Differences Between E-Bike Battery and Battery Pack

E-bikes are the big trend on two wheels. Ride through the city with minimal effort, improve your health, and protect the environment. These are the main arguments for the electrified bicycle. To ensure you're always ready to ride, a second battery is recommended. These are now available in every suitable shape and various capacity sizes.

But what do you do if there’s a defect? A new battery is often very expensive. Isn't a suitable battery pack enough? With it, you can save up to 50% of the cost compared to a complete battery. But you’ll need some specific technical knowledge and skills for the conversion. I'll show you exactly what those are below.

The complete battery

The typical e-bike battery consists of a plastic casing with an integrated charge indicator and the contact point for power delivery to the bike. Many batteries also have a separate charging socket. Ideally, the casing also has a handle – for easy removal and insertion of the battery. No special technical knowledge is required for use and replacement. Except for a bit of strength – the batteries are a bit heavy.

The battery pack

Battery packs or cell blocks are not designed for quick replacement. They are only worth buying if you want to replace the defective cell block of your e-bike battery.

The blocks consist of individual battery cells that are connected in parallel and in series to achieve higher voltage and capacity. Parallel connection increases capacity (Ah), and series connection increases voltage. Both are essential for e-bike batteries.

The individual cells of the battery pack are glued together and additionally fixed with either plastic film or cable ties.

A typical e-bike battery

A typical battery pack/cell block for e-bike batteries

The battery pack consists of 50 individual cells: 10S5P = 10 serial and 5 parallel. The cell block thus delivers 36 V (10 * 3.6 V per cell) and 10 Ah (5 * 2 Ah per cell).

Details

Typically, e-bike batteries have a voltage of 36 volts and a capacity of 10 Ah (10,000 mAh). To achieve this battery performance, individual cells with 3.6 volts and 2 Ah are connected. First, 5 cells are connected in parallel, resulting in a capacity of 10Ah (5 * 2 Ah = 10 Ah). Then, 10 of these 5-cell blocks are connected in series to achieve a total voltage of 36 volts (3.6 V * 10 = 36 V). The resulting battery pack consists of 50 individual cells (technical info: 10s5p = 10 serial and 5 parallel). However, no wiring or charging electronics are soldered or attached. These important components are found only in the casing of the e-bike battery and are not included with typical battery packs. Please keep that in mind when ordering.

The assembly

To give you a better idea of how an e-bike battery is constructed, I’ve created a small photo series in which I disassemble a battery. This allows you to take a closer look at the individual steps and especially the interior.

The cell block of this e-bike battery is in a plastic housing, held together by 4 screws and some plastic clips.

After opening, the charging electronics including the wiring are revealed.

The contact socket alone is soldered with 5 wires.

Various wires lead from the circuit board to the cells. Due to the number of wires, they are secured with tape.

You can clearly see the cells arranged in 10-cell blocks and the wiring. Due to the shape of the casing, a uniform rectangular layout is not possible.

The circuit board with the electronics is precisely placed on the cell block.

The circuit board is attached using clips, making it easy and quick to remove.

Due to the special construction, the arrangement and wiring of the individual cells is more complex, making it harder to replace the cell block. The fine soldered wires are visible here as well.

As you can see, the inside of an e-bike battery is quite complex and replacing the cell block requires at least soldering tools and a good understanding of electrical engineering.

Here you’ll find some useful videos and forum posts on e-bikes and DIY:

But please remember that such a conversion or replacement is always done at your own risk. Only carry out such work if you have the right soldering tools, know-how, and experience with electrical systems.

Do you have any questions or comments on this post? Then feel free to write your thoughts and suggestions in the comments.

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