Batteries are a product that we all use. For remote controls, lights, photo equipment, music players, toys, weather stations and lots of other indispensable gadgets.
But have you ever thought about what you really get for your money when you fork out X number of kroner or euros for some common, non-rechargeable batteries in the kiosk, the supermarket, the online store, or where else you shop?
From the battery manufacturers you do not get much help. On food and beverages there must be detailed declarations, so you can see how much you sin. A battery may be called something with Super, Plus, Ultra, High, Power, Heavy Duty, Eco or the like, but how much power it can really deliver, you are not told anything about – unless you read a test magazine such as Datatid TechLife. Then you will discover, that there can be a huge difference in how long batteries can keep an electric car running and how much power they provide for your money.
In principle, a battery may be tested just like any other container holding something. Pour the contents into a measuring cup and see how much there is. This is easy enough with liquids, but of course a bit harder with electricity.
We could also let a battery-powered rabbit drum and use a smartphone as a stopwatch, but why not make it possible to reach directly comparable Ah values? Therefore, we chose a method that could be realized with existing instruments in our test lab. Please turn to the next page for the technical explanation.
We expose batteries to a load that corresponds to the operation of relatively light-duty devices such as smaller portable radios, lights, photo equipment and toys. The test is based on the same principles as the AA battery tests we conducted in the spring, but we have taken into account the lower capacity of AAA batteries this time and chosen a less demanding load.
The antique Brüel & Kjær Level Recorder Type 2307 in Datatid TechLife’s HiFi laboratory can also document battery discharge with high precision. It takes almost seven hours to print the red curve on the paper sheet.
The usage situation for AAA batteries is simulated by means of a 5.8 ohms (5.822 ohms, to be exact) precision resistor that is connected to a battery under test, after which we record the discharge process under this constant load until the battery is flat.
The battery test is performed at room temperature. If batteries are to be used outdoors, for example in bicycle lights, their capacity decreases at low temperatures. Therefore, we recommend that you do not leave lights on a bicycle in the cold season, but rather transport detachable lights in a pocket or bag. This also avoids the disappearance of lights from a parked bike.
The recording of discharge processes has been done with an analogue Brüel & Kjær Type 2307 Level Recorder – an instrument that uses ink and paper in rolls. This antique apparatus contains a mechanical gearbox that reminds us of Jens Olsen’s World Clock at the Copenhagen City
Hall, and makes it possible to forward the chart paper very slowly. At a paper speed of 0.01 mm/s, one hour corresponds to 36 mm. This means that one length of our 250 mm chart paper equals nearly seven (6.94) hours – perfect for our purposes. The precision of the recorder has been checked regularly with an absolutely contemporary Tektronix TBS 1052B digital storage oscilloscope.