MPPT Volts to Current Conversion
My buddy picked up 6 300 watt panels today - because he wants to be able to feed his ravenous Starlink - without running the generator. The starlink uses 190 watts of power at 120v - it's a pig for p...
Forum Discussion
Where did you get the 30 volts open circuit and 8 amps numbers? They don't add up. The open circuit voltage of a panel is always higher than it's maximum power voltage. The maximum power voltage multiplied by the maximum power current should equal their rated wattage.
Most 300 watt panels will probably have a Vmp of around 30 and a Voc of around 37. They will usually have a Imp of around 10 amps.
Either way, Vmp x Imp = rated watts. Rated watts / battery charging voltage = potential charging amps. If you really have 6 300 watt panels for a total of 1,800 watts / 12 volts (if the batteries are very low) you could see 150 amps of charge current. I'm really curious what charge controller you have that can handle that much power.
To treat a battery well and make it have a long happy life a charge current of about 10% of capacity is usually recommended. Most people will go up to about 20% of capacity as a good compromise between battery life and quicker recharges. Going up to 25% won't really hurt anything except overall long term battery lifespan and even then it's not that much difference.
I don't think 100 Ah GC batteries exist. They are likely at least 200 Ah if not 225. You'll never be able to get 150 amps to flow into them even if the controller will output that much. The voltage will rise the set point really fast and controller will back off. That's the whole point of a charge controller.
So, I wouldn't worry about hurting the batteries but for the most part that big solar array is going to waste because the batteries (and likely the controller) can't handle it's output.
Most 300 watt panels will probably have a Vmp of around 30 and a Voc of around 37. They will usually have a Imp of around 10 amps.
Either way, Vmp x Imp = rated watts. Rated watts / battery charging voltage = potential charging amps. If you really have 6 300 watt panels for a total of 1,800 watts / 12 volts (if the batteries are very low) you could see 150 amps of charge current. I'm really curious what charge controller you have that can handle that much power.
To treat a battery well and make it have a long happy life a charge current of about 10% of capacity is usually recommended. Most people will go up to about 20% of capacity as a good compromise between battery life and quicker recharges. Going up to 25% won't really hurt anything except overall long term battery lifespan and even then it's not that much difference.
I don't think 100 Ah GC batteries exist. They are likely at least 200 Ah if not 225. You'll never be able to get 150 amps to flow into them even if the controller will output that much. The voltage will rise the set point really fast and controller will back off. That's the whole point of a charge controller.
So, I wouldn't worry about hurting the batteries but for the most part that big solar array is going to waste because the batteries (and likely the controller) can't handle it's output.
