USING CIRCUIT BREAKER OR FUSE IS ESSENTIAL FOR SAFE AND PROPER FUNCTIONING OF YOUR BIKE

A circuit breaker and a fuse both serve the essential function of protecting electrical circuits from overload or short circuits. Every controller on the market needs to be paired with the circuit breaker or fuse to ensure its proper and safe functioning.

Removing/deleting the circuit breaker or fuse on an electric motorcycle can lead to damage to your bike and property and will void the 2-year warranty of Torp products.

The following instructions are general safety measures that apply to electric motorcycles in general. As each setup is different, please consult professionals for specific advice.

CIRCUIT BREAKER

Stock SurRon Light Bee / Talaria circuit breaker is model DZ47-125, rated at 100A continuous. This circuit breaker can easily handle 20-25kW of peak power.
In case your stock circuit breaker is tripping due to the increased power or due to longer periods of high power overload, we suggest using a circuit breaker model DZ47-125, rated at 125A continuous.
Please check the circuit breaker chart to see how much power a stock SurRon Light Bee / Talaria circuit breaker can handle.

How can a 100A circuit breaker handle 300A? That makes no sense, right?

Actually, it does—once you understand how circuit breakers work.

A 100A circuit breaker is designed to handle 100 amps continuously without tripping. However, it can withstand short bursts of much higher current, such as 300A for up to 15 seconds, depending on its thermal and magnetic response curves.

This short-duration tolerance is more than enough for high-power e-bikes, like 20kW setups, where such peaks are common during hard acceleration or hill climbs. That’s why a properly rated breaker remains a safe and smart choice—even in powerful builds.

FUSE

In case you are using so much power even a circuit breaker rated at 125A continuous can`t handle, you should replace the circuit breaker with the fuse.

How to know what fuse to select?

-It is essential to install the fuse rated for higher voltage. The fuse rated at 12-36V is not suitable as it probably won`t protect your system in case of a short circuit.

-You should choose the fuse based on the peak battery current, but avoid matching it exactly. For example, if your peak current is 500A, don’t use a 500A fuse — that would be too high. A fuse rated that high offers no protection and is essentially the same as not having a fuse at all.

Search for the fuse chart when selecting the fuse so you can make an informed decision. For optimal protection, we suggest selecting a fuse rated for 150-250A.

Why Do We Prefer Circuit Breakers Over Fuses?

Circuit breakers, unlike fuses, provide two levels of protection:

  • Thermal protection
  • Magnetic protection

Magnetic protection reacts instantly to very high currents, such as those caused by a short circuit, and trips the breaker immediately.
Thermal protection, on the other hand, responds to prolonged overloads by detecting heat buildup and tripping the breaker once a certain temperature is reached—this takes more time.

Fuses offer protection similar to the thermal function of a breaker. They melt when excessive current generates enough heat, interrupting the circuit. However, fuses do not provide magnetic protection and must be replaced once they blow, unlike circuit breakers, which can simply be reset.

IF YOU ARE UPGRADING BATTERY WIRING TO HIGHER GAUGE WIRES OR QS8 CONNECTOR

In this case, it is essential to reinstall the circuit breaker as it was on the stock wiring. See the photo and follow the short instructions video.

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TORP CONTROLLERS AND PRE-CHARGE CIRCUIT

Torp controllers do not require a pre-charge circuit for protection. However, you can use the pre-charge in the form of a resistor or QS8 connector which has an integrated pre-charge circuit. This will protect your connectors and circuit breaker from sparking when connected.

The precharge circuit is not a replacement for a fuse or circuit breaker as it has a completely different purpose.

BATTERY BYPASS IS NOT RECOMMENDED

Torp Controllers are designed to communicate with the stock battery’s BMS, enabling enhanced power without the need to bypass the battery. Bypassing your battery results in the loss of crucial protection mechanisms and does not significantly increase power output.

PROTECTION SETUPS IN STOCK E-BIKES

  • SurRon Light Bee: BMS overcurrent protection + circuit breaker
  • Talaria MX3/MX4: BMS overcurrent protection + circuit breaker
  • Talaria XXX: BMS overcurrent protection + internal fuse (inside the battery)
  • Talaria MX5: BMS overcurrent protection + internal fuse (inside the battery)
  • SurRon Ultra Bee: BMS + fuse located on the battery, under the rubber cover

As you can see, every stock e-bike comes equipped with both a BMS and either a circuit breaker or a fuse—and there’s a good reason for that.

Even when upgrading or modifying your bike, having a properly rated fuse or circuit breaker, along with a non-bypassed BMS, is essential to ensure the reliable and safe operation of the entire system.