AAA battery question

[Randall]

I picked up a cool LED flashlight a while back that I absolutely love. It has a linear array of super bright LEDS running down the side, and a strong magnet on it that allows for sticking it in various places on a chassis. I use it all the time. My question is, it has 3 AAA batteries in it, and recently it got a lot less bright pretty quickly. I figured the batteries were dying, but in fact two of the batteries were at 1.1v, and the other was almost dead flat. Since, all three are in series, what would cause this? I popped a slightly used replacement in, and it got really bright again. Just a faulty unit?

[SoulFetish]

I picked up a cool LED flashlight a while back that I absolutely love. It has a linear array of super bright LEDS running down the side, and a strong magnet on it that allows for sticking it in various places on a chassis. I use it all the time. My question is, it has 3 AAA batteries in it, and recently it got a lot less bright pretty quickly. I figured the batteries were dying, but in fact two of the batteries were at 1.1v, and the other was almost dead flat. Since, all three are in series, what would cause this? I popped a slightly used replacement in, and it got really bright again. Just a faulty unit?

Thats what I would guess. Where did you buy the batteries? They could be stored for a while in an area where they are exposed to high heat. That would kill the expected shelf-life.
I bought a pack of AA a few months back from a surplus "Big Lots" type place and half of them were DOA. If you can find it, each battery has a date code. Sometimes that can be useful. Probably just got a bummer. Maybe get a set of rechargeables you can cycle in that flashlight. I find that the nice headlamp I attached to my magnifying visor eats through AAA really quickly. I should mod it to take a small 3.7V li-ion battery to give me more run time.

[Leo_Gnardo]

By coincidence I bought the same kind of flashlight last week, about $8 at Home Despot. It's an instant hit on the workbench and I plan on buying more, for the car & home. In these days where super cheap deals on mystery brand batteries are offered, it's no wonder some of them turn out dodgy. I noticed Harbor Freight was offering a big pak of triple-A's free with any purchase. That cheap!

Even supposed hi quality batteries have their problems. I had a couple DuraCell alkaline AAA's go leaky inside a thermometer/hygrometer recently. Grrrr....

I s'pose we have to not take our battery operated gadgets for granted, open 'em up, measure, replace more often.

Also, I notice LED flashlights as well as AC operated LED lamps can induce noise into audio circuits, that's foxed me a couple times.

[SoulFetish]

By coincidence I bought the same kind of flashlight last week, about $8 at Home Despot. It's an instant hit on the workbench and I plan on buying more, for the car & home. In these days where super cheap deals on mystery brand batteries are offered, it's no wonder some of them turn out dodgy. I noticed Harbor Freight was offering a big pak of triple-A's free with any purchase. That cheap!

Even supposed hi quality batteries have their problems. I had a couple DuraCell alkaline AAA's go leaky inside a thermometer/hygrometer recently. Grrrr....

I s'pose we have to not take our battery operated gadgets for granted, open 'em up, measure, replace more often.

Also, I notice LED flashlights as well as AC operated LED lamps can induce noise into audio circuits, that's foxed me a couple times.

I've was getting this strange buzzy audible noise coupling in on a amp i was working on recently and after a moment I realized that the beam from my led light would induce noise when the light hit the plates of a 12AX7

[J M Fahey]

it got a lot less bright pretty quickly. I figured the batteries were dying, but in fact two of the batteries were at 1.1v, and the other was almost dead flat. Since, all three are in series, what would cause this? I popped a slightly used replacement in, and it got really bright again. Just a faulty unit?

Not at all, just normal production spread.

In fact, consider all three dead since 1.1V no load is already equivalent to being in coma.

Alkaline battery discharge curves:



see that they hold reasonably well but at the end they drop catastrophically, with even a slight extra discharge.

I think the 1.1V ones are just at the left of the death point, the almost flat one slightly to the right.

You replaced the deadest one, but I bet the survivors won´t last much longer.

In batteries, in general, the damage parameter is not just voltage (which we measure easily) but much more important, internal resistance (which is harder).

Personally I test Zinc Carbon and Alkalines by shorting them (for a second or two) with meter set to 10A DC scale.

Fresh AA give me almost 2A , I consider them "good" down to 1 A , this means internal resistance is around 1 ohm.
They hold this quite a long time, until suddenly current drops to 200mA or less: 10 ohm or more internal resistance which means they are a mess inside ... although under no load such as a meter they apparently hold reasonable voltage.

So I trust the current capability a way more reliable indicator than plain voltage.

Of course: do not short rechargeables and even less LiIon or similar modern ones, unless you want a Nuke in your hands.

[Leo_Gnardo]

I've was getting this strange buzzy audible noise coupling in on a amp i was working on recently and after a moment I realized that the beam from my led light would induce noise when the light hit the plates of a 12AX7

Yes, that's part of it. But even without the light hitting a tube, there's a power oscillator in many LED lamps that induces a midrange buzz in nearby circuitry. Can't wait for the electronic radiation conspiracy theorists to tackle this one!

[SoulFetish]

there's a power oscillator in many LED lamps that induces a midrange buzz in nearby circuitry. Can't wait for the electronic radiation conspiracy theorists to tackle this one!

Thank John H. Titor that I haven’t removed my tinfoil hat since the spring of ‘07!

[J M Fahey]

I haven’t removed my tinfoil hat since the spring of ‘07!

Just a *HAT????*
But that leaves all the rest unprotected!!!!!

I have not left my full shield since 1969!!!!!!



but ... but ... don´t you have to leave some parts of your body unshielded at least ... um ..... a few times in the day? ....

Well, not unless surrounded by brave Knights which man a protective ring around me.

In any other occasion, I can only trust: