EEVblog #518 - 9V Alkaline Battery Construction

[IanB]

The prismatic construction is all battery inside with no air spaces, whereas the 6 AAAA cells are trying to fit circles into a rectangular shape. There are gaps between the cylinders. So in principle, the stacked pile batteries might have greater capacity than the cylindrical cell batteries.

[alm]

I'm not a battery specialist at all, but wouldn't the pile construction have a larger anode/cathode surface, which reduces the output impedance but reduces the capacity by taking up more space? I'm imagining the cathode/anode as surfaces, so their volume should be pretty much linear with the surface area of the cell, i.e. ~6 times the volume wasted in the 6xAAAA construction. The shorter distance between anode and cathode should also help lowering the output impedance by improving mixing within the battery, assuming everything else being equal.

[IanB]

Well broadly speaking the capacity of a battery is directly related to the volume it occupies. If there are air spaces in the battery the air is taking up empty space that otherwise could be occupied by more battery.

The anode and cathode electrodes are not solid but rather of powder/granular construction, so their surface area is related to the fineness of the granules, the volume of powder, and perhaps the porosity of the material. The design of a battery can be tuned by adjusting various parameters like these to balance capacity, internal resistance and power delivery. Within certain limits the characteristics of a battery can be changed by the designer to meet different requirements.

[Jon Chandler]

I wonder if either design is better in terms of potential leakage.

[Dread]

I started using only Duracell batteries about 2 years ago due to several leakage issues I had with Energizers.
This video was great because now I have confirmed my suspicion. If Energizer cuts corners on the cell connections its safe to assume they also cut corners in the cell construction. Hence the leaks.

[con-f-use]

If Energizer cuts corners on the cell connections its safe to assume they also cut corners in the cell construction.

I take issue with that statement. You could say if Energizer cuts money on unnecessary material and work it is safe to assume they put it into higher quality cells. You would have to do statistics that go beyond your personal experience to make any statement.

That being said, energizer batteries ruined a perfectly nice Maglite for me because of leakage. It was just sitting in my shelf for 2 month of dry conditions. R.I.P.

[G7PSK]

I heard a story that the pile connection was introduced by ever ready during WW2. The story goes that a radio engineer was sent to Ever ready by the SOE to see if they could make a battery for small radio sets that was smaller and lighter than what was already being used. The management told the man from the SOE that there was no way of improving the HT batteries that they were already making, on the way out one of Ever Ready's technicians approached and said that yes they did have a more compact and powerful battery but it was being kept back as it would last to long and reduce the sales and profits, he then proceeded to show the SOE man the pile format of battery, the SOE then went back and persuaded Ever Ready to start manufacturing the pile. And the rest as they say is history.

I wonder if the heat from welding cells together could be detrimental on so small a cell and that is why Energizer use the presure system which probably costs more to assemble than welding.   

[Psi]

Just for interest, here's an old rechargeable NiCd 9V i had laying around.

[saturation]

It would have been good to see which design provides more mAh.  The datasheets are hard to compare since they aren't loaded in a standard way.  Nevertheless, looking at Varta's 620 ohm load at 6v terminal voltage against 500 ohm of Duracell and interpolating from there 620 ohms should be and were 6V ends, they look close.  Same can be said of the 180 ohm load of Varta versus 200 ohm loads of Duracell and interpolating were 180 ohms would be.

http://cellpacksolutions.com/pdf/data_sheets/technical/4022.pdf

http://ww2.duracell.com/media/en-US/pdf/gtcl/Product_Data_Sheet/NA_DATASHEETS/MN1604_US_CT.pdf

[SeanB]

From my experience the major difference in performance between the cylindrical cell and the plate cell is in current delivery for a sustained period. The cylindrical cells can deliver around 10A in the 9V pack for about 5 seconds, the plate ones reach around 100ma in the same period, and fade rapidly as the cells polarise from reaction byproducts, delivering around 30mA intro a short circuit. Thus the plate cells are good for any low power draw like a meter without a backlight or other low draw load, while the cylindrical ones are best for pulse loads like smoke alarms and other pulsed draw loads.

[Steffen]

German Varta batteries? Lol. On the Varta is written "Made in Malaysia". German engeneering - maybe, but this battery has been made in Malaysia.

[SeanB]

Tip Dave missed was to show the inner of the rebranded battery case, as often the case shows who the original manufacturer is, as they use the same metal sheet but turn it inside out for the rebranded units. The white lining looks like it had a brand name on it which will be the original brand.

 I have had some rebranded batteries that turned out to be made by Duracell, but they cost half the price of the Duracell unit. Eveready and Energiser often are the same cell, you can tell from the construction and the tooling marks that they are made on the same production plant, and often the batch codes are from the same printer ( if it has either a slant or a defective dot pattern or other distinctive character in the print) so they are the same cell, and similar in price.

