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sbleiweiss · 10-24-2021, 10:12 AM

I foolishly forgot to plug my motorhome into shorepower when I returned it to its garage. It sat that way for 5 days with the inverter on but not much else. I came back to find the low voltage alarm beeping and input voltage shown on the inverter of 10.6. I plugged it into 50 amp shorepower and in about 18 hours the input voltage has risen to 12.5.

I am used to seeing input voltage showing 13.6 when bulk charging and 13.1 when float charging. Why is it showing 12.5? Do you think I need to replace the two 6 volt three year old batteries? Or does it just need more charge time?

It is a Xantrex XM 1800 if that matters. I don't have any testing equipment for batteries. Thanks.

Old-Biscuit · 10-24-2021, 10:14 AM

Check battery water levels and give it more charge time

Any Auto Parts Store......hydrometer
Check each battery cell and compare readings

sbleiweiss · 10-24-2021, 11:03 AM

Thanks Old-Biscuit. I checked water levels and they all needed some water added, which I did. I read that a hydrometer shouldn't be used shortly after adding water. Still reading 12.5 currently. I'll see what it reaches tonight.

But if I usually see what the charger is doing (i.e. float at 13.1 or bulk at 13.6) why am I now seeing what is apparently the battery charge level versus what the charger is doing? Am I misunderstanding something here?

153stars · 10-24-2021, 12:20 PM

Maybe when inverter reset the battery temp probe went wonky. If it has one try to unplug it.

sbleiweiss · 10-24-2021, 12:24 PM

Its hardwired 153stars.

twinboat · 10-24-2021, 12:40 PM

The XM 1800 is just an inverter. It does not charge batteries.

How much water did the batteries take. If more the 1/2 gallon then the batteries may be cooked.

Ray,IN · 10-24-2021, 01:39 PM

Some battery chargers in MH's will not begin to charge a dead battery, you must use a stand-alone charger until they are partially charged, then switch back to MH battery charger.
Do not leave the inverter on, it draws on the battery bank even without a load.
Your batteries cannot be tested until they are at the maximum charge level they can accept.

sbleiweiss · 10-24-2021, 01:57 PM

Quote:

Originally Posted by twinboat

The XM 1800 is just an inverter. It does not charge batteries.

How much water did the batteries take. If more the 1/2 gallon then the batteries may be cooked.

Took only about a quart and a half total. No plates were exposed. My MH has a charger, I don't know if it is part of the inverter or separate.

sbleiweiss · 10-24-2021, 01:58 PM

Quote:

Originally Posted by Ray,IN

Some battery chargers in MH's will not begin to charge a dead battery, you must use a stand-alone charger until they are partially charged, then switch back to MH battery charger.
.

Does the fact that they have come back from 10.6 to 12.5 mean that the onboard charger is charging them?

twinboat · 10-24-2021, 03:05 PM

If they came up to 12 volts from 10.5 volts, something must be charging them unless the inverter was powering something. Then the battery volts may have bounced up once the load was removed.

10.5 volts is a deep cycle. It's not damaging to your batteries, anything below that can be.

You have a separate converter/charger. It will charge low batteries but the Use / Store switch near the door must be on.

sbleiweiss · 10-24-2021, 04:09 PM

Quote:

Originally Posted by twinboat

If they came up to 12 volts from 10.5 volts, something must be charging them unless the inverter was powering something. Then the battery volts may have bounced up once the load was removed.

10.5 volts is a deep cycle. It's not damaging to your batteries, anything below that can be.

You have a separate converter/charger. It will charge low batteries but the Use / Store switch near the door must be on.

Nothing was running on the inverter. The Use/Store switch has been on Use. But the charging seems to have hung up at 12.5. It has not increased in the last several hours. And I still don't understand why I usually see the charging numbers (13.1 or 13.6); now I am seeing the battery level number of 12.5.

paddler1954 · 10-25-2021, 03:26 AM

My I suggest you un-plug from shore power, inverter off, does the battery voltage drop off pretty quickly? If so, that would suggest you have a bad battery. If the battery voltage holds after a half hour or so, then fire up your engine and let the alternator charge up your batteries. I'm making the assumption that a gasser can charge both the starting batteries and house batteries from the motor's alternator.

Kenrbass · 10-25-2021, 04:56 AM

If you check the voltage of each 6 volt battery, that may tell you something. They should be pretty equal, but if one is 6.3 and the other is less that tells you one of them is bad. After charging a day with the water added (distilled water) you can hydro test. At 3 years old with issues, I would be putting a new pair in myself.
From the auto world, 12.6 is fully charged without the charger on and 13.8 to 14.2 with the charger running.

sbleiweiss · 10-27-2021, 08:21 AM

Update from OP. My batteries are charging up, but one of them has a dead cell according to hydrometer. Leaving on trip soon, but will change out the batteries when we get to CA. An Interstate Battery store is holding two for me. Does anyone see any problem with our driving for two days on these batteries? We will stay in parks with 50 amps and be charging from alternator during the driving day. Only stops without power will be fuel or rest stops for short stops. Thanks to everyone that responded.