9v batteries - teardown

[Sooner Boomer]

I've got a lot of hobbies. Seems like most, if not all, need some kind of battery. A lot need 9 volt batteries. Here's a teardown and examination of several different brands/types of batteries. While stompboxes might need high current surges, the battery design and construction are still relevant.

https://www.rocketryforum.com/threads/9-volt-batteries-part-1-the-tear-down-battery-no-1-thru-no-5.176938/

https://www.rocketryforum.com/threads/9-volt-batteries-part-1-the-tear-down-no-6-thru-no-11.176939/

[Clint Eastwood]

The links lead to a site with a lot of cookie wall and pop up stuff to start with.. no thanks.

[R.G.]

I found the teardown interesting.  It is a pretty straightforward dive into 9V brands.

I didn't get a lot of popups, but then I use an ad and banner blocker and a popup blocker. I only got the ubiquitous Google "log in with Google" popup and the "join, become a member" overlay.

[Sooner Boomer]

The links lead to a site with a lot of cookie wall and pop up stuff to start with.. no thanks.

Were you looking at the site with Netscape Navigator or Internet Explorer?

[Mark Hammer]

I saw everything without any problems.  The main takehome is something I posted about 15 years ago: alkalines use 6 discrete sub-AAA cells tht are spot welded together, while carbon-zinc use a half-dozen bare "slugs" stacked on top of each other.

I have a bunch of old "Polapulse" batteries in a bag in the garage.  These were used in Polaroid cameras, and provided a bit over 5VDC.  The government organization I was working in processed applicants to the management training program, and because there were so many to evaluate in a day, the administrator would take a Polaroid pic of each applicant and clip it to the file as the candidate moved through each stage of evaluation.  Having read a bit about Polapulses, I asked the administrator for the spent cartridges and removed the batteries.



They were designed to provide a big burst of current to power the flash and the motor that squeezed the developing fluid onto the picture as it moved it into and out of position.  Those cameras were not designed/intended to take lots of photos in rapid succession, so the battery in the film cartridge always had an opportunity to recover after each use.  Besides, the cartridges only held about a dozen photo blanks, so none of those batteries would get fully exhausted.  I haven't pulled them out in a few years, but even after a decade or more, they still provided a strong 5V.

But here was the message I took away: surface area between cells plays a role in instantaneous current delivery.  That's one of the factors at play in the infamous "dying carbon-zinc battery" thing.  Carbon-zincs can give more instantaneous current, even when they get older, partly due to their internal chemistry, but also because of the use of flat slugs with larger contact area between slugs.  As they get old, not only does the voltage drop, but so does the ability to sustain that current delivery.  When a fuzz only needs a couple of milliamps to run, an older carbon-zinc can provide a kind of compression by responding to pick attack and then needing to "catch its breath", before recovering.  But much like today's solar eclipse, several things need to align to experience the legendary "dying battery on a Fuzz Face" thing.  From what I understand, Eric Johnson does not rely on that anymore.  I imagine it was just more predictable and less frustrating to use other pedals that could provide a similar sound, with a robust stable supply, due to their design.

[PRR]

"Polapulse" batteries

Some historical papers:
http://lateralscience.blogspot.com/2015/02/the-polapulse-battery.html