I think you are just making assumptions are not TRUE leading you to the wrong conclusions. Let's start with the first oversight of comparing input current and voltages with output voltage and current. With a

It is an important to understand the formula, because if you did you would know Output Current is always higher than Input Current period end of story

So take one of your panels, assuming the battery is discharged, and you input say

The other issue you are likely not considering is your battery is nearly fully charged. So with just one panel the battery charge is just low enough to accept full charge POWER, but when second panel is added the charger is in the CV mode and the batteries cannot take full power when nearly charged up. It wil be more than one panel, but not full power of both panels.

If you want to see what the controller and panels can do is apply a heavy load that drags the voltage down to 12 volts. So if you have 200 watts of panels, try a 400 watt load.

**MPPT Controller Output Current = Panel Wattage / Battery Voltage.**It is an important to understand the formula, because if you did you would know Output Current is always higher than Input Current period end of story

**.**A MPPT Controller is a POWER CONVERTER, not a series or shunt voltage regulator like PWM.So take one of your panels, assuming the battery is discharged, and you input say

*=*__17.6 volts @ 5.68 amps__**100 watts**input to the controller. MPPT is a Power Converter and the power is 100 WATTS. On the output you measure the voltage and current and see*=*__12.4 volts @ 8.1 amps__**100 watts**, same as input power. Voltage and Current will NOT BE EQUAL between Input and Output.*. We have converted 100 watts being input at 17.6 volts @ 5.68 amps and converted to 100 watts into 12.4 volts @ 8.1 amps.***Power****will be equal***Power is Equal between In and Out.*The other issue you are likely not considering is your battery is nearly fully charged. So with just one panel the battery charge is just low enough to accept full charge POWER, but when second panel is added the charger is in the CV mode and the batteries cannot take full power when nearly charged up. It wil be more than one panel, but not full power of both panels.

If you want to see what the controller and panels can do is apply a heavy load that drags the voltage down to 12 volts. So if you have 200 watts of panels, try a 400 watt load.

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