy it, cheap components, but a bargain price used. It makes modifications easier, so you can easily stretch the bike 4-8", because that motor is going to have you wheelie-ing all the time on a regular bike unless you're wasting its potential with not enough amps. Throttle control is different than a motorcycle or pedaling, so 1 wheel isn't as fun as on a gasser.

You already know about torque arms, so a couple more requirements less commonly mentioned are a drip loop on the wire going into the motor and a precharge resistor, even if only to use manually for rare connect / disconnect of your pack.

Have fun. You're going to love it !

John
 
pelle242 said:
As a VERY general rule of thumb you need 10-20 watt hours per kilometer which would equal 16-32 Wh per mile.
Now watts is voltage * amps. Your voltage for 20S is 3.7 volts per cell times 20 = 74V.
A 20S 5000mAh pack would be 5 * 74 = 370Wh which would last about 11 to 23 miles.
Click to expand...
You definitely got it right. However, the 10-20 wh/km numbers are for ZERO pedaling. If the motor is used in assist mode to enhance the pedaling, you could easily cut those #s in half, to 5-10wh/km and the range would double.
 
A 5 ah 72v pack will do ya fine. Your power use will be similar to my racing bike, which can go 4 miles on 5 ah of 20s lipo easily without risking overdischarge.

Don't go smaller though, because the pack will sag more at the end of the ride. 5 ah would be the minimum, unless the deal on 4 ah packs is that much better price. I wouldn't let price drive my choice for a small pack like that though. I'd go for the best nano packs for sure, for the better performance.

From what I read, the 5304 is the motor. But really, a 9c 2807 like my racing bike will be plenty of pep. And easy on the controller. 40 mph not fast enough, just get the 120v lyens controller and run 24s or 26s. I almost get into the 50 mph club on 26s. ( have hit 51 mph on a slight downhill)

Not sure what the wattage is on 26s, the CA maxes out on 100v. At 100v, I see about 3500 watts. :twisted:
 
He said a 5403, which is the new big boy, so 10-20wh/km is low unless he lets all that fun potential go untapped. With the new Xlytes coming out, why would anyone want to buy the old one unless it was at clearance pricing?
 
John in CR said:
He said a 5403, which is the new big boy, so 10-20wh/km is low unless he lets all that fun potential go untapped. With the new Xlytes coming out, why would anyone want to buy the old one unless it was at clearance pricing?
Click to expand...

Thanks for all the replies guys, what is this Xlytes? Please more info on this....
 
By the way, here's some feedback on running on 5ah..

I ran my MAC 36v / 30a ( 1100w peak ) setup today for the first time on 5ah of 36v 20c zippy.. full throttle, hills, and lots of start and stop!!
Those suckers get quite warm when you draw some serious amps from them!!!

Like always, i recommend having more amp hours than you need. I cannot imagine how hot they get on > 30amps.
Another option is to buy the 35c or nanotech badboys so that heat is not an issue.
 
Just for reference, my 9C 2807 averages about 35 watt hours per mile in hilly terrain (loop, up and down included), and up to about 65 watt hours per mile when climbing steep grades (averaging about 6%). That is at 20-25 mph (less on the steeper grades). So if you are going to go faster you can scale that up.

Watt hours per mile is the most useful way to estimate range. One fellow I know with an electric motorcycle uses 125 watt hours per mile for his bike in stop and go 0-45 mph usage.
 
VoKuS said:
John in CR said:
He said a 5403, which is the new big boy, so 10-20wh/km is low unless he lets all that fun potential go untapped. With the new Xlytes coming out, why would anyone want to buy the old one unless it was at clearance pricing?
Click to expand...

Thanks for all the replies guys, what is this Xlytes? Please more info on this....
Click to expand...

New Xlytes (Crystalyte) hub motors are discussed here

http://endless-sphere.com/forums/viewtopic.php?f=2&t=24593&start=30

1Ah per mile is always a safe battery consumption calculation.
 
Might still be fine for 2 miles, even with a larger 5403 motor, on 5 ah of nano packs. If not, more is a click away.
 
I get 2 to 2.5 miles per ah (n on my small minimotor, 1.75 -2.0 miles with my 9c and only 1 mile per ah with my BMC. All with no pedaling! I like this combination, because I can get speed with one setup, distance with another and my 9c can be overvolted and tamed with my Cycle Analyst. 8)
 
Alan B said:
If you are going to make a round trip on 20S 5AH that is about 80 volts and 400 watt hours to go 4 miles. So 100 watt hours per mile would be available. Sounds like almost motorcycle power levels, so should be adequate.
Click to expand...

Agreed, I would expect 10 miles out of that pack reliably.
 
Alan B said:
ChinaPhil said:
...

1Ah per mile is always a safe battery consumption calculation.
Click to expand...

Depends on the voltage... 12, 24, 36, 48, 60, 72, 84, 96 !!!

Watt Hours is better by compensating for varying voltages.
Click to expand...

WH is "better" for those with sharp math minds and/or widely differing voltages from 40-60v applications. However, for simplicity and on the spot estimation many of us still find AH/mile to be useful for range estimates. Also the fact that Lipo is sold by AH influences my habit to use 1AH/mile formula.

It's along the lines of lbs/mile too - where roughly 1lb of Lipo will get you 1 mile range. I just prefer the easy numbers to process in my old, abused mind and experience has taught many of us that 1AH/mile and/or 1lb/mile to be fairly accurate Lipo range guess-timation.
 
The lipos I'm buying are 6S 5AH and 2 pounds, so 24V times 5 is 120 watt hours divided by 2 pounds or 60 watt hours per pound. So most bike systems are closer to 1.7 miles per lipo pound at an average 35 watt hours per mile.

Headways are about 3.4V times 16AH for the larger cells which is 54 watt hours for a one pound cell, so a bit less but about 1.5 miles per pound at the average 35 watt hours per mile.

On a 36 volt system 1AH is 36 watt hours so is very close to an amp hour per mile for the average 35 watt hour per mile bike.
 
Alan B said:
The lipos I'm buying are 6S 5AH and 2 pounds, so 24V times 5 is 120 watt hours divided by 2 pounds or 60 watt hours per pound. So most bike systems are closer to 1.7 miles per lipo pound at an average 35 watt hours per mile.

Headways are about 3.4V times 16AH for the larger cells which is 54 watt hours for a one pound cell, so a bit less but about 1.5 miles per pound at the average 35 watt hours per mile.

On a 36 volt system 1AH is 36 watt hours so is very close to an amp hour per mile for the average 35 watt hour per mile bike.
Click to expand...

Well done but I dare say most never draw the full 5AH from our Lipo. Even when pushing things I stop around 4AH from a 5AH brick. I use those 2lb 6S 5AH too - so if you "guesstimate" 4AH actual real world capacity in 12S configuration that would put us around 4lb total, right? SAFE to assume 4 miles from that 4AH and therefore 4lbs bringing us back to 1lb/mile.

This is very rough formula stuff and not trying to be argumentative just showing how some of us have grown to estimate these things. And in most cases seems to work out pretty close.
 
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