When to Replace AGM

kdcampergirl · May 7

Purchased a ‘20 400 about 5 weeks ago. We live in FL but will be spending 4mos in MN this summer. AGMs original. Wondering if we should replace now before we start our long trip up to MN? I know the AGMs have a longer lifespan. Have a 100ah Weize LiP04 from my T@G which probably isn’t powerful enough. Thoughts? We camp both boondocking (3-5 days) and shore power. TIA!

elbolillo · May 7

AGMs have a longer lifespan compared to what? What is the total ah of the AGMs? Are they the original batteries that came with the 400?

kdcampergirl · May 7

To clarify…I understand AGMs have a longer lifespans compared to lead acid. I read they can last 6-8 yrs. Yes, as stated, original. Don’t know the ah and not sure what difference that makes.

TourDeForth · May 7

If you’re not comfortable with using a volt meter you can take the agm battery to an auto parts store and have it tested. They can test the voltage, internal resistance and capacity.

However, If you have a volt meter you can test the voltage and internal resistance yourself, make sure your battery is charged up. With the battery off (under no load) a healthy agm battery should have a voltage of 12.8v or higher. Then measure the resistance of the battery, a good battery will measure 5 ohms or less, a weak battery will be at 10 ohms or higher. Next turn on your battery switch, load up the battery with lights and appliances/radios that you would use off grid, wait about 15 to 20 seconds. Check the voltage under load, a healthy agm battery should stay in the 10-12v range.

pthomas745 · May 7

Is this the "dual 6V" AGM or the single large AGM? In either case, trying to get them out to test somewhere will be an all day heavy lifting chore. And another day to put them back in! In each case, the original 400 batteries were of the 225 amp hour rating, with about 135 of those amp hours "usable".

You are generally correct in what you say about "how long" an AGM battery might last. That "lifespan" is estimated for a well cared for battery. Did the previous owner let the battery sit at a low state of charge for a while? Did the battery get discharged well below the 40-50 percent level often? Each of these sorts of events can shorten any lead acid battery's "lifespan". A lead acid battery only has so many charge and discharge cycles available.

So, this battery setup is at least 5 years old. (*Edit..see note below about taking a picture to see if they have been changed out) The Harris dual 6V batteries have been known to fail catastrophically in some 400s, with bulging cases, overheating, etc.

If the tests that TourDeForth runs through with the voltmeter, and these batteries are holding a charge, then maybe they are fairly "healthy".

If you have the Victron app up and running, you can see how they are charging, and with the battery switch off and the solar off, you can see how they might be holding a charge.

As a comparison: your 400 currently has "about" 135 amp hours available for powering the trailer on 12V. (On paper.) Your Wieze lithium battery has about 90 amp hours available all by itself. And, it will last for years.

I'd vote for a lithium battery setup...there are many owners who have swapped in single 200-230 amp hour lithium batteries into the spot where the large AGM is located. A quick adjustment to the Victron solar controller to charge the lithium and you will be on your way.

Take pictures of the battery space you have. It is possible the batteries were updated somewhere between 2020 and today. Many owners have swapped out original AGM's for newer AGM's, also.

kdcampergirl · May 7

I have a volt meter and will try this out later tosay. Great advice. Thank you!

kdcampergirl · May 7

@pthomas745…is this Paul Thomas who’s also active in the FB groups?
And, yes, I’ll take pics when I get home. I agree with you on the lithium. I’d like to use just the one I have now and add a 2nd if needed.

Grumpy_G · May 7

Also consider that a 100Ah LiFePo battery can be discharged down to 5% without much voltage drop compared to lead-acid batteries (regular or AGM). The useable capacity of your LiFePo battery probably exceeds the useable capacity of the old AGM batteries.
AGM batteries also have the tendency to "die overnight", at least for automotive applications. Drive the car one day, park overnight, next morning merely a click. No amount of charging gets the battery back to life.

kdcampergirl · May 7

So, I unplugged from power and used my voltmeter. Each battery has a charge of about 6.3 so that’s good. Tried to turn on fridge (3way) but wouldn’t work on battery. Might go leave the fan and some lights on to see how quickly they go down.
Bad news: can’t find brand bc i
cent lift them.
Good news: they’re not original to the unit since there’s a 11/21 sticker on each! See pics.
FWIW battery on control showing 2/3 but I’d trust voltmeter instead.

TourDeForth said:

If you’re not comfortable with using a volt meter you can take the agm battery to an auto parts store and have it tested. They can test the voltage, internal resistance and capacity.

