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09-21-2020, 09:55 AM
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#1
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Senior Member
Winnebago Owners Club Freightliner Owners Club
Join Date: Jul 2014
Location: Ohio
Posts: 185
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AGM battery voltage level
Does this look like an accurate voltage chart for 3 new agm batteries?
Mine don't hold a charge like this. Mine seem to stay closer to 12 volt.
https://linksharing.samsungcloud.com/QwOpPDWRF87N
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09-21-2020, 10:36 AM
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#2
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Senior Member
Join Date: Jul 2014
Posts: 35,417
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That chart may be for flooded batteries, AGM have about .1 volt more at 100% charge.
You will need to have no draw on the batteries, for at least a few hours, before measuring the battery voltage and comparing it to the charts.
Yes, an AGM fully charged should show 12.7 volts.
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09-21-2020, 03:43 PM
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#3
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Senior Member
Winnebago Owners Club Freightliner Owners Club
Join Date: Jul 2014
Location: Ohio
Posts: 185
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maybe that's it...I have never measured them having not had a load on them for a couple of hours.
Do folks keep their inverters on while plugged into shore power or turn it off?
__________________
2008 Itasca Meridian 39z.
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09-21-2020, 04:20 PM
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#4
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Senior Member
Join Date: Jul 2014
Posts: 35,417
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Quote:
Originally Posted by kongmen
maybe that's it...I have never measured them having not had a load on them for a couple of hours.
Do folks keep their inverters on while plugged into shore power or turn it off?
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In your rig it won't matter. While on shore power, the inverter/charger becomes a charger only. The shore power is passing thru the inverter to whatever it powers.
If it senses a loss of shore power it will come on to power stuff. If you shut it off, it won't.
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09-25-2020, 08:25 AM
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#5
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Senior Member
Winnebago Owners Club Freightliner Owners Club
Join Date: Jul 2014
Location: Ohio
Posts: 185
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When I look at the 3 different options for checking voltage,onnan energy command, inverter, toggle switch for coach they all read within 2 or 3 tenths of a volt. After 4 days of 50 amp shore power they all read 13.5 before unplugging from 50 amp power. Right after unplugging they now read 12.1 - 12.3 volts. The chassis batteries read 12.5 volts. I don't understand the drop in voltage. I am leaving the refrigerator on at 425 watts maybe that's it don't know.
__________________
2008 Itasca Meridian 39z.
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09-25-2020, 08:16 PM
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#6
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Senior Member
Winnebago Owners Club Freightliner Owners Club
Join Date: Jul 2014
Location: Ohio
Posts: 185
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Something is wrong with These batteries. 13.5 volts after 4 days on 50 amp shore power (inverter showing float mode so batteries were fully charged) 12.2 volts 20 minutes after unplugging. Now 11.8 volts after driving 7 hours and running a norcold refrigerator at 425 watts.
Batteries are only 2 months old. Duracell 31 AGM from Sam's club.
Any ideas?
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09-26-2020, 01:53 AM
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#7
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Senior Member
Join Date: Jul 2014
Posts: 35,417
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7 hours of 425 watts equals 236 AH from your batteries 300 AH of batteries. Your voltage readings make sense.
425 wats at 12.6 volts is 34 Amps. 34 amps for 1 hour is 34 AH. 7 hours X 34 AH = 234 AH from your 300 AH battery bank.
If your engine charging system was connecting to your house batteries, like it should, you would be ok after the trip. Big chance its not connecting.
Now you need to check your isolation/charging solenoid system.
The thing that fails most often, is the solenoid. You can locate it by pushing on and off the boost or emergency start button, while listening for it to clunk.
Find it, check it, and if bad replace it.
With engine running, engine battery voltage should read on both large terminals of it.
Why are you running a gas/electric fridge on your batteries while driving ?
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09-26-2020, 04:53 AM
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#8
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Senior Member
Fleetwood Owners Club Ford Super Duty Owner
Join Date: Jun 2012
Location: SoCal
Posts: 15,749
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Battery voltage / SoC chart for estimating status of lead acid battery type.
__________________
Vince and Susan
2011 Tiffin Phaeton 40QTH (Cummins ISC/Freightliner)
Flat towing a modified 2005 Jeep (Rubicon Wrangler)
Previously a 2002 Fleetwood Pace Arrow 37A and a 1995 Safari Trek 2830.
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09-26-2020, 07:50 PM
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#9
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Senior Member
Winnebago Owners Club Freightliner Owners Club
Join Date: Jul 2014
Location: Ohio
Posts: 185
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twinboat thanks for the info.
I will check the solenoid.
I was running the fridge on battery power because I thought as long as I was driving why not use the engine generated power?
I'm new at rving. It looks like I will be using gas for the fridge when not plugged into shore power.
How do people with residential refrigerators power their fridges while not plugged into shore power?
__________________
2008 Itasca Meridian 39z.
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09-26-2020, 07:55 PM
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#10
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Senior Member
Join Date: Jul 2014
Posts: 35,417
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They run them with inverters like you tried but the isolation solenoid needs to be working. You can run yours on battery but you need to fix the charging.
Residential fridges use about 1/3 the power of a gas/electric model, so even without chassis charging, they can go for much longer.
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09-26-2020, 07:55 PM
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#11
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Senior Member
Damon Owners Club
Join Date: Apr 2020
Location: Clovis NM
Posts: 4,389
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Generator, or a large battery bank with an inverter. What many people fail to understand is that when the 120VAC draw is 400 watts, or about 4 amps, when you are drawing from a 12VDC battery bank, the amperage draw goes up by times 10. So the 4 amps becomes 40 from the battery.
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2006 Damon Daybreak 3276 35'with 5 Star Tuner. 3 200 Amp Lithium batteries and 2000 watt PSW inverter/charger. 2013 Elantra on a Master Tow dolly.
Retired USAF
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09-27-2020, 07:08 AM
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#12
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Senior Member
Winnebago Owners Club Freightliner Owners Club
Join Date: Jul 2014
Location: Ohio
Posts: 185
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Thanks again fellas.
I think I'll just keep it on gas while not plugged in. I'm going to see if the batteries charge at all while driving. If they charge during a drive without the fridge on then I can assume the solenoid is working?
__________________
2008 Itasca Meridian 39z.
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09-27-2020, 07:32 AM
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#13
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Senior Member
Join Date: Jul 2014
Posts: 35,417
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Like I said, they should have charged even with the fridge running.
It will work your alternator pretty hard but it should be rated at 160 amps.
Run it on gas and see if your getting charging.
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