Request for AA Battery Donation - Scientific Experiment

[tom66]

[cross posted to EEVBlog]

Hi all,

I put together http://www.batteryshowdown.com/ (including the analyser itself) over last summer as part of my internship at a local engineering firm, BitBox Ltd.

The results were very surpising -- it appears cheap alkalines perform far better than their price would suggest! And, it was hugely successful, with over 70,000 hits. Now, I'm back for more!

We have had lots of requests to test various different batteries. Ray-O-Vac is the most common request from most American readers; I can't buy them in the UK, so if anyone can source them, that would be appreciated. But if you see any battery that we have not tested (and it's not in the to-be-tested list below), let me know by sending a message. We need batteries in retail packaging with a receipt for pricing information; we'll need at least two and four are good so we can do repeats or in case one test gets messed up. Feel free to nick a few batteries from the pack for your own purposes, but please do not send in used or old battery packs as it will affect the results. We're only testing AA cells for now, as we expect the results to be roughly similar over the whole range.

For now, we're testing alkaline, lithium, ni-oxy hydroxide and zinc chloride cells. We will test rechargeables another time -- the analyser requires a re-design for that.

I am in the process of adding (testing):
* Ikea "Alkalisk" (cheap 10p/ea)
* ReadyCell (cheapest alkaline at 9.9p/ea)
* PowerCell Ultra Alkaline
* Maplin extralonglife Alkaline
* Sony "New Ultra" Zinc
* Kodak Zinc
* Sainsbury's long life
* Morrisons Saver Zinc
* JCB Zinc

If anyone would like to donate batteries please let me know via PM. They need to be posted to the UK, and we may be able to contribute the cost back for some donations. You can have your name put on an acknowledgements page if you like.

To be released as well, full schematics, PCB layout and software for the analyser. Hopefully by tomorrow.

[mariushm]

Re: Request for AA Battery Donation - Scientific Experiment

I pm'ed you on eevblog

[gilly1984]

Re: Request for AA Battery Donation - Scientific Experiment

I see you have covered all the poundland ones. Them kodaks are crap and sometimes you get dud ones in the pack.

Also the sony ones from poundland, to me they are the same as the kodaks.

How do i know? I worked in poundland for 6 months. Unless you are using said batteries for a remote they are useless.

Let me know if you need me to send you some and i will get you some.

[Taxman]

Re: Request for AA Battery Donation - Scientific Experiment

Gilly's point just hit a nerve with me. I'd looked at the reults prior to reading his post and wasn't surprised to see how bad the Panasonics performed. They were another pound shop special that seem useful only for remote controls. I put them in my camera last week (only because I didn't have any of my rechargeables charged up at the time) and they died after literally a matter of minutes and only a few photos.

Can I be impertinent and give you a tip for your website? In my opinion, the graphs would look better if you rotated them 90 degrees.

Great project, kudos to you and your team.

[tom66]

Re: Request for AA Battery Donation - Scientific Experiment

I see you have covered all the poundland ones. Them kodaks are crap and sometimes you get dud ones in the pack.

Also the sony ones from poundland, to me they are the same as the kodaks.

How do i know? I worked in poundland for 6 months. Unless you are using said batteries for a remote they are useless.

Let me know if you need me to send you some and i will get you some.

The Kodaks are sold in two variants, zinc and alkaline.
The alkalines performed surprisingly well, some of the best, especially when price is considered.
The zincs, I am in the process of testing, but expect them to be rubbish. But they do state on the pack "not suitable for digital cameras or photography equipment; low power devices only"

If you find a battery we haven't tested let me know. But I did raid Poundland in Basingstoke and in Leeds so I think I've seen all of their offerings.

Gilly's point just hit a nerve with me. I'd looked at the reults prior to reading his post and wasn't surprised to see how bad the Panasonics performed. They were another pound shop special that seem useful only for remote controls. I put them in my camera last week (only because I didn't have any of my rechargeables charged up at the time) and they died after literally a matter of minutes and only a few photos.

Can I be impertinent and give you a tip for your website? In my opinion, the graphs would look better if you rotated them 90 degrees.

Great project, kudos to you and your team.

The Panasonic alkalines seem to be average to poor performers, but the worst surprise was the Evolta cells -- despite holding a Guinness World Record, they performed the worst for any alkaline!! Obviously GWR just sold the brand to the highest bidder. Sigh.

