E-bike battery safety and care
To get the best from your e-bike, look after its batteries carefully
Just like your motorhome battery, it’s important to look after your electric bike batteries to maximise the range and ensure they remain safe. The lithium ion batteries found on bikes do degrade (very slowly) by their nature. However, good care of a battery will both prevent damage and stop it losing unnecessary capacity, so try to follow these tips:
TEMPERATURE
Batteries have an optimum operating temperature – around 20˚C – so try to avoid extremes of temperature.
Charge them indoors in very cold weather and keep the batteries inside until needed. It’s even more important to avoid very hot temperatures, such as leaving them directly in the sun or even just in an enclosed, unventilated space on a hot day like an awning.
Note, though, e-bike battery fires are very rare as modern lithium batteries have safeguards built in. But getting a battery too hot is never a good idea.
Extreme heat and cold will also degrade the battery cells and reduce charge capacity. At best this will reduce the range of your e-bike and, at worst, it will mean laying out a pretty large wodge of cash for a replacement.
E-bike batteries are generally safe in very cold conditions, but the cold will affect short-term range performance (and possibly long term if left in very cold temperatures for a long time).
MOVEMENT
Avoid vibration and shock to a battery through rough handling. Along with extremes of temperature, this is an area to pay special attention to.
Damaged cells, plus extreme temperature, is a recipe for failure of one or more cells.
GOOD CHARGING HABITS
Recharge the battery to a high level after every ride and disconnect the charger once the battery is full.
You may see advice that says only charge to 80-90% of battery capacity to give it a longer life. This may be true with cheaper batteries, but higherquality ones may well have a lower
‘full charge’ threshold for this very reason – to protect battery life. Either way, it won’t hurt to make a practice of disconnecting your battery when it’s not quite fully charged.
You’ll appreciate why regular charging is important when you know how batteries work. Virtually all e-bike batteries contain a BMS (battery
management system). This acts to protect the ‘health’ of the battery cells when in use, so they are not overcharged and stay within their optimum voltage, so avoiding damage.
The BMS can also switch the battery into ‘sleep’ mode if the voltage drops too low. This might happen if you leave a battery nearly empty for a long time (months or years). This happens as the BMS draws a small current to keep operating and effectively flattens a nearly empty battery. Once in sleep mode it may be difficult to ‘wake’ the battery up again as the voltage has dropped so low the BMS thinks there might be a safety problem (even though that’s unlikely). Keeping the battery in a high state of charge when in regular use means this is not going to happen.
Always use the approved charger. The best ‘smart’ chargers ‘talk’ electronically to the BMS and cut off power at full charge capacity. A charger not specifically made for that battery risks damage by overcharging.
STORAGE WITHOUT CHARGING
Long-term storage isn’t great for e-bike batteries, but if you do need to store it for a period of months, check what the maker’s recommended discharged state is for storage. For example, Bosch recommends a charge level of 30-60% charge on all its batteries). Again, store away from direct heat and at room temperature. If there is a smoke detector, store it near that for extra safety.
BUY GOOD-QUALITY BATTERIES
Be wary of cheaper batteries with suspiciously high claims for battery life and the number of charge cycles – they may be easier to overcharge. They may also represent greater fire risk (rare though this is). Be especially wary of cheap, high-performance, models as they may push battery performance to the max, leading to failure more quickly.
Manufacturers of premium-quality e-bike batteries may attain so-called UL certification. This new voluntary testing standard – UL 2849 – is aimed at all electric components on pedalassist and throttle power e-bikes. Bosch, Panasonic and Trek have already endorsed it.
CLEANING TIPS
Good-quality batteries are waterproof and can be ridden in heavy rain and even ford streams, but they are not specifically protected against pressurised water. Cleaning an e-bike with a pressure washer is a bad idea.
If you get dirt in the contacts when the battery is off the e-bike, cleaning with a small soft brush is best and apply some electrical contact cleaner spray if needed.
KNOW YOUR GUARANTEE
More likely than catastrophic failure is gradual decline in battery capacity and range. A good guarantee will specify how much charge your battery is guaranteed to hold after a set time and/or a number of charge cycles. For example, Bosch guarantees its batteries to hold a minimum of 60% of full charge capacity for two years or 500 charge cycles (whichever is first).
But a good-quality battery should give good range for much longer than that. Bosch actually states that the battery should be good for around eight or nine years or 1,000 full charge cycles.