Radrunner top speed gradually lowers with battery drain

[HondaZ50M]

Top speed gradully decreases with battery drain.

Fully charged it'll do 20mph, at 80% 18mph, 60% 16mph, 40% 15mph

Is this normal?

I could understand if battery was getting low.

[santacruzpaul]

Seems to me to be normal for e-bikes, There are video's on YouTube on this subject.

[handlebar]

Top speed gradully decreases with battery drain.

Fully charged it'll do 20mph, at 80% 18mph, 60% 16mph, 40% 15mph

Is this normal?

I could understand if battery was getting low.

An electric motor is like a generator that produces "back EMF" - voltage against the applied voltage. The faster it turns, the more back EMF it produces.

The battery puts out less voltage as it discharges, so it won't turn the motor as fast. When fully charged, mine is also peppier at slow speeds.

[joeliniowa]

That's right, the "ride out" is faster than the "ride back" plus or minus points for wind.