AGM deep discharge question

[Sandman]

I have a call in to Oliver and have searched the forums, but need some advice about rapid depletion of our AGM batteries, so I apologize if this information is in the forums.

We have a 2024 Legacy Elite 1 purchased new in November. We have only used it previously with shore power when camping (twice). It has 2 Lifeline deep cycle AGM batteries and has been out in the AZ sun with the solar panels charging  since we got it.

Earlier this week we went camping without shore power. It was sunny every day and the battery charged to 100%. At night, with the inverter on running the TV, Truma furnace and refrigerator, the batteries ran down to 10v in less than 90 minutes. I plugged the  trailer into the 30 amp outlet on my powerboost F150 and recharged, but it ran down again.

The next day it fully recharged with solar, and that evening it behaved the same (ran down quickly.)

I reviewed the battery monitor data and found that it had, in the past, been discharged nearly fully, but not in the last 60 days when data was recorded.

I checked the battery connections and voltmeter reads each battery at 6 volts after fully charged.

Are my batteries toast because of the prior deep discharge and is it worth trying to salvage them?

Thanks in advance and I’ll add some screen shots from the battery monitor.

The lower trend is for the last 60 days, with my last 2 nights discharged to about 10 volts, which should be far less than 85% of capacity, I think.

 

 

[topgun2]

There are a number of factors that determine state of charge, life of an AGM battery(s), charging an AGM battery(s), etc..  HERE is a discussion of these factors.

In any case it appears that you have seriously discharged your battery(s) multiple times to levels that are very low - well beyond 50% of capacity.

Hopefully you will be able to bring them back to life but it appears to me that you will be very lucky to do that.  In addition to investigating your batteries, I would also make sure that your charger is operating properly to include being set at the proper charge rates.

Good luck!

Bill

[John Dorrer]

Never discharge below 50%. 12.3 is a safe bottom number. 

 

It only takes one time to go below 50% to damage AGM batteries. They aren't forgiving. It doesn't mean they are toast. Fully charged then, remove them from the trailer and take them to a place that can conduct a load test.

 

You have a lot of things going, fridge, furnace, inverter, television, and additional draws not mentioned. It doesn't take much for the deep dive.

[Sandman]

Thanks, Bill.

I naively assumed that the solar panels would maintain adequate charge while in storage.

Since I can’t review the battery history more than 60 days ago, I’m wondering if the batteries were bad at the time of purchase.

Now to decide to replace with AGM or Lithium.

Appreciate your help.

[Rivernerd]

3 hours ago, Sandman said:

The lower trend is for the last 60 days, with my last 2 nights discharged to about 10 volts, which should be far less than 85% of capacity, I think.

Discharge down to 10 volts on a 12V AGM battery (it appears your two 6v batteries are wired in series, making the two of them operate as one 12V battery) is well below 50% of capacity, which is not good.  A lead/acid battery (like an AGM), even a "deep cycle" one, should not be discharged below about 50% of capacity.  Said another way, a fully charged 400Ah AGM battery only gives you about 200 Ah of usable power before it begins to sustain damage.

The usual charge range for a 12V AGM battery is a high of about 13V when full charged down to a low of about 11V when fully discharged.  As Topgun2 has advised, the fact that your batteries read only 10V when fully discharged and 12V (each one at 6V) when fully charged suggests they have been damaged by discharge too deeply, too many times.

Also, I suspect your AGM battery system was not designed to operate 120V appliances through the inverter for hours at a time.

2 hours ago, Sandman said:

Now to decide to replace with AGM or Lithium

If you want to be able to run 120V appliances (like the TV) off the inverter for hours at a time without shore power or a generator, you need a very high Ah lithium battery bank.  Lithium batteries provide much more usable capacity per Ah than do AGMs.  And, you may also need a more powerful inverter.

The conversion from AGM to lithium is neither cheap nor easy, but many on this forum have done it.  Below is one starting point for that journey.

 

Edited February 1 by Rivernerd

[Galway Girl]

Our original AGM's lasted about 2 years  (with 1 year warranty) from the battery maker.

They were OK until we drew them well below the 60% point a couple times.   After trying multiple ways to bring them back to life, a friend of ours (who worked at Interstate Batteries local HQ) had me bring them in for testing.  All 4 - 6V AGM's were toast.

That's what triggered me to go do the Lithium Conversion.

All that said, given a Nov 2024 purchase date, you should be within some warranty either with the battery maker or with Oliver.
Start with Oliver with a service ticket and see if you can get them replaced via some warranty.

