I have set up a hybrid off grid solar power system which uses a sort of reverse grid tie backup for the battery bank.
When we are home we can use all the solar power that is available at any given time. But when we are gone we have to shut off anything non essential to save the battery bank from harm in case a storm comes through.
I often turn on a cryptocurrency mining rig on a sunny day and leave it running. We work far from home now and cant just run back to the house quick. So we generally leave everything off when we are away. But solar power not used is wasted. I prefer to use every bit of available energy for something.
So I designed this Arduino micro computer controlled battery charger backup system so we can leave devices running if we are gone for the day.
The controller will turn on the battery charger only if the battery bank voltage falls below a set point. Then, once the batteries come back up a bit, the charger is shut off again. This is only for emergency backup and only to be used if we are not home and left something running.
One example is a beautiful sunny day when I had a cryptocurrency mining rig running and we went to a town on the beach 1.5 hours away. Sadly at 5 pm we had to leave although we did not want to because I had to shut down the mining rig before the sun was too far down. This would allow the batteries to top back up before night. If we had this backup system in place we would not have had to rush home.