Author Topic: Its all about the range  (Read 402 times)

Offline Haroun

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Its all about the range
« on: January 09, 2020, 05:51:25 PM »
I have a dirt bike I use as a "technical" trail bike.  Kinda like trials riding with a seat.  It weighs 99kg (with ICE).  Has about 25HP, but rarely sees wide open. Like trials bikes, its all about low down torque and controlling it.

I am at a decision point.  As a hobby project, I was planning to convert this bike to EFI. Part something to do and part more precise control.  But then I though, maybe electric might be the thing.  However, my concern is the range.

I am not new to electric vehicles.  I converted a new beetle to electric about 18 years ago.  A lead sled with AC motor and regen.  Hevay car, 26 SLA and crappy range.

I read through most of the postings here, and figure the 5KW would be OK for my needs with reduction gearing a la Electric Motion Trials bike.  My concern is the range. 

Today, My usage of this bike varies from 50km technical trail riding to 150km small adventure tours.  And this is not flat land here.  Lots of ups and downs.  The adventure tours are often +1000m climbs.  And the rider is a big guy.  100kg easy.

Obviously more batteries the better.  There are a couple of tipping points:

(1) physical room on the bike for more batteries
(2) extra weight of more batteries

I think I could probably fit a 48V 30Ah battery pack.  My new projected bike weight is +8kg more (ouch!).    Any idea how to calculate the range of this battery pack?

Any other thoughts or comments?

Offline Bikemad

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Re: Its all about the range
« Reply #1 on: January 09, 2020, 08:23:48 PM »
Hi Haroun andto the forum.

I think your required range is going to be very difficult to achieve with electric power, as the 48V 30Ah pack is probably less than 20% of what you will actually require to achieve 150km range.

The Zero S ZF7.2 information shows a range of 89 miles (143 km) under stop/start city driving conditions, or 45 miles (72 km) at a constant 70mph (113 km/h) with the 7.2kWh battery pack.

Your proposed 48V 30Ah battery pack only has an energy storage capacity of 1.44kWh.
This would give a range of ~18 miles (~29 km) on a Zero S when driven in the city, and a lot less on +1000m climbs.

The Electric Motion Epure Sport information quotes a range of 43km with a 50.4V battery, but they don't state the Ah rating of the battery.
However, they do mention that a 25A charger takes 2hrs 15 minutes to charge the battery, so I'm guessing the battery is likely to be around 50Ah giving an energy storage capacity of ~2.5kWh (50V x 50Ah). On this basis, this bike would require a battery 3.5 times bigger to achieve your required 150 km range (~8.75kWh) with trial riding conditions.

If the Epure Sport manages 17.2 km for every 1 kWh, this would give a range of nearly 25 km with a single 48V 30Ah battery.
This means you would need at least 6 x 48V 30Ah batteries in series to travel 150 km (48V x 180Ah = 8.64kWh).

Unfortunately, it doesn't look like an electric conversion is going to be viable for your particular requirements/expectations.  :(


Offline Haroun

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Re: Its all about the range
« Reply #2 on: January 10, 2020, 02:59:58 AM »
Alan, - excellent info.  I will digest and re-assess.


Offline Haroun

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Re: Its all about the range
« Reply #3 on: January 13, 2020, 05:45:29 AM »
I took GPS data from 4 of my favorite rides over the years.   I calculate the energy requirements based on rolling resistance, air resistance, energy to get up a hill, acceleration.

These are the numbers I used for the bike:

Mass   200   kg
Frontal Area   1.5   m^2
Drag Coeff   0.6   
Air Density   1.2   kg/m^3
Tire rolling resistance coefficient   0.025   
Drive Efficiency   0.9   
Other losses   0.8   
Pack Voltage 48V

So from the GPS data, this is what I get for the rides.

Typical weekend technical ride 28km elevation gain 650m 1.6kWhr 33Ahr
Long technical weekend ride 81km elevation gain 1406m 2.7 kWhr  56Ahr 
Adventure ride up Mtn 62km elevation gain 2800m  2.9 kWhr    60Ahr
Very Long event (required two tanks of gas) 95km elevation gain 3800m  4.2kWhr   88Ahr

I don't expect the bike to be able to handle the long trips.  I can get another ICE bike for that stuff.  It would be useful to me if I could get 2kWhr at 80% DOD I would be very satisfied.  That means a  2.5kWhr  53Ahr battery.  So, if I picked their 50Ahr battery - that puts the bike at 119kg.  That'd be a pain. 

*sigh*  ah well...
« Last Edit: January 13, 2020, 12:08:53 PM by Haroun »