Cold Weather Charging

From the Forum, Brian Wismann provided this information about cold weather charging:

"[T]he issue with cold weather (sub-freezing) charging is metallic lithium plating in the actual cell. This can cause permanent degradation to your batteries, and it's best to avoid if at all possible. You can read more about it here:

Link to Battery University website.

One thing to remember is that what we're really concerned about is the temperature of the battery and less so the ambient tempertaure. If you've just completed a ride at 32F, it's unlikely that your batteries are also at 32F as discharging requires current and current generates heat (especially with increased impedance due to the cold temperatures). Given the thermal mass of the batteries, they'll also stay warm for a considerable amount of time following the ride. So... worst case scenario and to be avoided is charging the bike outdoors in sub-zero temperatures after the bike has been sitting in that environment for serveral hours."

More on Cold Weather Charging

A forum member asked:

Are the batteries fine for storage lasting approximately 5-6 months in temperatures down to about -30*C ? Can the batteries and charging/management system be easily removed for indoor storage and charging? Or is it advisable to acquire heated storage for the bike (some places offer battery charging, I'm sure they would plug in the bike periodically during storage)?

Brian Wismann answered:

This storage period and temperature are fine, although that is REALLY cold. At this storage length, you'll want the batteries to be around 50% State of Charge. The self discharge of these (or any) lithium ion batteries is not significant over this period, so you don't need to worry about the batteries draining themselves down to nothing as this would take years. You do, however, need to worry about storing at full charge levels as this can reduce the overall capacity "retention" (new batt term alert!) of the battery pack at the end of the storage cycle.

Still More on Cold Weather Charging

Another forum member indicated:

As a "tester" I was told fairly straight forward... "go ahead a drive at any temp...lower than stated in the manual? Go for it. It will be good test info as Oregon doesn't get that cold. But don't charge under 32 degrees."

So I don't charge when under 32 degrees.

But I do have a dilemma...what about this: it is 35 degrees and I start charging...but overnight the temps drop below 32 degrees...so I should stop charging...the thing is, once charging the battery temp is always higher than air temp...so my garage could be 28 degrees (not often) but the bike shows 45 degrees because of charging... Confusing. I think battery temp trumps air temp...but I ain't sure just yet till I hear from Brammo.

Brian Wismann answered:

Battery temp trumps air temp, but what you're seeing displayed on the dash is psuedo-ambient air temp measured from a temperature sensor in the upper harness underneath the upper bodywork. As long as it's above freezing when you start charging you will be fine. The only case where it would be questionable is if you let the bike sit overnight in a below freezing garage and then started charging in sub-freezing temperatures. There is a thermal mass to the batteries that take awhile to change temperature. After a ride in almost any ambient temperature, they remain warm enough to charge for the 3-4 hours it will require. There is very little current flowing during the balancing phase, so no need to worry about this.