LiFePo4 batteries still charged after 2 winters

[corn18]

Just went out to check the camper in storage. Been sitting there unused for 18 months. My 2xSOK batteries were still at 13.5V. So they survived 2 winters without being charged (or used). Pretty cool. And last winter it got really cold (-20 deg F). We will be using them again this season.

 

[sunshine_eggo]

Just went out to check the camper in storage. Been sitting there unused for 18 months. My 2xSOK batteries were still at 13.5V. So they survived 2 winters without being charged (or used). Pretty cool. And last winter it got really cold (-20 deg F). We will be using them again this season.

I assume you meant LFP. LiPo is lithium-polymer.

Cell spec is typically 1%/month, and most cells are much less than that. The biggest danger is the BMS draining a trickle, but most BMS will go into low power/standby mode at some point.

I had a set of 280Ah cells that lost 0.2% after 5 months.

 

[corn18]

Yup, LiFePo4. 2xSOK 12v 206 Ah. I was worried they might still be frozen

 

[HarryN]

it isn't all that easy to tell if a Li cell has been damaged by freezing or not. The effects can be on a microscopic surface scale that build over time.

It has been a while since I did in depth reading on the subject and of course battery quality has improved over time. 20 years ago that would have been frowned upon but 20 years in battery technology is a long time.

 

[featherlite]

batteries were still at 13.5V.

What is the state of charge?

 

[corn18]

Victron monitor say 100%. Seems to match this chart:

 

[featherlite]

Hmmm ,,,, after 18 months, with an average self discharge of 2%/mo., I would have expected a state of charge of approx. 64%.

 

[robbob2112]

Not sure about the SOK batteries, but my LFP batteries state they should be stored at 50% charge.