How far should I expect to go?

[deronmoped]

If I build a 36V 10Ah pack using BMI or some other top of the line Lithium batteries, how much range should I expect to get from them. Here is my general riding conditions.

1) Standard mountain style bike with street tires at 65 PSI.

2) My total weight will be 250 Lbs. That's bike, motor, battery, me...

3) This is a pedal assist bike, not sure how many watts I will be inputting, this could vary a lot, depending on riding environment, going slow on sidewalks, to going fast on the street.

4) Most of my riding is on level streets, there are usually only a couple of steep hills I will encounter. Probably about a total of a mile at around ten degrees.

5) Top speed should be just under 30 MPH, I really do not expect to maintain that speed, maybe a cursing speed of 25 MPH on flat smooth roads with minimum head wind.

So to figure this out I would need to know the usable capacity of the battery pack and how many watts on average I will be putting in. Then take away how fast I burn the juice up. I have seen plenty of figures thrown out there, but I would like to narrow the range down a little for my circumstance. This will help me understand if this battery pack will work out for me.

Thanks, Deron.

 

[tailwind]

Justin has a table on his web site that gives some typical values for wh/km.
Its about half way down the page.

http://ebikes.ca/batteries.shtml

I found these values to about right for my daily commute which sounds similar to yours.
I average 8wh/km, because I like to peddle to help the motor along.

Greg

 

[voicecoils]

He states 25 mph = ~40kph.

So, according to the link above, that's 12 wh/km. IF you have a 36v 10Ah pack, you'll have about 360Wh of energy available.

360Wh / 12 Wh/km = 30 km. So, if you pedal a decent amount and maintain 40kph you should be able to travel 30km before your pack is completely dead in a time of 45min.

If you pedal heap and therefore average 8 wh/km then you might get 45km out of the pack.

 

[dogman dan]

Don't forget that you can cut that range in half if it gets real windy, or you have 10 psi in the tire and it's going fast. I set up my bike to have a 25% reserve capacity for such things, and as soon as It got chilly, not even really cold, I started to run out a mile from the house, or as I rode up the driveway if slightly warmer. I can't even make it to within 4 miles of the house coming home if it gets windy now. I suppose I could slow down, but my right hand won't obey the brain.

 

[Anonymous]

Yes, I think 12 wh/km is not realistic unless you're going much slower. Using 56v 12ah I am only getting a range of about 30km using LiMn with a top speed just under 40kph and pretty much full throttle on the trip. Granted I'm using an inefficient brushed motor, but it still seems too optimistic based on stats that others have posted. The wh/km is much higher than 12 for me, it's in the 18-22 range, obviously gets worse when windy and up inclines, and in the winter the capacity drops from temperature. Next year I plan to at least double, hopefully triple capacity, I'd like to end up with 56v 36ah for some serious range.

 

[dogman dan]

I'm riding a brushed gearless hub too, so I get a better apreciation of how things affect range! Even if the 12 is a valid number, reality has a way of intruding on theoretical range. 10 pounds of gear in backpack can affect range to some degree.

 

[deronmoped]

I have a real life example on my other bike using a Ping 24V 20Ah pack. Doing the usual type of riding I do, I was able to go 45 kilometers and I still had power to spare. Not sure how juice I had left, I should have just rode around to finish the pack off to give me a idea what the total range was. My top speed with this pack was 32 KPH. This works out to 10.6 WH/KM with a unknown amount of reserve leftover.

With the new 36V 10AH pack I plan on going faster, about 40 KPH, this will burn the juice up faster making my WH/KM higher. One other thing I need to know is, how many more watts can I get out of a better battery. Or will a better battery not last as long, being able to draw the current out faster then what could be done with a lesser battery.

I'm guessing the WH/KM can vary wildly from person to person. What is needed is some sort of WH/KM meter that a person can strap on a bike without a motor. They then can take it on one of their usual rides and get a idea of how many watts they put into the ride. They then can input a desired speed increase they want and get a figure of how many extra watts will be needed.

Deron.

 

[Alex Lar]

I have BL36 all original gears 36V 12 A/h acid battery on 26" bike
My body weight 250lbs / he he / plus weight of bike.
I try to keep 1 way 10km max and back to home. In any weather conditions I have extra 4-5 km to ride, so total average 24km. I think with lifepo4 12a/h I can have extra 10km at list..

 

[tailwind]

Lets say its 12wh/km.
For a 36V 10Ah pack will give you 360wh. 360/12 = 30km

how many more watts can I get out of a better battery

Most of the LiFePO4 batteries that we talk about here are very good to excellent and will give you the stated capacity.

Or will a better battery not last as long

It will last just as long. If you up the amps on the controller then you have the potential to drain the batteries quicker.

I had the same problem as you. I didnt know what my average wh/km would be.
So I ended up building a pack that I thought would be larger than I would need. Its turned out ok because its given me more options with how I ride the bike and were I can go.
For example it lets me take a detour into the city if I need to or take the scenic route home or if its a monster headwind I can just sit back and let the bike do the work and I dont have to charge at work.

IMO its better to have a pack that is larger than you will need.

Greg

 

[dogman dan]

I agree, get the 20ah Deron. It's possible you may have bms cutouts on hills with the 10. Costs a bundle though, but if your bike is going to draw more than 15 amps cruising, you may need the 20 ah pack. The 24v 20 ah pack can actually put out more amps than a 10ah 36v.

Oops, I forgot you were going to a high discharge cell. As Emily Latilla used to say, " Oh, that's different" .

 

[fifthmass]

To give you my own input on your question the best I have ever gotten is 17 wh/mile (10.6 wh/km) at 15 mph/25 kph with constant pedalling.

I have a generic mtb and total rig weight with my fat ass onboard is 290 lbs (132 KG). I run a Clye 408 at 48 volts with a 20ah version 2 Ping pack.

With constant moderate pedaling with motor assist at 15 mph/25 kph I get 60-63 miles (97-100 km) before I get the first yellow LVC warning on the throttle. Flat out full throttle with no pedalling my range is 35-38 miles (56-61 km). You may do slightly better since your total weight is 50 lbs less than my rig. Based on your 36v 10 ah pack I would guesstimate 22-24 miles (35-39 km) range with moderate assist.

My data seems in the range of most so far. You'll be similar I'm sure.

Regards, Bill

 

[recumbent]

If you choose the minimum voltage and minimum amperage like you did, then expect minimal satisfaction.

The sweet spot is 48 volts and >12amp/hr's, this way your battery pack will last much longer (yrs) and you will have considerable more enjoyment & fexibility, life is short.