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Old 07-11-2019, 05:04 PM   #21
alg
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Default Carado Banff AGM Battery Voltage Question

Iím a new RV owner, new to the group and need HELP with a AGM battery voltage question.

BACKGROUND: I have a 2018 Hymer Carado Banff RAM ProMaster 2500 (gas 3.6L engine) that has an AGM battery listed as 105 AH @ 20hrs. The other day I missed shutting off the Frig and now notice the monitor voltage display at 12.4 volts with the Battery Disconnect switch enabled but when the Inverter switch is also enabled the display then reads to 13.4 volts. Iím concerned since YouTube RV AGM battery videos note that an AGM battery reading at 12.4 volts is about 75% charged.

Which RV monitor display of AGM voltage is the one of concern to know about the battery charge percentage . . . Only with the Battery Disconnect switch enabled or with both the Battery Disconnect switch and Inverter switch enabled? As usual the Carado Owners Manual is useless about explaining this detail concern.

Now recharging the battery by home hookup and can speed up charging by starting engine using the generator unit (GU) for an hour or so (about 2,500-3,000 watts watts/hr charge). Naturally would have been smarter to keep a better eye on the voltage, install a Low Voltage Cutout Unit or have more than one AGM battery connected in parallel, or pair of lithium iron phosphate batteries.

I have a number of other questions for another time about adding another AGM battery in parallel or replacing with a pair of lithium Iron Phosphate batteries, access to current AGM battery and whether any Inverter/Charger unit parameters might be required. Hopefully there are some RV motor home battery experts out there.
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Old 07-11-2019, 07:12 PM   #22
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Default You will find more on this Facebook group

There is a Facebook group called Carado and Sunlight owners with 600 members. There is a mixture of vans with ecotreks and agm batteries. Our Banff has ecotreks so I can't help more with your questions.

https://www.facebook.com/groups/461889954253973/
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Old 07-11-2019, 07:29 PM   #23
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Quote:
Originally Posted by alg View Post
.............and now notice the monitor voltage display at 12.4 volts with the Battery Disconnect switch enabled but when the Inverter switch is also enabled the display then reads to 13.4 volts. ..............
Is the rig plugged into shore power when you see 13.4V?

Does your RV have solar panels?
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Old 07-24-2019, 09:36 PM   #24
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Unless Carado's are very different than other Roadtrek/Hymer, the inverter will draw 100 watts of power from the batteries when turned on even with nothing else running. If you are plugged into shore power, it will charge the batteries if you have the batteries on.

Voltage is only an accurate measure of depth of charge with no load either charging or discharging. For instance, my refrigerator kicking in usually knocks a couple tenths off the voltage that come back as soon as it stops running.

That 13.4 reading is probably the charger. If I am parked in the sun with my solar panel I usually have a 13.1 reading. The 12.4 reading may indicate depth of charge if nothing else is on. But that is still only a rough estimate. You really need to not only turn everything off but let it rest overnight or longer to get a completely accurate reading.

Voltage is at best a rough indicator of the depth of charge. BTW, for AGM batteries I think 12.4 is less than 75%. You would expect 12.6 at 75% with 12.8+ fully charged and 12.3 at 50%. The voltages are a little different than standard flooded lead acid batteries. If you are concerned about precision, you might want to check with the battery manufacturer. Frankly, given all the uncertainties of voltage I don't worry about it. If you are over 12 volts you are probably OK, but the closer you get to that point the harder it is on the battery.
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Old 07-24-2019, 10:12 PM   #25
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One AGM is standard on a 2018 Banff. One of the available options was to add two Ecotrek lithium iron batteries. I'm pretty sure I have an AGM plus the two lithium batteries. You can fairly easily check to see if you have the lithium batteries, which are mounted on the underside of the Banff as is the AGM. 13.1v is a good voltage on the lithium batteries. If my Banff's voltage drops to 12.4v, power is either off or about to go off. I've seen much higher voltages but not since Dan Neeley reset my Balmar and solar controller. If you have the lithium batteries and if they are Rev. H, then you likely need to change or hire someone to change the settings. If they are Rev. L, that is less urgent because Rev. L has built-in protection against overcharging. Some Banff owners have Rev. H and some have Rev. L. There are some documents in the Facebook newsgroup on what settings you want. If the inverter actually draws 100W when it's on, that might explain why my power goes off at night when boondocking even though I turn it on only to run my BiPAP machine. That suggests that I should leave the inverter off at night and use the smaller lithium batteries I have for the BiPAP. They can be charged in the daytime when there is good solar production.
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Old 07-24-2019, 10:55 PM   #26
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For lithium batteries voltage is virtually useless as a measure of charge. It will tell you when it is fully charged and when it is starting to reach full discharge but doesn't change much at anywhere in between. I am not surprised that 12.4 volts would indicate you are just about out of juice.
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