AGMs & Maintainers

[Tin_Pusher]

This topic is not RV related but there is more battery expertise here than anywhere else I know of. Mostly over my head 🙂

I have this AGM battery in my Seadeoo. I used this maintainer on my wet cells, it worked great for them.

The AGM says it needs an "automatic temperature sensing voltage-regulated charger", such as, I suppose, this..

I disconnect the batery for storage, but even so I'm down to about 12.3 volts.

So, the questions is, can I use my current maintainer with this battery without shortening its life, or do I need to shell out for a new mantainer?

Thanks in advance.

[Tin_Pusher]

Almot, they pretty much all used wet cells as OEM equipment. They have a vent overboard. They are just motorcycle batteries, really. I changed to AGM because one, obviously, you don't have to water 'em, and two, it was hard to see thru the case and read the level and three, I never owned one that had the electrolyte levels clearly marked. When is it low? How much is too much?

I didn't study up that much, it's just a battery, and just sort of figured I'd use the same old maintainer in the same old way, which was to hook it up and leave it whenever the Seadoo was not near a body of water. Months, over the winter, to a week or two during the summer.

After reading westends' last post (and others also) I am going to forget all the AGM stuff, and just treat it like a battery 🙂

On edit: 15 years? Impressive 🙂

[westend]

The difference between an AGM of that size and a FLA battery maintained is that an AGM likes to gulp a lot of current to perform well and the FLA will sip until it's full. That's why your battery maintainer delivers the low current and maintains that low current when powered and connected. Your AGM will survive better if fed even small sipping rather than sitting idle and no electrons served. It will lose little voltage while in storage so intervals between use becomes important. The small charge delivered by the engine is enough to maintain sufficient power and charge just a small bit. It is dumber than a battery charger.

FWIW, I maintain a few disconnected batteries, both AGM and FLA. I use these 12V batteries for emergency pumping duties, vehicle replacements, and any other use I find around the house. I have multiple chargers and 12V power supplies available. What works for me best is to use a reclaimed 12V wall wart. Unloaded it outputs 16VDC at a maximum of 3 amps. I connect it to a battery and watch voltage rise. After three of four days voltage will rise to 14V. At that point, I disconnect it. The battery is fully charged and is left to discharge until I get to it in a few monthes. My method is not perfect because i don't continually float but I have good luck with longevity. I have one Diehard that is 15 yrs old.

[Almot]

Spill-able battery on a Sea Doo wouldn't be a good idea.

[Sam_Spade]

Tin Pusher wrote:

Seriously considering going back to a wet-cell when this one gives it up.

That would be sad.

Even if you treat it exactly like a wet-cell.....or worse....an AGM will typically last twice as long.

And it is much better choice for things that might end up upside down at one time or another.

[Tin_Pusher]

Almot, red31, thanks for the links, and thanks to the rest for your input, however confusing I may have found it 🙂

I am going to connect the maintainer over the weekend, see if I can up the SOC.

Seriously considering going back to a wet-cell when this one gives it up.

One thing to keep in mind, this battery has only one purpose in life: It is to start the Seadoo. Which it did, even at 12.4 V 🙂

[Almot]

Tin Pusher wrote:
Manual doesn't say much of anything at all, just a bunch of cautions and warnings.

This isn't a manual. Should be something like this, see the graph on page 11 - Self Discharge of VRLA at Different Temperatures:
East Penn Deka.
Or order the manual for your exact model. Shouldn't be much difference.

[time2roll]

Tin Pusher wrote:
On the maintainer 15 hrs yesterday, after resting overnite getting 12.69 V, didn't really gain that much. But good enough for now I guess.

Resting voltage on an AGM is a bit higher. I would leave the Battery Minder on for a week minimum.

See link below and scroll to page 13 to see resting voltage should be 12.80 or higher.
Battery is not yet fully charged.

[RJsfishin]

You have to just love the advice given here.

I believe the battery is toast already.
Then take the advice to pump 4 amps into a 10 AH battery, and toast it for good !! Real smart !

[red31]

Tin Pusher wrote:
If it had a real manual maybe I wouldn't have to fish around on a forum like this for information 🙂

http://www.eastpennmanufacturing.com/contact/

[MEXICOWANDERER]

I would have because of it's long-term low state of charge put four amperes through it amd let voltage rise to 15 then disconnected it. But then agai that'me 🙂

[Tin_Pusher]

On the maintainer 15 hrs yesterday, after resting overnite getting 12.69 V, didn't really gain that much. But good enough for now I guess.

Almot, you'd lose that bet. Manual doesn't say much of anything at all, just a bunch of cautions and warnings. If it had a real manual maybe I wouldn't have to fish around on a forum like this for information 🙂

[Almot]

pianotuna wrote:
Fully charge; disconnect; leave in place; repeat in 3 months.

x2.
I bet the manual for this Duracell says that when fully charged, it will stay above 60% for 6 months at 90F. Slow self-discharge is one of the reasons why people buy AGM.

Shouldn't be a problem for 3 months, unless they damaged it already.

[Tin_Pusher]

pianotuna, went from 12.3x to 12.6x (didn't pay much attention the 1/100). Will post in the AM, after todays charge, maybe 15 hrs.

[pianotuna]

Tin,

What was the voltage after charging for 8 hours?