Battery Drain

[candrews768]

I have a 2018 Classic 33 that came with two Napa Marine 8270. Research say thay are 80AH Batteries, label says 650 Wet. Really not clear.


I get them charged to 12.9 but they discharge rather quickly. I get the rig down to no lights etc. Refrig only (propane). The discharge goes from 12.9 to 12.3 in three hours. down to 12.0 with heat on (propane). Airstream says the batteries are good after asking them to test.



Should these discharge that quickly?

[DaveP]

No. They are weak at best. If they are under warranty, ask for replacements.

[uncle_bob]

Hi

Welcome to the wonders of a modern Classic.....

The control system and other "fun" stuff is likely pulling about 2A. It does vary a bit. There are lots of things contributing. The inverter is sitting there pulling power when it's turned off (yes that sounds crazy).

Next up, your absorption fridge pulls about an amp for the control board and other odds and ends.

Net result is sitting there doing nothing, whole world turned off, you are dumping around 3A or so. In a day of continuing to do nothing, you will go through about 72AH.

Your wet cell batteries were rated at 80AH when new. The pair of them will give you 80AH of usable capacity when new. They are only "bad" when they get to 80% of that, so 64 AH.

Full charge should read up around 13.2V on the battery posts with the charger running. Even at that voltage, it will take hours to complete the charge. Figure running on shore power overnight to get a full charge.

Even with that full charge, you won't get a full day's operation out of batteries that are "on the edge". (Yes this is why folks put 400AH or more of Lithium in Classics .... )

Working all this out from voltages is highly problematic. You really need a shunt based battery monitor to tell what's going on. There are a lot of them out there. The Victron BMV712 is a good one.

If you *really* want to nuke the battery, leave a couple lights on in the storage compartments ..... zoom .....

Fun !!

Bob

[candrews768]

Thank You, now I am gonna have a drink

Originally Posted by uncle_bob

Hi

Welcome to the wonders of a modern Classic.....

The control system and other "fun" stuff is likely pulling about 2A. It does vary a bit. There are lots of things contributing. The inverter is sitting there pulling power when it's turned off (yes that sounds crazy).

Next up, your absorption fridge pulls about an amp for the control board and other odds and ends.

Net result is sitting there doing nothing, whole world turned off, you are dumping around 3A or so. In a day of continuing to do nothing, you will go through about 72AH.

Your wet cell batteries were rated at 80AH when new. The pair of them will give you 80AH of usable capacity when new. They are only "bad" when they get to 80% of that, so 64 AH.

Full charge should read up around 13.2V on the battery posts with the charger running. Even at that voltage, it will take hours to complete the charge. Figure running on shore power overnight to get a full charge.

Even with that full charge, you won't get a full day's operation out of batteries that are "on the edge". (Yes this is why folks put 400AH or more of Lithium in Classics .... )

Working all this out from voltages is highly problematic. You really need a shunt based battery monitor to tell what's going on. There are a lot of them out there. The Victron BMV712 is a good one.

If you *really* want to nuke the battery, leave a couple lights on in the storage compartments ..... zoom .....

Fun !!

Bob

[OTRA15]

Depending on your finances, long-term intended camping patterns, and lots of other variables, you might consider upgrading all systems to include lithium batteries, correct lithium battery charger/converter, solar panels, DC-to-DC charging from the tow vehicle, and so forth. At a minimum, you probably need new batteries ASAP IMO.

FYI on the desktop version of this site [not the App] the search function in the blue box above works great FYI.

"Lithium battery solar upgrade site:airforums.com" results here:

https://www.google.com/search?q=Lith...=airforums.com

Lots of good reading while drinking!

[Bill M.]

"....... three hours. down to 12.0 with heat on (propane)"

Simply put, the batteries are bad.

Your test is better for deep discharge batteries than whatever "test" Airstream used. Those batteries are at least 3 years old. Maybe up to 4. That is a lifetime for flooded cell batteries. And the furnace is a pretty large draw. A good test.

New batteries like those will cost less than $200 and will do much better.

If you are sticking with flooded cells get used to changing them every 3 years if you actually boondocking some. More frequently probably if you actually run the furnace.

I have been a victim of "battery tests" several times. Not all battery tests give an accurate result for deep cycle batteries.

[candrews768]

thanks all

[uncle_bob]

Originally Posted by candrews768

Thank You, now I am gonna have a drink

Hi

Have two ....

Bob

[candrews768]

You are spot on. With everthing off except the battery disconnect the draw remained at 2.3
I used the generator display to get that.

Originally Posted by uncle_bob

Hi

Have two ....

Bob

[uncle_bob]

Hi

If you will be off grid, get a shunt based monitor. You will go nuts without it ... If you ever upgrade to Lithium's it will work fine with them as well.

Bob

[rwnash]

Your trailer is much newer and with may more "features" than mine - so what I have to offer may not apply.

As others have indicated, you probably need new batteries. Next, depending on how you use your trailer, you may need to track down what is using all your power. (If you plug in every evening your current setup may work.) We used to stay off the grid fairly often before the pandemic and our two wet cell batteries last well over a week with careful use. (The furnace blower is a big consumer.) Get a volt/amp meter and learn how to use it; you may be surprised at where the electricity is going.

I killed a set of batteries one trip and did not understand why. It turns out our refrigerator has "anti-sweat" heaters that use quite a large amount of power. I can't remember how I found it, but there was a small inconspicuous switch that I turned off and eliminated about 1 amp of draw. (I believe that current refrigerators have eliminated the switch so the heaters are always on - but you can disconnect the wire going to them.) There are many "parasitic" draws with today's electronic devices.

If you spend the time you can track down what is using the current and decide if you need it. I don't think that Wally had an inverter on his overseas caravans - and if he did he would have had a switch to turn it off.

Good luck, Whit Nash

[uncle_bob]

Originally Posted by rwnash

......

If you spend the time you can track down what is using the current and decide if you need it. I don't think that Wally had an inverter on his overseas caravans - and if he did he would have had a switch to turn it off.

Good luck, Whit Nash

Hi

A big chunk of current on all the "newer" Classics goes into the computerized management system. They are far from the only RV with this sort of thing. The problem is, if you turn it off, everything goes off (including the fridge).

Past that, yes indeed, understand your loads and act accordingly.

Bob