AGM house batteries - bad advice?

[APROTOmobil]

Ok, every body, I'm a little perplexed ... We bought our very well maintained 2003 Winnebago Itasca Sunflyer in 02 2022. Came across some issues with the house batteries over the summer and decided to replace them in September. For a recommendation we asked 'JustAnswer', and received the advice to get 3 Duralast AGM Deep Cycle 710 CCM Marine/RV batteries. What we did and installed them. The Motorhome has been in storage from October to end of January, main switch disconnected. After a week on shore power we got on the road and figured the following situation, which we, again, put on JustAnswer:
"In our 2003 Winnebago Itasca Sunflyer we exchanged the house batteries for 3 Duralast AGM Deep Cycle 710 CCM at the beginning of last September. When they are fully charged: how much should we get out of those with our 2000 A inverter? We feel we are not getting enough 110 V before the inverter stops working because the house batteries fall below the required charge. But: the 12 V lighting stays on and keeps on working for hours after that happened. What's the reason for this kind of behaviour? What do we have to do?"
And this is the comment we received:
"Part of the problem is that AGM is not a good fit for inverters. They can be easily ruined since you can't draw them down like you can lead-acid batteries. That is what needs to be changed."
We asked back:
"But AGM batteries have been recommended to us, actually from sb else here on Justanswer. And they are only e few months old. It also says "deep cycle" in the description and as it seems everybody around us switched from lead acid to AGM."
And the answer was:
"I am not sure why. You can't fully discharge AGM batteries like you can lead-acid batteries so they won't deliver power as long. And they can be easily ruined. Someone was not informed apparently."

Your general comments on this matter are as welcome as specific experience with Heart Interface Freedom 20 Inverter / Xantrex EMS. Can it be
some mistake we made in setting up the Freedom Remote panel (see pictures) after changing the batteries?
We've been told, neither battery capacity nor idle mode needs to be set for this type of battery.
Wrong?
Thanks a lot for your input!

[n2zon]

What 120V loads are you using the inverter for?

[NXR]

"You can't fully discharge AGM batteries like you can lead-acid batteries so they won't deliver power as long. And they can be easily ruined. Someone was not informed apparently."

Yeah, the person who wrote that is ill-informed. An AGM battery is a type of lead-acid battery. Discharging flooded lead acid batteries too far can damage them, generally below 50%. AGMs supposedly can be discharged a bit further but I still abide with not letting them get below 12.0 VDC. AGMs also are supposed to charge faster than flooded lead-acid batteries.

When dealing with house batteries you want to know their Reserve Capacity in minutes, not the CCA.

Is this the battery you bought? https://www.autozone.com/batteries-s...ca/1006723_0_0

If so, that's a pretty small battery for house batteries with a reserve capacity of 120 minutes.

The Reserve Capacity is a test that should never be done for real. 25 amps is pulled from the batteries until the voltage reaches 10.5 VDC.

At 10.5 VDC the batteries are so far discharged that the cells are prone to reversing polarity, thus suffering permanent damage. But it's a good test number because it's a standardized test for comparison purposes.

Two 120 minute Reserve Capacity batteries in parallel gives you about 120 minutes of real capacity when discharging them at 25 amps. Three probably would give you about 3 hours at 25 amps or maybe 6 hours at 12 or 13 amps.

Inverters are massive power hogs. If you try to power a television that uses 120 volts AC and 2 amps from an inverter, you must pull more than 20 amps out of the batteries.

BTW, you never said how much time you're getting out of the batteries when on the inverter. How many minutes do you get until what voltage is reached?

When using the batteries and inverter only, what does that panel show for the DC Amps?

Right now it shows you're on shore power and pulling about 15 amps from shore power. To power all of the same stuff from batteries and an inverter you would be drawing over 150 amps out of the batteries. They'd be run down in very little time.

Make sense?

Ray

[NXR]

FYI, we have two AGM 200 minute Reserve Capacity house batteries. That will give us roughly 200 minutes of use at 25 amps and since our 200 minutes is pretty close to what I think is your 180 minutes, you may be interested in the test I did when I installed them: https://www.forestriverforums.com/fo...ml#post2638386

Ray

[PJStough]

We had the same problem with our four 12 volt golf cart batteries with our 2000 watt inverter. Anytime we got close to pulling anything over 1500 watts, the draw would pull the battery voltage down below the low voltage cutoff unless the batteries were fairly close to fully charged.

To solve that problem I bought a 300 amp hour lithium iron phosphate battery, and even at 50% charge I can pull 1800 amps without an issue. I dont know, but I suspect that I could run the lithium battery down more than that without issue, but I have never had go any lower than 50%.

[twinboat]

A 2000 watt inverter should be running off about 400 AH of deep cycle batteries.

4 GP31 12 volt batteries or 4 GC2 6 volt batteries wired series / parallel.
You have about 150AH with your 3 batteries, less then half of what you need.

Keep in mind, 10 amps at 120 volts will cause your inverter to draw 100+ amps at 12 volts. To little capacity causes deep voltage drop to your inverter.

