Low voltage cutoff for cold lithium batteries

[koter]

I'm using lifepo-batteries in my electric motorcycle.
The motorcycle has 24 cells and thus a nominal voltage of around 77V.
During normal temperatures the voltage dips around 5-7 Volt when high power is pulled from the pack during max acceleration.
When the cells are cold, i.e. 0°C or below, the pack easily drops to 64V during acceleration. That would be 2.7V/cell.
I think the controller (Chinese) handles low voltage cutoff differently when there is a sudden voltage drop (acceleration) compared to normal running.

My question then if the cold battery might be damaged from a hard acceleration with these sudden voltage drops?

 

[nutnspecial]

I've read there is no harm in this, provided your level is set appropriate only to voltage.
Harm from cold is most likely to come from charging them when too cold, if at all. Logically I would think they would just sag 'up' when charging same as under draw, but have heard different opinions.

Other than that, you'll just want to keep them from freezing, which is well below 0c or 32f. Something like 01f or lower I've heard.

 

[koter]

It's not the cold itself I'm worried about. The cell can handle -45°C on discharge.
What I'm worried about is the voltage during acceleration going below what is normally the low voltage cutoff.

 

[ccmdr]

I've just stumbled on this myself, Table 4 here and the section before give good guidelines.

 

[koter]

Wow, that was really good.
So what they basically are saying is that under load or when it is cold, it is okay to go below the regular low voltage cutoff, since the voltage is lowered by higher internal resistance, not by battery energy depletion.

 

[ccmdr]

Thats exactly how I interpreted it .