12V Loss House Batteries

[Ed & Diane]

I am trying to chase a voltage loss when not plugged into power. Problem first appeared when plugged into a bad? 30 amp campground panel. At 95 F temp, turned on 1 AC, after a minute, lost all power. The park panel did not trip. Dry camp to and from Gillette. Checked dogbone, transfer switch, had house batts tested, [good], monitored batts. Allowed gen to run overnight, AGS, it cycled most of the night, 15 minutes on, 15 off, charger in absorb or float. Without shore or gen, after driving all day and running gen a lot, in evening we had 12.8v, in morning at 10.8v. Turned off breakers overnight. Problem pointing to the batts or the inverter?

Back home, 30A power. Tried to do more controlled testing. Pulled out the house batts and had them retested, they said they found a bad cell in each 6v batt. I am not confident of this test, because their mechanic (machine) was trying to set it for cranking amps. Cleaned all wire connectors in batt and service bay, back to the starter. Improved my power by 0,1V. With house batts sitting on the garage floor for 4 days, all batts held their charge, near 6.4v. Over the last few weeks, disconnect the shore power, batts in.

House batts, 6 AGM Lifeline, 900AH, age 5.5 years.

Inverter, Xantrex RS2000, 9 years old, (2nd one).

Disconnect 30A, at SL disable inverter and charger, 110v breakers off, subpanel inverter breaker off, fridge plugged in externally. No obvious power draws.
Batts stay at 12.8v all day 8-12 hours, in morning at 10.8v.

2 batts at 4,4v and 4 at 6.4v. wow, 4.4 +6.4 = 10.8. So lets disconnect the 2 BAD batts, 600AH, redo test.
All day at the 12.8v and in morning 10.8v. Again, 2 at 4.4v and 2 at 6.4v.

Tried as above, remove ground wire from bathroom fuse block. Same 12.8 to 10.8 in morning.
Tried as above, with ground wire at water bay remove, bathroom reconnected, same 12,8 to 10.8.

Remove the Xantrex temp sensor, no change. Even disconnected the solar panels, no change.

With batt disconnect switches turned off, I am able to maintain my 12.8v for a couple of days.

I even replaced my Sure Power Battery Separator.

I recharge the batteries between testing, 30A shore. Notice that the charger comes on in bulk for only a couple of minutes, and then to absorb. This is telling me that the batts are not severely discharged.

I would like to do another load test on "deep cycle" batteries to prove them. Previous AGMs had a life over 9 years.

I can spend $2000 for batts OR inverter. I'd like to do it right the first time.
I think the inverter has treated us right for the last 9 years.

What am I missing? Any further testing, or take it to a service center, (who?) and let them start over?

[Ed & Diane]

title should have been "2V loss house batteries".

Gremlins steal 2V overnight when no shore or gen power.

[c_oneil]

Sounds like you have investigated this pretty well so I am not sure how much I can help but the first thing I would check is that Diane isn't going out to the coach at night and running a hair dryer off the inverter.
Seriously though, let me throw out a couple ideas:
1. Do you have any way to put an amp meter on it to see how much current is actually drawing off your battery bank? I use a Victron battery monitor like this https://www.victronenergy.com/battery-monitors
700 series.

It reads out the amp charge or discharge rate at the moment and also keeps a running tally of amps over time for a total of amp-hours used. If you can measure the amp draw it would help you find the system that is drawing the power and discharging the bank. You would just keep turning things on and off while watching the amp draw till you find what is using all the power. With a monitor system that tracks amp-hours you can also confirm the amp-hour capacity of your battery bank and tell when they are getting tired.

2. Is you inverter not doing a proper charge cycle and just leaving a surface charge of 12.8 volts on the battery bank that is easily drawn down to 10.8 volts overnight? Don't understand why the bank would then hold a charge all day but not overnight.

[Old Scout]

...I probably can't add much to the discussion but do know that the RS2000 on our Alpines is connected directly to bats, so shutting off the bat switches doesn't kill/isolate the inverter from the house bats...so unless you disconnect the inverter or put it in hibernate mode [sleep], it will draw down the house bats in a few days [one fan runs continuously] ....tend to agree that 1- inverter is not producing a "quality" charge cycle, eg, bulk, absorb, float; and/or 2-your bats are showing their age......

[Ed & Diane]

I took the AGM batteries out and took them in for a load test. Fully charged they were at 6.7v. After a 75A load, it pulled them down in 9 to 11 minutes. My understanding, it should take 173 minutes for this load drop. So I am at 7% of the capacity for new batteries. Time to order new batteries.

I also removed the RS2000 inverter and had it tested at a Xantrex service center. They said everything was working properly and should continue to give me good service. Although it is no longer serviceable, everything looked good.

I expect the new batteries to resolve the erratic behavior.

[DrDaveMA]

Before you install the new batteries check the inverter to be sure it is set for AGM’s (and all the other parameters), particularly since a “service center” had it, they could have changed one or more and that could wreck new batteries.