I think you asked the wrong people for advice.

[153stars]

Many 12v "deep cycle" are start/deep cycle and just dont deep cycle like 12v GP31 true deep cycles, golf cart batts or some good 12v solar batts. If you see CCA they are hybrid start/deep. Also interested in what gauge your parallel batt cables used are.
If from autozone I think advertise no hassle 36 mo warranty, may you can trade in and sell off to boat guys, might be better for start and trolling motor. My 20' Searay IO cuddy boat would be happy with one or two of those.

[Sparky19053]

Originally Posted by twinboat

A 2000 watt inverter should be running off about 400 AH of deep cycle batteries.

Good information but could you please tell Winnie this. I have 200 AH of AGM connected to a 2000 watt inverter.

Of course they could be using the 2000 watt inverter to handle the inrush of the appliances. Just a guess

[Iceclimber]

First observation is if you plan on storing any battery, charge fully but you have to disconnect them otherwise parasitic draw will drain them. Just turning off the switch is not enough. They may had their life shortened considerably. I am running 6 fresh GC's flooded with my 3k inverter and with normal cold weather boondocking I need to charge every day. I am sure I will face judgement from folks that heat with candles and count every volt, but we are not those campers. We enjoy our RV to the fullest and that means power gets used. I have noted just running out all 4 slides will show a dip in capacity, and try telling the Admiral she can't used a hair dryer.
Get your batteries tested and then you will know if they have diminished capacity, I am betting the answer is yes. Also you have 12v batteries correct - they do not perform as well as 6v's but anyway.

[Gary RVRoamer]

Originally Posted by Sparky19053

Good information but could you please tell Winnie this. I have 200 AH of AGM connected to a 2000 watt inverter.

Of course they could be using the 2000 watt inverter to handle the inrush of the appliances. Just a guess

They didn't promise you that you could draw 2000W continuous, did they? RVs don't necessarily come equipped for maximum capacity anything. I'll bet the speedometer goes higher than the engine can deliver as well.
So folks who want to use the inverter heavily can add batteries, while those who do not save money up from and on future replacement.

[Winemaker2]

Originally Posted by 153stars

Many 12v "deep cycle" are start/deep cycle and just dont deep cycle like 12v GP31 true deep cycles, golf cart batts or some good 12v solar batts. If you see CCA they are hybrid start/deep. Also interested in what gauge your parallel batt cables used are.

If from autozone I think advertise no hassle 36 mo warranty, may you can trade in and sell off to boat guys, might be better for start and trolling motor. My 20' Searay IO cuddy boat would be happy with one or two of those.

Both Trojan and East Penn confirmed to me that when considering AGM (Unlike FLA) a GP 31 has deep cycle performance roughly equal to GCs. (And both serve start applications equally well). If you look, most AGMs spec BOTH AHs and CCA reflecting suitability for both applications.
You will note that FLAs will usually spec only AH or CCA as their designs are different and optimized for one or the other.

In neither type are they damaged by DOD >50%... that is a Myth and not supported by Trojan... they state that 80% DOD provides sufficient buffer to avoid damage.
You will see V reductions at higher DOD but recharge and all is well.

[NXR]

Originally Posted by Winemaker2

In neither type are they damaged by DOD >50%... that is a Myth and not supported by Trojan... they state that 80% DOD provides sufficient buffer to avoid damage.

With the qualification that the actual state of charge percentage may be dependent on the actual battery design parameters. Trojan may build theirs better.

I do agree that no permanent damage occurs at 51% but the real problem is that there is no easy way to determine when a particular design may have damage and 50% is a good number to use.

You will see V reductions at higher DOD but recharge and all is well.

That is a big difference between any type of lead-acid and lithium. Lead acid batteries experience a decrease in voltage as the state of charge depletes. Lithium's hold the output voltage constant until almost the end.

If you have an Automatic Generator Start system that fires up the generator when the house batteries drop to a certain voltage, but then upgrade to lithiums, your AGS may never attempt to start the generator until the batteries are so depleted that they may not be able to do it.

Ray

[computerguy]

Yep. I’d say the OP got some bad information.
Any forum user that just gives advice and doesn’t ask questions on specific use (when not given) is a bad place to get advice. Not knowing what the batteries are going to be in service for is always a question that needs to be used for. The size of the inverter is not that important when considering how long and how large a draw is needed.
Good the OP researched info before replacing just that forum was not a good place to go for it. Generally iRV2 has awesome info (yes, even here though I’ve seen bad info but generally corrected by a better informed user). Why this is my go to resource for anything RV related.

[MevetS]

Sites like the one you used, may be useful for generic information. However, you have arrived here where you should be able to receive more appropriate information. But never accept any information without doing some research into the "makes sense" department.

I would have to believe that there are more battery usage appropriate forums out there, if you do a search. Especially, when it comes to costs and potential damage that may be caused if the info isn't appropriate.

You may also be able to mine information from the inverter manufacturer.

My comment included.