Measuring how much battery used on a ride

MeDotOrg

Member
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

Well-Known Member
Battery voltage is a good indicator of charge;

1545991790982.jpg

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.
 

harryS

Well-Known Member
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.

cell capacity vs Voltage.jpg