Electric bike batteries: everything you need to know

If you're reading Cycling Weekly, you probably know something about bikes – which means you also know plenty about electric bikes. But one big difference is the battery used to power the best electric bikes.

If the battery is not charged, you can still pedal and roll on an electric bike, but you will lose its real utility and ultimately its fun, and you will be left with a heavy machine to carry on with.

>>> Read: Electric bikes and UK law

What are eBike batteries made of?

Electric bikes in the UK tend to come with either Lithium Ion (Li-Ion) or Lithium Polymer (LiPo) batteries. In China, on the other hand, lead acid batteries are still the most common ones used. In 2014 – according to the China Bicycle Association / IdTechEx  – 35 million eBikes were sold on the Chinese market, and just 2.8 million of them had lithium battery.

Because of problems with quality and weight, lead acid batteries are not common in the rest of the world. In Europe, for example, acid lead batteries represent less then one per cent of the total; while 96.5 per cent is taken by Li-Ion and two per cent by LiPo (source: Greenfinder market report).

Specifically, battery packs are made up from many cells: the lead acid ones are similar to those we use on our cars, while the lithium ones use the same technology as mobile phones. Apart from the chemical component inside their cells, the main feature that differentiates lead acid and lithium batteries is their size: the lead ones are heavy and have a short life (200 to 300 charge cycles), while the lithium ones are smaller and can last longer (from 500 to 1,000 charge cycles).

The LiPo batteries are a further development of the Li-Ion ones – they are relatively cheap and small in size, but their service charge is unclear and they are quite fragile.

How long will my battery last?

That's a tough one to answer. It depends on the power of the battery (typically 24, 36 or 48V), the power of the bike (limited in the UK to 250W), the bike's battery management system, and the way you ride. Some bikes allow you to choose different levels of assist to prioritise speed or battery life, which makes predictions of battery life even more difficult.

Typically you can expect somewhere between 25 and 70 miles of travel on a single charge of an ebike. If you're riding hard on full power expect less; manage your battery life well and you could get more.

Many retailers suggest charging the battery at least once a month if the bike is not ridden much, and say that the more the bike is ridden, the stronger the battery will be. All batteries, though, will deteriorate in time and they will need to be replaced and disposed. When that time comes, it’s best to ask your local retailer how to dispose of the battery, but bear in mind that local authorities should provide recycling and disposal facilities.

Watch: What's it like to ride an ebike?

Where are the batteries placed on an ebike?

The battery's placement on the bike depends on different factors, especially the shape of the bike’s frame. Most electric city bikes (more than a half) will have the battery mounted on the carrier rack, while mountain bikes usually have them on the down tube.

How much do electric bike batteries cost?

The batteries are the heaviest and the most expensive part of an electric bike. A lithium battery (36V and 10Ah) could cost around £200, but the prices do vary.

Technology is advancing fast, so check with your ebike retailer first to ensure that battery isn't outdated or difficult to replace.