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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?

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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?

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    \$\begingroup\$ The charge controller will do whatever the charge controller has been programmed to do. What charge controller are you using? What has it been programmed to do? \$\endgroup\$ – Neil_UK Oct 19 '17 at 8:04
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    \$\begingroup\$ It's usually the other way round: power is supplied to the load, and if there is any spare it's used to charge the battery. \$\endgroup\$ – pjc50 Oct 19 '17 at 9:42
  • \$\begingroup\$ @pjc50 That's the kind of info I was looking for. Can you please put that in the answers \$\endgroup\$ – VVK Oct 19 '17 at 9:50
  • \$\begingroup\$ @Neil_UK I'm using epever tracer charge controller. How would I know what its programmed to do? \$\endgroup\$ – VVK Feb 27 '18 at 2:04
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    \$\begingroup\$ You could try this. Open Goole, type in 'epever tracer charge controller'. There are several models. You know which one you're talking about, I don't. One on amazon has the model number '#484 Tracer2210A'. Now put that into google, find the manufacturer's site, then download the manual and RTFM. Like pjc50, I would guess that if you have a load, and sun, and a low battery, any charger that directed the output to your battery rather than your load would be tossed into the trash pretty quickly. I would guess it drives load first, then battery. Once battery is full, stops charging battery. \$\endgroup\$ – Neil_UK Feb 27 '18 at 6:33
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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.
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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.

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