Fatbike cuts out when accelerating, hitting bumps, or in the rain: causes
By the Sache Bikes workshop · updated 18-10-2026
If your fatbike cuts out while riding, the cause is usually a loose or dirty contact (battery moving in the holder, worn battery lock, loose connector) or a battery that sags under load when accelerating or going uphill. First, check whether the battery is securely fastened and whether the connectors are clean and dry. If that doesn't work, have it repaired in The Hague or Zoetermeer, often on the same day.
In short
- Cutting out over bumps almost always indicates a loose contact: battery, battery lock, battery holder or connector.
- Cutting out when accelerating or going uphill more often indicates a battery that can no longer handle the power demand.
- Cutting out in or after rain: moisture in a connector, the throttle, the display or the controller.
- Assistance stopping around 25 km/h is not a fault; that is the legal limit.
- Never open the battery yourself; fault investigation costs €30 and is waived if we perform the repair.
Pay close attention to when the bike cuts out: does everything cut out (including the display) or only the motor? During a shock, under high power, or randomly? That will point you in the right direction.
Most common causes
Battery is loose in the holder or the battery lock is worn
This is the classic cause of cutting out over speed bumps, curbs and cobblestones. If the battery has a little play, the contact points lose contact for a moment with every shock and the bike switches off; sometimes the display turns back on immediately, sometimes you have to restart. Cause: a worn battery lock, a damaged battery holder or cover, or dirty contact points.
Loose or oxidized connector in the wiring harness
There are several connector connections between the battery, controller, display, motor and sensors. A connector that is partially loose or has had moisture and dirt get into it will have intermittent contact. The problem is often at the head tube, where cables bend with every steering movement, or at the motor cable on the rear axle.
Battery sags under load
Does the bike cut out mainly when you accelerate hard, ride uphill or carry a heavy load, while it rides well on a flat road? Then the battery can no longer supply the required current: the voltage drops briefly and the controller switches off for protection. This happens more often with an older battery and in the cold. Causes are a depleted battery, a loose or broken intermediate cable from the battery to the controller, or a faulty battery.
Moisture after rain or cleaning
Water in the throttle, the light button, the display or a connector can cause a short circuit or an error message, causing the system to switch off. Once it dries, oxidation often remains and the problem returns. Also read fatbike got wet: water damage.
Brake sensor or controller
A brake sensor that makes intermittent contact interrupts the motor as if you were braking; the display then stays on. A controller that gets too hot or has an internal fault can also switch off, but this happens less often than a contact problem. Read controller fatbike broken: symptoms.
No fault: stopping around 25 km/h
Does only the assistance stop as soon as you ride around 25 km/h and return when you go slower? Then the bike is working exactly as it should. A pedal-assisted bike in the Netherlands may assist up to a maximum of 25 km/h, with a motor of maximum 250W. Read more about this on fatbike rules.
Check yourself: step by step
- Charge the battery completely with the original charger and try the same ride or hill again. If it no longer cuts out, the battery was probably too low for the power demand.
- Turn off the bike, remove the battery and look at the contact points in the holder and on the battery. Do you see dirt, green residue or discoloration? Then do not perform your own repair on the battery, but have it checked.
- Put the battery back, lock it, and try to see if it can still move. Play means: check the battery lock, holder or cover.
- Turn on the bike and carefully move the handlebars from left to right and then the cables at the head tube. If the display cuts out, you have found a bad contact.
- Squeeze both brakes a few times and release them. If the assistance does not return immediately, a brake sensor may be stuck.
- Note any error code and when the cut-out occurs; that speeds up the diagnosis.
Safety: never open a battery and do not try to repair battery cells yourself. Do not charge a damaged, swollen or overheating battery; bring it to the workshop.
When to go to the workshop?
Go to the workshop if you cannot find a clear cause after the above steps, if the battery has play in the holder, if you see burnt or oxidized contacts, or if the bike cuts out unexpectedly in traffic. In the workshop we measure the battery under load, check all connectors and contact points, and test the brake sensors, the controller and the wiring harness. After the repair, we set the display and the controller to the legal 25 km/h.
Get it repaired in The Hague or Zoetermeer
Cutting out is often difficult to reproduce. That is why we start with fault investigation, after which you will hear exactly what is wrong and what it will cost.
| Repair | Estimated price |
|---|---|
| Investigation costs (waived with repair) | €30 |
| Replace battery holder | €85 |
| Replace battery cover (incl. drilling) | €90 |
| Replace brake sensor | €25 |
| Replace wiring harness | €125 |
| Replace original controller | €150 |
Estimated prices incl. VAT and installation, excluding any parts unless otherwise stated. The investigation costs of €30 are waived if we perform the repair. If more is needed, we will discuss it first: we never do anything without your approval.
You can find us at Calandkade 44-45, 2521 AA The Hague (Tuesday to Saturday 10:00-18:00) and at Philipsstraat 3B in Zoetermeer (Monday to Saturday 10:00-18:00). If you bring the bike in the morning and the part is in stock, it is usually ready the same day. We repair all common brands, such as Ouxi, Qmwheel, 7GO, RSE, AGM, Windgoo and Koolux, even if you did not buy the bike from us. Home repair is also possible, excluding call-out costs. Replacing a wiring harness can sometimes take 1-2 working days; you will be informed in advance.
More information per repair:
- Have a fault investigated: The Hague or Zoetermeer
- Replace battery lock: The Hague or Zoetermeer
- Have battery checked: The Hague or Zoetermeer
- Replace wiring harness: The Hague or Zoetermeer
- Replace controller: The Hague or Zoetermeer
Book a time directly? Choose your repair on make an appointment: you will see the total price immediately and send your request via WhatsApp. You can also call or WhatsApp: +31 85 060 9232.
Order parts yourself
If you already know what is broken, you can also order the part separately. Look at battery locks, batteries, wiring harnesses and controllers, or in the complete overview of fatbike parts. We deliver in 1-3 working days (€8.95, free from €125) or you can pick up for free in The Hague or Zoetermeer. Not sure which part fits? Send a photo of the part and the model of your bike via WhatsApp.
Does your bike not turn on at all? Then read fatbike does not turn on.
Frequently asked questions
Why does my fatbike cut out when I ride over a speed bump?
Almost always due to a loose contact: the battery has play in the holder, the battery lock is worn, or a connector is not properly fastened. During a shock, the power cuts out briefly and the bike switches off.
My fatbike cuts out when accelerating, is my battery broken?
That is possible. A battery that sags under high power demand causes the controller to switch off. First charge it fully and try again. If it still happens, have the battery tested under load before buying a new one.
Can I open the battery myself to repair a contact?
No. Opening a battery is dangerous and can cause a fire. Always have battery problems checked in the workshop.
Does my bike cut out because of rain?
Moisture in a connector, the throttle or the display can cause the system to switch off. Let the bike dry inside and have it checked if the problem returns, because moisture causes oxidation.
The assistance always stops around 25 km/h, is that a fault?
No. A pedal-assisted bike in the Netherlands may assist up to 25 km/h. Above that, the motor deliberately stops.
How much does it cost to have cutting out investigated?
Fault investigation costs €30. That amount is waived if we perform the repair. You will hear what it costs before we start.
How quickly will my bike be ready?
Most repairs are ready the same day if you bring it in the morning and the part is in stock. A wiring harness or larger job can take 1-2 working days.