Might add a third panel

Almot wrote:
What furnace has to do with the discussion, is that it draws 12V :). In the OP low-use and solar-only scenario, furnace is probably the biggest item, and it does have zero-current alternatives, as posted.

Off-grid with solar only (no generator), when solar is small like the OP's, mandates shallow cycling. Even 450W might not bring it back to 97% if they start from 70% in the morning and the day is not super-bright. So, bigger battery will be a bonus, bringing the morning charge level higher.

With the addition of FanTastic fan this item will become #1 in summer, drawing as much AH as the winter furnace, and in Ca they might need fan in the night as well. This is where bigger battery comes handy again.

Forget about "enough current to charge 4*6" - the objective is staying above 80% where high current is not important. This shallow-cycle objective is applicable only to low-use low-latitude scenarios like the one discussed here. OTH, if you run 110V appliances or it's not the South, you start in the morning from less than 60% and then high current (relatively to battery size) becomes important.

The 3rd panel would help on a dark day, feeding in few extra AH, so that the evening charge level won't drop too much and you'll start (hopefully) from close to 80% in the morning.

I agree with everything stated in your reply. I have a couple things in the works for "emergencies" or "extreme situations". What I would like to be most prepared for is the "worst average". Right now I visualize the "worst average" as a less than 30 degree night, keeping the trailer @ 55 degrees while running two C-Pap machines.................not sure if I mentioned the C-Pappers. We run both of them with humidifiers off. And of course any scenario presented here would be while boondocking or dry camping.

What furnace has to do with the discussion, is that it draws 12V :). In the OP low-use and solar-only scenario, furnace is probably the biggest item, and it does have zero-current alternatives, as posted.

Off-grid with solar only (no generator), when solar is small like the OP's, mandates shallow cycling. Even 450W might not bring it back to 97% if they start from 70% in the morning and the day is not super-bright. So, bigger battery will be a bonus, bringing the morning charge level higher.

With the addition of FanTastic fan this item will become #1 in summer, drawing as much AH as the winter furnace, and in Ca they might need fan in the night as well. This is where bigger battery comes handy again.

Forget about "enough current to charge 4*6" - the objective is staying above 80% where high current is not important. This shallow-cycle objective is applicable only to low-use low-latitude scenarios like the one discussed here. OTH, if you run 110V appliances or it's not the South, you start in the morning from less than 60% and then high current (relatively to battery size) becomes important.

The 3rd panel would help on a dark day, feeding in few extra AH, so that the evening charge level won't drop too much and you'll start (hopefully) from close to 80% in the morning.

Thanks for all the advise. Sounds like a plan to start working on.

In a completely unrelated subject that has nothing to do with this discussion... Today I learned that my new furnace will actually shut down when I run out of propane rather than just pump cold air around continuously like all my others did.

2oldman wrote:
... and it's an Atwood.

Was also Atwood in my trailer, model 8525-IV. Could fall asleep when dead tired and if it would run all the time, it's on/off cycling that is annoying. I don't find this noise any comforting or necessary, when it can easily be helped. Noise is a subjective annoyance, of course.

Back to the topic of panel wattage. In this particular scenario with low energy use, charging starts in the morning from high charge level, so they already don't need a lot of charging current with 2*6V.

Increasing the bank will bring the cycle higher yet, i.e. if the cycle was, say, 70-90% before, it will be 85-95% now, and at this point battery needs very little current. 300W would (probably) handle 85-95% cycle of 4*6V too, with skies clear enough. 450W won't hurt though.

ScottG wrote:
More likely just old like me and has CHS (cant hear stuff) :W:B

lol.. no, I hear just fine. I do hear lots of comments about loud furnaces but that's never been my problem. Any space heater is much more annoying than my furnace which is why I recently spend a few hundred having the failing blower motor replaced. Lasted 15 years.

ScottG wrote:

2oldman wrote:

Almot wrote:

2oldman wrote:
I can barely hear mine.

Must be a big rig, furnace far away from the bedroom.

That, and it's an Atwood.

More likely just old like me and has CHS (cant hear stuff) :W:B

If it’s cold enough outside....the “roar” of the furnace is quite comforting! ;)

2oldman wrote:

Almot wrote:

2oldman wrote:
I can barely hear mine.

Must be a big rig, furnace far away from the bedroom.

That, and it's an Atwood.

More likely just old like me and has CHS (cant hear stuff) :W:B

450 watts of panels are adequate to maintain up to about 750 amp-hours of battery bank.

Available power would be 2.25 kwh per day based on 5 hours of sunlight each day.

Almot wrote:

2oldman wrote:
I can barely hear mine.

Must be a big rig, furnace far away from the bedroom.

That, and it's an Atwood.