AGM maintenance

jules2go

Hello wonderful helpers on this forum, 
With the cold weather setting in where I live, I'm back to battery questions. I have a lead acid battery (I think? It's the kind that has to be "watered") and again it drained overnight with the Alde heater set at about 60 degrees. I last put water in it maybe a month ago. I'm tired of this battery problem, and think I'll go buy an AGM today. I don't know if the problem was not enough water in that thing, or what; maybe some chilly nights drained it, too. 

What is required to keep an AGM charged when boondocking? I have factory-installed solar on my roof. I've gotten pretty good, I think, with conserving power over the summer/fall; basically kept my 3-way fridge going all the time and that was the only 24/7 draw. Will freezing temps drain an AGM? Will the solar do a better job of charging an AGM compared to lead acid? Does an AGM have to be taken inside the house in the winter? 

Please share your thoughts, and thanks in advance for reading my post. 

ColoradoSun

There is no problem with leaving the AGM batteries out over the winter. Your solar will keep it fully charged assuming you have the battery cutoff switch in the off position. Actually I often leave ours with the battery switch in the on position and the solar keeps it fully charged.

pthomas745

Before going out and spending for another battery........have you tested the current battery?  What did you use to determine it is "dead"?  Without figuring out what the issue is with this battery...the next, more expensive battery might wind up with the same problem.  And, Btw...I've had a standard, boring Interstate lead acid battery for 5 years now, still going strong, never even had the caps open.   It is "maintenance free", and when I tried to open the cover to check...when I had my hammer and a screwdriver in my hand I realized this was not really necessary.  But, that is just me.

A slightly larger AGM would be a good upgrade.  A Group 27 AGM (100 amp hours) will give you about 50 usable amp hours, about 25 percent more than you have in your stock battery.  You will need a slightly larger battery box.  With a 3 way fridge, though, you have the option of keeping a "smaller" Group 24 battery.

https://www.amazon.com/dp/B00S1RT58C/?coliid=I2067L1222PJQW&colid=3DJSJON9VK2CS&psc=1&ref_=lv_ov_lig_dp_it

So....how are you "monitoring" your battery? 

jules2go

@pthomas745 -- the battery indicator light on the wall by the sink. I've got the Victron app on my phone, but forgot to look at it last night. This morning I went to look and the battery light had all four lights red; last night when Alde said low battery it had only one lit. 

Denny16

Are you running the 3-way fridge on battery 12VDC or propane?  If you are trying to run it on 12VDC only, this is what is draining your battery, as the 3-way uses quite a bit of power on 12VDC mode, unlike the newer 2-way compressor fridges.  That said, it’s draw is small whilst running on propane.
 Cheers  

pthomas745

The best way to monitor your battery is with the trailer battery switch off, and no charging coming in to the battery: disconnected from shore power, and no solar input.  (It can be dark outside...or you can turn the "Charging" off in the Victron app).  That is the only way to get an accurate voltage reading from a battery: when it is "at rest".  So, just shut the trailer off, wait a few minutes, and let all the chemical reactions in the battery settle down.  Of course, this means the Victron app will be the only way to see your battery voltage, since the "blinking lights" in the trailer won't work.  Trying to monitor a battery that is being used by the trailer and being charged by shore power or solar is chasing a phantom.  When I run my fan in my trailer, even on low, the battery voltage displayed by my Victron monitor is always very low.  Turn the fan off.....and the voltage jumps considerably.

So, if you can, take a reading with the switch off/charging off, and get a good "rested" reading, and go from there.  Charge the battery for a day, turn everything off again, and see what you get, and see if the battery will then hold the charge. 

The Alde running on propane uses very little battery power.  (About .060 of an amp "when running".)  So, something else must be up with your battery, and you were fairly "low" before nightfall.

  Get some nice stable rested readings and see where you are then.

jules2go

@Denny16 fridge on propane; I never run the fridge on battery, either shore or propane. Right now though I'm only trying to run the Alde heat, don't have the fridge on at all.

jules2go

@pthomas745 thanks I will try and do this. 

jules2go

I just went out to check the water in the battery, and realized that it says "dual purpose". If I recall correctly, that is not the preferred battery. Maybe this is part of my problem. It's the one the dealer installed when I bought it. What do you think?

Mickerly

I'm a victim of the dealership battery too. "Marine deep cycle" and "Dual Use" are inexpensive and therefore the battery of choice of the dealership. Not true deep cycle like an AGM or GEL. Looking at replacing mine with AGM too.

Everyone is correct, run your fridge on propane. It works best on gas.  It will eat batteries on electric power. If it's not running correctly on on gas, you have spiders, soot in the chimney or it's been stored un-level which causes the ammonia to not flow right.

pthomas745

Battery manufacturers dance as hard as they can to straddle as many different segments of the market as possible with one product.  A battery for a boat might need to: provide 12V power....and provide enough "cranking amps" to turn over a boat's engine when needed.  Almost any battery can provide enough "cranking amps" to turn over a motor. Not on a long term basis, however.    But, if they call it a marine battery....an RV person won't buy it, because it is for a "boat".  If they call it and RV deep cycle battery, a boat owner won't buy it.  (there are other specs for "marine use", also.  A "dual purpose" battery may try to split the difference on "cranking amps" that might be occasionally needed to turn over an engine and enough "deep cycle" power to handle your trailer.  It is a very common battery type.

