Re: Quality of Alcaline AA batteries

On 9/10/09 18:57 , Alan Browne wrote:
Mort wrote:
ray wrote:
On Mon, 07 Sep 2009 08:48:15 -0700, Walter R. wrote:

I use alkaline AA batteries for my cameras. I can always be sure that I
can take photos because, unlike rechargeable batteries, their energy
does not evaporate over a few weeks. If they get tired I just put in a
new set without having to worry if they are still good.

There is a great difference in cost between brand name AA Alkaline
(e.g.
Energizer) and generic AA Alkaline, especially if bought in bulk packs.
It's difficult to test generics because there are so many "brands"
around.

How can I reconcile cost with quality under these circumstances?

Even the best alkalines don't really have much capacity. We've
switched to Lithium (non-rechargeable) batteries in my wife's Nikon
Coolpix - gets a LOT of pictures from one battery though they are
fairly expensive. I've not done a cost analysis, but my gut feeling
is they are probably more cost effective than alkalines.
Please make sure that your equipment can safely take AA lithiums. They
seem to have lower internal resistance than alkalines, and therefore
higher current flow, which could burn out some delicate circuits.

No. Current flows when it _can_ - that is according to the
resistance/demand of the circuit. Most NiMH are actually lower voltage
than alkaline batts. So damage is less likely.


Largely true where the circuit current draw isn't expected to draw down suppy voltage due to the internal resistance of the battery. By example, early carbon zinc battery powered devices were expected to do just that under heavy drain. Because batteries were so inefficient. To compensate for the lower supply voltage, extra cells were added to make up the difference to deliver the correct current supply to the circuit.

Came along alkalines, with a higher current per volt output, and in unregulated circuits, suddenly supply voltage exceeded maximum rated voltage of components, resulting in failure of active components.

Some early Zenith Transoceanics experience this.

Drop a NiMH or even NiCad cells in place of the original carbon zincs, and even with the lower voltage, supply voltage can easily exceed operating parameters for the original circuit.

Applied to today's design...alkalines are usually inadequate for high drain devices built today. NiMH and NiCads are the better choice, for the reason you state below. That said, high drain devices designed for alkalines were designed with the internal battery resistance included in total circuit load. Toss in NiMH cells with their lower internal resistance, and current delivery can rise dramatically, in fact, doing damage to both active and passive components in the circuit, despite lower no-load voltage.

Yes, you really can damage circuitry through over current delivery by changing battery types. Precisely because, as you've said, current flows were it CAN according to the resistance/demand of the circuit. Lower the resistance of the supply and you lower the total resistance of the circuit, increasing current proportionally.




But, because they can deliver more current, they are great for attached
camera flashes - recharge the caps real quick.

.

Relevant Pages

  • Re: Saturation in transformers.
    ... >> the saturation ... Once again, it is not a short circuit, ever. ... >> a voltage across a coil? ... > Er, it might, or might not, depending on the time, the resistance ...
    (rec.audio.tubes)
  • Re: Faraday "magnetic" induction without a magnetic field.
    ... >> and compared to the voltage across the other resistor =>> agreement. ... > either the left or right side of the circuit -There is no reason to ... > no induced voltage in these parts, then all the induced voltage would ... > fact that the bars are assumed to have 0 resistance). ...
    (sci.physics.electromag)
  • Re: eliminating CMRR problems -- was, 3 dB bandwidth
    ... > been using all NMOS strings, in a totem-pole push-pull circuit. ... what PMOS parts are you using and what is their voltage ... The resistance is across the supply voltage of 1KV, ... The overall bandwidth is limited by the op amp. ...
    (sci.electronics.design)
  • Re: Saturation in transformers.
    ... >>> voltage ... >>> and the coil becomes a short circuit when the steels field ... > the saturation ... Er, it might, or might not, depending on the time, the resistance ...
    (rec.audio.tubes)
  • Re: Simple capacitor circuit (slowly illuminating LED)
    ... >> across the capacitor is proportional to the charge it contains and second ... I took my multimeter and measured the voltage ... I left the circuit closed for two hours just to see if it ... > Now, at their lowest, the resistance of the capacitor and ...
    (sci.electronics.basics)
Loading