Bike Battery Bad? The Load Test

Bike Battery Bad? The Load Test

Another year, another bike. This one is much lighter than the last one, but has terrible range. Let’s dig in.

So I have had 3 ebikes that I have commuted in the winter from home to work. Same route, same weather, etc. The Voltbike Yukon (bike #2) was 750W, rear hub, 48V @ 17.5AH. I would charge it about every 3rd day in winter.

The Biktrix Jugernaut Ultra Beast (bike #3) was 1500W mid drive, 2 x 48V @ 15AH. It was also a super heavy bike. I would charge it about every 3rd day in winter.

Both of these two had 26×4.8 snow tires with carbide studs.

The current bike (Biktrix Duo) has 1000W mid drive, 1x 52V @ 17.5AH, mid drive. It needs to be charged daily or it runs out of juice.

Now, its reasonable to assume I drive all 3 the same fashion. Same amount of assist, same path, same weather, same distance. The current one is by far the lightest, and has the least resistance tires. I would expect it to have the best range (even tho the juggernaut had more watt-hours).

So, time to bring some science. And by science I mean jury-rigged hackery. Now, I don’t have a big enough load tester to discharge @ 1C. The battery is ~1kWh, so 1C would be a 1000W load. Instead I have acquired a 250W load. So, we will discharge at C/5 (20%). This should be very easy on it.

You can see in the photo above the beautiful setup:

  • tailgate of truck
  • old phone set to timelapse
  • digital load
  • 2 keys to a previous bike battery shoved into the receptacle

A 52V battery has a peak voltage of 58.8V, is at 50% capacity at 52V, and is dead somewhere around 46V. Place your bets.

Update, below the results.

2 Responses to “Bike Battery Bad? The Load Test”

  1. Your math seems a bit off. Back of napkin: approx 200W for 4h should be around 800W*h
    Even ignoring the tail, after 3h of over 200W should be well over 600W*h

    • Don’t think so, the voltage drops a lot. Its not a constant 200W, its a constant 4A.

      — edit, suddenly a wild math error. Turns out there are 24 hours in a day, not 14! Updated chart.

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