# How are the cells of 8.4V "9V" rechargeable batteries oriented? **URL:** \ **Category:** Factual Questions\ **Created:** [January 8, 2004, 11:20am UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397 "2004-01-08T11:20:07Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![Mikahw](https://avatars.discourse-cdn.com/v4/letter/m/e9bcb4/32.png) [@Mikahw](https://boards.straightdope.com/u/Mikahw)\ **Post date:** [January 8, 2004, 11:20am UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/1 "2004-01-08T11:20:07Z")
Alkaline batteries output 1.5 volts, so six cells are needed to make 9 volts. It’s easy to see how six cells would fit in the rectangular shape of a 9V battery, as seen [here](http://electronics.howstuffworks.com/battery4.htm) Ni-Cd/Ni-MH cells, on the other hand, put out approximately 1.2 volts. To get 8.4 volts out of those, you’d need seven cells, right? How could seven cells fit in the form factor of a 9V battery without empty space? Or, is that how they do it? Add empty space? I could see a 2x4 arrangement working, with one of those spaces just empty instead of a cell. ---
**Author:** ![Mikahw](https://avatars.discourse-cdn.com/v4/letter/m/e9bcb4/32.png) [@Mikahw](https://boards.straightdope.com/u/Mikahw)\ **Post date:** [January 8, 2004, 11:21am UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/2 "2004-01-08T11:21:58Z")
Well, I suppose I could have said that alkaline **cells** output 1.5V. Guess I need to preview 30 times before posting, right? 😉 ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 8, 2004, 11:39am UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/3 "2004-01-08T11:39:26Z")
A 9v (PP3) battery contains six AAAA 1.5v cells (AAAAis a real, but uncommon cell size), wired in series to give 9V. I haven’t checked myself, but I suspect that half of them will be positive-terminal-up and half down, in a sort of checker pattern, to facilitate the series wiring. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 8, 2004, 11:40am UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/4 "2004-01-08T11:40:29Z")
And I completely misread your question; sorry. ---
**Author:** ![P.Nym](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@P.Nym](https://boards.straightdope.com/u/P.Nym)\ **Post date:** [January 8, 2004, 2:12pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/5 "2004-01-08T14:12:13Z")
Every “9v” rechargable I’ve seen is actually limited to 7.2v. Is there someone putting out a 8.4v rechargable cell? I was just shopping for batteries last week, and I didn’t see one. ---
**Author:** ![Lagged2Death](https://avatars.discourse-cdn.com/v4/letter/l/ac8455/32.png) [@Lagged2Death](https://boards.straightdope.com/u/Lagged2Death)\ **Post date:** [January 8, 2004, 2:24pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/6 "2004-01-08T14:24:35Z")
At least some rechargeable “9v” batteries [claim to make 9.4v to 9.6v,](http://www.thomas-distributing.com/9v_nimh_batteries.htm) presumeably using 8 cells x 1.2v. ---
**Author:** ![P.Nym](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@P.Nym](https://boards.straightdope.com/u/P.Nym)\ **Post date:** [January 8, 2004, 2:38pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/7 "2004-01-08T14:38:01Z")
Nevermind my last post. Looks like there are some 8.4 and 9.6 rectangular batteries out there. I just haven’t seen them in the local hardware stores (or the DigiKey catalog) yet. Glad to see it, too–the 7.2v batteries were just about worthless. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 8, 2004, 3:20pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/8 "2004-01-08T15:20:57Z")
All the 9v rechargeables I’ve seen have a curved base; whether this is just to set them apart from alkalines or whether it reflects some kind of internal layout (such as disc-shaped batteries staked edge-on), I couldn’t say. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [January 8, 2004, 3:39pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/9 "2004-01-08T15:39:53Z")
> [@](#): > > \*Originally posted by Mikahw \* > \*\*Alkaline batteries output 1.5 volts, so six cells are needed to make 9 volts. It’s easy to see how six cells would fit in the rectangular shape of a 9V battery, as seen [here](http://electronics.howstuffworks.com/battery4.htm) I have opened quite a few 9v batteries and _never_ seen that internal arrangement of 6 cylindrical cells side by side. Rather, I have always seen 6 flat, rectangular, cells stacked on top of each other. In which case you can make them thinner and stack more. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [January 8, 2004, 3:40pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/10 "2004-01-08T15:40:57Z")
Well, I’ll be a dead battery. I always assumed that a 9v unit was a stack of 6 rectangular-cross-section cells in series, head-to-tail, requiring minimal strapping. Now I see that they are 6 cylindrical cells instead. Why would manufacturers do this? A rectangular arrangement would provide a greater capacity for the same voltage. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [January 8, 2004, 3:59pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/11 "2004-01-08T15:59:07Z")
Here’s [a site](http://www.aalmps.com/battery.htm) showing a commercial rechargable “9v” battery. The label says “7.2v”, and the site says “Inside this plastic case you will find 6 - 120 mah nicad cells,” and they are all cylindrical. I haven’t been able to find a picture of a rectangular cell arrangement yet. Could rechargables be built different from non-rechargables? ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [January 8, 2004, 4:20pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/12 "2004-01-08T16:20:16Z")
