How To Repair Electric Bike Batteries: The SIMPLE Method

by | Apr 19, 2019 | How to Guide, Tuning & Maintenance | 0 comments

Nowadays, advancements in technology mean that e-bike batteries can deliver more power and last longer than ever before. However, just like any other mechanical component these units can sometimes become damaged due to normal wear and tear. In such situations, it’s important to know how to repair electric bike batteries so that you can continue riding your e-bike without inconvenience.

Electric Bike


What’s an E-bike Battery and How Does it Work?


Most electric bicycles use the lithium-ion battery type, which is unique from the lead acid 12-volt battery that’s commonly found in vehicles. Unlike their lead-based counterparts, these e-bike batteries are lighter weight and also have the ability to hold a charge for significantly longer periods. 

However, these power cells also have a limited lifespan, just like any other type of battery. They usually lose their capacity after every full charge and discharge, which is a phenomenon commonly known as a ‘cycle’. Generally, the more cycles an e-bike battery is able to complete, the greater its capacity to degenerate. Consequently, your bicycle’s assisted cycling range may also decrease with time as the power cell degrades gradually. 

Nevertheless, this slump in battery performance won’t occur suddenly over a few days or weeks. It typically happens over a much longer period until you slowly start to notice changes. Sometimes, it can take several months or even years before you notice a problem that’s affecting your battery and needs to be fixed. 

However, there are still a few electric bicycles on the market that run on lead energy cells. These lead batteries may weigh as much as 5.5kgs for a single unit, with the capacity to deliver only 5Ah of power, compared to a lithium-based battery which at only 1.2kgs can deliver a power capacity of up to 8.8Ah. 

Similarly, different e-bike batteries have their own unique levels of durability depending on the manufacturer. Generally, larger lithium-ion batteries have a longer lifespan than their smaller counterparts, since they are less likely to expend a high portion of their power in a single go. This helps to improve the battery’s longevity.


Factors That Cause E-bike Batteries to Fail

In most cases, electric cell damage occurs due to 4 main factors: overheating; overcharging/high-voltage; deep discharge; and high discharge/charge current. When a battery experiences any of these conditions for a long period, it is manifest in the bike’s decreased assisted range. Sometimes, in worse-case scenarios, the machine may even be impractical to operate since the distance it can cover is negligible.

A lithium-ion bike battery may suffer if left outside in sun for extended periods of time and exposed to high environmental temperatures. It may also suffer if the cell’s own internal temperatures rise beyond what it can normally accommodate, which typically happens when the cell is left plugged in for a long time after reaching its full charge. In both cases, the battery may swell and become ineffective due to changes in the unit’s chemical composition and exposure to abnormally high temperatures. 

During overcharging, the battery’s voltage capacity steadily rises and surpasses the safety ceiling, commonly known as max voltage. When this happens frequently, the cell unit eventually loses its capacity to keep a charge and becomes dysfunctional. The more time a battery spends on the charger after reaching full capacity, the higher the chances of a negative chemical reaction being provoked inside the cell. Basically, its internal resistance capacity will slowly build up and once it reaches a critical level with time, the lithium-cell is rendered useless.


Some e-bike batteries have a built-in safety mechanism known as battery management system (BMS), which helps to prevent overheating. Not all of them have this particular function, however, and can therefore easily be affected by temperature fluctuations. As a safety precaution, it’s always recommended that you unplug your e-bike after a complete charge in order to avoid overheating. 

Similarly, extreme cold such as is commonly witnessed in winter can damage a lithium-ion bike battery, since these units are typically not designed for use in cold weather environments. When a battery is frozen, it means that the vital chemical reactions necessary for it to operate and provide power won’t be functional. Even if the cell luckily jump starts in harsh conditions, it still won’t be able to reach full charge capacity and provide sufficient levels of power to propel the machine for longer periods of time. 

