Battery date codes are painfully unstandardized and you’re better off without them

While diagnosing an electrical issue last week, I suspected that the battery was tired. The terminals were banged up, the case was covered in grime, and the manufacturer’s decal was peeling and faded. It barely passed a quick health check, so I started looking for a date code on the battery case to see if a preemptive replacement was the smart move. After finally finding and deciphering the date code, I found that the ol’ bat-tree had given eight years of service, and I promptly dropped in a new one.

Problem solved, right?

The new battery helped to solve the electrical gremlins, but I was still bothered by an issue that has annoyed techs for ages: the confusing, unnecessary, and wholly unstandardized date decoding process. Is it so hard for battery manufacturers to mark perishable components with simple date markings that anyone can read? The tire industry solved the exact same problem without any trouble: WWYY. Easy! Standardized date codes are actually required by the Department of Transportation for all tires sold in the United States, and this system helps to quickly identify safety equipment in need of replacement. If only this bright idea could be applied somewhere else…

Modern battery date decoding is a task to avoid if possible. Join me as I describe a sequence of events you’ve probably experienced a time or two:

You want to find the age of a customer’s battery. You start by looking at the top of the battery and hoping for a simple MM/YY sticker or an in-service date written in paint pen. Today is not your lucky day, so you peek around the sides of the case with a flashlight. Sorry, Charlie, you’ll need to remove the battery to see the code stamped near the bottom of this case, fully obscured by the tray lip. And somebody deleted the battery carry handle for your inconvenience.

You remove the battery and finally see the relevant code in the mix of marks on the case: D3. Letters are almost always months, so you can be reasonably certain that a) this battery was made in a month of April sometime between now and the debut of the maintenance-free automotive battery in 1971, and b) its zodiac sign is Aries: a leader, self-confident, passionate, all very good qualities for a battery. The month part of the code is practically useless for techs and customers alike outside of warranty claims. So you move on.

That leaves the numeral part of this example code, 3. Let’s say you’re working on a 1994 Suburban. The code D3 could belong to the original battery, a 2003, a 2013, or a 2023, depending on who made the battery and when it was installed. A tech or half-decent DIYer won’t have much trouble figuring out the correct year, but this is another area where existing date code systems have room for improvement.

Date of manufacture isn’t the important code for techs

Even if you decode the date of manufacture for an automotive battery, I think most techs would rather know the date of installation. A battery can sit on a shelf for a long time with minimal degradation. Batteries in use are a very different story.

So do everyone a favor and write the date of installation on the battery with a paint pen or metallic marker. That eliminates all the guesswork and codebreaking for owners, other techs, and maybe even your future self. Besides, most battery warranties go by in-service date, not date of manufacture. (Of course, if you see two dates on a battery, the more recent of the two should be the in-service date. Unless it’s a modified DeLorean.)

In-service dates can help reduce hassle for you and your customers

When that battery is nearing the end of its life, look at that in-service date, and tell your customer about it while also handing over the printout from your battery tester. I don’t think you’ll have any trouble selling a new battery before issues begin.

As modern cars and trucks become more complex, their electrical systems also become more sensitive to variations in the electrical system. An iffy battery wasn’t really a big deal on older cars. Today, a faulty battery can cause all kinds of bizarre glitches and problems, and keeping a close eye on battery health can save you—and your customers—many hours of frustration.

In my opinion, a battery should not die of old age while still in service. It’s up to you, your attention to detail, and your paint pen to identify and replace batteries that have outlived their usefulness before they leave your customers stranded.