Deciphering battery date codes?

The "Costco" (my experience) 3/24 is the date that the battery was filled with electrolyte. And from past research, a new in box "sealed" lead acid battery (or "dry charged") battery had a shelf life of around 18 months maximum.

And, as always there is the aging factor of for every 10C/18F over 25C/77F (room temperature), the "thing" ages 2x faster... Keeping "things" cool and in a stable temperature (possibly humidity controlled depending on "the thing's susceptibility to humidity) is a big help (I.e. cellar in sealed/desiccant packed "bags"). Warm/Hot storage (and thermal cycling) is very detrimental to long term storage of "stuff".

Ideally, one should only purchase flooded cell Lead Acid Batteries up to 30 days from "fill date" (assuming batteries are not recharged every 30 days--And I have never seen Costco with equipment to recharge their racked batteries). For AGM batteries, storage upwards of 6 months from date of mfg between charges/placing in service). (again the 10C / 2x aging factor applies here too).

And I have been guilty of not looking at the date tag on Costco batteries when in a rush to replace a failed battery and getting the vehicle moving again (shame on me--I know better).

If you plan on storing batteries--Then having scheduled charging routine (or a true maintenance charger, NOT a cheap "trickle charger") is really the only way I have seen that can let you "store" your lead acid batteries (1 month FLA/6 month AGM and storage temperatures). Is the only way you will get 5-7+ year storage life for prepping.

For Lead Acid batteries--You are probably looking at (ideally) 5% to 10% rate of charge sizing of charger (I.e., 100 AH battery, 5 to 10 amp charger output current). For "float chargers" suggest >1% of battery AH capacity (FLA batteries needing >1% because of higher self discharge rate vs AGM).

With FLA, always watch battery electrolyte levels for "Float charging" (24x7x365 connected chargers). If float voltage is >13.6-13.8 VDC or so, you can, over time, "boil the battery dry" (gassing) and drop electrolyte levels below the top of plates--Exposing to air and ruining the batteries (again FLA type).

Otherwise, look at LiFePO4 or similar batteries and enough of them for "emergency backup power system". At least those Lithium Ion batteries will last many years without maintenance (check with a volt meter once a year for 20%-80% SoC for storage suggested).

-Bill "my 2 cents worth" B.