Measuring how much battery used on a ride

[MeDotOrg]

If this has been answered in another thread I apologize. With an electric bike, speed and distance are not the only part of your performatnce equation. The other part is how much electrical assist you used. The other day I went on a 44 mile loop that I've done several times. It's a pretty hilly ride (for me). I deliberately used less boost than I had, and my average speed went down 2 mph. But I felt that the power I contributed actually increased. I have a Bosch Purion display, which tells me estimated mileage left at any given assist level, but that's a pretty inaccurate measurement. Is there anything that will accurately measure the charge used in a battery before or after the ride? It's a removeable bosch battery, so an external device would work.

 

[Sierratim]

Battery voltage is a good indicator of charge;

Measure your battery voltage before and after a ride. The change in 'Battery %' is your usage for the ride. This is of course a function of your battery's nominal voltage; 36C, 48V, etc.

 

[MeDotOrg]

Thanks for the chart. Much Appreciated!

 

[harryS]

I ran across this chart from the endless sphere forum. Shows measured state of charge (SOC) vs voltage for new cells and also after 700 charge cycles on various higher quality cells popular for ebikes. It shows that SOC vs Voltage doesn't change, although the capacity will decrease. The other thing it shows, as opposed to the above chart, is that 50% SOC is close to 3.7V/cell while the above chart says 3.6V.

When my 36V pack is down at 36.0V, it's more like 67% gone, per these numbers. Multiply the cell voltages by 10X, 13X, and 14X respectively for 36, 48, and 62V batteries.

 

[AguassissiM]

@MeDotOrg

You can always install one of these:

Yes I know it looks goofy and takes up a lot of space... I m too old to care...

 

[6zfshdb]

The problem with using voltage to determine power use is, it is not linear and readings will vary as the battery ages.
I use this gauge which measures actual AH used. It can be programmed for the actual capacity of your battery and can be adjusted for capacity loss over time.

AiLi Battery Monitor Voltmeter Ammeter Voltage Current Meter 8-80V 0-100A Auto Car Motor Boat Caravan RV Motorhome - - Amazon.com

AiLi Battery Monitor Voltmeter Ammeter Voltage Current Meter 8-80V 0-100A Auto Car Motor Boat Caravan RV Motorhome - - Amazon.com

www.amazon.com

It reads voltage, real time current draw, AH remaining and % charge remaining. The bar gauge reads out in 10% increments rather than the 20% increments on many other gauges.
Check out this thread to see how to make a case for it and mount to your bars:

Accurate Battery Gauge Project

I've searched in vain for some time now for an accurate, programmable, handlebar mounted battery gauge. Some high end bikes come equipped with this type of gauge and the displays on many others are up-gradable. Unfortunately, the controller on my bike isn't one of them. The battery gauges on...

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