storing AGM batteries for the winter.

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I have optima batteries for my bassboat and I store them in my cellar for the winter. I charge them up when I first get them indoors. will check on them in a month to see if the charge is holding. keep checking every month to be sure they are at 12.6- 12.7. usually once they reach the desired voltage they stay there all winter. I store them up off the concrete floor on a wooden bench.other than that I just wipe the outside of them down to clean any dirt off them. I do have a good marine charger that I use.
 
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What matrass said. Just monitor the state of charge and put the charger on them monthly to keep them topped off. You can also put battery maintainers on all three or use only one and move it to a different battery each week or so.
 
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Best batteries I have ever used in a car. How do they compare to conventional batteries in their deep cycle flavor?
 
While on topic of AGM, can someone shed the 411 on why you use them.

My Bavarian mobile is on the fritz. It's a combo of alot of things.....GRRR, I suspect the LCM module has gone south and coincentally, my Odyssey AGM battery needs to be replaced. A wild guess would be 6 or 7 years of typical northeast 4 season weather+ a Fairly Intricate High End Audio System.

The car is another keeper for another year and I'll most likely give it to my brother. Debating whether I should spring 2X for a AGM replacement again
 
AGM batteries are supposed to be better in high temperature locations. There are also other features, such as little corrosion on terminals, capability to mount in any orientation, etc. My anecdotal observation in a very old car was that they lasted twice as long as a conventional battery and gave WEEKS of warning prior to not being able to start the car compared to a couple of weak starts (days). I am sold.
 
It's generally thought that heat kills lead/acid batteries, as the internal reactions accelerate during higher temps.

It's also generally thought that cold storage reduces the life less than warm storage. However, there is I believe, an optimum temperature for this. But, PowerSonic's website says 50degF or LESS. Others say 59F. I found one reference to -20 deg C as a lower limit for optimum life.
 
I have an Optima simply because I wanted to try one. It's not very old so I can't much one way or the other.
 
Optima, IIRC is a gel cell, which is a variant on AGM, but not really an AGM battery.

AGM uses an absorbed glass mat, like a sponge, to hold essentially the exact amount of electrolyte. This is different than a gel cell which uses silica gel to solidify the electolyte for spill reasons. In an AGM, the electrolyte is wicked.

Now, the main thing with these batteries is that as opposed to flooded batteries, even low maintenance ones, there is a valve that prevents gas from escaping so that the H and O can recombine to form water. This prevents dry-out and change in acid concentration to a range that is not optimal for life and performance.

So in theory they can last a lot longer, especially when left on float service in cold temperatures.

Nothing kills lead acid (or any) batteries better than heat. Heat drives side reactions and other degradation. It is well established that a small temperature rise (single digits over room temp) will half the life of a lead acid battery.

The good news? Storing cold slows all this.

The bad side? Cold temperatures drop the cell voltage. Not a big deal if not under load, but a bigger issue if put under load because then the current flow goes up to meet the power demand, etc.

The best thing, as said, is to keep it on a float charger that is thermally compensated, as the required float voltage is temperature dependent. It is also best to have a smart charger that can actually vary current at that voltage very well.
 
Optima batteries ARE AGM. I have owned two red tops. I never got more than three years out of a battery in my old Accord and I had quite a few conventional batteries in it during its life. I had a few that didn't even last a year. My first Red Top lasted six years and the second was still in the car when I got rid of it. It had been in for four years and was still fine. Plus, instead of a few weak starts and then "jump start time" the Optima provided weaker starts for two months before I figured out it needed to be replaced. Try that with a standard lead/acid battery.

I should mention that the Accord's battery was not insulated and picked up a lot of engine heat.

http://www.optimabatteries.com/us/en/products/redtop/
 
Our experience here was VERY poor with Optima batteries.

Not one could last more than two years and we even had issues with their warranty!

Never again, too expensive and poor durability in our usage.
 
^I have heard this from a couple of guys on my Honda forum, but my experience was just the opposite. When I have to replace the battery on my Mazda we'll see what happens. I really like the fact that the batteries last and stay really clean (no acid to leak).
 
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