Off-Grid Battery Considerations

It is late August and there are storms in the gulf. Due to the weather for the last few days, my battery has not been to 100% SOC (state of charge). Lead acid batteries need to get there once every three or four days. The forecast for today is 75% cloud cover and my battery was at 83% at daybreak. The lack of sun also did not trigger a mini-split operation for two days and the inside humidity was at 85%. Temperature was OK, but it was stuffy. So I hit the generator for about 1.5 hours.

My inside humidity dropped to 65%, in the “normal” range. My battery hit 90% and I expect the sun to top it off within a few hours, even under the cloudy conditions.

This is an example of the load management and adjustments required to live without a grid power connection. If you have a grid connection, I can configure the system to take care of this automatically. You will have to play a role when the grid is down, but it is completely invisible if the grid is there.

Lithium batteries make off-grid a lot easier. They can operate at a partial state of charge without a problem. However, the mini-split air-conditioner is still operated from solar, not battery. This means that you won’t get any air-conditioning and humidity reduction unless the sun is out in force. So even with a lithium battery, you will still have to consider a generator run to satisfy that need. But a lithium battery will allow you to simply wait out many low-sun conditions without generator assistance as the sun will often come to the rescue. You are relieved of the lead-acid requirement to hit 100% SOC twice a week, and that is a lot of load off your mind!

Lithium batteries has been around for some time and we understand the technology well. However, they have only recently been introduced into the off-grid market at a reasonable cost level. Maintenance free AGM (lead-acid) are still a good option if you need to keep the initial cost down. But if you have the funds, lithium is well worth considering.