If we look at a datasheet for a solar charge controller, we can find many different voltages.
- PV input voltage
- MPPT voltage range
- Minimum input voltage or start-up voltage
But what are they, and what do they mean?
This article aims to bring clarity to that.
MPPT Start-up Voltage
This is the voltage at which the MPPT will start working (120VDC in the example). If the voltage is under this voltage, the MPPT will not put power into the battery.
MPPT Voltage Range
For this example, the MPPT Voltage Range is 120V DC to 450V DC. While the max input voltage is 500VDC. So What doe MPPT voltage range mean?
When the voltage input to an MPPT charge controller falls outside its specified range of 120VDC to 450VDC, its efficiency and functionality are affected.
Below 120VDC, the controller may not effectively perform maximum power point tracking, leading to reduced energy harvesting efficiency, and it might not even activate if the voltage is below the startup threshold.
Above 450VDC, while still within the maximum input limit, the controller can operate but with decreased MPPT efficiency, potentially leading to suboptimal energy conversion. Consistently operating outside this optimal range can also stress the system, potentially reducing the lifespan of the charge controller.
Nominal DC Volt/Max DC voltage
Nominal means that the MPPT will be the most efficient at this voltage level (360VDC).
The maximum voltage will be 500VDC. If you exceed this voltage, the charge controller will be damaged.
Max input voltage = Voc * panels in series * 1.25
Why do we need the additional 1.25 safety factor?
Because a solar panel will measure more than the Voc on a sunny cold day.
If you didn’t include the safety factor, the charge controller will get damaged on a cold sunny day.
Do you want to know how to select an MPPT charge controller? Read my guide about it here.
What is the minimum input voltage for MPPT solar charge controller?
The minimum input voltage should be at least 5 volts over your battery voltage OR the minimum specified in the manual.
If the voltage is not high enough, the charge controller will not start.
What is PV input voltage?
This is a voltage range where powerpoint tracking works the most efficiently.