Measure Your Battery's Real Capacity on a Test Ride

Why this happens

Displayed range is an estimate that changes with riding style, temperature and the vehicle's software. Measuring the distance ridden over a known drop in charge, then measuring the energy needed to refill the pack from the wall, gives you a practical capacity figure. Repeating the same test every few months shows how your battery is ageing.

What you need

Step by step

1. 1

   Prepare a fair test

   Set tyre pressures to the manufacturer's figures and choose a route you ride regularly, ideally a loop you can repeat. Pick a day with normal weather and plan to ride solo with your usual load. Test results are only comparable if the conditions are similar, so write down the temperature, riding mode and any luggage.

2. 2

   Charge to full and let it settle

   Charge fully with the original charger and leave it on until the charger indicates complete, so the BMS has a chance to finish. Unplug, note the display charge level (it should read 100 percent) and the odometer. Reset a trip meter if you have one.

3. 3

   Ride the route normally

   Ride in your normal mode, obeying speed limits and traffic rules. Do not try to ride unusually gently or aggressively; the aim is a realistic figure. Ride until the display shows around 20 to 30 percent remaining. Do not run the battery to empty for the test; deep discharges add stress and risk leaving you stranded.

   Tip: Stop at regular points to note distance and charge level; the log shows whether the gauge is linear.

4. 4

   Record distance and charge used

   At the end, note the distance ridden and the percentage used. For example, if you rode 50 km and used 75 percent of the gauge, a rough full-gauge range in those conditions is 50 divided by 0.75, about 67 km. This is your practical range estimate, which already includes your riding style and route.

5. 5

   Measure the recharge energy

   Let the battery cool for at least half an hour. Plug the charger into the energy meter, the meter into a properly earthed wall socket, reset the meter and charge back to full. Record the kWh shown when the charger indicates complete. This is the energy taken from the wall, which includes charger losses, so the energy actually stored in the pack is somewhat less.

6. 6

   Calculate Wh/km and estimated capacity

   Divide the wall energy in Wh by the distance ridden to get wall-to-wheel Wh per km. Then divide the wall energy by the fraction of gauge used to estimate the wall energy for a full charge. Compare this with the battery's rated kWh from the label; the wall figure will be a little higher than the rated pack energy on a healthy battery because of charger and charging losses.

7. 7

   Repeat and track

   Do the same test every three to six months on the same route in similar weather. Log the date, distance, gauge used, recharge kWh and conditions. A gradual reduction over a year or two is normal ageing. A sharp drop between two tests, or a gauge that falls suddenly near the end, is a reason to ask the service centre for a battery diagnostic.

How to tell it worked

You have a real-world range figure, a wall-to-wheel Wh/km figure and an estimated full-charge energy for your pack, logged with conditions so you can compare future tests.

Questions