Rick's Free Auto Repair Advice

Best car battery

Which car battery is best?

So the battery in your car has died and you’re shopping for the best car battery for it. Well, this is the article for you. We’ll talk the characteristics that make for the best car battery, along with some valuable information on the best way to change your own car battery.

What kills car batteries?

Car battery construction has improved considerably over the last 50-yrs. The Batteries Council International’s study “Failure modes from batteries removed from service,” car battery life chartdemonstrates that a typical car battery now last 55-months in2010, compared to just 34-months in 1962.

Today’s batteries are maintenance free, so they don’t need regular doses of water to maintain electrolyte levels and the terminals are sealed better, so they don’t corrode as often. That’s the good news. The bad news is that today’s batteries are far more sensitive to abuse. If you drain a modern battery by leaving your lights on, you’re far more likely to cause permanent damage to the plates, preventing the battery from recovering fully after recharging.

What happens when you leave your lights on?

Today’s cars have far more electronics than car from the ‘60’s. Power hungry options like heated seats, rear window defoggers, and “always-on” computers can drain a battery quickly if you drive short distances.

And it’s not just the electrical devices in your car. To make a maintenance free battery, manufacturer’s had to alter the materials used in the plate grid. First, the manufacturers had to reduce the amount of “gassing” that occurred during recharging because that led to water loss. So they replaced the Antimony in plates with Calcium. Calcium reduced gassing and water loss by 80%. And Calcium reduced the self-discharge that normally occurs in a “wet cell,” even when there’s no current draw.

The downside to adding Calcium comes during recharge. With Antimony, the high gassing agitated the acid during recharge and actually helped mix the acid. Without that high level of gassing, the acid becomes stratified. So the acid weight can be 1.17 near the top of the plate and 1.35 near the bottom. That leads to sulphation and grid corrosion, causing underused capacity and premature failure.

Avoiding deep car battery discharge

A car battery is a “wet cell” and it loses a percentage of its charge every day, even with no current draw on it. The amount of self discharge depends on the ambient temperature. A warmer ambient temperature results in more chemical activity in the battery and faster self-discharge. Then there’s the issue of parasitic draw caused by the vehicle’s computer. Every modern vehicle draws power from the battery even when the engine is off. This “keep alive” memory maintains all the “learned values” in the computer. In addition to learning the changes your engine and transmission have undergone since the day it came off the factory floor, the computer also retains the learned values from your anti-pinch windows, closed throttle, power sliding doors, HVAC actuators, and security system. Once you lose battery power, your vehicle forgets those values. When you replace the battery, the computer can relearn some values on its own. But others must go through a “re-learn” process conducted by a technician using a scan tool. That’ll cost you at least $125. So it’s really important that you don’t let your battery get to the point of complete failure.

A typical battery will discharge enough in 30 days that voltage drop to the point where the computer forgets its learned values. Starting the car and letting it idle will NOT recharge the battery enough to replace the power lost. In fact, starting and idling does more harm than good because it can’t even replace the power used to start the engine, let alone replace the charge lost due to parasitic load. If you don’t plan to drive your car for more than a week, either attach a battery maintainer, or have someone drive it AT HIGHWAY SPEED every two weeks for at least 15-mins.

Heat and corrosion are the #1 car battery killers

The kind of battery terminal corrosion in this photo is not the norm. corroded battery posts and battery terminalsA battery terminal can look just fine, yet be almost 90% non-conductive. In those cases the battery can start the vehicle fine one day and be dead as a door nail the next morning. In fact, that type of go/no-go situation happens often during seasonal changes where underhood temperatures can be around 140° while running, and overnight temperatures can dip down to 30ۥ or less. The temperature extremes cause expansion and contraction at the battery terminals, allowing more corrosion and high voltage drops. So clean your battery terminals by providing backup power, removing the terminals and cleaning with a battery wire brush, and applying a dielectric grease to the battery post. But follow this procedure before disconnecting the battery terminals.

Next, when starting a vehicle that’s been sitting unused for long periods, turn off all electrical accessories before turning the key, especially if you’re starting during cold weather.

Now let’s talk about the effects of heat and cold. Most car owners think that cold weather kills batteries. While batteries fail often in cold weather, they were most likely poisoned in warm weather. Read this statement from Bill Darden, author of batteryfaq.org

“Even though battery capacity at high temperatures is higher, battery life is shortened. Battery capacity is reduced by 50% at -22 degrees F – but battery LIFE increases by about 60%. Battery life is reduced at higher temperatures – for every 15 degrees F over 77, battery life is cut in half. This holds true for ANY type of Lead-Acid battery, whether sealed, gelled, AGM, industrial or whatever.”

High heat is the reason many car makers install a battery insulator around car batteries stored under the hood. And, its one of the reasons car makers are moving the battery to other locations in the vehicle.

How to tell if a car battery is going to fail

As a battery fails it sends out warning signals. If you ignore them, prepare to be stranded some day. If your headlights dim while idling, the problem can be a dying battery or a weak alternator. Either way, you must take action and have the battery and charging system tested. Slow cranking is another sign of a problem. Don’t ignore it. The root problem may be something as simple as corrosion at the terminals. If left uncorrected, the voltage drop can result deep battery discharge and excessive heat loads for the alternator, causing it to fail. At that point you’ve turned a $25 terminal cleaning job into a $600 repair bill for a new battery and alternator.

