8 month storage for eve 280K's

[Tribune]

Looking for suggestions on leaving my batteries for 8 months storage unattended. I have 840 Ah of 3p4s Eve 280K's running a REC Bms. Split charge/load busses and two 15 amp DC-DC chargers going to my start batteries (catamaran). 900 w of solar through a Midnight Classic 150. When I was running the T105's, I would disconnect the main solar bank and hang a 50w panel through a PWM controller and everything was perfect returning to the boat. We do 4 months/year on boat and 8 months storage. Would I be best just disconnecting all loads and charge from the LiFePo4 and leave at say 60 or 70% charge? The self discharge should only be about 25% or so (?). I would hook the 50 w up to the start batteries in this case. Or, should I hook the 50w up to the LiFePo4 and leave the DC-DC's connected (through the load bus with Bms connected)? Trying to minimize the loss of capacity to the batteries while using the most fail safe option while away.

 

[chrisski]

I found no good guidance on storage of lithium 280 ah cells.

I store In the summer months when outside temps reach 120 and storage temps are 105. At the start of the four month storage season, I discharge the batteries to 50%. I then shut all power draw off and disconnect the SCCs. When the summer is over, I simply turn the 1650 watts of panels on and in a couple days the batteries are ready for the winter season.

In theory the best thing for me to do would be to pull the batteries and move them to a climate controlled area. In practice disassembling 200 LBS of 16 cells has its own issues, like breaking a stud, dropping a wrench on it, etc.

So I accept that storing in hot temps will degrade the life of the cells, but since I expect 20 more seasons out of them, I will still meet my storage needs. With 100 days of use a year, just won’t have the thousands of cycles required to severely degrade the cells.

That is my technique I developed.

 

[Tribune]

Thanks Chrisski. What were you getting for a self discharge value during the storage? I too have to accept the storage temp hit. Tropics on a boat so my low cell temps are 85 and charging with engine heat added they run to 105. Because the boat will be totally unattended I am looking to avoid any failure points on maintaining. With everything disconnected, while maybe not the best, nothing to fail except a little capacity loss perhaps because of not charging every 6 months.

 

[chrisski]

Thanks Chrisski. What were you getting for a self discharge value during the storage? I too have to accept the storage temp hit. Tropics on a boat so my low cell temps are 85 and charging with engine heat added they run to 105. Because the boat will be totally unattended I am looking to avoid any failure points on maintaining. With everything disconnected, while maybe not the best, nothing to fail except a little capacity loss perhaps because of not charging every 6 months.

I wish I’d measured it, but I did not. The only thing still running was the BMS and Bluetooth Victron shunt.

 

[Tribune]

I wish I’d measured it, but I did not. The only thing still running was the BMS and Bluetooth Victron shunt.

So you only store 4 months and start at 50%. What % is showing when you return after the storage period?

 

[chrisski]

So you only store 4 months and start at 50%. What % is showing when you return after the storage period?

I can’t remember exactly, but very little if any loss. The problem with that though is the shunt only measures what’s after it, and the BMS is before it.

I feel that there may have been an actual 30% to 40% SOC versus what the shunt said around 50%, but I did not write data down.

This year I will measure. I will put the RV in storage in a few weeks and write some data down like SOC before, ah used before storage, and SOC after storage, ah used after storage. SOC after charge and ah into the batteries.

 

[Tribune]

Got it, thanks.