The Cats KnackersThis morning, after Lady A left, we really were intending to get on with some proper work. After the recent ‘playtimes’ over at the TCK Allotment, we thought we’d better get on with yet more paperwork, then do some kind of planning for next week.

Alas, it was not to be, as we received a call from Dean up at The Forum, telling us our long-awaited magnesium bars had arrived all the way from Hong Kong.The Cats Knackers

This meant there was no way on earth we were doing the paperwork.

So may we present to you, a lit hyper-bright LED:-

Nothing really special about this at all, is there?

Nothing special, that is, until you follow those wires back, and you arrive at these:-

The Cats KnackersFour assorted clean jam and preserve jars with weird-looking things in them, covered in what looks like a clear liquid.

Well, Dear Reader, the ‘weird things’ in those jars are magnesium rods, wrapped in pieces of clean dust sheet we had left over from the renovation a few years ago. The bars are then wrapped in thick, multi-strand copper wire. Judicious use of black plastic tie-wraps made sure everything stayed in place.

The clear liquid is in fact plain old tap water.

The outputs are the magnesium as -ve with the copper wire as +ve.

The individual output of each ‘pot’ is a little over 1.1 volts, with the current being about 10mA. Therefore, as they’re wired in series, this means the voltage is just under 4.5 volts at 10mA.

No, that’s not a Big Lot of current or voltage, but with some optimisation and tweaking, we think we can at least get the current much higher.

The Cats KnackersWe could have added table salt to the tap water, and that would certainly have greatly increased both current and voltage (…we think…), but in doing so, this would gradually eat away at the magnesium rods, or coat them in something that would eventually stop them working. But we didn’t. We wanted to build batteries that last.

If the numerous videos on the subject are to be believed, then you can kiss Duracell goodbye. Yes, the current is only a fraction of that given out by even an ‘AAA’ cell, but unlike a ‘normal’ alkaline battery, magnesium/copper batteries don’t wear out.

So why did we go to all this trouble when we could have been doing exciting stuff like paperwork and planning?

Well, aside from desperately enjoying being 8 years old again, this is a tiny part of the TCK ‘Master Plan’ to bring power down to our otherwise bereft allotment.

Not at all because we find this tremendously good fun.

Perish the very thought. Work is meant to be pointless and soul-destroying. Work is not meant to be fun. If someone enjoys what they do for a living, then they must be deluded, or mad. Or they must be a crook.

The Cats KnackersAnyway… Back to the plot, and just how bright do you think this LED would be?

To the left is your answer.

Yes, the LED we used is a high-efficiency model, but even so, it’s pretty good.

Now, getting back to the maths, and according to Wikipedia, an alkaline AAA battery is rated between 860 – 1,200mAh.

This mean in theory, at 10mA, three AAA batteries (to give 4.5 volts) should last up to 120 hours. Or 5 days continuously. …In theory.

So, Dear Reader, the new unit is now on the kitchen side, connected up, and we’ll tell you all about whether it lasts any longer than that.

The only slight problem (…or ‘challenge’, if you will…) will be that the tap water will gradually evaporate, but we’ll keep topping them up if needs be.

Longer-term, we’ve bought some terminal posts from the Bay of E, and we’ve noticed that the jar from the ‘Old El Paso’ chillies is the perfect size for our creation, so we’ll have to go and buy some more of these, then we have a cunning plan to properly mount the magnesium and copper in the jars with the two terminals mounted on top. As these terminals are air-tight, it means we can fill the jars up, screw them shut, and the water should last for months, if not years if they remain unopened.

Baghdad battery, anyone?



Categories: TCK Blog

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