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Winter advice needed - battery will not be used for 9 months

Hi Everyone. I have an off-grid summer farm on a fjord about 400 km north of the arctic circle, boat access only. Need to shut down the system from september until may. Mid winter will see several months no direct sunlight / darkness, with weeks at temperatures below freezing, from 0 to -12. It's 4 x 320 watt panals with a 7KW LiPo Car battery (Nissan) and an Victron Easy Solar II GX. Dealer says i should charge the battery full, turn everything off and walk away. Is this the correct advice? Any input gladly appreciated.

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2 Answers
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Obo answered ·

Try the off gird calculator on PVGIS (input your location, battery details, panel size and energy consumption) to get a view on whether the solar will produce enough power to keep the batteries topped up.


There are risks to leaving LIPO batteries over a long winter, as they will discharge and may get damaged.


On the other hand, if the PV does not produce enough power, then the standby consumption of your Easy Solar will drain the batteries and also leave them in a discharged state, thus risking damaging the batteries.


If you go the route of leaving them on, make sure all other loads are switched off/disconnected.

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hav avatar image hav commented ·
hav answered · 0 secs ago

Thanks Obo. Had a look at the calculator. But realistically, it is pretty much dark here for a couple straight months becasue the farm is shadowed by a north facing wall thru the arctic winter. It ewas a once in a lifetime mission to get the battery in here.... so do not have the option to take it out ....

Fortunately the fjord location heeps the temps moderated until nearly christmas ... so will hope for the best

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tstr7119 answered ·

You should be fine. NMC batteries have a self discharge rate of 1-3% / Month rising with higher temperatures and higher charge levels so a 9 month disconnect should pose no significant problems. I would disconnect the battery from the system to be certain that you dont have any vampire drain from any connected systems.

temperatures below -20 degrees celsius could potentially destroy your batteries so I would say thats the greatest danger to your system

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hav avatar image hav commented ·
Thanks. Def gonna disconnect the battery. When you say under -20, are we taking days, or weeks for damage to occur?
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tstr7119 avatar image tstr7119 hav commented ·
I dont think anyone knows for sure, below -20 is genreally considered bad and I have seen estimates from a couple of days to a couple of weeks before battery can get seriously damaged
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