ARB Amp Draw and 12 volt plugs

JohnDanielsCPA

Does anyone know how to determine whether the 12 volt socket in your car can generate enough amps to support an ARB?  I know what the ARB’s amp draw is.  I just can’t seem to find any information on how many amps are generated by the 12 volt plug in my car.

Sharon_is_SAM

Found this:

"Usually they have a fuse. Look in the fuse box and see what the lighter socket fuse is. It should be marked with a number like 10 or 20 in Amps.

Take that value and multiply by 12 V and that’s your maximum sustained wattage."

JohnDanielsCPA

Thanks!

George101

How many watts does the Arb need?

JohnDanielsCPA

@Sam got me thinking.  I was able to determine the rear plug (power port is what Ford calls it) is on a 20 amp fuse.  The ARB manual requires a 15 amp fuse.  So I think I’m going to be fine.  The ARB is “rated” for 5.1 amps (per the manual), but typically only draws an average of 1 amp under normal operating conditions.  

Luckyj

The only thing with those plugs is that the wire is usually very small.  Like 16-18 ga.

but it will work.  Just be carrfull to see if it is always on or only when ingnition is on.  Might have to install a direct battery line, and if you do so, go with at least 10 ga.

Photomom

There is very likely a sticker or at least a note in your user manual specifying the maximum wattage that your car’s 12v outlets can supply. If your ARB can draw 5.1 amps at 12 volts, that equates to 61.2 watts. If your car can supply more, you should be fine.

The limit applies to all the outlets, in my Highlander I have 3 outlets, 120 watts combined wattage. See pic for example sticker.

Tabaz

I have the same 50 Qt. ARB as mentioned above (1 amp per hour under normal conditions). I'd like to have a stand alone battery to power it.  I plan on recharging the battery via solar each day when boondocking.  How large of a battery do I need (would like to get the smallest practical size?  I'm assuming an AGM because it will be inside the vehicle.

ColoradoJon

Tabaz said:

I have the same 50 Qt. ARB as mentioned above (1 amp per hour under normal conditions). I'd like to have a stand alone battery to power it.  I plan on recharging the battery via solar each day when boondocking.  How large of a battery do I need (would like to get the smallest practical size?  I'm assuming an AGM because it will be inside the vehicle.

That depends!  1 amp per hour x 24 hours in a day = 24 amps total used minimum.  Most likely need more than that, so add 50%, = 36 amps.  Double that number to account for draw down limits (50%) gives you a minimum battery capacity of 72 amp hours.  That's a good ballpark figure, and about the size of a good class 24 12v battery.  Personally I wouldn't worry about the 50% draw down limit.  Go ahead and draw it down more if it's just going to run the ARB.  You will lose some service life but the battery would be cheap enough

Tabaz

Thanks Jon! It will only be powering the ARB.  I'll start looking for a 40 to 50 amp AGM (assuming they make them).

ColoradoJon

Check out this Keyko 55 amp AGM battery on Amazon:

Keyko Battery

SKU KT-12550-HRT.  They say its for wheelchairs/Mobility, and Solar.  37 lbs. with a built in strap handle.  Seems like it would do the trick at $125.

Photomom

@JohnDanielsCPA, how is your ARB working? Not happy with mine - see separate post.

Tabaz

Thanks again Jon.  Will also check my local battery retailer.

JohnDanielsCPA

@Photomom too early to tell.  I was running it empty and noticed quite a difference between the ARB temperature and my digital thermometer.  I calibrated my digital thermometer to my home refrigerator and found it to be off by 2 degrees, so close enough.  But I am getting a 6 degree difference between the ARB and the thermometer.  I am headed out of town for a week, but when I get back, I’ll calibrate the ARB to the thermometer.  What I am actually surprised at is the temperature swings between how far the temps will rise before the compressor kicks on to cool it back down.  That range is about 6 degrees.

Anyway, I think what others have said is probably true; that is, once you get something to cool inside the ARB, the temps will probably moderate to a more acceptable level.  Since we have a year to return the ARB to REI, we have plenty of time to “test” it and see if it’s going to work.  That’s the main reason I paid a bit extra and bought it from REI; so I would have the option to return it if it doesn’t work out very well.  But it has to be better than the onboard refrigerator I have now.  It’s absolutely terrible - the worst RV refrigerator I have ever owned.  It has been impossible to get it to hold even a reasonable range of temperature, and I have not been in extreme temperatures.

Sharon_is_SAM

@JohnDanielsCPA, your ARB temp experience is similar to ours.  I used an Accurite temperature gauge to monitor ARB vs galley temperatures.  I kept lowering the temperature because I did not like the Accurite reading.  I am going to test it this week with 2.5 gallons of water in it.  I will also get an accurate thermometer to calibrate.  I believe I read that the ARB temp gauge is located more centrally within the unit, so I may check there and at the bottom.

JohnDanielsCPA

@SAM, your statement that the ARB temp guage is located more centrally within the unit is consistent with a test I did.  I placed three bottles of soda water within the ARB; one at the front, one in the center and one in the “dairy” compartment.  After several hours, the bottle in the center of the unit was the coldest.

Sharon_is_SAM

I tried using a frig thermometer but I could not locate a position that corrolated to the ARB display.  I ended up recalibrating the display to the temperature found at the bottom. I have found the Accurite to read 3-4 degrees higher than the ARB and the dairy area is up to 10 degrees higher than the bottom.

CanyonTravelers

You can change the calibration of the ARB to match an accurate reading.  Youtube has videos that show you how to do this.....