Inside Another 9 V Battery

A long time ago, I discovered some quasi-AAAA cells inside 9 V batteries:

Inside a 9V battery

Inside a 9V battery

It occurred to me that I should dismantle a defunct Rayovac Maximum 9 V alkaline battery from the most recent batch (*) to see what it looked like:

Rayovac Maximum 9V battery - interior

Rayovac Maximum 9V battery – interior


A closer look at those pancake cells:

Rayovac Maximum 9V battery - detail

Rayovac Maximum 9V battery – detail

They look like separate cells bonded into a stack, although there’s no easy way to probe the inter-cell contacts; the leftmost cell probably died first.

(*) Which has apparently outlived the Rayovac Maximum brand, as they don’t appear on the Rayovac site.


  1. #1 by tantris on 2016-10-31 - 10:44

    You can separate the pancake stack and reuse them if you need small 3V or 4.5V packs , but you’d probably have to print a battery enclosure …
    Oh – black finger warning, btw.

    • #2 by Ed on 2016-10-31 - 19:49

      The cells seemed pretty well bonded together, although I didn’t try all that hard to break them apart: I knew they’d spatter electrolyte over everything nearby!

  2. #3 by madbodger on 2016-10-31 - 11:50

    I think the flat cells are ANSI F22 or F24 cells (Eveready calls them a type 118P). The cylindrical ones are ANSI LR61. So the ANSI code for a 9V battery is 6F22, 6F24, or 6LR61, depending on its construction. A slightly smaller pancake cell is the F20 (Eveready calls them a type 112), and a 510 volt photoflash battery contains 336 of ’em, ANSI code 336F20.

    • #4 by Ed on 2016-10-31 - 19:54

      Back in the day, I built a xenon strobe bike taillight from a steel funnel and three 90 V batteries; one wintry evening, the local radio station’s traffic helicopter spotted me. I must have been stone crazy…

  3. #5 by RL on 2016-10-31 - 15:15

    I’ve given up on buying Rayovac batteries. In my experience, they are far more likely (guaranteed!) to leak vs Energizer or Duracell. A few years ago, I purchased a couple of tubs of 24 AA cells with an expiration date of 2022, and most of them leaked while sitting on the shelf in the basement. Its gotten to the point of where I won’t even leave a Rayovac battery in any equipment for more than a day or two. Instead, I store them in a ziplock bag outside the device.

    • #6 by Ed on 2016-10-31 - 19:57

      So far, so good, perhaps because all the active ingredients remained sealed inside those thick-walled plastic cells. Long ago, some off-brand cells did the rot-on-the-shelf trick and I swore not to make that mistake again: the most recent AA and AAA alkaline cells say “Amazon Basics” and haven’t been noticeably different than the more-or-less name brands.

      • #7 by RCPete on 2016-11-01 - 19:06

        The Kirkland (Costco house brand) AAs rate as a “meh”. Not horrible, but they seem to leak a bit sooner than Duracell if you forget to swap them. (Note to self; swap all batteries in flashlights in the cars.)

  4. #8 by Raj on 2016-11-02 - 07:12

    The alkaline batteries when they leak don’t damage PCBs as much as the zinc batteries leaks. I have started to put folded tissue around AAs etc to absorb the pee! Works.