Brammo Owners Forum

BrammoBrian posted this information on another thread but I wanted to make sure it had its own space.  I have also posted it on the Brammo Forum Wiki.

Guys,

Probably should move this thread over to another topic, but the 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:

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

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.

Yes, the Enertia 3.1 Valence batteries also have this restriction to charging, hence the statement in the owner's manual about recommended charging temperature. 

The internal battery temperature is recorded and monitored in the VCU, but not displayed on the current version of the Dash firmware.  It may be displayed on the "secret screen" during charging - I'll have to double check. 

Craig,

This storage period and temperature are fine, although that is REALLY friggin' 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. 

May have answered my own question..

From protomech

Leyden Energy hasn't published any real datasheets for their Lithium Ion batteries (Enertia+ and Empulse), but they list these specs:
Discharge: -30°C to 60°C
Charge: -20°C to 60°C

Valence has published a datasheet (pdf) for their U-Charge XP batteries used in the Enertia. They list these specs:
Discharge: -10°C to 50°C (122°F)
Charge: 0°C to 45°C (113°F)
Storage: -40°C to 50°C

So, it would seem that the Empulse and Enertia plus are cleared for charging in temps down to -4f..  YEA for all midwesterners with unheated (or no) garages.