Tuesday, February 24, 2009

The mechanical battery tester

Updated 2011/11/17

I have often wondered if the claims of a battery manufacturer are true. Is one brand of battery better than another? I have devised a way to determine which locally available battery is best. I am choosing to test the 'AA' sized cell, as this is the size I use most often. I will acquire four cells of each brand and then submit these cells to a test that will drain each unit totally. The end result will provide me with a quantifiable value that can be compared to other cells under test.

My test setup is a machine that operates a counter. When a cell is attached, a switch is thrown and an electric motor drives a mechanical counter. When the cell has been drained, the motor stops running and the counter stops. I record the value, label the dead cell and a fresh cell is fed into the machine. I will be testing four of each brand to ensure good results.

My results;


Type
Count
Price, ea.
Purchased
Energizer Lithium
1812
$4.37
IGA
Energizer Lithium
1807
$4.37
IGA
Energizer Lithium
1795
$4.37
IGA
Energizer Lithium
1771
$4.37
IGA
Duracell Copper Top
1457
$1.07
Canadian Tire
Energizer (regular)
1404
$1.17
Canadian Tire
Duracell Copper Top
1400
$1.07
Canadian Tire
Duracell Copper Top
1400
$1.07
Canadian Tire
Kirkland Alkaline
1400
$0.31
Costco
Kirkland Alkaline
1390
$0.31
Costco
Kirkland Alkaline
1380
$0.31
Costco
Energizer (regular)
1380
$1.17
Canadian Tire
Energizer Titanium
1370
$1.49
Canadian Tire
Kirkland Alkaline
1358
$0.31
Costco
Duracell Copper Top
1357
$1.07
Canadian Tire
President's Choice
Long Life
1337
$1.25
Loblaws
Energizer Titanium
1332
$1.49
Canadian Tire
Energizer (regular)
1320
$1.17
Canadian Tire
InfiniCell
1285
$1.25
The Source
Energizer (regular)
1284
$1.17
Canadian Tire
President's Choice
Long Life
1284
$1.25
Loblaws
InfiniCell
1260
$1.25
The Source
President's Choice
Long Life
1260
$1.25
Loblaws
InfiniCell
1253
$1.25
The Source
Truly Power Plus
1242
$0.20
Zellers
Energizer Titanium
1235
$1.49
Canadian Tire
Eveready Gold
1234
$1.32
Canadian Tire
Eveready Gold
1220
$1.32
Canadian Tire
Eveready Gold
1200
$1.32
Canadian Tire
Truly Power Plus
1183
$0.20
Zellers
President's Choice
Long Life
1183
$1.25
Loblaws
InfiniCell
1178
$1.25
The Source
Truly Power Plus
1176
$0.20
Zellers
Eveready Gold
1170
$1.32
Canadian Tire
Truly Power Plus
1164
$0.20
Zellers
Energizer Titanium
1133
$1.49
Canadian Tire
Panasonic Alkaline
1112
$0.15
Dollar Store
Panasonic EVOLTA
1110
$1.25
Future Shop
Panasonic Alkaline
1106
$0.15
Dollar Store
Power Fist Alkaline
1100
$1.00
Princess Auto
Power Fist Alkaline
1100
$1.00
Princess Auto
Power Fist Alkaline
1089
$1.00
Princess Auto
Power Fist Alkaline
1085
$1.00
Princess Auto
Panasonic EVOLTA
1083
$1.25
Future Shop
Panasonic EVOLTA
1070
$1.25
Future Shop
Panasonic Alkaline
1051
$0.15
Dollar Store
Panasonic Alkaline
1026
$0.15
Dollar Store



One of my goals for this test setup was to provide a relatively heavy current draw. I wanted to simulate the effects of todays electronic devices, such as digital cameras or Radio Controlled toys. To achieve this I have inserted a 10 ohm resistor across the motor. This resistor alone, when connected to a 1.5V AA cell, draws 150 mA. This causes a heat dissipation of 225 mW or about a 1/4 Watt. With the motor running in the circuit too, the total current draw is greater than the resistor alone. I included the motor because I needed a way to figure out how long an AA cell would last. This is why I made the gearing system to drive the mechanical counter. As the counter operates, it continually increases its count. When the combination of the resistor and motor has finally depleted the stored energy in the AA cell, the counter stops. I now have a quantifiable result I can use to compare against other AA cells. As each cell is submitted to the same conditions, my results should provide a reliable means of determining which is the best.

There is also a matter of value for your money. If I have two cells that finish with the highest numbers, I will have to decide which one would be more economical. For example, the Kirkland AA and the Duracell Copper Top AA both have results in the region of 1400 counts. As it costs about $4.00 for a package of four of the Duracell brand and you can get a package of Kirkland cells, 40 in a package, for $10, I would consider the Kirkland cells to be the better value.

My testing is done purely out of scientific curiosity and I am not seeking to defame nor to promote any particular brand or manufacturer. Any results posted here are my own opinion and are open to interpretation.

3 comments:

  1. I can see how the counter helps you do the "timing" because you're obviously not going to sit and watch it until it fails. It would be somewhat useful to see the time to failure - but probably not worthwhile to manually measure. Do the batteries typically run faster at first, and then drag out the last couple hundred revolutions for a longer time? i.e. I imagine the different battery types have a different power curve (high power at first, then low power later).

    Dave Martin

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  2. A typical cell lasts for about 18 hours. At first the counts tick over pretty fast. As the cell is depleted of energy, the system slows down and the count also slows. Rather than create a control system for a timer, I used the counter to record an absolute value that can be quantified. Given that each cell is subjected to the same test, a person can make a judgment on which cell is better, based on the resulting counter value.

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  3. Paul,

    I know nothing about electricity but was also curious about this same issue. Thanks for the great test and results. Now well informed, I'm off to buy some batteries.

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