Peaty

Re-posted with permission from John B. the author (thanks John)

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With all the talk about buying new car batteries, thought I'd give my take (very long-winded - sorry!) on the process. Hope that this
helps...

Number one consider the battery type. You'll want a 12 volt "car" battery, not a "deep cycle" or other purpose battery. Most car
batteries nowadays are a wet cell lead/acid type. Some are sealed, "maintenance free" types (never have to add water), while others have removable vent caps so that you can check the electrolyte level and add water (distilled, preferably), as necessary. The "maintenance free" types tend to perform a little better than the open vent types. However, in hot climates, the open vent types can be topped off with water as evaporation occurs, and thus tend to outlive the "maintenance free" types in which you can't replace lost fluid.

Before you trade in your original OEM battery, you'll want to have a look at it and write down a couple of things. Somewhere on top
you should see written the "CCA" (cold cranking amps) rating, "RC" (reserve capacity, in minutes) rating, and the "GROUP" code (a code used to describe battery's physical size/geometry, and terminal locations).

The "CCA" and "RC" values (and maybe the "GROUP" code, too) are also listed in the owner's manual in the "Specifications"
section near the back (just in case the writing on top
of your battery is incomplete or illegible).

When shopping for a new battery, fist consider the "CCA" (cold cranking amps) rating. This is the amperage that the new, fully
charged battery can deliver at 0 degrees Fahrenheit for 30 seconds of cranking without dropping below 7.2 volts (whew!). You'll want to buy a new battery with at least as high a CCA rating as the original OEM battery. Consider getting a battery with a much higher CCA rating if you live in a place where it gets truly cold (North Dakota, Minnesota, Alaska, etc.). Beware when shopping - many batteries also list a "CA" rating (cranking amps - measured at 32 ° F), "HCA" rating (hot cranking amps - measured at 80° F), or even a "MCA" rating (marine cranking amps - once again measured at 32° F). These ratings will invariably be higher than the "CCA" rating (due to the higher measurement temps - battery performance increases with rising temperature), and serve primarily as a sales gimmick to confuse or distract you. The "CCA" rating is the only important one, and the one you need to look/ask for.

"RC" (reserve capacity) is a measurement of how many minutes the brand new battery can put out 25 amps at 80° Fahrenheit before the voltage falls below 10.5 volts. Once again, get a new battery with the same or higher "RC" rating than the original OEM
battery. Generally speaking, more "RC" is a good thing, as more battery plates are necessary for the extended capacity (all else
being equal, a battery with a high "RC" rating will tend to be heavier than a battery with lower "RC"), and battery's useful life will be somewhat longer - important in hot climates that tend to kill car batteries more quickly.

The "GROUP" code is just a convenient system for describing the battery's physical dimensions / geometry and terminal ("post")
locations. Picking a new battery with the same "GROUP" rating as the original OEM battery will ensure the easiest possible
installation, as battery's base dimensions, height, and post locations will match your car's mounting/wiring hardware almost exactly.

Of course, you can put in a battery with a different "GROUP" rating, but you may have to work a bit/modify/change hardware to get it to fit properly.

Try to buy the freshest battery possible - they do have a shelf life! If you buy a battery that's already 9 months old off the shelf, that may be nine months less that you'll get out of the battery's total life. There is usually a sticker somewhere on the top or sides which has the date of manufacture listed on it. This is usually a small, round sticker, and the code on it may be of a "9-03" (month - year) type, or "B-04" (month as letter - A = Jan., B = Feb., etc. - and year) type.

Although there are a bewildering number of battery "brands" available out there (Sears "Diehard", "Autocraft", Wal-Mart brands, etc.), its good to remember that there are only a few companies that actually manufacture these batteries (Excide, Johnson Controls, etc.), so differences between brand names may not be that big - different labels may hide physically identical batteries. Try to gage expected performance/life with price to get the best value. Short term warranties may be worth the extra money paid for them if they cover complete battery failure in the first year or two of service. Long term, pro-rated warranties are less cost effective - make sure you're not paying a premium for this type of coverage.


Finally, a handy trick for maximizing your battery's cold weather performance -- buy and install a "battery blanket" or "battery warming plate". These are electric heaters (~100W) that you plug in (similar to your engine's "block heater", if you have one installed) and warm the battery prior to start-up. Have to leave them plugged in for one to several hours (depending on how cold it is outside) to get the desired effect. The difference between a cold and warm battery for starting you car is astounding! Used these for years while attending college in Fairbanks, AK, and they make ALL the difference.

--John B. 12/27/03

__________________
Peaty

cheeze@sunflower.com

2010 Legacy 3.6R Limited

2006 B9 Tribeca - 7 pass Ltd (wifes ride)

1999 Miata - Daily Runabout

 

Peaty

Just to add some safety information about changing out a car battery.

---> Wear Safety Goggles!

---> Always, when disconnecting a battery undo the Negative first then the Positive pole.

---> When installing a battery or hooking it back up. Do that in reverse order the Positive first then the Negative pole.

The reason for this is it reduces the possibility of the tool you are using hitting a part of the car and creating an arc and sparking. Batteries produce Hydrogen and Oxygen gas and they can explode with a spark. I never thought this was really likely to happen but, I was unlucky enough to have this happen once. We were trouble shooting a car and checking for spark. My friend chose to look at the spark of a plug too close to the battery and when I turned the car over it blew the top of the battery off. It sounded like a gun shot and battery acid went everywhere. He was fortunate to not get any acid in his eyes but he did end up with some nasty burns.

This is the same reason when jump starting a car you make the last connection with the negative cable (black) and you do it away from the battery on the motor block somewhere.


Peaty 12/27/03

__________________
Peaty

cheeze@sunflower.com

2010 Legacy 3.6R Limited

2006 B9 Tribeca - 7 pass Ltd (wifes ride)

1999 Miata - Daily Runabout