If we look at a datasheet for a solar charge controller we can find many different voltages.
- minimum input voltage or start up voltage
- PV input voltage
- MPPT voltage range
But what are they, and what do they mean?
This article aims to bring clarity to that.
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.
Start-up voltage
This is the voltage at which the MPPT will start working (120VDC). If the voltage is below this level, the MPPT will not put power into the battery.
MPPT voltage range
The MPPT will operate between these values (120VDC-450VDC). The MPPT will not deliver power to the batteries when the voltage is out of this range.
I guarantee this guide will save you $100s on buying the right components by having a good design and sizing.
You can get the book for a reasonable price on amazon
FAQ
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.
If the voltage is not high enough, the charge controller will not start.
What is PV input voltage?
This is a voltage range in which the MPPT works the most efficiently.
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I’m an off-grid enthusiast. I created this website to give clear and straight-to-the-point advice about solar power. I’m also the author of the book ‘Off-grid solar power simplified‘. Read more about me on my about page, check out my Youtube channel, or send me a message.
Yes Nick. I have a 200 AH lithium ion battery a 2000 watt converter and a 100 amp controller. My friend and I hooked all this up yesterday. And we’re running off of four 25 Watt solar panels last night It ran my big seventy inch t v with no problem and then today it kept shutting itself off and just a little while ago The whole system shut down there is no read out on the MPPT controller. The battery or the converter I had planned to add more batteries. That’s why I got a 100 amp. MPPT controller should I have got a smaller one until I get more batteries? 4/24/2023 8:30 ÇMT
If I understand correctly, you have a total of 100W solar panels? The ideal current of your inverter and charge controller will draw that load. So you don’t have enough solar panels to power your loads. Your battery is empty. i recommend getting a battery monitor (shunt).