Are the alkaline batteries passivated for storage? - Page 1
Forum section: electronics / general

author: tchicago
author_rank: Regular Contributor
timestamp: June 23, 2025, 11:29:59 pm
content: I noticed that the AA batteries that were slightly used are much more likely to leak than the batteries from the same box that were not touched yet. For example, I used a few AA's in the flashlight for just a couple minutes at camping, and then removed from the flashlight and set aside for 6+ months. Then I find them leaked. Whereas rest of unused batteries in the same box that these came from - are nice and clean. Noticed this many times.Could this be due to some intentional passivation by the manufacturer to prolong the storage? My theory is that once they see some discharge current, it dissolves some passivation layer and the battery becomes fully active and therefore more likely to leak.The passivation of batteries is not something unheard of, here is one example:https://www.jauch.com/blog/en/passivation-lithium-thionyl-chloride-batteries/(for Li-thionyl)

author: electr_peter
author_rank: Unknown
timestamp: June 24, 2025, 10:12:37 am
content: Small amount of gases are released inside when alkaline is used which leads to more pressure which can sometimes push electrolyte past the seals. It is very complex chemical & engineering topic. Not sure about passivation for alkalines.

author: Gyro
author_rank: Super Contributor
timestamp: June 24, 2025, 10:40:11 am
content: Quote from: tchicago on June 23, 2025, 11:29:59 pmThe passivation in Lithium Thionyl Chloride isn't a one time thing, it happens whenever current hasn't been drawn for a while. The initial voltage drop can be a pain in applications with intermittent current draw. It's a side effect of the chemistry rather than a 'feature'.I don't think there is any specific passivation mechanism built into standard Alkaline cells, it's very much the (bad) luck of the draw, as evidenced by the number of DuraHell, and whatever the Energizer equivalent is, threads on the forum. There have certainly been many cases of cells leaking while still in the packaging and well within date. I think Dave even did a study on it.As electr_peter says, it comes down to building internal pressure and indifferent seal quality, coupled with country of manufacture. The problem seems worst in small diameter cells (AA and AAA), I've never had a D cell leak. I don't have an explanation for what you've seen, apart from maybe the mechanical handling of inserting the cells into the flashlight - the impact as they hit the end when dropped in or the tail spring pressure. It's not something I've seen personally, although you clearly have.

author: Haenk
author_rank: Super Contributor
timestamp: June 25, 2025, 05:15:56 pm
content: The alkalines seemingly don't have passivation. It is just the pressure inside the cell rises faster when in use; the redox reaction does happen with no load as well, but much slower - therefor building pressure way slower, meaning less likely to leak.

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: June 25, 2025, 06:16:43 pm
content: I've had plenty of AA batteries leak in the original factory bubble packaging. DuraHell batteries seem to be the worst. This occurs years before the date listed on the packaging, and it's not storage conditions--I store unused batteries at 20C.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: June 28, 2025, 08:50:36 pm
content: I don't know about the chemistry but there used to be mercury in alkaline cells, like in the '90s. I have 30+ year old Radio Shack gold Enercell alkaline cells, not a trace of leaking, and they still output enough mA to light a LED.