wrote:
Although fifteen or so years ago you could get up to ten years out of
a typical set of Japanese gel cell batteries, these days it seems that
three to five is about all you can expect from the Chinese knock offs
that have flooded the market.

I put these same size batteries in computer UPSes; one of them is on its
third set of batteries since I got it in about 2000. I have had pretty
good luck with Panasonic and Power-Sonic brands, and pretty bad luck
with all the others I have tried. All the previous Power-Sonics I have
bought were made in Mexico, but the ones I bought in 2013 were made in
China. I put them in my old UPS but their longevity remains to be seen.

If the utility power is going out more often in your area for some
reason, the alarms will probably go through batteries quicker as well.

I used to keep replacements in my van but I found that if they weren't
used within a certain time frame they would sulfate.

How about connecting them to the van's electrical system when the
ignition is running? That system is *designed* to charge a 12 volt
lead-acid battery. Okay, it's not exactly the right voltage for a
sealed battery, and you probably don't need to charge them every day.
Maybe only hook them up to the van every Monday or every first of the
month or something like that.

I guess what I'm asking, if anyone knows, how much life span is gone
or lost by these batteries just sitting in a box for fourteen months?

Power-Sonic claims that their batteries can be stored for a year before
recharging is required. They also advise charging a new battery after
6 months of storage after *you* get it, to account for the time it sat
in the warehouse.

Paper page 10, PDF page 12 of
http://www.power-sonic.com/images/po...hManual-Lo.pdf
has a chart of self-discharge over time at various temperatures. It
also claims that if the battery is allowed to self-discharge to less
than 60% of its nominal capacity, charging the battery may not restore
full capacity. According to the chart, this 60% point is hit in a
little over 12 months if the battery is stored at 20 C (68 F). At
30 C (86 F) it happens in 8 months, and at 10 C (50 F) it's over 18
months.

The chart doesn't talk about *how much* capacity is permanently lost,
just that it won't be back to 100% capacity.

Matt Roberds