Solar charge voltage settings for a backup system and prevent diminished battery life?

[brandonboosted]

My victron 250/100 will be here soon and I am currently in research stage to figure out what settings I should use. My biggest concern is my long term use for this system is (as of now) just a backup for my house. Current use case will be running some of my crypto miners and or a 12k mini split to provide backup and supplemental ac/heat. The LONG TERM use case I just want to be able to have backup power to run lights, fridge, freezer, fans ect. Based on my research for storage and the battery data sheet SOC should be 10-30% but would be almost useless if I need backup power. Maybe there is no good answer here but any advice is appreciated.

By build
Victron 250/100
2000w pannels
560ah lifepo4 DIY, Daly 250A
4000w Inverter

 

[iamrich]

Not sure where 10-30% SOC would come from. I would never drive my batteries to 10% unless it was an emergency (even then I probably still wouldn't). I like to keep my batteries sitting at 80-90% SOC when the sun is up.

 

[brandonboosted]

Not sure where 10-30% SOC would come from. I would never drive my batteries to 10% unless it was an emergency (even then I probably still wouldn't). I like to keep my batteries sitting at 80-90% SOC when the sun is up.

The storage SOC on the data sheet for longer that 3 months recommends 10-30%.

 

[Bob B]

I think it is just one of the drawback of using one of these batteries for backup power. If you want to have reliable backup you are going to need to keep them charged.

You could mitigate it a little by having a pack a little larger than you think you need and keep it 75-80% charged.

 

[chrisski]

Because of things like you mentioned about storage requirements at certain discharge rates, I’ve found no practical battery to make a high capacity storage device without risk keeping them floated at a high state of charge and breaking the storage rule.

I’ve been told that Gel batteries were made for this purpose, to be continually floated and used very few times when the power goes down, but the spec sheets I’ve read for gel lead acid batteries do not support this.

I would recommend looking at gel batteries used in the telecom industry. It’s the closest I can think of, but I have not found a spec sheet to match that statement.

 

[Hedges]

If you aren't cycling them hundreds of times per year you aren't expecting to use much of their cycle life anyway.
If you can cycle them moderately and reduce utility bills (e.g. reduced consumption at peak rates) they might pay for themselves.

They do need to get charged high enough and held long enough on occasion to rebalance, or you'll end up with some cells sitting at low SoC and others at high SoC. After periodically doing that, you could draw back down to 50% or 30% an store there at moderate temperatures.