Charging your electric bike: Everything you need to know about e-bike batteries

Knowing how to look after your battery can get more from it on a ride and also extend its overall life

19:30, Saturday 17th February 2024

Alex Hunt

Junior Tech Writer

E-bike batteries come in various shapes and sizes

Taking some time to understand the power unit behind your e-bike motor is the best way to get the most out of it and keep it powering you up the climbs for many rides to come.

As with anything bike-related, it is far from a straightforward topic, with different e-bikes using lead acid, nickel or lithium-ion, all with their own properties. Making sure you know how to look after the batteries during use, charging, and storage is crucial to their overall performance.

E-bike batteries are generally a pricey item to replace and although they do have a finite lifespan there are ways to maximise this. With this in mind, we take a deeper look at how exactly to use and care for your battery.

What is meant by the term ‘charge cycle’?

The life of an e-bike battery is rated in something known as charge cycles. For the most part, any time you charge and deplete your battery from any level this counts as one charge cycle.

This means that charging your battery to 50% and then running it back to 0% is considered the same as fully charging it to 100%. Some smart systems do not count small partial charges as individual charge cycles but instead wait until there have been enough to constitute one complete cycle.

Charging and depleting a battery from any level is typically considered a charge cycle and will be counted in the batteries software

The amount of charge cycles that an e-bike battery is good for depends from manufacturer to manufacturer, as well as other factors. Things such as the temperatures it has been exposed to in use, the temperature it has been exposed to whilst charging, and the depth of each discharge can all affect the life of a battery but, as a rough guideline, you can expect between 700 and 1,000 cycles from a battery.

How can I make my battery last longer?

Most e-bike batteries are made from lithium-ion which means that you can increase the charge cycles a battery is capable of by only charging the battery to 80%. The optimum charge level will vary by manufacturer but charging to this optimal level can extend the life of a battery by hundreds of charge cycles.

Read more: 8 e-bike safety tips for beginners

What happens towards the end of my e-bike battery’s life?

When the battery reaches its charge cycle limit, it will continue to work, but it will be at a greatly reduced capacity. As the cells inside the battery degrade over time, they are able to hold less energy. This means that older e-bike batteries will have significantly reduced range compared to a new battery.

For some riders, this might not be a big deal but if you are a fan of an adventure ride into the back of beyond then making sure you have a battery you can depend on is a worthwhile investment.

What is inside an e-bike battery?

E-bike batteries use a series of cells that are all connected together. If these were removed from the battery, individually they would look similar to typical household batteries.

E-bike batteries are a combination of rechargeable cells and a battery management system

Along with all the cells, there is also some circuitry that looks after the battery. This is known as the battery management system or (BMS) and regulates the power the battery supplies and regulates the power each cell generates to prevent overheating.

What types of batteries are there?

Lead acid battery

This is very similar to the types of batteries commonly fitted to non-electric cars. Much like car batteries, these are typically very heavy and bulky units that tend to be mounted externally to the frame of the bike. Lead acid bike batteries have a limited charge cycle lifespan meaning that quickly you could find yourself needing to source a replacement.

Nickel

These are considered the next step up from lead, they are a little bit lighter and more compact and the charge cycle lifespan is also increased by around double. These are still typically fitted to more budget e-bikes but represent a better option than lead acid.

Lithium-ion

These batteries have the best charge cycle lifespan and can be made into more complex shapes than the alternatives. This allows lithium-ion batteries to be commonly fitted inside the downtube of the bike frame. This has the added benefit of concealing it from the elements and knocks or scrapes.

Read more: 10 benefits of riding an e-bike

How do I know what battery will last longer?

E-bike batteries are rated using a Watt-hour scale, and this essentially means how many Watts the battery could theoretically supply for one continuous hour. Typically e-bikes can have batteries ranging from 300 Whr all the way up to 900 Whr. The bigger the battery will do nothing to increase the power of the bike but it will increase the range.

Range extenders can be a great way to boost the range of your e-bike

For bikes with smaller and lighter batteries, range extenders can commonly be fitted in the form of a bottle-shaped battery into one of the bottle cages. These can provide an additional 180 Whr increasing the usable range of the bike.

How do I charge my battery?

Most e-bikes will have a charging port somewhere on the frame, this allows you to directly plug a charger into the bike to top up the battery. Some bike brands will also allow you to remove the battery from the bike to charge it. This has the added benefit of allowing you to bring the battery inside a house, hotel or cafe, without needing to bring the whole bike.

Bikes with removable batteries also allow for spares to be carried around or kept in your car so that when the first battery goes flat you can simply swap it out for a fresh one.

Charging your bike on a timer prevents it from being left on charge for longer than needed

The amount of time it takes for an e-bike battery to charge greatly depends on the size of the battery and the power of the charger. Some systems like the Bosch e-bike system use a fast charger that can fully charge a battery in three hours or can charge from 50% to full in an hour. As a general rule, the bigger the battery the longer it will take to charge with some bigger batteries taking around six hours.

What types of chargers are there?

When you get an e-bike, you will be provided with a standard home charger, these are great for charging the batteries quickly and efficiently. However, they are bulky and heavy to carry with you out on an epic ride. Most e-bike system manufacturers will also produce a lightweight slimmed-down charger. These will not offer the same output as the bigger unit but are far easier to carry in a bar bag or backpack if you are planning on stopping for a recharge mid-ride.

What is the best way of storing my e-bike battery?

Batteries have an optimal storage temperature, typically around 20 degrees Celsius. If you take the battery to either end of the temperature extremes it is going to struggle and could even malfunction as a result. Keeping batteries above freezing and out of direct sunlight is the best way to look after them. Batteries should be kept at a nice stable and controlled temperature.

Although the BMS inside the battery should regulate the charge coming into the battery, it is always best practice to avoid leaving it on charge for hours after it has been fully charged. If you are going to leave a battery unattended whilst on charge it can be a good idea to use a time plug that will cut out after a predetermined period.

If you plan on storing your battery for an extended period it is worth charging it to only around 60% of its capacity. This will ensure that the battery lifespan is maximised.

My battery has come to the end of its usable life, how can I dispose of it?

The best course of action when the time comes to dispose of an old battery is to take it to your local e-bike dealer. They should have the ability to send the batteries back to the manufacturer for disposal or recycling which will prevent the components of the battery from being incinerated or thrown in landfill.

If you have an e-bike or are in the market for one and want to find out more about it, make sure to check out our latest e-bike content.