Getting maximum range safely from your electric vehicle

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arsharpe
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Location: Hampshire, Basingstoke
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Getting maximum range safely from your electric vehicle

Postby arsharpe » Fri Sep 11, 2009 7:55 am

This summarises the process that I go through to consistently travel the maximum range in both our Berlingo and 106. It has been used on many occasions going to and from my parents and my gliding club both of which are about 54 miles (Berlingo range is spec'd at 60 miles)

The process accounts for almost all the variables that will affect range.

a) wind speed
b) slightly reduced tyre pressures or slightly binding brakes
c) rain (about 10-15% reduction in range) and
d) to a certain extent smallish hills.

Determining Absolute Max Range

The process relies on knowing the absolute max range at a low speed like 35 mph and this is the only risky bit of it so a tow vehicle is put on standby. If the batteries are in good condition then this is not a problem and you will get home ok.

I am lucky we have a suitable ring road (about 10 miles long and approximately circles our home), but any route near your home will do. This minimises any tow home that may be required if the batteries are faulty.

Fully charge the vehicle and reset the trip counter (if you want to verify the linearity of the energy display you also need to note the charge regularly through out the journey)

Choose a suitable given (low speed) for your vehicle. For the Berlingo and 106 it was 35 mph (max speed they can do is 60 mph). Continually drive the route until the charge meter indicates that for the next run you will not get home. Then choose another (ideally circular) route nearer to home and repeat the process until for the next run you will not get home. Then for the Berlingo/106 drive within about 1-2 miles of home ideally at the chosen speed until the red light comes on (normally means about 5 miles left at <30 mph) and then head home. You should get home on the red light.

Note down the total mileage and any linearity figures you have.

Process

The main assumptions are:-
a) the energy meter is accurate and linear - and my tests have shown this to be the case.
b) the energy usage is predominently a non-linear function of speed (well actually more accurately air speed) - so slowing down will reduce energy usage/mile.
c) the route is known including the distance
d) the route is similar (e.g. number of junctions, etc) to your test route. (that was one of the things that went wrong with me in the first L2B run, came home via backroads with lots of start/stops)

The process is :-
a) Taking the maximum (usually measured range at lowest speed) calculate the expected remaining charge at keys points (usually every 5 miles)
b) Use a variable maximum speed and do not go more than that speed (even down hill - where the regen will recharge the battery)
c) At start choose an initial maximum speed depending on your planned distance and route (for Berlingo/106 going max range usually about 35 mph)
d) At each key point check the actual remaining charge against the expected charge.
e) If it is below target reduce the max speed a bit usually about 3-5 miles depending on how bad it is untill you are back on target and then increase max speed a little less. If it continues to be below target after doing this a couple of times stop and check tyre pressures and binding brakes.
f) If you are above target you can afford to increase speed a little usually about 3-5 miles.
g) Continue this process until you get to your destination

If you are like me you will find the first few times when the charge meter is heading for 0% to be a bit nerve racking but I can assure you if you check the charge plan at every point during the journey it will be fine.

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