12-volt refrigerator issue 2021 Micro Minnie 2108DS

[dougs]

We recently did our first extended (6-day) boon docking trip with our 2021 2108DS, but experienced sporadic trouble with the Dometic DMC4101 12-volt refrigerator. Usually it worked fine, when on our 12-volt lead-acid battery or when I fired up our Champion 2500 generator. But several nights, with generator obviously off, refrigerator stopped even though our Victron Smart Shunt monitor showed the battery at more than 70 percent charged with more than 11 volts remaining. Manual says that refrigerator should work from 10.5 to 17 volts. The "idiot lights'' in the RV showed no battery power even when monitor showed 70 percent. When I started generator and charged battery the next day, refrigerator worked fine again. So did my battery fall below 10.5 volts, causing the refrigerator to stop, despite what my battery monitor said? Or was it something else? The fridge made a clicking sound one night; I powered it off and turned it back on, which stopped the noise. We're newbies; got the RV, our first, last spring, and haven't had any trouble with the fridge until now.

[creativepart]

There are too many variables concerning the installation, setup, and configuration of the Victron BMK for us to judge the readings you are seeing and their validity.

With a 12v battery showing 11v you should realize that your battery is 90 - 95% depleted regardless of what your Victron BMK says is your state of charge. And at 10.5v it is totally dead and possibly ruined if not fully recharged immediately.

If setup correctly a 70% state of charge should show a voltage of ~12.4v. So, perhaps you need to revisit your BMK installation and configuration.

You should strive to keep your battery between ~12.7v and 12.1v

[bigb]

Also two points to keep in mind, when there is a load on the battery it will have a lower voltage than when it it unloaded, so the fridge load probably took the battery down below it's threshold and shut down which in turn made the battery voltage rise a bit which is what you saw on the monitor. Voltage is not always an accurate way to get snapshots of lead acid battery state of charge because it is not accurate while any load or any charge is present and it is not accurate for some period of time after the load/charge has been removed, often for up to several hours.
The other point is the Smart Shunt, it does not and cannot tell how much battery is remaining by sampling voltage, it is merely a counting device that tracks how much current is going out and how much is coming in. Like Creativepart said if it is not initially configured correctly, or if it is not wired to include every single load and every charging source, it will not be accurate. There will also be some "drift" in the accuracy as the battery ages or suffers damage from over-depletion.

[bigb]

Trying to simplify this further, as CP stated at 11 volts the battery was more than done. Even if the fridge says it will run on 10.5 volts, as soon as it tries to start on that 11 volt battery it will pull it down below 10.5 and click off. So to answer your question, yes the battery dipped below 10.5 volts.

IMHO the manufacturers that put out a unit with a 12 volt fridge and single 12 volt "Marine Deep Cycle" battery (which is not a true deep cycle battery at all) and a single 100 watt solar panel are giving you barely enough to prove that it works and to get it sold and down the road. It is not enough to dry camp. You may want to consider true GC-2 6 volt deep cycle batteries wired in series, or if the budget allows, Lithium and all the goodies that go with Lithium, and more solar.