Important Battery Lingo You Need To Know! Things Like Watts And Amps Explained!

When you are looking for a new bicycle battery, charger, or electric bicycle, you will soon come across terms that may not mean much to you. For example, think of Watt-hours, amperes, and capacity. Knowing the meaning of these terms can certainly help you choose the right battery or charger for your electric bicycle! In this article, we explain exactly what the different terms mean, how they differ and why they are important for purchasing a new bicycle battery.  

Watt 

Watt is a unit of power. For e-bikes, this means the energy that the electric motor of your e-bike consumes per unit of time. When people talk about ‘Watt’, it is usually not about the bicycle battery itself, but about the motor. Wat-hours, on the other hand, is interesting when it comes to bicycle batteries.  

Watt-hours (Wh)  

The unit Watt-hours (Wh) indicates how much energy the battery can supply. The higher the Wh value of a battery, the longer you can cycle with an electric bicycle. The Watt-hours are not always mentioned in the product description of a battery, but you can easily calculate this yourself. For batteries, the following formula applies to the calculation of Watts:

for most bicycle batteries:  

Wh = Voltage (V) x Ampere per hour (Ah) 

Take, for example, a Bosch PowerPack 700 Frame Active bicycle battery. This battery has a capacity of 20.7 amps per hour (Ah) and a voltage of 36V. The total capacity of the bicycle battery is then 745.2 Wh (20.7 x 36 = 745.2).   

Ampere hour (Ah) and Voltage (V) 

In product descriptions of bicycle batteries, the capacity of a battery is usually expressed in ampere-hours. Ampere hour is the unit that indicates how long a battery can supply power for 1 hour. For example; a battery with 10Ah (ampere hour) can supply 10 amps for 1 hour. Batteries can vary greatly in Ah, and the Ah value varies between 6.6Ah and 28Ah. The final capacity and price of the battery cannot be measured with Ah alone, and must always be in combination with the Voltage of the battery.  

Voltage, expressed as ‘V’ indicates how much voltage there is at the connection of the battery. The higher the voltage, the fewer amps it takes to achieve the same effect.   

Voltage is mentioned for both our batteries and our chargers. To find the right charger for your bicycle battery, you can therefore look at V-value. To properly charge your battery, the charger must have an output voltage that is higher than the voltage of the battery. So a battery with a capacity of 36V needs a charger of, for example, 42V.  

Capacity 

In product descriptions, there is often referred to the ‘capacity’ of the battery. This is actually another word for Watt-hours (or Ah x V) and is expressed in Wh. So you could say that a certain battery has a capacity of 745.2Wh OR has a capacity of 20.7Ah and 36V. The capacity is the charging capacity of a battery, and how long the battery can provide energy to the motor of your electric bicycle. The higher the capacity of the battery, the more energy can be stored in the battery, and therefore the longer you can cycle with an e-bike.  

The price of a bicycle battery is partly determined by the capacity of the battery. For batteries with a higher capacity you pay a bit more, but then you can enjoy your pedal support for longer.  

Good to know:  

Bicycle batteries with a high capacity are often also somewhat larger and/or heavier than batteries with a small capacity.  

2A/3A/4A Chargers 

There are also different types of chargers to choose from, namely: 2A, 3A, and 4A chargers. This is usually mentioned in the title of the product. The A stands for ampere, just like with ampere hour (Ah). A 2A charger is therefore a charger that can charge your bicycle battery at 2 amps per hour. A 3A charger is slightly higher and can charge 3 amps per hour, and a 4A charger – also called a ‘fast charger’ – can charge 4 amps per hour.  

Do you have a battery with a capacity of 16V and a 4A charger? Then it only takes 4 hours before your battery is fully charged.  

Nm 

Nm has nothing to do with the battery, but with the motor of the electric bicycle. Nm stands for Newton meters of the motor of the e-bike. These Newton meters determine how ‘strong’ the motor of your e-bike is and how fast the electric bicycle accelerates. The number of Nm in e-bike motors usually differs between 20, 30, or 50 Nm. 

We hope this information can help you better understand the different bicycle battery terms and choose the right battery or charger for your e-bike.