In my internship my task this week is to build a battery tester. This draws a fixed current from a single cell (AA or AAA) and accumulate mAh until the cell is dead (0.8V or less under load.)
I finished it today, so tested two batteries, new in packets. One was a Tesco Alkaline (30p each). The other was Energizer Ultra Alkaline (81p each.)
Final mAh from the batteries? Tesco=1181 mAh; Energizer=1249mAh. At 1 amp constant current discharge.
ESR of the Tesco cells also tested at a low 60mOhm new from packet; Energizer was 75mOhm. End ESR was about the same around 110mOhm.
The Energizer only just beat the Tesco one - but it costs almost 3x as much! This has changed my opinion of cheaper batteries. Full results will be published soon.
I also tested a zinc chloride, also Tesco, and as expected it only had around 110mAh. It was flat within 6.5 minutes at 1A discharge!
I am also going to test Poundland special ones (Alkalines) - 16.7p each - I'm not expecting much! I'm also planning to see how much of a difference it makes to test at 100mA instead of 1000mA, and also different load characteristics, such as simulated constant power (similar to a switching converter) and constant resistance (similar to a light bulb) characteristics.