pianotuna
Regina, SK, Canada
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Hi John,
The OP really needs to do an energy audit. I think the guesstimate numbers are quite high on the fridge. It is a small "bar" fridge.
Regards, Don
Kustom Koach Class C 28'5" 256 watts Unisolar, 875 amp hours in two battery banks 12 volt batteries, 2500 MSW watt inverter.
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westend
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smkettner wrote:How long is the trailer? Can you fit 2,3 or 4 of the large 24v panels (~65"x40") without shade issues? Or are you inclined to accumulate 4 to 8+ 12v panels as budget allows? Since you mention full time and possibly extreme conditions I would think you would pretty much cover the roof as much as practical.
How about a roof pic?
Picture of the roof with the white elastomeric drying:
As you can see, there are only two roof vents, a heater stack, and a plumbing vent, the latter two are towards the side and rear. The roof measures 19' x 7'6". I don't see any shade issues if I use 2" or 3" angle as attachments. I would probably make any attachments with hinge points to tilt the panels, no sense in giving up wattts if I'm able to tilt them.
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westend
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full_mosey wrote:Let's start with 2 x grp31 batteries for 2 x 110AH = 220AH.
The largest load will be the fridge. That is 1.3A x 120V = 156W. With an estimated 33% duty cycle we would have 8H x 156W = 1248WH daily.
Now these Watts must be provided by an inverter so we need to convert this into equivalent battery draw. 1248 / 10 = 125AH per day.
125AH is more than 50% of the 220AH battery bank and you are out of power on day one.
HTH;
John
Hey John, thanks for breaking out the calculator (pencil, good mathematical brain?  ). Remember, I also have 100 AH of AGM to start with but your math gives me caution about storage.
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westend
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pianotuna wrote:Hi John,
The OP really needs to do an energy audit. I think the guesstimate numbers are quite high on the fridge. It is a small "bar" fridge. I'm on my way to the store for a Kill-a-watt meter. I agree, we need some harder numbers.
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CJW8
Arizona
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I am not a proponent of sealed batteries UNLESS you are going to be camping in extream cold for a long time. Lead Acid batteries stored on the tongue if a travel trailer at -20F will lose a lot of capacity which I'm sure is published somewhere. However sealed batteries stored inside at +50 to +70F will lose very little capacity. I would consider sealed batteries stored inside such as under the dinette seats.
2013 F350 PSD FX4 SB CC, 18,000 Superglide
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mena661
Southern California
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CJW8 wrote:I am not a proponent of sealed batteries UNLESS you are going to be camping in extream cold for a long time. Lead Acid batteries stored on the tongue if a travel trailer at -20F will lose a lot of capacity which I'm sure is published somewhere. However sealed batteries stored inside at +50 to +70F will lose very little capacity. I would consider sealed batteries stored inside such as under the dinette seats. X2. On the tongue you'd lose ~55% of capacity at those temps. I'd use AGM's also and keep them inside.
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full_mosey
Oklahoma
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pianotuna wrote:Hi John,
The OP really needs to do an energy audit. I think the guesstimate numbers are quite high on the fridge. It is a small "bar" fridge.
Energy audit, yes!
The issue is how important it is to do the energy audit. I simply took the biggest load because we need to get past that first and it will serve as an example of what we mean by an energy audit.
I have run tests on a similar sized dorm fridge with external coils. I managed to get the daily WH below 720 by glueing pink foam sheets to the outsides. We need to consider worst case.
Even if the fridge SWAG is halved, westend is out of power on day two. Let's say it is 60AH daily.
Extending the SWAG to estimate solar sourced charging Amps to replace ~60AH I divide 60/4 = 15A. The 4 represents a worst case solar day plus other losses.
Now what size solar array is needed?; 18V x 15A = 270W.
HTH;
John
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smkettner
Southern California
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With that wide open space I recommend a couple large 24v panels.
No air conditioner leaves you mega space.
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JiminDenver
Denver, Co
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West
My big panel is 66"x39" and is 230w, you should easily be able to get 4 on your roof for 920 w total. They require a MPPT controller but may be cheaper total than a bunch of smaller panels and a cheaper controller.
Actually you might be able to fit 6 up there for over 1380w if mounted side by side
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westend
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Ok, first part of the energy audit is under way. I bought a small dorm fridge and have had it running for a bit. Ambient is 90 or so in shade. The kill-a-watt is showing .97 amps. It should go down since this is an hour after startup and I put some water bottles and tea inside so that will be transferring heat for a bit. I will haqve a running tabulation in a few hours. The DC side I will measure with a clamp meter.
For information, if I use the TT in the winter for solar and DC use, it won't be in ND or anywhere cold. I know this may be confusing, it's even confusing for me but if I park in cold climates, I'll have full hookups.
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