PV Gap

Shirley Said:

Solar panel, battery, and inverter connection question...?

We Answered:

Hey J, Brutus is correct, the panel and the battery will share the load that the inverter is pulling, and this is what you want to have happen. When a panel charges a battery, some of the power is lost in gassing and heating of the plates and liquid inside the battery, so you have some losses. If the power from the panel goes straight to the inverter, there is no loss in charging, so it is actually more efficient to run loads during the day, and not run the battery down at night to recharge the next day, then to run loads at night and live with the charge losses during the day.

We have a home that is run almost entirely on solar and wind power, and it has taken us some time to get used to doing electric chores during the day, like washing clothes and running vacuum cleaners and such, but it gives you more use out of your system in the end. There are articles covering this in Home Power Magazine, I would suggest subscribing to it, since you are already involved in solar power, it is an inexpensive publication for the information you get from it.

One word of caution, make sure when you hook it all up, that the panel is wired to the battery seperatley from the inverter wiring. If you have a situatution where the panel is disconnected from the battery, but still connected to the inverter, it can cause an overvoltage situation at the inverter. We have two sets of wires from our battery bank, one goes to the shutoff that feeds the inverter and other loads, the other goes through a separate fuse and out to the panels and wind turbine control box.

Also, there is a rule of thumb about charge controllers. If you are using lead acid batteries and you know the amp hour capacity, Divide it by 50. If the resultant number is less than the short circuit current rating on your panel, then there is no need to install a charge controller. You can get more information about this in Richard Perez's book, "The Complete Battery Book." Take care, Rudydoo