Why does the battery on my electric bike run out so quickly?
You spent €2,400 on an electric bike. The manufacturer promised you a range of 120 kilometers. But after three weeks in February, you can barely reach 45 kilometers. The indicator drops from 80% to 40% in ten minutes. You wonder if you bought a defective model.
Probably not. Your battery isn't lying, but the range calculator is exaggerating a little. Why? Let me explain.
Written by: Jos Mans | February 10, 2026 | Reading time: 6minutes
About the author: Jos Mans
Jos is a writer and cyclist, most often both at the same time. With thousands of miles under his belt and just as many words on paper, he combines his two great passions: being on the move and telling stories.
Key findings
- Cold weather immediately reduces mileage by 20 to 30 percent: at 5°C, the battery temporarily performs less efficiently due to higher internal resistance.
- tires pressure tires stop-and-go driving don't help either: tires cost 15% more energy, and city driving another 30%.
- Measure your consumption in Wh/km: "it's running out quickly" then becomes a concrete figure: 10 Wh/km = normal, 20 Wh/km = there's clearly something wrong.
The average bike commuter overestimates their range requirements.
Most people who complain about low autonomy make one of these two errors in reasoning.
The first: compare winter range with the manufacturer's summer promise. Bosch tests at 20°C, with no wind, on flat ground, in eco mode, with a 70 kg cyclist. You weigh 85 kg, you ride in tour mode, it's 5°C and the wind is blowing at 25 km/h from the northwest. Result: 40% less range, very easily.
The second mistake is more subtle. A 500 Wh battery seems significantly smaller than a 625 Wh battery. The actual difference: 10 to 15 kilometers in normal use. The additional cost: €300 to €400.
For a typical bike commuter who travels 25 km a day, this difference is insignificant. You recharge every night anyway. But psychologically, you feel like you're "missing out on something."
The fear of autonomy is marketing, not mathematics. If you know how many Wh you consume per kilometer, that fear quickly disappears:
- 500 Wh battery at 10 Wh/km = 50 km
- At 12 Wh/km = 42 km
- Urban journeys with many stops: 15–20 Wh/km = 25 to 35 km
So you don't have a technical defect, but unfavorable conditions.
Manufacturers aren't really helping
Let's be honest. Gazelle advertises "up to 150 km of range" for its Ultimate C380 with a 500 Wh battery. In small print: "based on ideal conditions." Shimano no longer publishes range figures, only a link to a calculator with 23 variables. Yamaha simply says, "it depends on usage."
And that's true. They know that any figure becomes false as soon as the wind is no longer favorable.
What manufacturers don't tell you about their tests
Bosch is testing its motors with its Range Assistant, which claims a range of up to 200 km with a 625 Wh battery. This is not a lie, but a strategic choice.
Their protocol:
- eco mode
- speed of 60–70 rpm
- no stoppage
- 64–72 °F
- 0–2% slope
In other words: a perfect Sunday morning in June, out in the country.
In real life, you ride in tour mode at least, because eco mode seems too sluggish. You stop at every traffic light. It's October, and it's raining. Your tires at 3 bars instead of 4.5 because it's more comfortable. You have 5 kg of groceries in your panniers. Each factor costs you 5 to 15% of your range.
Shimano is more honest. Their Steps systems no longer give an estimated range, only a percentage. Less disappointment, but more difficult planning. Their manual clearly states: "Climbs, headwinds, and temperatures below 10°C significantly reduce range." In practice, "significantly" means 30 to 50%.
The industry hides behind variables, but the math is simple: more weight, more wind resistance, more stops, cold battery = more Wh/km.
- 500 Wh battery at 8 Wh/km = 62 km
- At 16 Wh/km = 31 km
It is not defective: there is simply more resistance.
Diagnosis: faulty battery or unrealistic expectations?
Here's how to tell the difference between a temporary dip and a real problem.
Step 1: Check the conditions
If the temperature is below 10°C, you immediately lose 15 to 25% of your range due to increased internal resistance in the cells. Shimano recommends keeping the battery indoors before setting off. Gain: approximately 10%.
Step 2: Check the tires pressure
Bosch specifies this in its manual: for maximum range, ride with the maximum permitted pressure. Example: 3.5–4.5 bar. Most people ride at 3.5 bar for comfort. Difference in rolling resistance: 12 to 15%. Over a distance of 60 km, this represents a loss of 8 to 10 km.
