Electrical Issue: Converter, Battery, Something Else?

[ScandentTrek]

Hey folks! Long time reader, first post!
So we've lived full-time in our 1997 Fleetwood Mallard 30ft for almost 4 years. Until recently we were plugged in at a full-time RV park and had no electrical issues.
We recently moved to a new location (MIL's house) with no 30amp connection. We're plugged into the house (15amp house plug with appropriate dogbone converter plug and surge protector) and while we plan to be here for a while (4 months or more), we aren't sure if adding a 30amp plug is in the future.
Since we got here we've been having a new and odd electrical issue.
Our on-demand water heater (DC) started turning on and off randomly, causing it to beep at unexpected times. Sometimes it actually flickers so quickly it doesn't beep, but we can see the display flashing on and off. We also noticed that our range fan (on the same circuit) has similar power fluctuations, causing the speed to rise and drop rhythmically. None of our other DC appliances have this issue. None of our AC appliances are having an issue. We've even been able to run our AC unit through these heat waves.
We discovered that if we turn off our converter, we don't have this problem. Without the converter, everything runs smoothly, although of course this slowly drains the battery.
Now, we tried changing the outlet we are plugged into, not using a GFCI outlet in case that's the issue, but it didn't make a difference.
Our battery is still charging nicely, and the converter seems to be in working order. On battery power only, everything works perfectly. Turn the converter on and eventually, some hours later (but not immediately), the flickering starts again. Turn the converter off, and immediately the flickering stops and everything is good.
I don't want to do too much guessing, but I'm wondering if there is an issue with the converter when it goes into maintenance mode after the battery is fully charged again. Or this is a problem with using 15amp shore power instead of 30amp? Possibly the battery?
Has anyone had a similar issue? How would we go about troubleshooting this?
We're just praying it's not a problem with the wiring behind the walls. Thanks in advance!

[ScandentTrek]

MFL wrote:

bgum wrote:
I can't figure out how you're doing all that on 15 amps. That circuit is over loaded.

^This...running the AC alone on a 15A circuit, would be a heavy load. Any additional electrical load should trip the breaker. The converter charger is likely overloading, so helps to shut it off.

To be there that long, a 30 amp circuit, with 10/2 minimum wire would be a wise investment. I used 8/2 to run 75'.

Jerry

We haven't had an issue with the breakers tripping. Our AC unit is as old as the trailer and fairly small.
How would using too much AC power (not enough to trip the breaker) cause the converter charger to overload? I would think the breakers (in the house or in the trailer) would trip first before any kind of overload could occur.

[MFL]

bgum wrote:
I can't figure out how you're doing all that on 15 amps. That circuit is over loaded.

^This...running the AC alone on a 15A circuit, would be a heavy load. Any additional electrical load should trip the breaker. The converter charger is likely overloading, so helps to shut it off.

To be there that long, a 30 amp circuit, with 10/2 minimum wire would be a wise investment. I used 8/2 to run 75'.

Jerry

[cooldavidt]

your battery sounds like it is quite old. If so it probably doesn't have much capacity. Did you test it when it was hooked up? You need to test it unconnected to get a good idea..



You need to look at the load capacity. A shop can do that.

https://purkeys.net/load-testing-vehicle-batteries-in-three-steps/#:~:text=Take%20the%20rated%20CCA%20of,you%20let%20the%20load%20off.

It doesn't sound quite safe to me.

[ScandentTrek]

I found the owner's manual for the converter, with troubleshooting steps included.
https://www.hayseed.net/~jpk5lad/RV%20Information/MagnaTek%20Pwr%20Converter/RV%20Binder1.pdf

It has a diagram for testing the converter output, so I'll do that in a minute. I can't shut off the shore power without losing our Starlink, so I'm waiting for a better time.
I just tested my battery and the voltage is 13.8 when the converter is On, and 13.3 when the converter is Off. As I stood there with the multimeter attached, the voltage slowly dropped from 13.3 to 13.1 in about a minute, with the converter off, slowly losing voltage.

[ScandentTrek]

Converter is a MagneTek Series 6300A Power Center - original to the trailer.
No idea about the battery. It was on the trailer when we bought it and the info has flaked off.
How do I check the output of the converter? I've opened it up and looked inside, but I'm not sure where to put the voltmeter. There are a variety of different connections and wires in there.

[bgum]

I can't figure out how you're doing all that on 15 amps. That circuit is over loaded.

[enblethen]

It could be dirty battery connections.
What is make and model of your converter?
How old are the coach batteries?
Do you have a voltmeter? Check the converter output for voltage. Operate the coach battery disconnect and see if voltage increase. If it does batteries could be failing.
Verify AC voltage at receptacle.
Doubt whether it is a concealed wiring issue.