Battery showdown - part of my internship

Discussion in 'Off-Topic' started by tom66, Sep 13, 2012.

  1. tom66

    Thread Starter Senior Member

    May 9, 2009
    2,613
    214
    As part of my internship at BitBox Ltd. (a local firm specialising in electronics engineer and embedded software design), I was set the task to prototype, design, manufacture (schematic capture, PCB layout, soldering SMD etc.) and program a battery tester. I wrote software and protocols on both ARM microcontrollers and Windows PCs. The results were VERY surprising... it seems that cheap batteries perform very well compared to expensive Duracell and Energizer cells...

    http://www.batteryshowdown.com/

    I also designed the website for the results.

    Comments welcome!
     
    Georacer and #12 like this.
  2. Markd77

    Senior Member

    Sep 7, 2009
    2,803
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    Very nice, professional looking website.
    I remember a Gadget Show test that was a little less scientific:
    http://gadgetshow.channel5.com/gadget-show/videos/news/news-batteries
    It would be interesting to see more analysis, for example £/Ah and £/Wh (actually the mouseover caption and scale on the cost graph are contradicting), and Wh to other voltages which would be useful for things like torches and my DSLR which are only useful down to 1.2V or so. I get around ten times the number of photos with Lithium over alkaline.
     
  3. tom66

    Thread Starter Senior Member

    May 9, 2009
    2,613
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    Good catch on the title text - fixed that.

    Most alkaline batteries were more or less the same, in terms of discharge curves. Once they fell below 1V or so, they only had a little extra life left. My logger stops accumulating mAh past 0.8V. The lithiums probably do so well because they hold a steady voltage for most of their life and current draw doesn't significantly impact performance.

    This graph shows how much the chemistries differ at high discharge currents:
    http://www.batteryshowdown.com/static/images/curve-1000ma-135.png

    Most of the lifetime of the alkaline chemistry is spent below 1.2V; so if your camera cuts out then, that would easily explain a 10x increase in photos. But in terms of real energy capacity, the lithium cell only does 3x as well in high discharge and 1.5x as well in low discharge applications. The lithium cell also has a slower roll off near the end.

    I've seen that Gadget Show test and I believe they came to a conclusion that the Morrisons Extra Long Life cell did very well, which is one of the reasons I tried to test it, and I backed up their findings, as it does have a high capacity, but it's not value for money.
     
  4. #12

    Expert

    Nov 30, 2010
    16,284
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    A worthwhile exercise! I applaud you.
     
  5. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    Very, very interesting stuff! Well done!

    Do you have access to some IKEA 10-pack batteries maybe?
     
  6. tom66

    Thread Starter Senior Member

    May 9, 2009
    2,613
    214
    Unfortunately no, I have stopped testing batteries for now. If anyone wants to send batteries in, there is a contact link on the homepage. They will be tested in the winter term or perhaps earlier, if time permits.
     
  7. BSomer

    Member

    Dec 28, 2011
    433
    106
    Well done study. Thank you. I did not even know that zinc type cells were still available, at least I have not noticed any around here.
     
  8. tom66

    Thread Starter Senior Member

    May 9, 2009
    2,613
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    Here you can still buy zinc cells in packs of 12 or so for £1 or 99p.
     
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