[EEVblog]

It would have been good to see which design provides more mAh.

At what load?
Continuous? What type? constant power?, constant current?
Pulsed? Random mix?
That's the problem with this sort of stuff, to do it properly requires whole sets of characteristic curves.

[EEVblog]

German Varta batteries?

Yes, their AA's and AAA's are made in Germany, hence my mistake assuming the 9V ones were too.

[Ed.Kloonk]

Duracell are a more expensive battery than Energizer IMO? I often buy the AA and AAA and the Duracell seems dearer most of the time.

[IanB]

Duracell are a more expensive battery than Energizer IMO? I often buy the AA and AAA and the Duracell seems dearer most of the time.

Yes, I just bought a couple of 9 V batteries and Duracell were $3.99 each whereas Energizer were $3.59 each. I ended up buying Sony at $2.99 each.

The Sony are made in Malaysia, which is a screw-up on my part. I normally try to get alkaline batteries that are made in Japan (Fuji, Panasonic, Sanyo) as they seem to have the best quality of manufacture and lowest risk of leakage.

[retiredcaps]

Yes, I just bought a couple of 9 V batteries and Duracell were $3.99 each whereas Energizer were $3.59 each.

During Walmart Canada's Anniversary sale (going on right now) and Boxing Week (Dec 26 to Dec 31), they usually sell four 9V Duracell batteries (made in USA) for $5.97.  They have even have free shipping on walmart.ca for these batteries.  Batteries potentially have huge margins.

[SeanB]

Almost the same margin as razor blades. Wholesale prices are generally such that the price to buy most big brand batteries are essentially the same, the selling price is really a perception of brand reputation and some manufacturer RRP estimates.

[saturation]

Yes, that's why there are international standards, IEC.

To summarize, this RS site has the gist,

http://support.radioshack.com/support_tutorials/batteries/bt-alk-prem-9V.htm

For primary cells, IEC models typical uses, but for user's actual use YYMV.  But these sample tests allow one to compare batteries across makes and manufacturers.

For example, load with 270 ohms, 1hr/daily or end voltage 5.4V, whichever is first, a standard battery should provide 7 hours of total discharge time.  There are other tests too, see below:

A free version of the whole IEC standard, get it while you can, for 9V p.47:

http://www.sztxr.com/file/IEC%2060086-2-2006.pdf

It would have been good to see which design provides more mAh.

At what load?
Continuous? What type? constant power?, constant current?
Pulsed? Random mix?
That's the problem with this sort of stuff, to do it properly requires whole sets of characteristic curves.

[DK]

Almost the same margin as razor blades.

Which is presumably why Gillette bought Duracell back in the 1990s.

[EEVblog]

Yes, that's why there are international standards, IEC.

Sure. That's ok for defining a standard to do general battery comparison, but that's hardly indicative of performance over a lot of varied real world scenarios. To do that you need characteristic curves. The IEC standards are not some magic figure, they are just that, a standard, so that manufacturers at least put the same data in their datasheets so the user can compare them.

[Displaser]

I wonder if either design is better in terms of potential leakage.

I started using Energizer some years back after having experienced a leak/damaged gear with Duracell. I'd be curious to hear from more forum members on this as well.     

[ResR]

I had experience with leaking Varta and Energizer 9V batteries, the plastic case of the cell inner working is much more prone to break and release it's juice when deep discharged with one led and 4,7k resistor (nightlight using old batteries from recycle box at the stores). Duracell in the other hand seems to take discharging quite well until the cells start to break through the bottom and the top. Once I dismantled a Duracell 6F22 in a public place and one of the AAAA cells exploded from the gas pressure inside just after taking off the cover.

[saturation]

Yes, a curve is preferred but a single digit has its purpose, just as accuracy curves for DMMs per range are more telling than a single digit reflecting all the ranges of the DMM.
Curves are online, as you know, for many name brand batteries.

To avoid leakage issues, and because most 9v applications are low current, and most batteries come from mixed QC made-in-China types, I've switched all my 9v uses to LSD NiMH last year.  I've never seen an NiMH battery leak other than when overcharged or melt its electrodes in a dead short.

I wonder if either design is better in terms of potential leakage.

I started using Energizer some years back after having experienced a leak/damaged gear with Duracell. I'd be curious to hear from more forum members on this as well.     

Yes, that's why there are international standards, IEC.

Sure. That's ok for defining a standard to do general battery comparison, but that's hardly indicative of performance over a lot of varied real world scenarios. To do that you need characteristic curves. The IEC standards are not some magic figure, they are just that, a standard, so that manufacturers at least put the same data in their datasheets so the user can compare them.

[Steffen]

Yes, their AA's and AAA's are made in Germany...

True,
have checked some Varta batteries:
AA = made in Germany
1.55V coin cell (15+ years old, never used) = Made in Germany
15+ years old rechargable 9V block 220mAh = Made in Singapore.