Solar Panel Voc-MPPT?
Wondering if there is any relationship between measured Voc and MPPT performance with a 24v panel. My 12v panel has a Voc rating of 21.9 and Isc of 8.2, but I often see 8.2ish when Voc is only 20....
Forum Discussion
pianotuna:
the morningstars (at least mine) allow for custom setpoints. For the big writeup I did, I used the factory setpoints. But when camping, since we seldom (closer to never) get to full charge on solar. Therefore I wanted to always be in absorption mode if possible. normally it will drop to float after a set time. I modified the setpoints. here is what I did
Absorption voltage 14.5
float voltage: disabled
Equalize: 14.9V
time between equalize: 7 days
equalize duration: 120minutes
equalize time out: 180 minutes
so it will stay in absorption mode unless it equalizes and go up to 14.5V for output voltage to keep stuffing current in.
And I use the remote temp sensor as well so setpoint voltages will do a temperature compensation.
WARNING. I would NOT advise anyone to use this profile unless you understand the possible consequences. And for sure do NOT use this profile if you can get at or near full charge!! I suspect it would boil the batteries dry in short order.
On our last trip out, it was fall and trees kept us from getting sun all day and I've got 160W of solar for almost 500AH of battery, so i was loosing about 6% of capacity/day. after 8 days we were down to just under 50%SOC per the trimetric, and ready to pack up. So it kept me from needing to run the generator.
If I understand the morningstar default algorithm (which I will admit I may not be fully understanding) , it will drop out of absorption after 3 hours of charging. At least that is what the manual says. And since I can't get to anything close to full charge in 3 hours i don't want it to do that.
the morningstars (at least mine) allow for custom setpoints. For the big writeup I did, I used the factory setpoints. But when camping, since we seldom (closer to never) get to full charge on solar. Therefore I wanted to always be in absorption mode if possible. normally it will drop to float after a set time. I modified the setpoints. here is what I did
Absorption voltage 14.5
float voltage: disabled
Equalize: 14.9V
time between equalize: 7 days
equalize duration: 120minutes
equalize time out: 180 minutes
so it will stay in absorption mode unless it equalizes and go up to 14.5V for output voltage to keep stuffing current in.
And I use the remote temp sensor as well so setpoint voltages will do a temperature compensation.
WARNING. I would NOT advise anyone to use this profile unless you understand the possible consequences. And for sure do NOT use this profile if you can get at or near full charge!! I suspect it would boil the batteries dry in short order.
On our last trip out, it was fall and trees kept us from getting sun all day and I've got 160W of solar for almost 500AH of battery, so i was loosing about 6% of capacity/day. after 8 days we were down to just under 50%SOC per the trimetric, and ready to pack up. So it kept me from needing to run the generator.
If I understand the morningstar default algorithm (which I will admit I may not be fully understanding) , it will drop out of absorption after 3 hours of charging. At least that is what the manual says. And since I can't get to anything close to full charge in 3 hours i don't want it to do that.
