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 Saturday at 06:50 PM 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 yesterday at 01:47 AM 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 yesterday at 01:32 PM 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.