Car Battery Know How: Cold Cranking Amps and Reserve Capacity

NAPA KNOW HOW car battery replacement

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August 2, 2013 4:26 pm

A car battery wears out just like any other battery and needs to be replaced.  There are a couple of things you should understand when looking for a new car battery: one is cold cranking amps and the other is reserve capacity.

Let’s start with cold cranking amps.  This can be thought of as the power output used to start a cold engine.  The number of cold cranking amps you need depends on your vehicle and where you live, specifically how cold it is where you live.  The two factors are that the colder an engine is, the more power it takes to turn the engine over to get it started.  It has all that cold, sluggish oil to contend with.  The other factor is that the chemical reaction in the car battery that creates electrical energy is less efficient in the cold.

So the colder it gets, more power is needed, but the available power drops.

So if you live where it’s cold, you need a car battery with more cold cranking amps than you do where its moderate or hot.  You should always get at least as many cold cranking amps as the manufacturer recommends, but may want to upgrade if you live where it gets real cold.

An important note: Batteries may also list the Cranking Amps – CA – number.  It is the Cold Cranking Amps – or CCA – that is the important number here.  CCA is the number to use in your comparisons.

Now with all this talk of cold temperatures, it’s important to note that heat is the real enemy of long battery life.  In other words, the damage that’s done over the hot summer months shows up with the increased demands on the battery when the weather turns cold.

Now on to reserve capacity:  It’s a measurement of the number of minutes of reserve power the battery has at a given load.  The number is more important these days because of parasitic drain.  Parasitic drain is the battery energy that’s used when the key is off.  So, the power drawn by the security system, the remote start system, even the power the computers require to maintain their memory.

Reserves are also needed when you make very short trips.  You’re not driving long enough for the battery to recover the energy it used to start the engine.

So go with the minimum recommended by your manufacturer and upgrade if you need more.  Talk with your parts or service advisor about options.  If you need more from your battery, a larger capacity battery may be called for.

A car battery is a big ticket item, so the warranty gives piece of mind.  Be sure to ask about the warranty so you know what you’re getting.

Shop for a new car battery at NAPAonline.com, or call your local NAPA AUTO PARTS store or NAPA AutoCare Center for the KNOW HOW to keep your car or truck running its best.

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  • dbarto667

    Good info-thanks greatly

  • John

    does reserve capacity impact how fast a battery charges? if I make lots of short trips how long until my batter charges back up?