Furthermore, a battery can fail due to deep discharge, which occurs when the battery is using the power cells at maximum capacity more frequently. Generally, riders who regularly drain their lithium batteries down to 5 or 10% before recharging will wear it at a much faster rate. Plus battery life usually improves when the operator avoids deep discharge. This means you should charge your e-bike when it has between 40 and 80% remaining battery power, rather than waiting until the charge is at 5% and then quickly powering it to 80% before using the machine again. 

Likewise, high discharge should also be avoided, which occurs when you’re spending a huge amount of the battery power over a short duration of time. While this can temporarily help to increase your e-bike’s acceleration levels, it also has a negative effect on the battery’s lifespan.


How to Repair an E-Bike Battery

If your electric bike’s battery is no longer working due to any of the reasons mentioned above, then there are various steps you can take to repair the cell unit and make it functional again.

tools for e-bike maintenance

The process is quite simple and can be done at home by anyone. You’ll require some tools and accessories, which include a multi-meter, wire cutter, electric tape and an old e-bike battery from a nearby repair shop. Here are the steps you should follow:

Step 1

Open the old lithium battery from the repair shop, while taking care not to damage the delicate battery box found inside, since it will be used later on in the repair process.

Step 2

Remove a total of 6 individual cells from the battery, which are connected in a 2-2 parallel format. While doing this, ensure that you don’t cut the parallel link between these cells, only the series connection.

Step 3

Take out a multi-meter tool and assess the old battery’s voltage. Generally, if the reading is at 10.8 or above it means the volt batteries are in good condition, but anything below that means that the cell is a bad. You can proceed to do repairs with these cells, but if they aren’t in good enough condition then you can always get lithium cell replacements from a nearby e-bike dealer.

Step 4

Connect the cells, which are ready in a series format, using a piece of wire. Once they are attached to each other, the overall voltage of the entire battery pack should be between 36- 42 volts.

Step 5

Next, open your e-bike’s damaged battery and throw away the cells that are no longer useful, but keep the circuit intact. Also take extra precaution not to destroy the battery box while opening the e-bike battery.

Step 6

Attach the circuit to the lithium battery pack using a couple of copper wires. On the cell, you’ll see 4 wires emanating from the circuit, the longest of which is negatively charged. Similarly, the battery-pack will also have 4 wires: 3 are positively charged and 1 is negative.

Step 7

Recheck the circuit connection before packing the battery back into its housing. To do this, you’ll have to attach the battery circuit to the e-bike and push the power button to see whether it’s operational or not. If there’s no electrical reaction after the button has been pressed, don’t stress out. Simply connect the charger to the bike for 5-10 minutes before removing it again. In most cases this should solve the problem.

Step 8

Finally, gently put the battery and circuit back into the e-bike’s battery box. You can use some adhesive, such as tape or super glue, to ensure the battery-box joint fits tightly.


Safety and maintenance tips

Most e-bike batteries are durable equipment that can last for many years with proper care and maintenance. Even after doing your repairs it’s still important to take good care of your lithium-cell unit so that it can continue powering your bike for longer.

One of the ways to do this is by being mindful of the amount of time it typically takes you to charge your battery. Similarly, always ensure that the cell is kept in a cool environment away from excessive heat or cold. Additionally, if you’re planning to put the bike away for a long duration of time, such as over the holidays, find a trickle charger that can constantly keep the charge at 50% during this period, to prevent the cell from going totally flat or overcharging.

For e-bike owners, it’s also recommended to have your batteries and other components of the machine regularly serviced by an expert. This way, you’ll be able to detect problems before they arise and become costly to fix. When properly maintained, e-bike batteries can last for between 5-10 years without requiring any major repairs or replacement.

To summarize, most electric bike batteries are made from lithium-ion cells that can become damaged due to overheating, overcharging, high discharge or deep discharge. In ‘How to repair electric bike batteries: The SIMPLE method’, the steps you can take to repair the damaged battery and get it working again are outlined simply and clearly. Just follow the guidelines mentioned above.

Don’t forget to pickup the right tools for the job, if you don’t already have them;

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