However, If you have a volt meter you can test the voltage and internal resistance yourself, make sure your battery is charged up. With the battery off (under no load) a healthy agm battery should have a voltage of 12.8v or higher. Then measure the resistance of the battery, a good battery will measure 5 ohms or less, a weak battery will be at 10 ohms or higher. Next turn on your battery switch, load up the battery with lights and appliances/radios that you would use off grid, wait about 15 to 20 seconds. Check the voltage under load, a healthy agm battery should stay in the 10-12v range.

pthomas745 · May 7

The battery is marked "8AGC2", which is a fairly standard 6V. Only a few companies make these sorts of batteries, and the different brands just slap a label on them.

What is interesting is the amp hour rating listed: 190 amp hours. So, instead of the 225 amp hours we mentioned earlier, your "usable" amp hours are probably closer to 100-114 amp hours. Which puts you very close to what your Weize 100 amp hour lithium can provide.

Good for you for having the voltmeter. If you have installed solar on your trailer, do you have a Victron solar controller? The App will help you a lot while watching your battery in this case.

kdcampergirl · May 7

pthomas745 said:

The battery is marked "8AGC2", which is a fairly standard 6V. Only a few companies make these sorts of batteries, and the different brands just slap a label on them.
What is interesting is the amp hour rating listed: 190 amp hours. So, instead of the 225 amp hours we mentioned earlier, your "usable" amp hours are probably closer to 100-114 amp hours. Which puts you very close to what your Weize 100 amp hour lithium can provide.
Good for you for having the voltmeter. If you have installed solar on your trailer, do you have a Victron solar controller? The App will help you a lot while watching your battery in this case.

Yes, the trailer has solar and the Victron! Interesting comment about the 190ah. No idea why the former owner installed that one. So, based on what you’re saying, I’d be good just installing my Weize instead of the existing 2 AGM batts?

kdcampergirl · May 7

Could be this one…70lbs??!!
https://www.solar-electric.com/deka-8agc2-intimidator-deep-cycle-battery.html?srsltid=AfmBOoo0ppLlS7nnD2UB7DJlm5dOWqUVpiHVRDe4xOoa1lkT2bxm9ApR#reviews

kdcampergirl · May 7

To complicate things (for me) the trailer also has an Aims Pure Sine Inverter. When I turn off my battery switch and the breakers (not hooked up to shore power) the inverter is still operating as I can hear the fan. Not sure how to turn this off since I should do this if I want to take out the AGMs.

Bill&Suze · May 7

The inverter in our '24 400 has an on/off switch located in the cubby next to the bed. Might yours be the same and the switch is set to 'on'?

kdcampergirl · May 8

I found it! Located just as you come in the door on the right! Thank you.

Cherokee · May 8

The best way to extend the life of these batteries id to keep them on a trickle charger at all times when the T@B is stored

Image: https://us.v-cdn.net/5021717/uploads/editor/jj/lgvim57ebest.jpg

pthomas745 · May 8

There could be a couple of reasons for the "2021" marked batteries in a 2020 trailer is the original batteries failed "out of the box" or....the original batteries were not handled properly and they needed to be replaced. It was fairly common for new owners to destroy their first lead acid batteries, according to legend. The learning curve on handling a new trailer and battery is a bit steep. Improvements in monitoring and great group advice helped owners get through those sorts of problems in recent years.

If the batteries needed to be replaced that soon, 2021 would have been mid-pandemic, and that could have been a factor on the smaller size.

The difference in your Weize and your current AGMs is only about 20 amp hours. If your AGM's are healthy, that change would be a bit of a wash.

kdcampergirl · May 8

Yeah, right now just trying thinking of leaving these as is and keeping my Weize charged in case I need to swap it out. Right now the AGMs seem to be fine even though we haven’t had the battery too long. We’re about to go on a long trip to MN from FL so I’ll bring the Weize and my portable panels with me just in case. Only reason I see changing the AGMs out now is weight. They’re way too heavy!!

pthomas745 · May 8

There are ways to "swap in" one battery while another is charging. Owners have carried "spare batteries" around and made them work in the trailer in several different ways, without removing the installed batteries.

You can connect an extra battery with a 7 pin plug adapter into the trailer's 7 pin plug. You can plug a battery into a 12V port with the proper connector from the battery. (The battery switch should be off in these cases).

https://tab-rv.vanillacommunity.com/discussion/7008/anyone-carry-a-spare-battery/p1

kdcampergirl · May 8

Good idea but why not just use a trickle charger? We’ll be stationary for a few months.

pthomas745 · May 8

If you are going to be on shore power, no, none of that "spare battery" stuff matters much.

Howdy, Stranger!

Quick Links

Categories

When to Replace AGM

Comments