We both have Wisper 7O5 t bikes approx two years old.recently moved house, before bikes were stored in part heated garage, new garage is much colder and more exposed. I’ve been told I would be better removing the batteries during winter as the cold does them no good. We don’t use the bikes much from Late November till March, probably doing maybe 20 miles a month. Should I remove the batteries and keep them in the house, i was thinking about putting them in Boiler room.

For storage cold is good, the only issue with cold batteries is they tend not to hold full capacity when charged so best to let them sit at ambient indoor temps for a day or two. I keep mine in the garage except for the one in daily use.

If not using much keep voltage lower at 37 - 38.5v and only charge 10-12 hrs before needed. When fully charged the ions react and cause a chemical reaction and fighting against each other so the forces need releasing , a lower voltage storage charge is easier and kinder for longer cell/battery life. Once a month just keep an eye on the voltage level to check all is well.

I have noticed they do t hold a charge well in very cold spells. Don’t quite get the lower voltage charge, charger supplied with bikes has no settings on it ?

For lower storage voltage you have to monitor the charge and check with a volt meter and cease the charging when it reaches the voltage you want. Cells don't usually go out of balance unless there is either bad cell group, faulty wire or a faulty bms , the next time you fully charge it will be balanced.

According to various internet sites, +15 degrees C is the ideal storage temperature for Li-on cells, but down to -20 degrees shouldn't harm them. At 15 degrees you can charge at the standard voltage : much below and it gets more complicated.

Personally, I choose to leave my battery in a cold garage as at lower temperatures self-discharge rates are less, as are secondary (unwanted) chemical reactions which age the cells. I bring it indoors to warm up before charging or use.

Whatever the temperature ***make sure*** that you do a partial charge on a regular basis - the aim is to keep the battery at around 40% charged. If left alone for too long, self discharge and leakage of current through the BMS could allow the voltage to fall below the threshold beneath which irreparable capacity loss occurs.