Hello
The Victron installation (Multiplus 48/5000; MPPT 150/60; Cerbo GX) is powered by 4 x 435W solar panels and the energy is stored in 4 Pylontech US300Cs. The system is installed in a chalet 1500m away in island mode (without connection to the grid). The winter season is coming and the temperature can drop to -25 degrees.
Given that the place is not accessible for 6 months because of the harsh winter conditions, what is the best solution:
Leave the system powered
Unplug the system (turn off the panels and turn off the Victron system and the 4 Pylontech US300Cs)
Disassemble the batteries and store them in a 20-degree location
If you read the pylontec manual. They can be stored in -20°C temps. Not that I have tried it. But it is there in the manual.
SOC it is stored at is important as as well. That is also stated in the manual. So read that for more information.
Obviously stored means switched off.
This temp is below working temps. So it follows that everything is switched off at that point.
The only other way is a battery warming compartment.
I would suggest leaving the system powered as the use itself will keep the batteries a little warmer. The system should be configured to derate the batteries at colder weather and then disconnect them when it gets too cold.
However, you should seek to protect from the extreme cold. They will discharge below zero but won’t charge. This is a protective process to avoid damage to the batteries.
I trust you have your generate on autostart by the Cerbo.
The best would be to install a thermostat controlled heating element of some kind to keep them above 10ºC.