Testing a car battery

But the only real way to determine a battery’s condition is to test it. The “load test” used to be the gold standard. But today, computerized conductance testers are far more accurate at predicting a battery’s health. Just connect the tester best car battery testerand enter the battery’s CCA rating. Then press the test button. The tester will run a conductance test and a simulated load test and give your the results.

I’m showing a Solar BA-9 tester here because it’s accurate and most affordable for the average DIYer. If you don’t want to invest in your own tester, find a battery store or auto parts store that will test your battery for free.

The Solar BA9 can also test marine batteries and your entire charging system.

test your car battery

How to buy a new car battery

There are only 3 car battery manufacturers in the U.S. They make all the brands sold by all auto parts stores, big box stores, and wholesale clubs. So there’s really no way to buy a battery based on brand. Here’s an example: A large auto parts store like Advance Auto Parts private labels their batteries under the AutoCraft brand. They further divide their offerings into Silver and Gold. Since you don’t know which company made the battery, you can only compare the two offerings based on the rated CCA and warranty.

Start by determining the recommended “group size” for your battery. Getting the recommended group size is critical to ensure the battery will fit in the battery tray and the battery terminals will be in the right location for the battery cables. Next, make sure the replacement battery has the same CCA rating (or as close as possible to the recommended CCA rating). Installing a battery with a greater CCA rating may sound like a good idea, but it’s not. To get more CCAs out of the same size battery, the manufacturers must use either thinner plates and more of them, or thicker plates with less electrolyte (battery acids). So the larger CCA battery may not perform as well over the long term as a battery with a lower CCA rating.

Cold cranking amps (CCA) defined

This number represents the number of amps a battery can deliver at 0 ° F for 30
seconds without dropping below 7.2 volts. Buy a battery with the highest CCA rating.

Cranking amps (CA) defined

The number of amps a battery can deliver 32 degrees F. This is also called marine cranking amps (MCA).

Hot cranking amps (HCA) defined

This term isn’t used much anymore but represents the number of amps a battery can deliver at 80 ° F.

Reserve Capacity (RC) defined

The number of minutes a fully charged battery at 80 ° F will discharge 25 amps until the battery drops below 10.5 volts. This rating is usually found on deep cycle marine batteries as amp hours (AH). This represents an amp draw for 20 Hours.  If you have a 100 AH rated battery and draw 5-amp and the battery provides that draw for 20 hours, it’s a 100AH battery.
Just be aware that current draw and draw time isn’t a linear relationship. For example, if you draw 100 amps from a 100AH battery, it will NOT provide power for 1 hour. As the draw increases, the actual AH rating decreases. In the case of a 100 amp draw, a 100AH battery will really only provide 64AH.

Next, review the battery CCA ratings. You want the battery with the highest CCA ratings available for your group size. That battery will cost more than another battery with a lower CCA. Don’t cheap out at this point. The lower CCA rated battery will let you down. Finally, buy the battery with the longest warranty. Yes, it will cost more. But it’s a better battery. Keep this in mind: the price difference between the lowest priced battery and the battery with the longest warranty and highest CCA rating will only be around $20. But the better battery will last longer and start your car better. How much is a no-start, late-for-work morning going to cost you? A single service call will eat up the difference in price.

Some people buy the largest battery that will fit in their battery tray. If the

car battery hold down bracket

This coat hanger isn’t an acceptable battery hold-down

battery is retained by a bottom hold-down and the flange on the larger battery corresponds to the old, that’ll work. Where people get into trouble is installing a larger battery that’s too tall (the terminals come in contact with the hood) or the old battery hold down doesn’t fit.

Remember, heat and vibration kills batteries. There’s enough vibration under the hood of a car the way it is. The last thing you need is to introduce battery movement by not securing it properly.

What car battery brand should I buy

In the U.S. all car batteries are made by just a handful of companies. They private label their batteries under many different store brands like Duralast for AutoZone, AutoCraft for Advance Auto Parts, DieHard for Sears, Duracell for Sam’s Club, EverStart for WalMart, Kirkland for Costco. Each retailer works with the battery manufacturer to develop a battery to meet a certain price point. In other words, the actual brand name is meaningless. Consumer Reports tested my brands of batteries and found that they differed in quality throughout the brand. So you’re left with the battery’s CCA and Reserve rating and its warranty. Period.

A good warranty has a certain period where you get a replacement battery for free for a certain period of time. After that period expires, you get a replacement battery for a pro-rated fee. Here’s an example; let’s say you pay more for a battery at a traditional auto parts store like NAPA, or O’Reiley. If you compare the terms of the warranty, you may find that the free replacement period on their batteries is 3-yrs before the pro-rated portion kicks in. Yet, a comparably priced battery from a big box retailer or wholesale club may only have a 1-yr free replacement period.

When a seller offers a 3-year free replacement period, it’s a pretty good sign you’re getting a better battery, and that makes it a better value overall.

So ignore the brand and read the specs. Follow this procedure before disconnecting the battery terminals. And KEEP THE RECEIPT in case the battery fails.

©, 2015 Rick Muscoplat

Posted on by Rick Muscoplat


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