So, even though your battery is "dual purpose" it doesn't necessarily make it "bad".  It will certainly work.  But a "true RV deep cycle" (like the Universal linked above) would still be a "better" battery.  In my reading I really think the "best" of the AGM or lead acid "deep cycle" batteries are the 6V ones.  Huge lead plates, built like tanks. 

Any battery, no matter which one or what design, needs to be handled with tender loving care for the longest life of the battery. And, sometimes, they just fail.  It happens to the best of them.

And, here is a better description from a boater's blog that explains this better than I can.

https://www.discoverboating.com/resources/marine-battery-basics

CrabTab

If you decide to go with a new AGM @jules2go, Renogy will be at least 15% off site wide starting 11/22. The 100AH AGM we have should be just under $200 at that time. I'm sure many other places will have sales over the next few weeks too.

jules2go

@CrabTab they have it now for that price. Thanks. 

jules2go

@pthomas745 and @Mickerly Thank you. All helpful info. I think I need an AGM. Is there one that might fit in my current battery box, I'm wondering, because boy that sure would be helpful! My current battery is a group 24, if that helps to know. Tomorrow I'm going to measure the footprint. 

pthomas745

A Group 24 will slot right into your current Group 24 box.  I'm not exactly sure of the shape and size of the current 320 tub.  I recently slotted a Group 31 battery into my 2017 Outback tub.

dragonsdofly

@pthomas745, we put a group 31 into our 2017 a couple of years ago, which has the original plastic tub. We did put a piece of exterior grade plywood in to support it, and had to mount it at a slight angle from the original position, but it is easily accomplished.

jules2go

@dragonsdofly This sounds hopeful. I'm going to look for a group 31 AGM today. So then an AGM in terms of maintenance  --  it can be in the trailer outdoors in the winter without regard to the outside temp? It does sometimes get down to the teens where I am. 

CrabTab

jules2go said:

I think I need an AGM. Is there one that might fit in my current battery box, I'm wondering, because boy that sure would be helpful! 

Group 31 Renogy AGM in a 2019 Boondock tub. It won't fit with a battery box. 

jules2go said:

So then an AGM in terms of maintenance  --  it can be in the trailer outdoors in the winter without regard to the outside temp? It does sometimes get down to the teens where I am. 

Consider that the battery in your truck sees the same temps.

jules2go said:

@CrabTab they have it now for that price. Thanks. 

It is currently 7% off. They are advertising 15% cyber week (starting 11/22).

AnOldUR

jules2go said:

... I'm going to look for a group 31 AGM today ...

Not a great endorsement since we have nothing to compare it to, but our Vmaxtanks VMAXSLR125 AGM has made a huge difference over the stock battery. Recently completed a 2-1/2 week trip with about half our stays being dry camping. By the end we found it was no longer necessary to worry about power consumption. Ran our 12V (compressor type) fridge 24/7. Streamed a movie before sleeping every night. Used lights and water pump when needed. Resting voltage never dropped below 12.4. We do have factory solar and a 100W suitcase to help offset the drain. Best of luck finding what works for you.

jules2go

@CrabTab Yours just fits in there. Since the group 31 is too long for my group 24 box, I could maybe stand it on its side, since that's supposed to be doable, and put some wood in there to take up the extra space to support it. I'm going to get a new box or maybe strap like you have, but I'm going to have to find someone to help me with that because it involves too many tools and so forth. I've got a Thanksgiving trip and need the new battery before I go. 

pthomas745

An AGM can be set in any position except upside down.

dragonsdofly

@jules2go, our group 31 is a deep cycle wet cell. It cannot be in any position but sitting on the bottom, but we have the small standard plastic tub. We do not have it in a battery box, but it is covered by a plastic lid. As I mentioned, it is mounted on a piece of exterior grade plywood, attached to the A-frame of the trailer. 

A group 31 refers to the battery's measurements. If a group 31 wet cell fits in the standard plastic tub, a group 31 AGM should fit as well. Good luck!

Oh, and btw, our flooded wet cell sits out all winter, but it is plugged in to shore power. We check it, and fill it if necessary as we cover it. Usually sits 5 or more months like that, until the spring when we uncover and check it again. We have stored it once through the winter unplugged. In November, with no load, battery read 12.7 with a multi-meter. In April, still with no load, it read 12.6. Battery switch was in the off position, stored covered with no solar or additional charger and we had nearly 2 weeks of nearly -10°F weather that year. A well charged, healthy battery, wet cell or AGM can sit for months in a static condition without much loss of charge.

ScottG

@jules2go, like @dragonsdofly, I have a group 31 wet cell installed in the older style plastic tub. It's even in a box. The box I installed claims to be for a group 27, but it was on the long side and swallowed an Interstate group 31 without protest. There may be variation in battery brands so it pays to check sizes carefully.

You can see more details here. The steel frame I made was probably overkill--you could accomplish the same thing with just a simple piece of wood to extend and angle the platform.

jules2go

@ScottG Thank you, that's helpful. 

YanniLazarus

Don't be afraid to keep your agm battery in the tub without a battery box...

Denny16

Just be sure to cover and protect the battery terminals from getting shorted.
 Cheers 

jules2go

Thanks everyone for helping with my questions again.