Also here's my blog page on the conversion from AGM to Lithium with more details:

https://4-ever-hitched.com/ggs-blog/f/lithium-battery-upgrade?blogcategory=Electrical+Upgrades

 

Sandman - if you have a chance, please update your signature page to include details about which trailer you own and which options you have installed.  That way we can look at the signature and see more quickly how we might help answer questions.

 

Edited February 2 by Galway Girl

[jd1923]

10 hours ago, Sandman said:

At night, with the inverter on running the TV, Truma furnace and refrigerator, the batteries ran down to 10v in less than 90 minutes.

So far, you have received very good advice, but not causal reasoning, except for this pertinent blurb from @Rivernerd

9 hours ago, Rivernerd said:

suspect your AGM battery system was not designed to operate 120V appliances through the inverter for hours at a time.

Amen. What you wrote above is not possible on two simple LA or AGM batteries (basically the same thing).

You can watch TV all night on inverter, run coffee machines or the microwave for a few minutes, but NO-WAY the fridge and furnace All-Night-Long! The science is not there.

We have LP for that and if you have a fridge w/o LP you need better batteries to dry camp, period.

We have 600AH Epoch liFePO4 batteries. Just stopped to camp today, immediately turned the LP on for fridge and later tonight for furnace.

Onetime we stopped at a friend’s house, left the fridge on DC (inverter) for longer than two days! We still had 30%, two LA batteries would have boiled over or went dead to ground in one day! 🤣

If you want to Boondock, you need to upgrade. Not to worry re your AGMs, they’re likely toast. It gives you the perfect reason to move into the future!

[Mike and Carol]

Maybe we should start a thread on managing resources while boondocking.  When we had AGM’s we did a lot of no hook up camping, mostly at National Parks, COE and FS areas, Harvest Hosts and of course Quartzsite.  No 30a hookup meant fridge on propane, hot water on propane, boil water on propane stovetop for pour over coffee, etc.  The only electrical load on the batteries was the furnace fan, lights and water pump.  We seldom use the inverter, an occasional minute or two of microwave and maybe a blow dry after a shower.  Keeping an eye on where the battery charge was happened frequently.  If we weren’t back to near 100% by mid-afternoon the generator came out (happened at Glacier and Grand Teton, some dark cold days!).  Our AGM’s lasted 5 years and got replaced because two were starting to leak.  Now with Lithiums (just 300ah) we still camp the same when boondocking and rarely get down to 80% charge by morning.  It’s a mistake to think that solar allows the same kind of camping off grid as with FHU.  Mike

[John Dorrer]

Lithium batteries are the way to go. I spent 8 years in a truck camper with 2-12 volt AGM's and a 12v compressor fridge. I got 4.5 years out of the batteries before replacement. We also had only 100w solar on the roof, with an 80w portable panel and eventually a Honda 2200i. We did replace the 100w panel for 2-100w Zamp panel for the last 3 years, before purchasing the Oliver.

 

Most of our camping was deep in the back country, so no Hook-ups.  I can say this, we never got lower than 12.2. We managed our system very well. At night to save we used battery powered lights to see. 

 

It is so much better not having to be on "Battery Watch"

Edited February 2 by John Dorrer
Updated Comment

[GraniteStaters]

We try to never have our AGM batteries discharged beyond 12.6V.  This can be very challenging in cold weather as our Dometic Furnace squirrel cage can use a lot of Ah overnight.  If you can keep your SOC over 80 percent at all times, we never go below 90 percent, you will double the life of your batteries otherwise you can expect only so many cycles.  The advantage of Lithium is that they can be discharged more deeply and cycled many more times.  The usual expectation for LiFePO batteries is about 3000 cycles.  The best you can hope for AGMs are 750 cycles if you keep SOC above 90 percent.

[SeaDawg]

On 2/1/2025 at 9:54 AM, Sandman said:

Earlier this week we went camping without shore power. It was sunny every day and the battery charged to 100%. At night, with the inverter on running the TV, Truma furnace and refrigerator, the batteries ran down to 10v in less than 90 minutes. I plugged the  trailer into the 30 amp outlet on my powerboost F150 and recharged, but it ran down again.

The next day it fully recharged with solar, and that evening it behaved the same (ran down quickly.)

Have you pulled the batteries, and had them checked? The 12v compressor fridge really doesn't draw that much power, nor, likely, your television.  Our 12v dc draws about 20 to  26 ah overnight.

We have run a compressor fridge on agm batteries for several years.

We don't have an inverter, and dont use the television. Do you have the standard 6 gallon water heater? Since you normally camp with hookups, could it have inadvertently been left on 110 electric? That would definitely drag the batteries down, very quickly. 

