Do month-year coloured dots on batteries signify install-by expiration date?

Question

As per How do you know if the replacement battery is a good one?, it may be the case that I've purchased a battery that may not be at its best.

I got it from a VW dealer installed on 2016-10-01; it had the coloured dot of "9/16", but also an inscription of 3216 near its negative terminal, which, if read as 2016-W32, would correspond to the week of 2016-08-08/14.

I've noticed that these coloured dots are often one month ahead of the current month, e.g., in mid-August 2016, I vaguely recall already seeing a couple of "9/16" dots at a Walmart.

Various sources may indicate that the lead-acid batteries may self-discharge between as low as "5% per month" (per BatteryUniversity) to as high as "approximately 4% a week" (per ProgressiveDyn). And here in Texas with 100°F / 38°C heat being all too common in the summer, it might indeed have self-discharged the full 25% during the nearly two months that it sat idle.

I've placed some fancy Stanley 15A charger onto it; it's been two hours, and it currently shows that it's still charging at a rate of 4.4A and is still only 75% charged (their indicator logic is defective?), and still hasn't reached the "float" mode.

Should I return this expired battery, and ask for one that's not been expired yet?

Answer 1

No, these are not sell-by dates or expiration dates. If batteries expired within a couple of months of manufacture, they'd be useless for their intended purpose. Getting a battery that's been manufactured in the same month you bought it would be unlikely. Batteries are big and heavy, and in many cases are manufactured overseas. A month or two one way or the other is not going to have a significant effect on battery life expectancy. Unless you buy a battery directly from the factory where it was manufactured, you're almost certainly going to be getting a battery that is weeks or months old.

If your battery isn't holding a charge after being in service for only a month or two, it's either defective, or you have a problem with your electrical system.

The self-discharge rates you mention refer to a battery losing charge without being under any sort of load. When it's in your car, it's being charged and discharged constantly. Lead-acid batteries are specifically chosen for automotive use because of their high tolerance for discharge/recharge cycles and long life expectancy compared to other battery types.

Answer 2

The "9/16" marker (at Walmart, at least) is the nominal date of manufacture - the actual date may be a few weeks earlier.

It's used for warranty replacements. Walmart batteries are often on a 3+2 warranty - if it fails within the first three years, you get a completely free replacement battery. If it fails in years 4 or 5, you get a pro-rated discount on a new battery.

How do they know when you purchased it? By your receipt, which you've probably lost. So they'll look at the marker sticker - that'll tell the assistant (and/or car owner) if it's worth looking up the actual purchase date for warranty on the computer. e.g. if a battery dated 09/08 comes in, you KNOW it's out of warranty.

Walmart runs a very tight stock control system. If they know (for example) that every September, they sell 60 batteries, then in August an automatic order is placed by head office for 60 batteries. These batteries will be delivered in mid to late August (exactly when depends on truck scheduling or available space on the truck). It's the September battery shipment, so they'll have '9/16' stickers on them. When they arrive at the store, they may go into warehouse storage (there's less of that than you think in a Walmart), or they may be put out on shelves. So it's possible that a battery with a September dot may be on the shelves in August.

Answer 3

I would give it a "Load Test" or take it to a auto parts location that provides the service. That way you will know exactly what condition the battery is in and what kind of future it may provide.

Answer 4

The little colored dot sticker is the date it was recharged. Wet batteries have a long shelf life if they are kept charged, and are usually charged once a month by the battery rep.

I was delivering to a battery company and asked about those little dot stickers. He reached behind the seat on the forklift and pulled out a roll and said "you mean these?" That was eye-opening! I had mentioned that I was at Costco and the sticker was current month so they must have really new batteries, he said they go and service (charge) them monthly.