I'm looking forward to a nice two week holiday but was wondering what the best practice is for my solar installation - if I understand properly, lithium batteries prefer to be cycled rather than storing at full charge for extended periods. Do I need to worry about this for a two week holiday where there will be minimal loads on my system (expect 1-2kWh/day consumption when the house is empty) or it not really applicable to LiFePO batteries?

 

I wonder how long LiFePO batteries will lie in shops or warehouse before they are sold. I bought my inverter and battery in January and only installed in April. How long did it lie at the shop before it was sold? When I started it up it was around 70%.

Do they charge it fully when it is manufactured?

Will you have loadshedding at night and the battery be used? Will you switch off your system completely and just use Eskom power?

The only thing I worry about when I go away for more than 3 days is whether the stuff in my freezer and fridge will be ok when I return because I always shut down my Inverter and Batter and I do not have solar so if our notoriously bad area goes down for 4 or more days (which has happened a few times) then the battery would have drained completely before that so best for me to have it shutdown during my trip and hope that the 3+ days downtime does not hit. Aspecially during summer.

Edited December 13, 20232 yr by TheMac

1 hour ago, Peter le Roux said:

I'm looking forward to a nice two week holiday but was wondering what the best practice is for my solar installation - if I understand properly, lithium batteries prefer to be cycled rather than storing at full charge for extended periods. Do I need to worry about this for a two week holiday where there will be minimal loads on my system (expect 1-2kWh/day consumption when the house is empty) or it not really applicable to LiFePO batteries?

 

1 to 2 kWh per day is very low. 

Anyway, my property ticks over at night at about 220w. That's fridges, wifi, security, stuff on standby. Just that would be 5ish kWh per day.

Anyway... over 6 hours (midnight to 6 am), my battery looses 8 to 10 percent. From 6pm to midnight would be the same. That's with a 10kWh battery.

So I would easily drop the batteries down to 80% from the late PM to useful PV coming in in the morning. Why do you think you wouldn't get some cycling if you just leave the system to its own devices?
 

Edited December 13, 20232 yr by Bobster.

12 hours ago, Peter le Roux said:

I'm looking forward to a nice two week holiday but was wondering what the best practice is for my solar installation - if I understand properly, lithium batteries prefer to be cycled rather than storing at full charge for extended periods. Do I need to worry about this for a two week holiday where there will be minimal loads on my system (expect 1-2kWh/day consumption when the house is empty) or it not really applicable to LiFePO batteries?

 

No guidance can be given without knowing what size battery, inverter and PV you have. 

Do you have remote access to see how the system is performing when away?

11 hours ago, Scorp007 said:

No guidance can be given without knowing what size battery, inverter and PV you have. 

Do you have remote access to see how the system is performing when away?

I had it in my signature but didn't realise signatures aren't visible on mobile. 5.6kWp of panels, 2 x 5.3kWh Sunsynk LiFePO, 8kw Sunsynk. I have access for remote monitoring and the geyser is switchable remotely with a CBI Astute.

 

22 hours ago, Bobster. said:

1 to 2 kWh per day is very low. 

Anyway, my property ticks over at night at about 220w. That's fridges, wifi, security, stuff on standby. Just that would be 5ish kWh per day.

Anyway... over 6 hours (midnight to 6 am), my battery looses 8 to 10 percent. From 6pm to midnight would be the same. That's with a 10kWh battery.

So I would easily drop the batteries down to 80% from the late PM to useful PV coming in in the morning. Why do you think you wouldn't get some cycling if you just leave the system to its own devices?
 

I suppose that's my question - is an idle overnight discharge enough to keep the battery happy with no major loads for two weeks? Or not something to be worried about?

20 minutes ago, Peter le Roux said:

I suppose that's my question - is an idle overnight discharge enough to keep the battery happy with no major loads for two weeks? Or not something to be worried about?

I see no huge problem with this, maybe just limit the charge rate to 1kW or less to limit how quickly they'd be up at full charge again...

LiIon NMC type battery cells will  be 100% happy, disconnected at 50% charge, but, then the BMS comes in, consumes some juice, not much, but trickling electrons away over time, the 18650 and similar cells NMC type LiIon cells, stored disconnected are perfect in a 50% charge state and 2 years later will function fine generally, not sure what LiFePO4 cells would like, but since a BMS is involved that will consume some power, it becomes a different scenario anyway...

So. I'd say, limit the charge current to less than 1kW/20A and let the system run, just keep an eye on it, maybe once in the morning and once after sunset to see whether its doing what you're expecting...

As you have 10kwh of battery power I will just set the discharge at 40% as you have about 3 days of discharge available based on the daily load of 2kwh. This is your reserve in case of a power failure. Battery will charge during the sun period and no risk even if days are cloudy. 

At least you can see while away so no stress.