What does the battery really cost?

It is a tool that turns a battery's specifications and your usage into the numbers that matter: how many kilometres the pack will cover in its life, what each kilometre costs in battery terms, and roughly which year you will need a replacement. It helps you judge whether a battery is good value before you buy.

Most e-bike batteries last several years and several hundred to over a thousand charge cycles before capacity falls to around 70 to 80 percent of new. In distance terms that is often 15,000 to 40,000 kilometres depending on capacity. Your real figure depends on how far you ride each year and how well you treat the pack.

Lifetime kilometres equals the battery's rated charge cycles multiplied by the kilometres you get per charge. For example, 800 cycles at 40 kilometres per charge is 32,000 lifetime kilometres. Dividing that by your annual distance gives the likely replacement year.

A charge cycle is one full discharge and recharge of the battery, equivalent to using 100 percent of its capacity. Two half discharges count as one cycle. Manufacturers rate batteries for a number of cycles before meaningful capacity loss, which is the figure we use to estimate lifespan.

Cost per kilometre is the replacement price of the battery divided by its lifetime kilometres. A 600 euro battery rated for 30,000 kilometres works out to about 0.02 euros per kilometre. This lets you compare a cheap battery with a short life against a pricier one that lasts much longer.

When capacity drops far enough that the bike no longer covers your needs, usually around the 70 percent mark. The calculator estimates the replacement year by dividing the battery's lifetime kilometres by your annual distance, so a low-mileage rider may keep a pack for many years while a daily long-distance commuter replaces sooner.

Degradation is the gradual, normal loss of capacity as a lithium-ion battery ages and is cycled. It is not a fault. A pack slowly holds less charge, so range shrinks over time. Our degradation curve assumes capacity falls toward a 70 percent end-of-life threshold, the point most riders notice meaningfully shorter range.

Replacement batteries typically cost roughly one to one-and-a-half euros per watt-hour, so a 500 Wh pack is often in the region of 500 to 750 euros. Because it is the most expensive part to replace, battery economics should be part of your buying decision, not an afterthought.

Avoid leaving the pack at 100 percent or fully empty for long periods, keep it out of extreme heat and cold, store it around half charge if you are not riding for weeks, and charge it indoors in winter. Gentle, partial charging and moderate temperatures are the biggest factors in slowing degradation.

Battery life is usually defined as the point where capacity has dropped to about 70 percent of when it was new. The battery still works below that, but range is noticeably reduced and most riders choose to replace it. We mark this threshold on the degradation chart so you can see when it is likely to arrive.