Why you should never leave your electric bike battery on the charger overnight (and it's not just because of the fire hazard)
This is how you drastically extend the battery life.
For most e-bike owners, it is the most normal thing in the world: after a long ride (or even every day), take the bike into the shed, plug in the charger, and head out again the next morning with a full battery. We all know by now that this entails a fire risk, but there is another important (financial) reason to disconnect the charger from the battery before going to bed.
A new battery for an e-bike easily costs 500 euros these days. It is by far the most expensive part of your bike, and yet we often treat the battery as a disposable product. Chemically speaking, the lithium-ion or lithium-polymer cells in the battery are most stable when charged between 20 and 80 percent. As soon as you leave the charger connected to the battery all night, you force the battery to remain in a state of high-voltage stress for hours. This causes the chemical composition in the battery to degrade much faster—in other words, it wears out. The result? Your battery wears out up to 30 percent faster than necessary. Instead of getting six or seven years out of a battery, it is practically 'finished' after just three years because the range has dropped to an all-time low. And yes, (most) batteries can be repaired or refurbished, but that costs quite a bit too. A lot less than buying new, but still...
Golden 80 percent rule
Don't want to have to shell out another 500 euros for a new battery in no time? Then treat your battery with more respect. Technicians advise against charging the battery beyond 80 percent if you don't have a long trip ahead of you immediately. For those times when you do need a full battery, the advice is: charge it just before you leave, and do not leave it on the charger all night.
A simple timer switch costing a few euros between your power outlet and the charger is the best investment you can make. Set it to cut off the power after three or four hours. Your bike mechanic probably won't give you this tip, but for your bank account, it is the most important maintenance hack there is.