Methodology
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Battery & charger reviews>Methodology

 

Review methodology – batteries


The Doc uses a scientific dooverlackie (the technical definition) that can put a load on a set of 4 batteries. A few observations about this test procedure:

  • 10 ohms is used for all batteries now. Some of the earlier tests on AA batteries used a 5 ohms load. (Alkaline batteries are not suitable for digital cameras as the power is demanded faster than what an alkaline battery can deliver. So while the battery may seem flat, in fact it is not. The battery if left for a little while will recover and give further power.)
  • A set of four batteries is used. The battery holder can be changed to allow for different size batteries.
  • Data is normally logged at 5 seconds intervals (but that can be varied from 1 second up to 600 seconds.)
  • Data that the scientific dooverlackie can log includes: battery temperature, ambient air temperate, humidity and voltage. Data is logged to a csv file for analysis in a spreadsheet or graphing program.
  • The test automatically cuts off at 3.6 volts. Batteries are generally considered flat at 0.9 volts. So 4 x .9 volts gives you 3.6 volts for a set of 4 batteries. The Doc has found that rechargeable alkaline batteries can last longer and the Doc has sometimes drained them down to 3.5 volts without adverse consequences (but do so at your own risk).
  • Ni-MH and Ni-Cd are drained and charged at least 10 times before being tested. As Ni-MH batteries, in particular, do not take a full charge straight away. The charger used to charge a set of batteries can affect battery performance. Some chargers are more effective in charging battery types than others. The Vencon Battery Analsyer is used as the benchmark charger.
  • Each battery test has its own report, in the form of 2 flash graphs.

The methodology is not perfect, but it does give some idea of what to expect from different battery brands. A different methodology will give a different result.

Battery tests are basically comparisons of different battery types and brands. But for any comparison you need a starting point. Since many people do not own rechargeable batteries, they may find it difficult to have a reference point for comparison. To establish a starting point, the Doc tested carbon zinc and alkaline batteries.

In the AAA size, the two primary cell alkaline batteries tested were the Duracell Ultra and Everyready Gold. Here is a graph of the results:

img3.gif

The load used on a set of 4 AAA batteries was 10 ohms. A fairly heavy load for AAA batteries, but needed as this is the load used in testing of the rechargeable batteries. In the real world this is a worst case test. The batteries would last longer in most situations.

In the AA size, the Doc also started with a set of K Mart carbon zinc batteries (purchased for the princely sum of $1) and the Duracell Ultra and Eveready Gold. Here is a graph of the results:

img4.gif

The load used on a set of 4 AA batteries was 5 ohms, designed to reflect the heavy drain on batteries by such devices as digital cameras. The Doc was a little surprised at the durability of the two alkaline batteries under such a heavy load. But we will see they cannot compete against leading brand Ni-MH batteries, which can be recharged over 500 times. The heavy drain of a 5 ohm load outstrips the ability of carbon zinc and alkaline batteries to deliver the power. What this means is that the battery will drop to 3.6 volts (the test cut off voltage), but the battery will not actually be completely drained. If left for several hours the battery will be able to used again. This is also true of other battery chemistries, but it is more evident with alkaline batteries. This graph clearly shows how an alkaline battery cannot compete against a high capacity Ni-MH.

img1.gif

Heat is important in two respects, first, ambient air temperature above 25 Celsius is not ideal during the charging process. Secondly, a good charger should not overheat the batteries. The higher the heat during charging and use, the shorter the overall battery life.

Living in Australia invariably means temperatures above 25 Celsius in summer. In addition to using a charger that does not overheat batteries, a simple but effective trick is to use a fan to help cool the charger and batteries during charging. The Doc uses a cheap desktop fan you can buy for a few dollars from the $2 shop. Warning: Do not use this type of fan for extended periods without a break, as the bearings are often plastic and they will melt and may cause a fire.
 

Review methodology – chargers


There are two types of reviews. The first is really just a comparison of the different features sets of the charges represented in a self-explanatory Table form, an industry overview if you will.

The second type of review is Charger specific. These reviews look at:

  • What is in the box
  • User Instructions
  • Charger type (Universal or Mini)
  • Battery sizes catered for
  • Battery types charged
  • Feature set
  • Safety features
  • Ease of Use
  • Performance
  • The charger in use
  • Overall rating
  • Conclusion

We are currently trying to determine criteria to test the charging performance using the Universal Battery Analyser. This will take some time.

Both reviews entail subjective analysis and involve various assumptions. For example, if the User instructions or the manufacturer’s website does clearly state the charger has a feature it is assumed it does not. This is especially so with safety features.
 

Charger Rankings


Chargers are ranked on the following on a scale of 10:

  • Feature set
  • Safety features
  • Ease of use
  • Versatility
  • Value of money
  • Overall ranking
  • Documentation
     

Documentation rankings


Documentation rankings are: Outstanding, Satisfactory, Unsatisfactory

Unsatisfactory: means insufficient information is given to properly operate the charger or the information is vague and imprecise.

Satisfactory: means sufficient information is given to operate the charger properly and basic safety instructions.

Outstanding: is given where a genuine effort is made to provide detailed, clear instructions on how to operate the charger, address safety issues, provide advice on good charging technique, etc
 

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