Living Off Grid – Operating Our Solar Power System – Part 2

Reader Contribution by Ed Essex
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In Part 1 we looked at the different components of a solar power system and what their purpose is. In Part 2 we discuss the actual hands on management of those components.

It sounds like the system operates by itself once it is set up, other than a little battery maintenance. That’s true but the system is not as efficient as it can be when it runs on “automatic.” What do I mean by efficiency?

By managing a few things myself I can extend the life of my batteries and backup generator and keep the fuel costs for the generator down.

The inverter is programmed to turn the generator on when the batteries go down to 60 percent capacity. That is fine for when we aren’t home but the rest of the time I choose to start the generator when my batteries are at 70 percent. I choose when to start the generator and when to turn it off. I choose the most opportune time to pump water which takes a lot of power. If the pump comes on automatically at night and I catch it on the monitor, I will go out to the panel and turn it off if I know it is going to be a sunny day tomorrow and can use the sun to pump rather than my reserve battery power.

Whether the sun or your generator charges batteries the following will occur:
1. Bulk charge – the batteries will accept the maximum charge possible
2. Absorb charge – in this mode the batteries will only accept a partial charge. They do this to protect themselves for reasons over my head. It’s enough for me to understand that they need to do it. I think it is kind of like eating. You don’t eat your whole meal in one bite. You take many bites but end up the same – full.
3. Float – a trickle charge to just maintain the batteries at 100 percent.

It is harmful to charge the batteries too fast or overcharge them. I am more efficient at generator use than the inverter. When my generator is charging it might be putting out as much as 140 amps. That is fine in bulk charge but when the inverter slows down the amperage to 60 amps (absorb mode) then the generator is still running at full capacity using fuel but not sending all of the amps to the batteries. That is inefficient. When they get into absorb mode I may choose to go hook up my smaller generator to charge with which only puts out about 45 amps.

I also choose when to equalize my batteries. My monitor will tell me it’s time and I will hold off for a bright sunny day so I can use solar power to equalize. That is more efficient than using generator power and paying generator fuel costs.

So in summary, I basically choose when to charge the batteries with a generator (when to start and stop the generator), when to pump water (my pump is 220V), when to equalize and whether to use the sun, batteries or generator to pump water. By doing those few things I can prolong the battery life and minimize my generator fuel costs. Seems like a lot of benefit for very little effort. I can do all of those things with the push of a button.
Besides that I just think it is a good idea to know what your system is doing at all times. Just by having some interaction with the system allows you to know if the system is working the way it should be – or not. You don’t have to become an expert. You just need to be familiar enough to know when all is well or not. By doing the things I do with my system, I can know at a glance that everything is working the way it should. Knowing all is well gives me a great peace of mind. I’m glad you can program these systems to be independent but I still want to know the programming is working. After all, we are on our own and striving to become more self sufficient. You can’t achieve that by programming alone.

Ed and Laurie Essex live off grid in the Okanogan Highlands of Washington State where they operate their website and