[Rolind]

We use about 50Ah in 24 hrs with the fridge alone. I’m not sure of the tv draw, but our inverter consumes about 3Ah just by being on with no ac load.

As you consider batteries for replacement, take a look at the Epoch 460Ah lithium batteries.  They are relatively inexpensive for their size and are getting great reviews.

[Sandman]

Thank you all for your input.

We have a legacy 1 so the battery compartment size is limiting. 

We’ve read Epoch’s great reviews. They not yet on Oliver approved list and we’re still under warranty. Still researching options.

[MAX Burner]

We've had 4x 6vDC AGMs in our AS that lasted 5+ years.  They're good but IMO not as good as the modern lithium options out there.  We're 100% pleased with the performance of our 300A-Hr lithium bank, especially now with our 200W solar tracker.  It behaves like a 400W module and our SOC is full by 1pm-ish even in the winter low sun angles of Quartzite.  A very nice combo for our style of boondocking, FYI.

But as @Mike and Carol stated previously, don't think solar is the same drill as a FHU when your boondocking.  One still needs to keep a "weather eye" on the charging data and the camping conditions (i.e., WX) at the time...  Just say'n

Press on, regardless....

[Sandman]

Update on the AGMs.

I had them load tested at an automotive shop and was told one battery was good and one was bad: no details or readouts were provided.

i called Lifeline battery and explained the history to a representative, who initially was skeptical about the readings done at the shop (he wanted more details that I didn’t have) and whether I had correctly attempted to recharge the batteries.

Eventually though, he agreed to send me two new AGMs at no charge and with free shipping! I was astonished, especially because he told me the batteries were manufactured 13 months before I purchased the trailer, and technically no longer under warranty.

I still don’t show any deep discharge on the Victron history in the 60 days before we noted the poor battery function last week. So I don’t know when the battery was damaged or if it was defective from the start.

At any rate, I’ve learned a lot and appreciate all the help on the forums.

I will be watching for lithium batteries on sale, and maybe my wife will get some for her next birthday!

 

 

[SeaDawg]

We are in year 7 or 8 with our agm batteries.  

Don't rush the change up to lithium, especially if you rarely boondock. When you do boondock, keep the batteries atv70 per centbor better, imo.

Great customer service from lifeline. You probably had a bad cell in one battery.  Best to replace both, at the same time.

Edited February 7 by SeaDawg

[topgun2]

12 hours ago, Sandman said:

Eventually though, he agreed to send me two new AGMs at no charge and with free shipping! I was astonished, especially because he told me the batteries were manufactured 13 months before I purchased the trailer, and technically no longer under warranty.

Truma - are you reading this?

Good for Lifeline!

I agree with SeaDawg - unless you have some compelling reason for switching to Li, simply keep those new AGM's for a few years and enjoy the savings.

Bill

[MAX Burner]

2 minutes ago, topgun2 said:

unless you have some compelling reason for switching to Li, simply keep those new AGM's for a few years and enjoy the savings.

By using the AGMs to their end-life, you'll enjoy even more savings because lithiums will certainly be less expensive 5 - 7+ years from now.  In fact, there may likely be a new battery technology by then that's even more efficient than Li....  just say'n

[rideandfly]

32 minutes ago, MAX Burner said:

By using the AGMs to their end-life, you'll enjoy even more savings because lithiums will certainly be less expensive 5 - 7+ years from now.  In fact, there may likely be a new battery technology by then that's even more efficient than Li....  just say'n

Agree, who knows what technology is going to be available in the future and Lithiums should come down in price, too.

Purchased our Ollie from the original owner during 2016 that had let the two original 12V batteries run down very low when stored, our Ollie did not originally have a battery master disconnect switch. Replaced them with two 12V AGM group 27 batteries that worked great. I had a good application for two 12V AGM group 27 batteries, so I replaced both AGMs with one BattleBorn 100AH Lithium. We don't have an inverter and can easily operate three days in the summer (furnace not needed) with the single 100AH Lithium starting at 100% SOC with refrigerator running on LP gas before a battery charge is needed.

Edited February 7 by rideandfly

[Patriot]

35 minutes ago, MAX Burner said:

By using the AGMs to their end-life, you'll enjoy even more savings because lithiums will certainly be less expensive 5 - 7+ years from now.

That is my dive plan Art. I plan to squeeze everything I can out of my present AGMs. We shall see.

[MAX Burner]

Hey, @Patriot - greetings from Sint Maarten, West Indies....   This was my dive plan yesterday - finding this shipwreck:  Can you make out the ship's STBD prop?

HA!