Should I disconnect my battery?

lisams58December 1, 2005

I need an opinion on disconnecting my car battery when I will be gone from home for an extended time. I have a 1985 Mazda 626 that I leave in Florida. It will sit without being run for 2-3 months at a time. Someone recommended I disconnect the battery, so that when we return to Florida and reconnect the battery the car should start without having to be charged.

Any advice or opinions are welcome!


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Depending on how old this battery is...I'd think that if it is four years or more, I would just replace it...
Otherwise, I would run a trickle charger, and it is probably better to disconnect the battery...

    Bookmark   December 1, 2005 at 7:29PM
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absolutely yank the cable on the battery, the two minutes restting your favorite rap stations and time display are well worth the effort.

    Bookmark   December 1, 2005 at 9:00PM
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If the battery is in good condition and fully charged, it should be ok if the storage period is no longer than 2 months. If you disconnect the battery, you may not only loose your radio and clock settings, but also the adjustments on the transmission shifting. After a battery disconnect, the transmission will revert to default shift timing and relearn these settings on subsequent shifts.

The main reason for disconnecting the battery is to preserve the battery by avoiding a dischagred condition. In northern climes, this is a factor since a discharged battery can freeze. This should not be a factor in Florida. Also, fully discharing a battery may reduce its cranking capacity, e.g., it may not return to the same capacity on recharging. Unless you have an unusual drain on your battery, it should hold for 2 months. The drains that I know of are clock, keeping alive the radio settings, keep alive transmission settings, anti-theft system, and key-fob lock/unlock funcions. Of these, the anti-theft and key-fob systems are probably the largest drains. However, if you wish to maintain as much charge as possible in the battery, disconnect the hot lead.

    Bookmark   December 2, 2005 at 4:02AM
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If it sits outside, I'd put a 2 or 3 watt solar cell charger/maintainer doohickey on the dash that plugs into the cigar lighter - unless its real exposed to vandal types who's temptation may be to bust a window to get at it.

If it sits in a garage I'd buy it a little BatteryMinder float charger/maintainer that plugs into the wall power. I've had a riding mower on one of those for close to six years.

Make sure the battery has a proper level of distilled water in it before you leave, just to be sure it doesn't die of thirst.

    Bookmark   December 3, 2005 at 3:10AM
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If it isn't drawing any current, which it won't be unless you have a short, there is no reason to disconnect it.

    Bookmark   December 4, 2005 at 12:27AM
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Batteries self discharge and car computer and usually a radio clock timer are ticking away something like a max of 25 milliamps an hour is the utoh point ... thats 18 amps per month, of a 100 amp battery that can only afford to loose 30 amps max otherwise its not got enuff oomph so it potentially looses half of its useable capacity per month ,,, while doing nuffin.

    Bookmark   December 5, 2005 at 11:25PM
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Convert your calculations to watt-hours, then compare. Amperes is a measure of current flow, not energy. (Watts x Time) is energy.

A lead-acid car battery self discharges 8 to 10 percent per month. Thus in a 2 month period, it will retain approximately 0.9 x 0.9 = 0.81, or 81% of the original charge (or loose 19%). To this drain, add other the other loads to estimate the loss of stored energy in the battery.

    Bookmark   December 6, 2005 at 3:41AM
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I dunno,, maybe I'm thinking wrong...

25 milliamp load.
= .025 amps per hour.
x 24 hrs
x 30 days
= 18 amp hours.

Auto Batteries are rated in Amp Hours capacity. Waste about 30 of them in a typical mid size car battery and its considered dead.

    Bookmark   December 6, 2005 at 1:57PM
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