Techno-talk: Which batteries are best

By Ron Zeeman, ,June 2001

The scene: The battery rack at Pick and Pay, the day before the caving trip.

Eeenie meenie mi’. no wait,’ these are cheaper,’but these are much prettier.’

Where’s the most bang for my buck.

A range of AA size penlight cell types were discharged at a constant current of 200mA down to an end voltage of 0.9v. After rest periods this was repeated twice for each cell and the total running hours recorded. Dividing this by the unit price from a four-pack a figure of merit in milliAmp hours/Cent was obtained for each type of cell.

The first two on the list are Leclanche Zinc Carbon types, the basic technology of which dates back to around 1868 whereas all the others are Manganese Alkaline developed much more recently. The Panasonic General Purpose cell, (the one with the green apple), was not even considered as previously similar tests showed this would be a waste of time. The rechargeable Alkaline is shown for interest.

TYPE

4-PACK COST

HOURS

mAHr

mAHr/Cent

Eveready Powerplus black

8-99

1hr 46min

353

1.6

Eveready Powerplus gold

10-99

3hr 15min

650

2.4

Eveready Alkaline plus

23-99

9hr 30min

1900

3.2

Duracell Alkaline MN1500

23-99

10hr 5min

2016

3.4

Duracell Ultra

25-99

11hr 9min

2230

3.4

Energizer Alkaline

20-99

10hr 12min

2040

3.9

Energizer Titanium

27-99

12hr 26min

2483

3.6

Pure Energy rechargeable

24-99

4hr 45min

950

N/A

What these numbers suggest is that if your caving lamp is fitted with a 0.5A (500mA) bulb then you can expect at least 4 hours from an Alkaline battery pack. In real life the hours should be longer because the lamp is not run continuously and rest periods help. Also the lamp current will fall as the voltage falls.

Right. The five alkaline types have similar performance with Energizer just ahead. Now to choose a winner. No cell is perfect. They all have some internal electrical resistance. As soon as you draw current the voltage falls. (This explains why a bulb for a 2 cell torch is rated at 2.5v and not 3v as you would expect). So this means that not all the energy you bought goes to the lamp but some goes to heating the cell itself. The cell with the lowest internal resistance wins my vote. To gauge this I short-circuited each cell and measured the Amps. The higher the current the better.

TYPE

AMPS

Eveready Alkaline Plus

3.4

Duracell Alkaline MN1500

3.8

Duracell Ultra

5.5

Energizer Alkaline

6.8

Energizer Titanium

7.1

That’s it then. I’m only buying Energizer from now on. Which type will depend on the price at the time. The rechargeable Pure Energy, while only giving half the running hours, is probably best value in the long term. As yet I don’t know what the cycle life is at high currents. I’ll let you know. Temperature has a significant effect on performance. Keep your spares snug and warm in your pocket. Technically these are cells. It’s only a battery when you join them together..Picky,picky.