This is from a Jaycar Electronics google cache, [Using and Discharging Ni-Cad Batteries](http://216.239.39.104/search?q=cache:kmJExnmFdM4J:www1.jaycar.com.au/images_uploaded/nicads.pdf+battery+9v+cell+arrangement+rectangular&hl=en&ie=UTF-8), so it doesn’t display well. I had to edit this extraction to make it readable. It doesn’t say anything about the internal cell shape. Italics all mine: > [@](#): > > There are a few complications with multi-cell NiCad batteries like _the small 9V single-ended rectangular type(usually 8.5V)_ and many of the integrated battery packs used in cordless phones, cordless power tools and camcorders. > > The main complication with these batteries is that _internally they have six, seven, eight or more individual NiCad cells connected in series,_ and inevitably some of these cells age at different rates to the others. This means that they gradually develop different charge capacities, and as the battery as a whole is charged and discharged repeatedly, these differences are accentuated-- a kind of “survival of the fittest” process occurs. > > The net result is that during discharge, some weak cellscan be discharged well below the 1.1V level, and even driven into reverse charge, before the others reach the fully discharged state. Then during recharging, the same cells tend to absorb most of the charge and overheat, while the others (which were perhaps not properly discharged) are improperly recharged and tend to suffer increased crystal growth. > > In short, multi-cell NiCad batteries tend to have a somewhat shorter working life than separate cells, and tend to be much harder to recondition or even cycle adequately. Unfortunately this is the price you pay for their convenience. ---
**Author:** ![alimarx](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@alimarx](https://boards.straightdope.com/u/alimarx)\ **Post date:** [January 8, 2004, 5:48pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/13 "2004-01-08T17:48:33Z")
Why hasn’t anyone made a 9V **cell**? Seems like it’d be cheaper and more reliable. ---
**Author:** ![P.Nym](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@P.Nym](https://boards.straightdope.com/u/P.Nym)\ **Post date:** [January 8, 2004, 6:04pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/14 "2004-01-08T18:04:36Z")
> [@](#): > > \*Originally posted by alimarx \* > \*\*Why hasn’t anyone made a 9V cell? \*\* What would you make it from? The voltage of a cell is a function of the materials used. You can change the amount of current a single cell delivers by making it larger, but you can’t up the voltage without switching materials. ---
**Author:** ![Lagged2Death](https://avatars.discourse-cdn.com/v4/letter/l/ac8455/32.png) [@Lagged2Death](https://boards.straightdope.com/u/Lagged2Death)\ **Post date:** [January 8, 2004, 6:05pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/15 "2004-01-08T18:05:50Z")
> [@](#): > > \*Originally posted by alimarx \* > \*\*Why hasn’t anyone made a 9V **cell**? Seems like it’d be cheaper and more reliable. \*\* The voltage produced by a cell is strictly a function of the chemical reactions going on inside the cell. [Most cell chemistries are below 4v,](http://library.solarbotics.net/pieces/parts_elect_pass_bat.html) and the most familiar and commonly-used ones are all around 1.5v. Designing a 9v cell would require that you find a chemical reaction that produced 9v, and found a way to package the reagents into a workable and economically-viable battery. I don’t know if that’s possible or not, but it’s not a simple matter of using stronger chemicals or making larger cells. ---
**Author:** ![Lagged2Death](https://avatars.discourse-cdn.com/v4/letter/l/ac8455/32.png) [@Lagged2Death](https://boards.straightdope.com/u/Lagged2Death)\ **Post date:** [January 8, 2004, 6:18pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/16 "2004-01-08T18:18:57Z")
> [@](#): > > \*Originally posted by Musicat \* > \*\*Now I see that they are 6 cylindrical cells instead. Why would manufacturers do this? A rectangular arrangement would provide a greater capacity for the same voltage. \*\* Well, as is becoming clear from the posts here (and as I’ve heard from other sources as well) that _some_ 9v batteries are made this way, others are not. There are (at least) 9v batteries with 6 cylindrical AAAA cells inside, with 6 flat cells inside, and even with 3 3v lithium cells inside. Maybe a company that makes both AAAA and 9v batteries uses the AAAA inside the 9v for economy, while a company that doesn’t make AAAA at all uses the flat cells. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [January 8, 2004, 6:19pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/17 "2004-01-08T18:19:53Z")
> [@](#): > > \*Originally posted by alimarx \* > Why hasn’t anyone made a 9V **cell**? Seems like it’d be cheaper and more reliable. AFAIK, a conventional wet or dry cell, regardless of the chemical composition(s) used, generates a maximum voltage in the 1 - 1.6 volt range. Maybe a chemist or a quantum physics major can explain why better than I can, but that’s the way it is. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [January 8, 2004, 6:22pm UTC](https://boards.straightdope.com/t/how-are-the-cells-of-8-4v-9v-rechargeable-batteries-oriented/223397/18 "2004-01-08T18:22:26Z")
> [@](#): > > \*Originally posted by Musicat \* > I always assumed that a 9v unit was a stack of 6 rectangular-cross-section cells in series, head-to-tail, requiring minimal strapping. That is, in fact, what it is in the majority of cases. I have opened batteries over the years (to keep the connector) and they were all like that. It is simpler and provides better use of space. I believe using cylindrical cells is exceptional and the battery will have less capacity.