GPak
Active Member
It is difficult to estimate because it depends on many factors such as:
How often sub-zero charging happens? and at how low temperature? and for how long time, per occurrence.
And most importantly at what current rate battery is charging (elephant in the room).
For LFP batteries, recommendations for sub-freezing charging could be summarized as:
“When charging LFP batteries below 0°C (32°F), the charge current must be reduced to 0.1C and below -10°C (14°F) it must be reduced to 0.05C.
Failure to reduce the current below freezing temperatures can cause irreversible damage to your battery”.
Most manufacturers simply prefer to cut charging at 0°C – it is easy to implement and better be safe than sorry.
Most Battery producer’s show on their data sheets charging temp range starting at 0°C - once again easy pass.
It seems like PC8 design intent is low temp charging with reduced current - advanced and more difficult to implement.
Per above recommendations the subfreezing charge rate for ~7.5Ah PC8 should be about 0.75A below 0°C and about 0.38A below -10°A (0.1C and 0.05C accordingly).
The fluctuating current during the low temp test by @Panzer Platform was about 0.8A-1.6A, double of recommended rate but probably still low enough to be acceptable without considerable/noticeable degradation, I guess.
Also, maybe current was rapidly fluctuating between 0.8A to 1.6A at about -10°C, because -10°C is transitional temperature from 0.8A to 1.6A?
If all the above guessing is correct then PC8 is really more advanced low temp implementation and preferred option, especially since B130X will completely cut the power to DVR below 0°C according to BBMC.
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