The graphs will be rotated for version 2

[ben7]

Re: Request for AA Battery Donation - Scientific Experiment

I wonder if I still have the data from the 9v battery testing I did years ago...

I know I tested Energizer, Duracell, CVS, Eveready, and I think a radioshack brand one too.

I had just a simple motor running off the batteries, I would run it until the motor stops.

But yeah, those are 9vs.

It would be even cooler if you could do this with an arduino or PIC, so DIY'ers can do tests like these also
(also cheaper than the ST datalogger board - I think)

-Ben

[tom66]

Re: Request for AA Battery Donation - Scientific Experiment

The STM32 board is £10. Pretty hard to beat that. 168 MHz 32-bit ARM Cortex-M4 with 256KB of RAM, built in hardware 32-bit FPU (add, subtract, multiply, 18-cycle divide and some other ops), plus something like 80 IOs, 12 ADCs, 2 DACs, Host and OTG USB 2.0... It's bloody power hungry though, wants about 160mA at 3.3V.

http://uk.farnell.com/stmicroelectro...ery/dp/2009276

Yeah, it's insane overkill, but it was recommended to me. I'd otherwise normally tack an STM32 straight on the board.

The source has been released, but I'm working on getting the binary blob unblobbed, currently it is proprietary.

[ben7]

Re: Request for AA Battery Donation - Scientific Experiment

The STM32 board is £10. Pretty hard to beat that. 168 MHz 32-bit ARM Cortex-M4 with 256KB of RAM, built in hardware 32-bit FPU (add, subtract, multiply, 18-cycle divide and some other ops), plus something like 80 IOs, 12 ADCs, 2 DACs, Host and OTG USB 2.0... It's bloody power hungry though, wants about 160mA at 3.3V.

http://uk.farnell.com/stmicroelectro...ery/dp/2009276

Yeah, it's insane overkill, but it was recommended to me. I'd otherwise normally tack an STM32 straight on the board.

The source has been released, but I'm working on getting the binary blob unblobbed, currently it is proprietary.

That's a very good deal!

Are the 'ARM' chips like microcontrollers?

[tom66]

Re: Request for AA Battery Donation - Scientific Experiment

Yes, the ARM devices are microcontrollers. RAM, Flash, ADC, DAC, etc. all on one chip. Not all ARM devices are though.

Just updated the showdown. Added a cut-off voltage option and 12 new battery brands:
http://www.batteryshowdown.com/index.html

[mariushm]

Re: Request for AA Battery Donation - Scientific Experiment

Tom, I wonder if the high drain test is really representative of how digital cameras actually work.

After all, they have about 20-40mA constant draw with the lens and lcd screen working as a viewfinder, but they also have peaks of load when snapping picture and right away charging the flash capacitor (if flash was used)

Wouldn't a continuous 1A charge heat up the batteries and potentially affect their output, how well they behave, how fast their voltage drops?

Maybe it would make more sense if you do something like:

constant current of 25mA
200mA for 5 seconds (simulate shot with no flash, writing to sd card etc)
wait 3 minutes
1-2A for 5 seconds (simulate shot with flash, with 5 seconds for recharging flash)
wait 3 minutes
repeat cycle

and measure voltage on the battery right before the high load is triggered and after... would the voltage sag down so much that a camera would potentially trigger it's "low battery" mode?

Some enable low battery at a voltage, but the threshold for good battery is a bit higher so some batteries could be still good for a few more shots but the camera rejects them, unless you maybe restart the camera.

[tom66]

Re: Request for AA Battery Donation - Scientific Experiment

I'm considering adding pulse tests; the issue here is though that I think that type of test would take too long, I'm really constrained on the time I have. The analyser is perfectly cable of pulse testing (it's not implemented in the software), though it's limited to about 1.2-1.3A maximum current for maximum dynamic range. I know some cameras, if you enable the NiMH or lithium mode, let you pull 5A(!!) from the batteries for fast flash charging. It is also why when using alkalines the cameras blank the LCD -- it's not got a high enough voltage to run the rest of the logic when pulling about 2A.

I also want to add cycle fast charge and discharge options for NiMH cells, but I'd have to redesign the analyser. Needs a 2V, 10A buck converter for charging NiMH at up to 2A each (5 batteries per analyser, 5 analysers, so I can test lots more at once.) And a dynamic ESR test, which runs a high frequency ac current through the battery, to measure the ESR as the battery discharges.