Step 3: Calculate your Wh/km
Note your starting percentage, ride 20 km, note the ending percentage. Example: from 80% to 60% = 20% consumed. 500 Wh battery × 20% = 100 Wh used / 20 km = 5 Wh/km. Excellent result. Above 12 Wh/km on flat terrain and under normal conditions, something is wrong.
Common mistakes that cause Wh/km to skyrocket
- Starting in too high a gear (the engine is straining unnecessarily)
- Constantly riding in high assistance mode (turbo mode consumes up to twice as much as tour mode)
- Many stops/restarts (the city is a range killer)
- tires
- Squeaky brakes
- Too much weight on board
Each factor costs 5 to 20% of battery life.
If your tires properly inflated, it's not freezing, you're driving economically or on flat terrain, and your consumption still exceeds 15 Wh/km, then there may be a technical problem.
Please check :
- battery contacts (oxidation = loss of efficiency)
- engine noises (bearings rubbing)
- brakes (must release completely)
Or simply: a battery that is older than expected, with a capacity of less than 70%.
Six practical solutions that work
- Keep the battery indoors in cold weather (Yamaha recommends 41–95°F for charging).
- inflate the tires the upper limit
- start more gently in a lower gear
- use a lower assistance mode when possible
- remove unnecessary luggage
- check that the brakes are not rubbing
Summary
| Factor | What's happening | Impact on autonomy | What should I do? | Normal or a problem? |
|---|---|---|---|---|
| Température basse (<10 °C) | Higher internal resistance, voltage drops faster | −20 to −30% | Battery indoors (60–68°F) before departure | Normal seasonal effect |
| tires pressure | Greater rolling resistance | −10 to −15% | Inflate to the upper limit | Common mistake |
| Stop-start city traffic | Repeated acceleration = power peaks | −20 to −30% | Smoother acceleration, lower assistance | Normal in the city |
| High assistance (Turbo) | Maximum constant assistance | Up to 2× more Wh/km | Use Tour/Eco mode as much as possible | Choice of use |
| Additional weight | More mass = more energy | −5 to −15% | Take only what you need | Normal effect |
| Brakes rubbing / mechanical resistance | Constant friction | −10 to −25% | Check for free rolling | Technical issue |
| Worn-out battery | Lower effective capacity | Sustained reduced range | Capacity test, replacement | Problème <70–75 % |
The math doesn't lie.
A battery that "discharges too quickly" is, in most cases, simply a battery that obeys the laws of physics. More resistance = more consumption.Less resistance = less consumption.
Manufacturers advertise battery life under conditions of minimal resistance. You ride in conditions of maximum resistance: cold, wind, city traffic, heavy panniers, tires .
The difference between 60 km and 40 km is not a defect. It is a calculation.
Measure your Wh/km. Adjust your expectations or conditions. The battery doesn't change, but tires pressure, temperature, and assistance mode do.
If your range remains structurally low despite optimal conditions, then yes, there is a problem. Otherwise, in 8 out of 10 cases, the answer is simple: winter, city driving, turbo mode. Fix these three points and your range will double.
The battery works. The motor pulls. The rest is math.
FAQ
Why does my battery drain much faster in winter?
Cold temperatures increase the internal resistance of lithium-ion cells, temporarily reducing performance by 20 to 30% below 5°C. Bosch and Shimano explicitly mention this. Solution: store the battery indoors at 15–20°C and install it just before departure. Immediate gain: 10 to 15%.
How many kilometers is it normal to get with a 500 Wh battery?
On flat terrain, in tour mode, at 15–20°C, with tires pressure: 60 to 70 km. In the city with lots of stops: 40 to 50 km. In cold weather, with wind, hills, or turbo mode: 30 to 40 km. The advertised 100–120 km is only achievable in perfect conditions.
How can I tell if my battery is worn out or if it's just the conditions?
Measure your consumption in Wh/km over several trips. Anything above 12 Wh/km on flat terrain and under normal conditions is suspicious. A rapid drop in percentage in cold weather when starting up is normal. If the range remains low in summer, on flat terrain, in eco mode and with tires , a capacity test is recommended.
Can I extend the life of my battery?
Yes. Shimano recommends storing the battery at 70% (not 100%) indoors, between 10 and 20°C, and recharging it every 6 months. Bosch recommends avoiding long periods at 0% or 100% and staying between 20 and 80% on a daily basis. By following these rules, a battery will last for 800 to 1,000 cycles instead of 500–600, giving it an extra 3 to 4 years of life.