not2bme said:
Doinit said:
90vmp array + 65.1v battery = 155.1v
This part of it is just pure nonsense. You repeat this in every one of your posts and that's what's driving everyone up the walls.
Ideally you want to be around 10-20V above your battery voltage to be optimal. Any more just make it less efficient. So for a 24V system the ideal panels should be around 40-50V yet I run mine at 3S for around 90V. Still fine. Using your maths of 90V+30V batt= 120V, so it doesn't add up at all. You have to just give up on that.
The 150V is just the max of the controller. Any higher than that the electronics might get fried. And the max the panel can produce (the Voc) must not exceed that number. So that's why that's there. Nothing to do with your other math.
This 150v total is roughly the best-optimal combined voltage for the 60v battery....maybe 160v but thats pushing it... nobody can argue that.. anything over is making the controller do more work-more losses.. this is not guess work.. due to the incoming voltage being more than the optimal 30% higher than battery voltage if the combined voltage is over 150v...
I didnt make this stuff up.. 80v is the optimal mppt voltage for the 60v battery, so having array Vmp 10v higher than 80v gives room to make sure 80v can be acquired from the array.. that equals 160v... and anyone with a lower (than 60v) voltage battery should absolutely make sure they do not have a combined voltage over 150v or they would have even more losses than a 60vbattery user due to the controller having to do more work- controller has to drop the arrays incoming volts more to achieve a lower battery voltage therefor more losses..
so for a 24v battery the array should only be about 10v higher than the optimal mppt voltage for that battery so theres less losses, because then the controller doesnt have to lower the voltage as much as it would with a higher voltage array.. I realize that with only a 10v higher array than the 24v battery isnt giving enough volts to supply enough amps so arrays volts have to be higher.. so this is why theres more losses with a 24v battery than a 60v battery, because with a 24v battery the array voltage has to be higher to supply more amps and controller has to make more amps, therefor have to have an array much higher than the optimal mppt voltage for the battery so more amps can be created = more losses.. more amps have to be created to have enough power to do anything with because 24v is so low
An mppt controller is made to use higher voltages than battery voltage and still be able to charge the battery.. but a pwm controller is more efficient because it doesnt have to lower the voltage.. but a pwm controller cannot get more power (than mppt controller)in the beginning and end of the day during low light conditions therefor making the mppt controller more efficient overall,, but again when an mppt controller has to lower voltage it is not as efficient as a pwm controller, so keeping the array voltage for a 60v battery close to the optimal mppt voltage is best to keep the mppts efficiency high so the controller doesnt have to lower the voltage as much.. and this number is 90vmp array for a 60v battery..
So in my opinion go-ahead and use an array a lot higher than battery voltage, higher than the 30% optimal,, really isnt going to hurt anything but it will not give u as much power from the array as an array that is optimally sized above the battery voltage..
Btw Red, I cant wire my panels at 4s as u have described because that would be 33.3vmp (on back of panels) x4= 133.2 Vmp and that would exceed the 150voc limit of the controller with a voc of over 160v. But I will try 2s with 45ish Vmp panels like I explained I will when we move into the next house. And since the Vmp would be closer to the optimal mppt for the 60v battery, Im sure I will get a better percentage of the power that the label (Vmp) on the panels says. How much more...?..probably not much but anything helps. Im hoping to gain back 200w from having less panels in series and closer to optimal mppt voltage for the battery.