When your electric bicycle needs a new battery, you have several options. It may take some time, but electric bicycle batteries do degrade over time. If your device is old and worn out, here are various choices to consider. Following the latest industry recommendations, which suggest replacing defective or scrap batteries with "authorized technically identical batteries," may not always be practical.
Batteries are the most expensive consumables on an electric bicycle, and replacing a battery typically costs several hundred pounds.The good news is that the quality of electric bicycle batteries is generally much better than in the early days of the industry. A two-year warranty is the minimum industry standard today, and the lifespan of high-quality electric bicycle batteries should be longer than that.
The bad news is that even with frequent use, electric bicycle batteries will eventually need to be replaced.
Option 1: Replace the battery within the warranty period
Electric bicycle batteries can fail in two main ways:
1. They may become unable to charge or provide power to the motor due to issues like faulty connections or a malfunctioning Battery Management System (BMS) chip.
2. Over time and repeated use, they may gradually lose capacity to the point where the range they provide becomes impractical. All lithium-ion batteries degrade with repeated use and charging. This, in itself, is not a fault, but it does mean that even the best electric bicycle batteries have a limited lifespan.
This is an important distinction because different battery warranties cover different battery faults. For example, ChamRider guarantees their own branded batteries to have at least 60% of the original charging capacity after 1,000 charge cycles . It is the dealer's job to determine the remaining battery capacity using diagnostic software. It widely quotes a guarantee of at least 60% of full charging capacity or 500 charge cycles within two years (whichever comes first) – although I was unable to find this information on their website.
However, many other companies may simply stipulate a two-year warranty. If your battery completely fails within two years, this should provide a clear solution, but if the available capacity drops significantly within that period, it may trigger various semantic debates.
Considering all the above factors, it is best to obtain as detailed a written battery warranty as possible from the retailer at the time of purchase. It must be said that finding a clear and detailed battery warranty on the websites of electric bicycle companies is a rather challenging task.
When does a battery degrade to the point of needing replacement?
By using an inline energy meter (such as this one), you can get a very approximate understanding of the capacity of your electric bicycle battery.
First, make sure your electric bicycle battery is completely depleted by using it until the battery is empty. You should know its rated capacity in watt-hours (Wh) – for more detailed information, refer to our battery article.
Now, charge it back up to full but use the inline power meter to measure the watt-hours consumed from start to finish (i.e., after the battery is fully charged).
Not all the electricity consumed by the meter goes into the battery. For example, the transformer that reduces the voltage from 240V to the voltage required by the electric bicycle battery is inefficient and loses some electricity.
Transformers vary, but a very rough working assumption is that 80% of the power from the socket ends up in the battery.
It's best to repeat this exercise a few times to get an average reading. Clearly, this method has its limitations, but it should at least indicate any very significant shortcomings in the battery's capacity and allow you to monitor it over time. If you notice a decrease in the battery's range, it can be used to help quantify the suspected performance decline.
Option 2: Purchase a like-for-like replacement
If your battery is out of warranty, the next logical step is to purchase a like-for-like replacement. Even for electric bicycles that are a decade or more old, it is often still possible, particularly for models equipped with high-quality motor systems from brands like Bosch, Shimano, Yamaha, and Brose.
The industry advice is to only replace with a battery from the same manufacturer and with identical specifications. There are good reasons for this – the battery, controller, and motor are all designed to work together safely, and using a "non-original" replacement pack may introduce uncontrolled risks.
That being said, you can choose to upgrade to a larger capacity battery offered by the same manufacturer. Some Bosch and Shimano batteries of different capacities are explicitly interchangeable.
If your battery is out of warranty, the next logical step is to purchase a like-for-like replacement. Unfortunately, this is not always an option. Electric bicycle technology is constantly evolving, and older batteries may no longer be in production.
Option 3: Refurbishment
If your product is out of warranty and direct replacement is not possible, the next obvious step is repair or "rejuvenation" (replacing the internal cells of the battery with new ones). Rejuvenation undoubtedly carries risks, especially if you use a non-professional company, so choosing the right place for rejuvenation is crucial.
As we reported in February, the industry view expressed by CONEBI is that only original OEM-certified batteries should be used as replacements for electric bicycles. This is certainly the ideal choice for obtaining high-quality replacements, but it is often simply not possible for older electric bicycles.
Hannes De Jong runs Heskon, a leading electric bicycle recycling and repair service in Europe. He acknowledges the concerns raised by CONEBI but believes that with the maturity of the industry, refurbishment may be the way forward.
"While there are safety risks with using a small, inexperienced company for recycling or repair, I believe certification can address many of the concerns raised by CONEBI," he told us. "Most importantly, the new EU legislation that is currently being formulated should make repair/reuse the first choice."
Similarly, ChamRider notes that there are currently no clear rules specifying that repair and refurbishment services work with original manufacturers or even require them to recertify the batteries. This is precisely why De Jong wants to introduce certification standards so that professional companies like Heskon can provide reliable and sustainable services while strengthening legal standards.
Mid-drive motors of high quality have been around for decades, and there are now a large number of electric bicycles no longer in production with proprietary electronics in their original batteries. Of course, in many cases, the original suppliers and/or manufacturers of the electric bicycles cannot be traced or have ceased operations. This is where things get tricky.
Whether it is repairing completely failed batteries or, more commonly, performing a full recharge due to the decreased capacity from years of use, there are companies in the industry with a long history and good reputation. We interviewed two of them to delve into what can be done and what cannot be done.
Conclusion
Although electric bicycle battery refurbishment is a hot topic in the industry and not without risks, it has significant sustainable potential and should be organized and certified to provide cost-effective and safe options for old electric bicycles, especially when original battery replacements from the manufacturer are not available.
Recently, a reader contacted us and, after having problematic batteries refurbished at Ebike Batteries in London, they are back on the road. Another option implied by advice given by original manufacturers to customers is that the bike cannot be used as an electric bicycle anymore. This essentially means discarding a perfectly functional electric bicycle.
As a final note on battery safety, it is worth emphasizing that even with high-quality batteries, other equally important measures need to be taken.
Unsupervised charging should be avoided, especially overnight. Similarly, whenever possible, you should always use the charger provided by the original manufacturer.
The one that comes with the battery should be well-matched and not cause overcharging. Using a different charger may result in malfunctions during the charging process.
Using replacement batteries from non-original manufacturers (whether or not involving dealers) may also void the warranty for your electric bicycle or kit. Consult your electric bicycle or kit company to understand their policies regarding the use of aftermarket replacement batteries.
It may not be crucial if it allows you to continue using an old electric bicycle that would otherwise be scrapped, but as you can see from the information above, you may have other options to consider before going down that path.
