reconsidering recomendataions on solar
so after 1 year using my solar my outcome is a little less than expected. I have 2 100W panels mounted on front slope of roof, and 1 additional panel mounded flat on roof behind the DS panel that i...
Forum Discussion
The 100W rated output of a solar panel is under ideal (lab) conditions which never occur in the wild. The incident angle of the sun is one problem, the temperature of the cells is another - I think the standard is 77 deg F when in practice on a sunny day the black cells will be too hot to touch. That reduces the output significantly.
Second as you know you are using a PWM controller which will throw away perhaps 20% of the available energy compared to a MPPT controller.
But the main problem you are running into is intrinsic in lead acid batteries: as they approach full charge, their acceptance rate goes down and to reach 100% requires 6-8 hours of charging at low rates, no matter what the source is. In the morning, the State Of Charge is low, the acceptance rate high and the panels cool - all good - but the sun is at a low angle and cannot produce as much current as the batteries would accept. Later in the day the SOC has come up, the acceptance rate has dropped, and you are now limited by the battery chemistry.
Good quality AGMs (Lifelines) will have a higher acceptance rate than flooded or poor quality AGM, but the difference is not dramatic. The main advantage of LFP batteries for a camper are they will accept a high rate of charge right to the top, dramatically cutting charge time to get to 100%. The other main advantage is they are tolerant of operating for long periods at a partial SOC, while lead acids (and AGMs in particular) are not.
I don't think you will see much benefit of increasing the size of the wiring. The energy lost in them is minimal. Far more is lost in the morning with the PWM controller. An extra panel would increase the morning charge rate by 33% (source limited) but probably do nothing at noon (acceptance rate limited).
AGMs need to be brought to a full SOC periodically (once a week minimum is recommended by Lifeline) or they will by short lived. Flooded cells are more tolerant of this IF you equalize them monthly which almost no one does. Carbon foam batteries (Firefly) are tolerant of partial SOC but at a cost of about $450 each. LFP batteries are ideal but are at least twice again that expensive. With your current setup, as long as you have a full charge event once a week or so (by driving or plugging in or an extra sunny day) and have enough charge to continue camping in between, there may be no reason to change anything.
Second as you know you are using a PWM controller which will throw away perhaps 20% of the available energy compared to a MPPT controller.
But the main problem you are running into is intrinsic in lead acid batteries: as they approach full charge, their acceptance rate goes down and to reach 100% requires 6-8 hours of charging at low rates, no matter what the source is. In the morning, the State Of Charge is low, the acceptance rate high and the panels cool - all good - but the sun is at a low angle and cannot produce as much current as the batteries would accept. Later in the day the SOC has come up, the acceptance rate has dropped, and you are now limited by the battery chemistry.
Good quality AGMs (Lifelines) will have a higher acceptance rate than flooded or poor quality AGM, but the difference is not dramatic. The main advantage of LFP batteries for a camper are they will accept a high rate of charge right to the top, dramatically cutting charge time to get to 100%. The other main advantage is they are tolerant of operating for long periods at a partial SOC, while lead acids (and AGMs in particular) are not.
I don't think you will see much benefit of increasing the size of the wiring. The energy lost in them is minimal. Far more is lost in the morning with the PWM controller. An extra panel would increase the morning charge rate by 33% (source limited) but probably do nothing at noon (acceptance rate limited).
AGMs need to be brought to a full SOC periodically (once a week minimum is recommended by Lifeline) or they will by short lived. Flooded cells are more tolerant of this IF you equalize them monthly which almost no one does. Carbon foam batteries (Firefly) are tolerant of partial SOC but at a cost of about $450 each. LFP batteries are ideal but are at least twice again that expensive. With your current setup, as long as you have a full charge event once a week or so (by driving or plugging in or an extra sunny day) and have enough charge to continue camping in between, there may be no reason to change anything.
