Re: Advice on more battery power
If your setup worked in the past but doesn't now, the battery might be getting near the end of its life, the refrigerator is causing the problem, or there might be a grounding problem with the battery. We had a 4 CF Norcold and it did seem to start drawing more power after several years of use. You might start by checking out the door seal. Take a dollar bill and close the door on it. When you pull it out, there should be a little resistance. If not, the seal might be getting old and brittle. You can replace it with a new seal which is easy to do. However, when I tried to do this a few years ago, the replacement seal I received was worse than the one I was trying to replace and I gave up on it. Someone mentioned on a past post that the compressors in these units are not the best and inefficiencies due to age could make the unit draw more power.
I'd start by checking out the refrigerator and seeing if you can determine why it might be pulling more power now if it is fact doing that. Next, check the cables serving the house battery and make sure that they are in good condition and not worn through which could cause the battery to ground out. How old is your battery? If you decide to add a second battery, both probably need to be new at the same time. So, you could first purchase a new one and see if that solves the problem. If not, you'd be in good position to add a second new battery. At that point, the other option is to replace the refrigerator.
For comparison purposes, we had a 4 CF Norcold and a single 4-D battery. Six months ago when I took some measurements on it, the battery was about 1-1/2 years old. With no lights on (these tests were done in the driveway and not while camping) and with the refrigerator at 6 o'clock, the house battery would drop to 12.2v in the morning. The battery is now 2 years old but with the Isotherm refrigerator (which doesn't draw down the battery at night), we will be at 12.4v or higher in the morning even after the furnace has been running for 2 hours.
'01 Ford EB50p Quigley 4WD