Are DIY Ebike Battery Repairs Feasible? Exploring Common Challenges and Solutions

The electric bike battery is one of the most important components as it transforms an ordinary bicycle into an electric one. On the other hand, it is also considered one of the most expensive parts of an electric bike, with prices ranging from $500 to $1000 for certain models.

Now, the question arises: Can electric bike batteries be repaired? Considering the cost of the battery and its significance to electric bike riders, it is a logical question to ask.

Can electric bike batteries be repaired?

 

Generally speaking, electric bike batteries can be repaired since their main components, such as the battery cells, BMS board, and wiring, can be easily replaced. Based on this, the battery can be repaired by changing these components.

 

Now let's discuss the most significant issues that can occur with electric bike batteries, their symptoms, and the possible solutions.

1.BMS Board Issues

The Battery Management System (BMS) is responsible for protecting the battery by regulating the flow of current into and out of the battery.

To understand how it works in practice, the BMS board is connected to all the cells in the battery and measures their individual capacities. When one cell discharges, the BMS completely shuts down the battery to prevent any potential damage.

From the functioning of the BMS, it becomes evident that charging or discharging is controlled by the BMS.

Therefore, if you find that the battery has some remaining charge but is unable to charge or discharge, it indicates a problem with the BMS.

 

How to solve the BMS Problems

To resolve BMS issues, there are generally two methods: resetting and replacing (I personally prefer replacement since BMS prices are not expensive either).

 

To reset the BMS, you can follow these steps:

1. Remove the outer cover of the battery.

2. Disconnect the cables connected to the BMS of the battery.

3. Connect the battery to the charger and start charging.

4. During charging, reconnect the BMS cables.

By performing the above steps, the BMS will be reset to its default settings.

Replacing the BMS Board.

BMS Main Cables

There are three main cables connected to the BMS:

 

(P-) cable is responsible for negative discharge to the connector.

 

(C-) cable is responsible for negative charging to the connector.

 

(B-) cable is responsible for the battery's negative terminal connection.

 

Tools Required:

Screwdriver

Soldering iron

Steps for replacing the BMS board:

1. Remove the outer cover of the battery.

2. Desolder the three main cables of the BMS.

3. Disconnect the connector connected to the battery.

4. Install the new BMS in the same position.

5. Resolder the main cables.

6. Connect the connector back to the battery.

7. Test the battery's charging.

If everything goes smoothly, reassemble the battery cover.

 

Important Note: In most cases, BMS damage is caused by faulty battery cells inside the battery. Therefore, it is advisable to measure the voltage of all the cells before reassembling the battery cover to ensure that all the cells are functioning properly.

 

2. Damage to One or More Cells

 

The second most common cause of electric bike battery failure is damage to one or more cells inside the battery.

 

In this case, you will be unable to operate the battery at all.

 

You can identify the damaged cells by individually measuring the voltage of each cell. You will find that most cells have a consistent reading (e.g., 4.1 or 3.8 volts). When you notice a significantly lower reading in a particular cell, that cell is the problem.

 

There can also be visible signs of battery damage that you can observe with the naked eye, such as the presence of black substances or cuts on the battery casing.

 

Note: Replacing battery cells requires specialized equipment to ensure the proper functioning of the battery, so it is best to have it done by a professional.

 

Don't worry, the cost will be minimal since you have already done all the work and identified the defect. All you need is to connect a new battery cell. You won't have to spend too much!

 

3. Wire Disconnection

 

The final major cause of battery failure is the presence of cut or disconnected wires inside the battery, whether it's in the main wiring of the battery or in the wires connected to the battery. This will result in the battery ceasing to function.

 

Usually, this issue occurs due to the battery being dropped or impacted on the ground. If you take good care of your electric bike's battery, you'll be safe from this.

 

To address this problem, simply remove the outer cover of the battery, locate the cut wires, and reconnect them.

 

Then, using a voltmeter, measure the voltage of the battery. If you find that the voltage reading is equal to the capacity of the same number of cells, you can determine the battery capacity using this formula (number of cells * 4.2 volts).

 

Connect the battery to a power source to ensure proper charging, and then close the battery cover.

 

4. Loose Battery Connection

 

When the battery is connected to the electric bike, it can cause damage or breakage to the battery pins, resulting in the battery ceasing to function.

 

You can visually inspect the pins to determine if the issue lies there, and in most cases, the battery will not be properly installed on the bike.

 

To address this issue, you can try modifying the pins using a screwdriver, but make sure to turn off the battery first.

 

Alternatively, you can replace the damaged parts within the battery entirely.

5. Charger Malfunction

 

The reason you are unable to use the battery may be due to a faulty charger rather than a problem with the battery itself. To determine if the issue is with the battery, try charging it with another charger or test the charger itself.

 

You can refer to this article, which provides detailed explanations on how to test an electric bike battery charger.

 

Conclusion

 

In general, electric bike batteries can be repaired by replacing internal cells, the BMS board, or fixing internal wiring.

 

One of the most significant issues that can occur with electric bike batteries is BMS damage, internal cell damage, or internal wire disconnection. Lastly, the battery pins may be damaged due to improper removal of the battery.