Power advice needed

[55AS]

Vintage trailer with no 12 volt system. At some point I plan to install a converter and 12 volt system but in the short term I want to go camping. I replaced the old LP fridge with a Norcold 410, which needs 12 volts to operate the control board. We generally camp with hookups but I would like to be able operate the fridge while boondocking for short periods.
I am thinking of installing a small lithium ion battery (no venting required) and smart charger that I can plug in to charge the battery when conencted to shore power. I have space below the fridge which makes the wiring easy. First question is what battery capacity I need since lithium batteries are $$. Here is the current draw info from the Norcold manual:

Propane Gas Operation
12 volts DC control voltage
(11.5 volts min. - 15.4 volts max.)
Current Draw
.37 Amps at 12 volts DC

.42 Amps at 15 volts DC

Is this max or continuous draw? If continuous, I would need about a 40 AH battery in order to run the fridge for three days (72 hrs x 0.4 amps = 29 AH). This seems like a pretty big ($$) battery to just run the control board.
Recommendations?

[Al and Missy]

I'm going to venture an opinion that the current listed is the maximum and only occurs when the control system has actuated the propane valve. The best way to determine this, however, is to measure it. HF and others sell inexpensive multimeters if you don't have one. Take a car battery and hook it up with the meter in series with the positive lead to the fridge. You will have to let it run long enough to cool off so that the propane valve shuts off. Once that happens you should see two different levels of current and you can time now long it spends in each mode to calculate an average.

As an alternative, you could just wire it to the tow vehicle and let the TV battery power it. If you have a 7-pin connector on the TT and connector on the TV just hook up the battery charge line to the fridge. Obviously won't work if you plan on disconnecting, but if not you should be good for several days. Just don't let the TV battery go down too far or you'll be stuck.

Al

[55AS]

Originally Posted by Al and Missy

I'm going to venture an opinion that the current listed is the maximum and only occurs when the control system has actuated the propane valve. The best way to determine this, however, is to measure it. HF and others sell inexpensive multimeters if you don't have one. Take a car battery and hook it up with the meter in series with the positive lead to the fridge. You will have to let it run long enough to cool off so that the propane valve shuts off. Once that happens you should see two different levels of current and you can time now long it spends in each mode to calculate an average.

As an alternative, you could just wire it to the tow vehicle and let the TV battery power it. If you have a 7-pin connector on the TT and connector on the TV just hook up the battery charge line to the fridge. Obviously won't work if you plan on disconnecting, but if not you should be good for several days. Just don't let the TV battery go down too far or you'll be stuck.


Al

That is a good option. I will do the test next time I have access.
I do have a 7 pin connector but not sure the TT end is connected to anything. Also, may want to boondock with TV disconnected. Anyone have real world measurements or specs for control board current draw?

[Al and Missy]

On my 2006 F150 the battery charge didn't appear to work. It turns out that when the truck was delivered new there was a plastic bag with a trailer brake harness adapter and a relay in it. The relay was to activate the battery charge pin. Apparently neither of the previous owners installed it and one threw it away. I bought a replacement relay and plugged it in and the battery charge pin was energized when the engine was running. So depending on your TV, don't despair if at first it doesn't appear to work. Try it with the engine running, and without.

On my Ram 2500 it is activated all the time.

Al

[55AS]

I have a 2014 F150 and the relay is still in the glove box. No point in installing it yet as the TT end of the charging line is not yet connected to anything :-)

[55AS]

No nobody knows the amount of current required to run the fridge control board??