Batteries

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… or alternatively, because their voltage is simply too low

MichaelG.

Surely most batteries have the capability to supply currents in excess of that required or the device would not function. The device itself is what determines how much. Just a thought.

We have two Canon cameras - Powershot A640 & Powershot A610. In both instances, the instruction guides say this:

"This camera uses AA-size alkaline batteries or Canon AA size NiMH batteries (sold separately).

While it is possible to use AA-size nickel-cadmium batteries, performance is unreliable and their use is not recommended."

We have used NiMH cells

Peter G. Shaw

That's usually so, but there are cases where the battery is chosen to limit the discharge rate, not always wisely! I read a safety report in the 80s describing how a technician was killed testing an air to air missile. Sweden if my memory is right.

The essence was that the missile was fired by the pilot passing an electric current through a wire filament that glowed white hot and flashed a powder charge to ignite the solid fuel propellant.

And to make sure the missile would work when fired in anger, the filament was periodically tested in storage for continuity with a special test set. A special battery with a built-in resistor ensured the tester wouldn't pass enough current to fire the missile. Unfortunately, the Health and Safety hadn't been thought out because the special battery was the same size and shape as a standard PP9. So one day, a technician replaced a flat tester battery with an ordinary PP9 and incinerated himself.

Dave

I don't know many people in my neck of the woods with missile launchers!!!

You would be surprisee at just how much current a relatively small primnary or secondary cell can deliver, even if only for a short time (No pun intended! )

It may be a 1500 Ma hr AA , but for a few seconds, it can probably deliver quite a few Amps..

Every time you engage the starter on your car, the starter probably draws several hundred amps from a battery of quite small amp hr capacity.

(A 4 litre diesel might well draw over 400 amps on a cold start, from a 75 or 100 amp hr battery. )

Howard

Hi

IIRC in ww2 there was a self destruct circuit on a bit of radar equipment with a test button, swap switch, Press Test put back in flight mode. I read of a story where a technician did not swap the switch before Pressing Test button,

Last night on PBS America they said the Norden bomb sight used a Thermite self destruct charge. That would go with a Bang

George

The story of the Norden Bomb-sight is amusing I think. Judging by what was said at the time, Americans were extremely proud of what they claimed to be the last word in precision bombing, and they took elaborate security precautions to stop anyone else learning how to make one. Including a self-destruct charge.

Unfortunately the Germans already knew all about the Norden from a spy, one of their rare successes. They weren't impressed by it, noting the Norden was considerably heavier, more complicated and expensive to make than their bomb-sight, which claimed similar performance.

Worse, it was found that a Norden super-accurate in the peaceful sky over a practice range in Arizona struggled to deliver in Europe. The problem was European bad weather - cloud, fog and rain - plus gunfire forcing the pilot to duck and weave.

Accuracy was a difficult problem. After photographing what was really underneath when bombs were dropped, the RAF found in 1941 that only 5% of their aircraft were within 5 miles of the target. So the RAF switched to electronic systems, only using optical sights when it was certain the target was in view. The AAF weren't far behind, suggesting maybe the Norden was something of a publicity stunt, possibly a propaganda boost that also disguised a shift to electronic methods.

Dave