How long a battery lasts for entirely depends on how you treat that lump of iron in the downtube, so here’s how to minimise any losses and keep powered for longer.
Just like your old phone that now needs charging every five minutes, e-bike batteries inevitably degrade over time and lose some of their energy content.Here’s how to keep them at their best for longer.
The less you charge and discharge your battery, the longer it’ll last you. It makes sense to try and eek out the power every time you ride then, and that means riding smart. E-bike motors are designed to work at a normal to high pedaling cadence, they’re most efficient like this and use the least amount of energy. Bosch recommends you keep your revs above 50, so avoid the slow grinds and make the most of that lovely spread of gears your bike comes with. Likewise, make the most of the modes your e-bike comes with – ideally you want to use the lowest power setting you can handle to eek out more range, but not if it reduces your revs to a slow crawl.
Gas too flat
The batteries themselves actually come with computer chips on them to regulate their output and charging. This means they’ll never completely drain to nothing and ruin themselves in the process. However, fully charging and discharging the battery every time you go out does put a higher load on it, so if you’re going out with full charge every ride and then walking it back to your car empty you’ll be rinsing that battery. Instead, try to stop before the battery is completely caput each ride… easier said than done.
Now this is a big one, it’s really important to charge your battery at room temperature, ideally somewhere between 10-20C° is optimal, and certainly not below freezing. Bosch says do it indoors, somewhere dry and with a smoke detector present (lithium-Ion batteries are proven to be very safe, but they can catch fire in very rare instances if they short circuit). Outside that temperature window you’ll have less power when you go out riding, and less life in your battery, because electrical resistance increases the colder things get.
Riding for a few hours in cold weather isn’t bad for your battery as it comes up to temperate whatever the ambient weather, but starting off with it warm is important. This means put it in the front with you and the heater if you drive a van and pop it in the bike immediately before riding. Don’t ride it straight out of your freezing cold shed either, warm it up in the house beforehand.
Don’t leave it in direct sunlight either this summer, just like your phone if it gets too hot the load on the battery increases. In theory the motor will automatically switch off if the battery overheats, just like on a laptop, but we’ve never experienced that (perhaps because we ride in drippy Britain).
If you’re not riding your e-bike for a few days, weeks or months then it’s important to leave it neither full nor empty. Bosch recommends leaving it at 30-60% capacity, Shimano says take it to 70%. Top up the charge every 6 months, and of course charge to full before riding again.
Cleaning and maintenance
Bosch says you should remove the battery before cleaning your bike, while Shimano says you should leave it in place to protect the terminals. Shimano’s advice is probably better in real world applications because without the battery in place there’s a hold load of exposed wiring that’s going to get splashed with muddy water. Both Shimano and Bosch recommend you stay away from hoses and pressure washers, and instead sponge it all clean.
We think the best thing to do is wash it gently with a hose and sponge in an upright position, then leave it to dry completely before turning it on.
If there’s mud or grime on your battery mount terminals (not the battery itself) you can clean them with a soft dry brush or cotton bud, Shimano says.
Finally, book yourself in to a dealer that specialises in your motor and have the status of your battery checked out. They’ll be able to tell you about your battery status and if you’re on course for a long life or if you’re wrecking the thing.
Four e-bike questions you were afraid to ask
1. Why does the charger heat up?
Converting the voltage from 240V in the UK down to 36V for Bosch or Shimano causes some energy loss as heat, typically 10% according to Bosch. The charging automatically shuts down when capacity is reached though so it doesn’t overcharge and increase it’s load.
2. Can the battery manufacturer crack open the case and just replace any dead cells, like Tesla does?
No, because the cells need to be perfectly matched to one another to avoid overcharging or over-discharging. This is possible, but it’s a complex process and therefore costs more money – fine on a £100,000 car, not so on a £5,000 e-bike. Just for interest, a Bosch PowerTube 625Wh battery has 50 cells inside.
3. How many cycles will I get from the battery?
It depends how you treat it. Shimano says it’ll do up to 1,000 charges, which equates to 7-10 years of regular riding before the battery dies. Clearly, you’re going to be replacing the bike before that happens though, so the theory is it lasts the life of the bike. Shimano guarantees a remaining battery capacity of 60% after 1,000 charge cycles.
Bosch’s warranty period guarantees at least 60% of the original energy content for 400Wh, 500Wh and 625Wh batteries and 70% of the original energy content for 300-Wh batteries within the warranty period (24months after purchase, or 36 months after the battery’s date of manufacture, or after 500 full charge cycles, whichever is soonest). The brand says it’ll last much longer than that though, years when properly looked after, evidenced by lab tests and customer feedback.
4. Where do batteries go to die?
Distributors of batteries, whether in bikes or phones or cars, are responsible for their recycling. There are different schemes across Europe for the return of those batteries, and in the UK Valpak runs the biggest compliance scheme. Perhaps not surprisingly, the UK doesn’t bother to recycle its own battery waste, instead we mostly export it to France, Germany and Poland.