Use and storage of auto jump-starter - portable power

I've got a Sears DieHard Portable Power 1150 unit. It can be used to jump start a car, has an air compressor, and even a small inverter. Does it make sense to always have the unit plugged in and charging constantly or to charge it to 100%, take it off the wall outlet until I use it and then charge it again? The instructions say to charge the internal battery every 2 or 3 months -or- leave it permanently connected to the AC wall outlet.
Just wondering if one way might prolong the internal battery more than the other.
Thanks, Walt
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I would assume it uses gel type sealed batteries. I would just plug it 2-3 months. As used in emergency lighting, they only last so long, perhaps 6 years or so.
greg
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that depends on how the internal charger is designed..
if it is designed poorly, having it plugged in all the time may overcharge the battery and boil away the electolyte... if this is the case then you are better off pluggin git in for 1 day per month or something like that...
If you have a good DVM check the volatge across the battery while it is plugged in and has been plugged in for a day or so.. if it is much above 13.8V then it is probably overcharging.
If the charger is designed correctly and holds the voltage to 13.8 V then you can leave it plugged in all the time...
Mark
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13.8 is 100% but if he lets it go below 12.6 or so as it sits months it will sulfate. I bet those cheap units are not very good at proper battery maintenance, that might need a maintainer. www.batteryuniversity.com might help him learn what he needs
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Hi Walt,
I have a similar jump-starter and air compressor combination that I keep in my car for one or two months at at time between charges. While I have used it during a recent two-week, 4500 mile road-trip with minimal charging, it has served me well.
Mine has a sealed lead-acid battery that likes to be charged every two or so months. As long as I take care of its needs, it takes care of my needs. If your model uses a lead-acid battery, it's better to fully charge it every 2-3 months or so. That's been my experience using a similar device during 2-3 month periods over the course of one year.
Brian
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Walter Cohen wrote:

I don't leave anything plugged in that consumes power all the time.
--
Claude Hopper :)

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lead acid batteries should be kept float-charged,and they tend to sulfate over time.
Note that similar computer UPS supplies keep their SLA(sealed lead acid) betteries float-charged while on AC power. After a few years,the batteries capacity diminishes due to that plate sulfation and need to be replaced.
--
Jim Yanik
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On Sun, 26 Oct 2008 09:02:56 -0400, "Walter Cohen"

I bought a similar unit in 2001. It's been plugged in ever since and used only twice. Still seems fine. YMMV
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