Teardown: Eveready General Purpose (No. 909) 6V Carbon-Zinc Lantern Battery

While going around the house looking for things to bin, I came across an old broken “dolphin-style” torch with missing parts. Of the parts that remained, the metal had oxidised and fatigued so much that the contacts to the switch and lamp just wouldn’t make and there was no way the torch would function again easily. I did find some spare globes for it though.

But then again, such incandescent bulb torches are so horribly dim and inefficient compared to LED torches that I had no qualms about letting this one go. It was a cheap knock-off torch anyway, but the fact it still had its rectangular 6V battery inside gave me an idea – why don’t I do a teardown?

The Battery

The 6V lantern battery seems to be an odd hold-over from a previous era when large chunky batteries were the norm. Used almost only in specific handheld torches and lanterns, I rarely ever needed to purchase any as I tended to prefer the torches that used more compact, smaller, lower-cost cylindrical cells (AA, C, D).

However, we did keep one such torch on standby – this was our “emergency” power outage torch. For this, I bought the battery below on clearance from Target for AU$2.80 in the early 2000’s from memory.

As it was a low cost lantern battery, it had a plastic shell and was relatively light compared to its alkaline counterparts which often had metal shells and felt solid. The connection to lantern batteries are made via springs at the top, with the battery taking the shape of a rounded rectangular prism.

Being about 16-years old at the time of rediscovery, the paper wrap printing was still surprisingly clear, with no signs of leakage externally. However, functionally, the battery was dead (as to be expected), as it had very much exceeded its shelf life. In Eveready’s range, General Purpose (blue) was at the “bottom” tier, with more premium batteries branded Heavy Duty (red), Extra Heavy Duty (black) or being alkaline type (Energizer, Eveready Gold).

Teardown

To open it up, some brute force was used to pry off the top cover. Underneath, we see a set of wires soldered to brass caps and zinc shells to form the four-cell series arrangement to obtain 6V.

The cells themselves are unsleeved bare F-size carbon-zinc cells from what I can tell, which look visually similar to D-size cells but longer. I do recall taking apart an even cheaper lantern battery at one stage to find lots of empty room and D-sized cells used instead, but apparently, they can also take on a lozenge form factor similar to 9V batteries.

The brass cap connects to the carbon rod which forms the positive terminal. There is also a little piece of wool near a plastic separator. This cell still had an intact casing, so probably was not entirely depleted.

However, as each cell is not made identically, it’s easily seen that the other cells in the pack were completely eaten-through, indicating they had been depleted entirely.

Conclusion

This posting shows the inside of a late-model Eveready 909 carbon-zinc “general purpose” 6V lantern battery. The battery comprises of a plastic shell containing four unsleeved F-sized cells soldered into a series circuit.

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