Long-term AGM battery storage

[NH2]

I've accepted a one-year teaching position in a remote village in Gambell, Alaska.
We found a covered storage facility that provides electricity in each storage bay. I plan on putting a 2amp battery maintainer on the truck batteries but am wondering about the coach batteries.
We have four, Lifeline AGM's connected to a Magnum Energy inverter/charger. When I went from flooded, lead-acid batteries to the Lifelines, I adjusted the charging algorithm to a Lifeline-specific setting.
NOTE: the Magnum has two AGM settings; one for Lifelines and one for all other manufacturers.
My question is...

• Should I plug the coach in and walk away letting the Magnum maintain the Lifelines for a year?
• Disconnect all batteries and purchase a battery maintainer for AGMs that's probably is not Lifeline-specific?

Thanks,

Mark

[Dennis M]

I would just leave the AGMs untouched. They have a very low internal discharge rate. I had an Optima AGM in a vintage race car. It sat untouched (battery disconnected) for two years. Flipped the battery kill switch on and it started the car immediately.

[Yarome]

Either way your golden, Mark.

 

If you're concerned, your mag will float them just fine, but personally, I would just let them self discharge. At 1.5-2%/30 they'll do just fine as long as you put them back on charge every 4-6 months. Health-wise.. the latter would be preferred (they prefer to be exercised anyway), but if there is any concern about having to put them back on duty without much notice then keeping them on float is really no big deal.

 

I certainly wouldn't go to any additional expense to put a tender on them.

[NH2]

 

they'll do just fine as long as you put them back on charge every 4-6 months.

 

1.5-2%/30

I hear ya but we'll be on an island 38 miles off the coast of Siberia for a year. The commute every 6 months would be a killer

 

Just want to clarify what you meant by: "1.5-2%/30"

I know the self-discharge rate for AGMs is about 1.5-2% per month. Is that what you meant by the above?

Thanks,

Mark

[Yarome]

Just want to clarify what you meant by: "1.5-2%/30"

I know the self-discharge rate for AGMs is about 1.5-2% per month. Is that what you meant by the above?

 

Correct. So even if you're 6 months out between service dates (disconnected) you'll be just fine. They would actually love you a little more with a partial discharge and back on charge vs. floating them.

[Yarome]

Just looked up average temps for your general region. Putting a good charge on and stored properly (enclosed with limited air space) you should be able to go 12 months and return with 70%+. At $300+ a pop.. I understand your concern on your investment, but I think you're still good without a tender.. and in the long run.. your lifelines will be much healthier than sitting on float for months on end.

[NH2]

Just looked up average temps for your general region.

Thanks Yarome.

I should have clarified from the get-go... the coach will be stored in the dry-side of Oregon while we are in Alaska.

I'll charge 'em up before I go and flick the battery disconnects.

Thanks to you & Dennis for your input. I appreciate you taking the time.

[oldjohnt]

Here's my take as an engineer, but I have no specs or data to go by so its ONLY a somewhat educated intuitive guess.

 

Okay your Magnum I consider HIGH QUALITY and it would most likely be fine if left connected assuming its correctly set to maintain the proper float charge for your particular AGM batteries ??? Is it ??? HOWEVER I advise against any "cheaper low quality" so called Tender as it cant be near the quality of your Magnum MAYBE NOT EVEN AGM COMPATIBLE and if it crapped out you could theoretically harm your expensive battery investment (or perhaps a fire hazard? it depends on quality and safety of tender). In fact, if the only two choices were a "low quality cheap tender" versus do nothing and let them self discharge to whatever ???, Id take my chances of doing nothing. That's a long time to leave something plugged into AC power with no monitoring!!!! Of course if you find a tender that's "good quality" and mates up to your particular AGM's, that's another story.

 

So for me its the Magnum or nothing and for safety sake I think Id do nothing even though statistics and opinions from a lot of folks would say with a Magnum there's no worry or concern. if I had my "druthers" and a person you could hire and trust to go there once a month or so to connect the Magnum a few days at a time THAT WOULD BE MY CHOICE.

 

John T

[Yarome]

the coach will be stored in the dry-side of Oregon while we are in Alaska.

I'll charge 'em up before I go and flick the battery disconnects.

 

That'll do, Mark. No worries.

[bigjim]

So just a thought that may be crazy. What about a timer type set up in the tender line? May be too much potential for more problems but I thought it might be worth batting around.

[oldjohnt]

Yo bigjim, you ask "What about a timer type set up in the tender line?"

 

FWIW (nothing) Actually, I don't consider that as crazy, but a "viable" alternative, HOWEVER instead of a possibly inferior "tender" I would just go ahead and use his quality Magnum Charger if he were to use some sort of a timer.

 

Maybe something like once a week or two it runs for a day if it has the capacity to re maintain that frequency (1 day on 7/14 off) even if there were a temporary power failure. Also, even if it never worked, I still consider that option as superior to a cheap inferior quality perhaps NOT AGM compatible tender. I would install such as an inline series stand alone timing device NOT mounted in or on the RV, maybe in a dry location up off a concrete floor outside the RV???????????

 

Engineers can always come up with more exotic more expensive more complicated way to spend another persons money lol lol Its in our DNA we just cant help it. As always we report and offer our opinions, methods and preferences BUT NOW YOU DECIDE.

 

NOTE A timer and relays and control circuit capable of maybe 1500 or more watts (depends on Magnums power) isn't any cheap off the shelf Home Depot Special, SO IS IT WORTH THE COST AND EFFORT?? If a "tender" were used that could well be a lower power device operable on a cheaper off the shelf timer, but again unless its high quality and AGM compatible I THINK ID RATHER JUST DO NOTHING then risk it, let them self discharge to whatever they may???

 

HAPPY MEMORIAL DAY AND THANKS TO ALL VETERANS "All gave some, some gave all" The wife and I placed flowers on our parents and dads and uncles (all WW II Vets, the Greatest Generation) graves, now today you cook out and listen to the race and give thanks for all our blessings

 

John T

[jimhanus]

I know I'm pushing my luck, but I have 2 Lifeline AGM batteries that are 7 and 8 years old. They are still working like new. We only boondock, and the batteries are always left in the TT. Haven't even seen them in years. I'm in Michigan, we put the trailer away in late October and bring it out in Spring. The batteries aren't touched or charged all winter (outdoors), and when I plug the trailer in to charge them the batteries are only down a few amps. These are group 31. Just my experience, YRMV.

 

Jim

[NH2]

Jim,

I'll keep the group posted when I return to my rig in early July. As I stated earlier, I charged them up and then hit the disconnect switches; no trickle or timed charging. When I left them last July, they were at 12.79v. I'll be curious to see what the voltage will be upon return.
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