Is the power from solar panel redirected to load when battery is full?

Question

When the solar panel attached to a charge controller then to a battery, simply stops the charging when the battery is full or Is the charge controller(MPPT) smart enough to redirect the power directly to the load when the battery is full?

For example: Lets consider that I have a 100 Watt solar panel, The MPPT charge controller is connected to 12V battery and the load is a 12V bulb. When the battery is fully charged does the charge controller transfers power directly to the load instead of battery?

Answer 1

Lets consider that I have a 100 Watt solar panel, The MPPT charge controller is connected to 12V battery and the load is a 12V bulb. When the battery is fully charged does the charge controller transfers power directly to the load instead of battery?

This is a meaningless question. Let's assume for a second the answer is "no". That would mean that the battery would discharge due to the load. That would mean the battery wouldn't be fully charged anymore. Which would mean the answer wouldn't be "no" anymore.

So you're asking what happens in a hypothetical split second in which the battery is fully charged.

In any event, most actual charge controllers just connect the battery and the load directly to each other whenever they want to supply power to the load. They then manage the connection between the solar panel and the battery+load to supply as much power to the load and battery as they possibly can, backing off if the battery voltage gets too high.

They don't care (and often don't know) how much of that power is going to the battery and how much is going to the load. There job is just to:

1. Get as much power to the load and battery as possible, except
2. Don't let the battery overcharge -- back off the power if that happens, and
3. Don't let the battery overdischarge -- shut off the load if that happens.

Answer 2

Power is useful work, and is measured in watts (in DC) - volts x amps. At any given voltage, a device will only draw so many amps. In a fixed voltage system, that means so many watts. It won't draw more power.

You would have to elevate the voltage to "shove the power down its throat" as it were. On most devices, that would burn it out.

What you're looking for is called DUMP

Most solar charge controllers have the usual terminals - panels, battery, and loads. When the loads have drawn all the power they want, and surplus power remains, it is used to charge the battery. If more power remains, the controller increases the impedance back to the panels to slow the amount of power coming in - effectively it blocks the solar panels from generating the power in the first place.

Some charge controllers have a fourth set of terminals called "DUMP". When the above situation arises, loads satiated, battery full -- power is then diverted to the DUMP terminals. Here, you connect loads that are helpful to run when you have excess power, but are not essential. Such as running an A/C unit, running an auxiliary heater in a water heater (storing the energy as heat or cold), running a pump to fill a hilltop cistern (storing energy as altitude), hydro backpumping if you have a microhydro system, etc.

Your cistern might be sized 5 times expected usage, and wired to use normal power only to fill the cistern to 20%, and fill the rest of the way to 100% using dump power. Normal power would rarely be used.

Still, if there are not enough loads on the DUMP terminals to use all the power available, it will not force the power, but will increase the impedance to the panels to slow down power generation.