AGM Battery Charging 2019 Minnie Plus TT

[Rocko111]

I have a 2019 Minnie Plus. The previous owner put a large AGM battery in the trailer. Battery probably about 3 years old now. Looking to get a new AGM battery from Amazon. Does the inverter charge an AGM battery the same as a regular battery? I have read you need a special charger for these batteries.
Not sure what kind of invertor trailer has or if its stock. Battery appears to be dead. Do you test AGM battery's just as you would a regular battery? Thanks for any information

Randy

[dkoldman]

Inverters do not charge batteries.

You probably are asking about Converters? AGMs do have a preferred charging profile.

I would suggest having the batteries load tested 1st to be sure.
2nd, I would upload copy of your Converter with the specifications.

Almost 4 years ago the Dealer I bought my AGMs from direct, would not sell me the AGMs until I shared what type of converter I had.

[creativepart]

Originally Posted by dkoldman

Inverters do not charge batteries.

Woah there… in the OP’s Minnie Plus travel trailer it is very unlikely that he has an inverter/charger. And as you said he probably does mean Converter. But inverters come in two flavors, those without chargers and those with chargers.

Mostly, inverter/chargers are common in some motorhomes, but also TTs with factory Lithium installations such as the FLX series from Winnebago. And a person could could buy and install an inverter/charger in any RV if they wanted to.

So, one cannot say “Inverters do not charge batteries.”

But I agree with you that the OP is likely meaning “Converter” when he says inverter.

[creativepart]

Originally Posted by Rocko111

Does the inverter charge an AGM battery the same as a regular battery? I have read you need a special charger for these batteries.

Randy, the converter in your 2019 Minnie Plus likely can properly charge your AGM battery.

Flooded Lead Acid batteries (FLA) and AGM batteries are basically the same chemistry just applied differently. AGM does have a slightly different charging profile than FLA batteries but your Minnie Plus is new enough that the OEM Converter in your TT should be capable of charging either just fine.

You test AGM batteries with a multimeter the same way as FLA batteries.

If your AGM battery is dead, as in below 11.0v, and it’s been that way for a long period of time it is likely that it is ruined, but it’s always worth putting a charger on it for 24-hrs to see if it will hold a charge.

If after a long charge to 12.8v you would need to put a load on it. If the voltage immediately drops back to ~11v then you know it’s completely dead. After you charge it you can take it to most national chain auto parts store and they’ll load test it for free.

If buying a replacement on Amazon, look for “12v Deep Cycle AGM batteries” they cost $200-$300. Renogy, Full River and others are good brands. If you find an AGM for a lot less than $200 it’s likely a Marine dual purpose battery. These are fine if you don’t need a lot of house battery power but much less effective and durable than a true deep cycle AGM.

[Morich]

There are times when language and usage gets us into all kinds of confusion and this is one!
Inverters use DC to "make" AC. Converters do the opposite and make DC from AC.
The problem seems to be a kind of loose use of the two. Some Winnebago list inverter when they likely should say inverter charger!
First all had converters to make DC for use and charging batteries.
Then small inverters were added for making AC while driving. So we had both!
Then it came along with combined making DC with converters and using that Dc to make AC but in the same box. But the names got messy.
We can often buy a portable generator that makes AC or we can buy what they call an inverter generator that makes AC!

I find the biggest difference in AGM and older style is the ease of dealing with the battery. AGM is absorbed glass mat as the liquid is not just water floating free and easy to spill but it is in glass mats and pretty well sealed! Great for cutting work on cleaning and filling but generally much the same as flooded otherwise.

I spent a long time cleaning and watching flooded batteries but when AGM came along, I became a glorified floor sweep and retired! I guess cleaning floors is not much different than cleaning batteries but it sure was boring!
The main kicker was the middle of the night calls when things did actually go wrong!

[MadMaxWinny]

Creative's second post is spot on. AGM's DO have their own charge algorithm, but it's so close to flooded batteries that you don't have to worry about the alternator, solar, etc. AGM's were (originally) developed to mil-spec, used in helicopters, subs, etc. I know everyone is hot to trot for Lithium, but you can't go wrong with AGM. I have some (very well cared for) AGMs that are well into their second decade of service.

[dkoldman]

Originally Posted by MadMaxWinny

Creative's second post is spot on. AGM's DO have their own charge algorithm, but it's so close to flooded batteries that you don't have to worry about the alternator, solar, etc. AGM's were (originally) developed to mil-spec, used in helicopters, subs, etc. I know everyone is hot to trot for Lithium, but you can't go wrong with AGM. I have some (very well cared for) AGMs that are well into their second decade of service.

3 1/2 years ago I did full evaluation and chose AGMs over Lithium 100% based on cost ( my rig was designed for FLA) but today I have seen where some Lithium batteries are selling for $170 ea which is about $100 cheaper than my AGMs that I will need to replace eventually.

With the above in mine, I see today I can go with high end equipment from the likes of Progressive Dynamics & Victron Energy to modify my coach to be able to use AGMs or Lithium for about $600. I am looking to do that now.

When / if that is done I would then be down to picking truly between AGM and Lithiums.

As long as I can buy a Lithium 100ah battery for $270 or less Lithium would win every time because of...

1. I can get more ah capacity out of the same Grouo 31 space
2. Rated to last twice as long as the equivalent AGM
3. 1/3 the weight, in fact I will free 100lbs if I convert to Lithium
4. No concern with batteries being discharged below 50% SOC

The irony though is 3 years ago, once I got the AGMs, I swore to never buy another FLA, soon I may be seeing the same about AGM, except for chassis battery.

[Rocko111]

Thanks for all your replies. You have been very helpful. I have learned a ton and will get a new battery within a few weeks. Leaning toward AGM as that's what's in it now.

Randy

[Rich Davis]

I have a 2022 Mini and replaced the stock battery with 2 6V AGM batteries from Amazon. I also have a 190 Watt roof panel and I got a portable 200 Watt Panel. I actually haven't had a chance to use the portable panel as the roof one has been sufficient. Sill me, should have tested the batteries before buying the portable panels. Could be come in handy in cloudy weather we will see. Basically, love the AGM Batteries.