Rick's Free Auto Repair Advice

How to buy a car battery

How to buy a car battery — CCA, RC, AH and warranty

Battery brand is mostly irrelevant

There are really only three U.S. car battery manufacturers—Johnson Controls, East Penn, and Exide. All the retailers like Autozone, Advance Auto Parts, O’Reily, Sears, Walmart, Costco, and Sams Club get their batteries from those three manufacturers.

Each retailer orders batteries custom built to their specifications and label them with their store brands. Or, they may license a brand name like Duracell or Interstate.

Some Internet web sites purport to name the battery manufacturer for each store’s brand. But that’s not accurate. Each retailer orders their batteries from each of the three manufacturers based on the manufacturers’ proximity to the store and their price on each battery at the time they order. Batteries are heavy, so it doesn’t make a lot of sense to ship them across country when you can get them from the nearest factory. In other words, auto parts stores and the big box stores get their batteries from the closest warehouse.

Even within a single brand, you may discover that one group size battery is made by one company and other sizes are made by one of the other two. So relying on brand alone isn’t a good buying strategy.

So you can see that there’s really no single answer to the question of who makes the best battery. But I can give you some battery buying tips.

Tip #1 Buy the right type of battery for your vehicle

SLI versus EFB or AGM battereies

Most older vehicles come with a flooded lead acid battery, also referred to as a standard lead acid (SLA) or starting, lighting, ignition (SLI). That’s a battery with lead plates and liquid battery acid.

But newer vehicles, expecially vehicles equipped with start/stop technology are usually equipped with an Enhanced Flooded Battery (EFB) or an Absorbed Glass Matt (AGM) batteries. EFB and AGM batteries use a sufuric acid/water electrolyte, but the batteries are built differently.

An EFB battery has a fleece covering surrounding the plates to keep more electrolyte in contact with the plates. In addition, they have recirculation funnels inside to prevent acid stratification. Generally, EFB batteries have more reserve capacity and higher amp hour ratings than an SLI battery.

An AGM battery is built with an absorbent material between the plates. They still use sulfuric acid, but it’s all absorbed in the mat. Car makers switched to AGM because they handle higher electrical loads better than flooded lead acid batteries.

If your car came with a flooded lead acid battery, replace it with the same type. Likewise, if your car came with an EFB or AGM battery DO NOT replace it with an SLI type battery.

Why? Because the charging system in your vehicle was built to handle the recharging protocol for the type of battery installed at the factory.

Installing an AGM battery in a car designed for an SLI battery can reduce the AGM battery’s life by more than 50%. That’s because conventional charging systems tend to charge at a much higher rate than an AGM system.

The reverse is also true; replacing an AGM with an SLI battery will kill the SLI battery within six months. That’s because the SLI battery will be contantly undercharged and develop sulfation.

Tip #2 Replace with the same battery group size

Once you determine if your battery is SLA or AGM, the next step is finding the “group size” for your car. Batteries are grouped according to their length, width and height as well as the location of their positive and negative posts. Find the group size and dimensions here. If you buy the wrong group size, the battery cables in your car may not reach the right terminals.

Should you buy a battery based on cold cranking amps?

Twenty years ago I would have told you to buy the battery that has the highest cold cranking amp (CCA) rating. Not anymore. Batteries in late model cars also list the Reserve Capacity (RC), a measure of how long the battery can output power with the engine off. Car makers are now emphasizing both CCA and RC because so many drivers run smartphones, tablets and laptops from the car’s power ports when the engine is off.

You can buy a battery with a higher CCA rating that’s the same group size to fit your car, but you shouldn’t. Here’s why:

This advice comes right from a leading battery expert at Johnson controls: Buy a battery with the same CCA rating that came with the car. To get more CCA’s out of the same size battery, the manufacturer can either use thinner plates and more of them or thicker plates with less battery acid. Thinner plates can warp when charged at a high rate after a deep discharge and thicker plates with less acid can also cause problems after a deep discharge. Bottom line: installing a battery with a higher CCA rating can actually REDUCE its life in your vehicle, especially in newer vehicles equipped with sophisticated power management systems that operate the charging system on software based on the factory CCA rating. Stick with the car maker’s recommendations—don’t second guess the engineers.

Once you match the CCA rating to the car maker’s specs, try to match the RC rating as well.

Tip #3 Match the factory battery’s RC and AH, especially if your vehicle has start/stop technology

Start/stop vehicles require a battery that can handle the longer periods of shut down. That’s where a battery’s reserve capacity and amp hour rating comes into play. In other words, CCA, RC and AH are all important if you have start/stop.

Tip #4 Buy the battery with the longest warranty

Batteries in late model vehicle rarely last beyond four years. So chances are good that you’ll be replacing the battery before the car dies. When you buy an 60- month battery, you’re getting more than just a longer warranty, you’re buying insurance too. When it fails, you’ll have a larger “pro-rated” credit to apply towards the purchase of your next battery.

Since the three major car battery manufacturers make all the batteries for all the auto parts retailers, independent shops, wholesale clubs, and big box stores, the battery’s brand name is irrelevant. It’s all about the warranty.

In years past, a battery would often carry a three-year over-the-counter free replacement warranty with an additional two years of pro-rated warranty. Those days are gone. Now, the best batteries carry a three-year warranty—period. Economy batteries have a one or two year warranty. Battery manufacturers have shortened their warranties because of the excessive under-hood heat in late model cars. Car makers pack so much equipment under the hood that car batteries now have to operate in a much hotter environment than older vehicles. As a result, they don’t last as long.

Tip #5 Buy from a store or shop that can provide the best service when you need help

Good luck getting your battery replaced under warranty if you buy from a big box store. They clerks in those stores are barely qualified to stock shelves, let alone conduct a proper battery test. Plus, the competency level of their service techs is, well, disappointing would be an understatement. It’s my opinion that it’s well worth the extra few bucks to buy a battery from a store or shop that has competent technicians who can professionally test, install and replace your battery.

Tip #6 Keep your battery receipt

If you ever need warranty service you’ll have to find the purchase date. Some stores keep that information, but most don’t. Since most stores print their receipts on thermal paper that fades over time, make a photocopy of the receipt using a copy machine. Then store the receipt in the glove box. That way you’ll have a readable receipt when you need it.

What’s changing in car battery technology? Read this

©, 2016 Rick Muscoplat


Posted on by Rick Muscoplat

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