Winter Battery Care – Electric Bikes

With replacement costs for some lithium ion batteries approaching $1,000, it makes sense to invest a bit of time caring for them!  Once you’ve parked your bike for the Canadian winter, it most likely will sit until the snow melts in spring.  A few easy actions now will ensure that your battery is rearing to go then, and for years to come.  I’ve tried to keep this article as simple as possible.  For further information on lithium ion battery care, check out the link at the bottom of this post.

A lithium ion battery will slowly discharge over time as it sits in storage.  If a battery is allowed to fully discharge, this will stress the cells in the battery, potentially irreparably damaging it.   At the least, you will reduce the capacity and life of the battery.  During normal riding, most electric bike batteries have a battery management system (BMS) which switches off the electrical system when the voltage drops to a certain point i.e. the battery is not allowed to fully discharge and the cells are protected.   However, the BMS will not prevent a battery from slowly discharging as it sits in storage.  Therefore, it is important to ensure that your battery retains some charge over the winter months.  Unfortunately, it is not ideal to put your battery in storage with 100% charge as this can also put some stress on the cells.  The following actions are therefore recommended for battery care:

·         Store your battery with a partial charge, ideally 40-80%.  While charging, you can check the number of green lights on the battery indicator … aim for two-three lights (four lights is fully charged).  With the latest Wisper charger, switch the output switch on the back of the charger to ‘39V’ for the perfect storage charge.  If you have a multi-meter, its easy to check the output voltage on the battery terminals to make sure you’re somewhere between about 36V and 39V after charging;

·         Depending on how fully charged the battery was initially, it will normally take about 1-2 hours to give the recommended partial charge;

·         If you end up charging your battery to 100% (the green light on the charging unit comes on), go for a ride to discharge it partially before storing the battery;

·         Check your battery every couple of months of storage and give it a top up if the battery indicator has dropped to one light (or the measured voltage has dropped below about 34V).  If you don’t have a battery indicator, it’s probably a good idea to charge the battery for about an hour every couple of months.  Again, be careful not to put the battery away fully charged;

·         Ideally, the battery should be stored in a cool place.  Significantly elevated temperatures over prolonged periods can reduce battery capacity.  Also avoid freezing the battery.

Correct storage of your battery as detailed above will significantly increase the lifespan of your battery.  A well maintained lithium battery will last up to five years, whereas a poorly maintained battery can be badly damaged over just one winter!

For more detailed information on batteries and how to care for them, check out the excellent online resource at the following link:

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

www.voltagebikes.ca