How to disable battery charging in an inverter?

Question

I installed solar retrofit to an already existing inverter battery setup.

Now during daytime,inverter will be in battery discharge mode by converting DC from battery to AC for appliances use.While battery gets charged from solar panels during daytime.

During night, solar retrofit will not be working and inverter will work as usual. That is,inverter charges battery (AC to DC) from the grid and every appliance connected to inverter uses grid and there is no solar charging. Only when there is a power outage,battery will be used to power appliances connected to inverter (DC to AC).

Are there any ways to charge battery only by solar and not by grid?

Thanks.

Answer 1

Good question and i can understand the background of this question.. because you are trying to save your grid consumption as low as possible… Okay here is the solution for the inverter that doesn't has option to enable or disable grid charging .. i will also tell you some of the major drawbacks…

1. The bypass grid output of the charge controller should not be taken to Inverter mains directly. Rather install a relay with 230v coil or a contactor with single phase supply. Ensure the relay output rating is choosen accordingly
2. In your charge controller , set the Battery to grid setting to 11.8v or little bit high (trying to keep DoD better).
3. The output of the charge controller grid must be connected to the coil of the relay or contactor.
4. Connect the Common to the grid output which powers the load( we are trying the inverse here )
5. Connect the NO to grid input mains from your Electricity board.
6. Connect the NC to inveter output that provide the power to load.
7. Connect the inverter mains input to the regular mains input through a smart plug or normal switch and set it to off Now when the battery /solar is sufficient enough, the bypass would be off and hence the relay will also be off. Since the relay is off, the contacts would be default and hence your load will be powered from inverter through NC contact Now when the bypass is on during night, the relay will be ON and hence the load will be connected to Electricity board through NO contact. The inverter would be still ON but with nil load. So some amount of battery would be consumed even now but with no load. Incase if you have a dc clamp meter you can measure how much current is consumed from battery for no load condition Now when there is a power cut, the bypass will be off and hence the relay will be off and the load will be powered by inverter with the available battery left. Everything works as usual but the battery never gets charged through inveter until the smart switch is turned on. Wait until the solar is available next day for the battery to get charged. But now if you find that it's extremely cloudy and no solar available then switch on the smart switch so that the battery gets charged from inverter. This solution might have some negatives as well..
8. Obviously you are going to stress the battery if incase your load is high during evening. Because it would reach the DoD soon and still will not be charged waiting for the next day.
9. You will load the inverter transformer which is used to supply load through battery all the time. May be if it is a poor inverter then it's efficiency goes for a toss soon. Thanks