One battery or two?

[pgandw]

Originally Posted by Eph 2.10

Looking to be running off battery only for 4 nights. No a/c. Only have single battery at the moment. Should I be getting a second?

Others have given there answers; here's mine. When we bought the A122, we anticipated fall and spring camping in the Colorado mountains with temps as low as 45 degree days, and high 20s at night. We wanted to be able to stay for a 4 day weekend on battery power without running the batteries below 50%. I did not want the hassles or expense of carrying a generator or solar (like to camp in shade, and like to leave campsite for other activities during the day).

From previous experience with a PUP, I knew the heater fan would be the issue. We don't use the stereo or a TV or CPAP, so the only battery use would be limited use of the LED lights, use of the water pump at meal time, and the heater fan and thermostat/controls. We learned with the PUP to manage the heat - set it in the low 50s at night, crank it up for a few minutes when people get up and dressed, and pretty much off during the day.

Dealer recommended 2 group 24 batteries, which he installed (and all there was room for on the tongue without major modification). What we learned was the A-frame doesn't need to run the heater near as much as the PUP did. You have less than 1/3 the volume of a same-sized box PUP in the A-frame. And the walls and roof are better insulated. We found we could keep the heat in the high 50s, use blankets instead of sleeping bags, and still not exceed 50% run time on the heater. Heater fan at 4 amps at 5 hours/night gives 20AH usage - the max heat we want to use per 24 hours.

When one of the dealer-installed batteries failed, taking the other one with it, I replaced them with Interstate GC-2 batteries from Costco ($150 for the pair). The 232AH (116AH usable) GC-2s give me an extra night and then some of reserve power compared to the 80AH Group 24s.

If the weather is warmer, we have that much more battery reserve. The 4 nights max is realistic for us and our camping style - we have never stayed at one site for more than 4 consecutive nights.

FWIW, keeping the vent cracked at night on even the coldest nights makes the heater fan work better (distributes heat more evenly) and more importantly, prevents condensation.

The A-frame does have parasitic losses for the following - stereo, CO/propane detector, thermostat, and possibly the water heater controls. I installed a 70mA fan (with a switch) on the fridge upper vent to improve it's cooling - but the fridge fan is not needed when temps are cold enough to run the heater a lot. I installed a switch to turn off the stereo - this does cause loss of all presets. The other items probably run about 12AH per 24 hour day.

Contrary to the claims of many, unless you have a high wall model, the fridge itself uses NO battery power when running on propane.

just what I have learned on my A-frame
Fred W
2014 Rockwood A122 A-frame
2008 Hyundai Entourage minivan

[Herk7769]

Originally Posted by pgandw

Contrary to the claims of many, unless you have a high wall model, the fridge itself uses NO battery power when running on propane.

Fred,

What model fridge do you have? My understanding of how propane heated evaporative refrigerators work is they use 12 volt DC to manage the fridge calling for the gas solenoid to open and close as needed to provide the heat for the evaporator. The hotter it is outside, the longer the propane valve is energized open, thus the more battery power is consumed. The computer boards that do all this magic are also DC, but use less juice than the solenoid valve.

Herk

[pgandw]

Originally Posted by Herk7769

Fred,

What model fridge do you have? My understanding of how propane heated evaporative refrigerators work is they use 12 volt DC to manage the fridge calling for the gas solenoid to open and close as needed to provide the heat for the evaporator. The hotter it is outside, the longer the propane valve is energized open, thus the more battery power is consumed. The computer boards that do all this magic are also DC, but use less juice than the solenoid valve.

Herk

Herk

Standard height A-frames and PUPs use smaller, manually metered, continuous run fridges with no freezers. Mine is a Dometic 4223. There is a manual propane metering valve, and a thermocouple-controlled propane shut-off valve. The thermocouple is basically a heat/flame sensor and shuts off the propane when the flame blows out. You have to bypass the thermocouple by pushing in the valve switch while lighting the fridge.

Yes, lighting is manual by simultaneously pushing in the shut-off valve and pushing the button for the piezio spark generator (like a cheap home gas grill). Once lit, the burner runs continuously with the flame size adjusted by the manual metering valve.

No 12V required by such a fridge in propane mode. AC mode likewise requires no DC. When the fridge AC switch is turned on, the power to the coil is regulated by an SCR very similar to a light dimmer in your house. The DC coil has no regulation at all. I do not see any interlocks to prevent operating in multiple modes simultaneously. My very similar PUP fridge had a mechanical interlock between the propane shutoff valve handle and the electric mode switches, but did not have a thermocouple shutoff.

Most of the high wall models have taller and bigger fridges which are functionally the same as most RV fridges.

Fred W
2014 Rockwood A122 A-frame
2008 Hyundai Entourage mininvan

[Herk7769]

Thank You PGandW, I had no idea there was such a simple fridge available on the PuPs. I learn something new about RVs just about every day.