question

nilo avatar image

Winter storage batteries -40C

Hi everyone!

About to install an Easysolar II gx system in my mountain cottage in Norway (-37 C this winter). My first off grid move and the fact of there being Victron is amazing. Thx!!

To make it as clear as possible: my question is NOT about charge or discharge but solely about idle storage aka long term effects of freezing electrolytes (freeze point being -30/35 C)

Neither interested in battery heating nor LTO solutions

Most LFP manufacturers define cold storage limit as: -20C

Only Victron and Mastervolt (which both use Winston cells (LYP) spec the batteries to -45C

Failed finding any real test data except one very interesting study that shows that deep freeze ( cryogenic freezing ) got no harmful effect.

This study does not address temperature-fluctuations around freeze point, and only measures short term effects. http://wrap.warwick.ac.uk/119502/13...erflash-cryogenic-freezing-Grandjean-2019.pdf.

It does match my understanding though that the electrolytes do NOT expand when it freezes (unlike water). If so any LFP battery would actually survive sub -30C temperatures ! ?

....this is a technical fringe question and I could just go with the winston/victron/lyp solution but if someone got the science/information I would really appreciate!


the best to you all, Nilo






Lithium Batteryoffgridtemperature
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2 Answers
nilo avatar image
nilo answered ·

thx porcini - but that is not an option. I will disconnect the batteries during winter periods while not there (max 2 months) - and will not even discharge below zero.


2 comments
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2 months would work well with fully charged long life OPzS cells, but if you don't want any maybe someone other knows about LFP

I will study those cells ! thx

porcini avatar image
porcini answered ·

Probably you should go with lead acid batteries in that case?

With rated acid density of ..

.. 1.28

SOC 100% --> -70°C
SOC 80% --> -40°C

.. 1.24

SOC 100% --> -46°C
SOC 80% --> -36°C


How long is the storage time?

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