getting the most from AA cells

[AJH]

A happy new year all and a poser.

My wife was given a camera which uses 2 AA cells. Because I doubt she will use it much I put 2 ordinary alkaline dry cells in it, it shows discharged after about 40 frames stored.

Now these cells still show 1.45V so I am wondering what piece of equipment would make use of the remaining charge. I am thinking probably a LED torch of some sort?

I could buy some NiMH cells for it, Nicads are expressly warned against, but my experience of NiMH is they are great for regular use then fail quickly but have a high self discharge if left for long periods.

AJH

[Mr Fixit]

I use NiMh in mine with no problems and they have more life than most Dry cells

[Harry Bloomfield]

AJH submitted this idea :

Pretty well anything which draws little current and sits doing nothing most of the time, like remote controls.

They should work well if you know you will be taking lots of photos over a short period. I keep a set of normal cells in mine year round, so it is always ready for instant use. If I plan a session with the camera, I then swap temporarily over to NiMH.

[ARWadsworth]

Would

work in your camera? Better that NiMH for camera use

Adam

[Dave Fawthrop]

| A happy new year all and a poser. |=20 | My wife was given a camera which uses 2 AA cells. Because I doubt she | will use it much I put 2 ordinary alkaline dry cells in it, it shows | discharged after about 40 frames stored. |=20 | Now these cells still show 1.45V so I am wondering what piece of | equipment would make use of the remaining charge. I am thinking | probably a LED torch of some sort? |=20 | I could buy some NiMH cells for it, Nicads are expressly warned | against, but my experience of NiMH is they are great for regular use | then fail quickly but have a high self discharge if left for long | periods.

I have a MAHA

in the car and keep my *numerous* high capacity NiMH batteries charged. Charge them all on the drive out. When one set dies, put another lot in. Charge all the dead ones on fast charge.

I like the MAHA charger because it switches each battery individually off charge when they are full.

My regular use (reading in bed with a torch, so that I do not wake June) LED torches have NiMH batteries, I also have three emergency ones scattered around which have cheap, Lidl, alkaline, because of the self discharge problem mentioned.

--=20 Dave Fawthrop Some of my Hobbies: VDU Glasses=20

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[Dave Fawthrop]

| AJH wrote: | > A happy new year all and a poser. | >

| > My wife was given a camera which uses 2 AA cells. Because I doubt she | > will use it much I put 2 ordinary alkaline dry cells in it, it shows | > discharged after about 40 frames stored. | >

| > Now these cells still show 1.45V so I am wondering what piece of | > equipment would make use of the remaining charge. I am thinking | > probably a LED torch of some sort? | >

| > I could buy some NiMH cells for it, Nicads are expressly warned | > against, but my experience of NiMH is they are great for regular use | > then fail quickly but have a high self discharge if left for long | > periods. | >

| > AJH | I use NiMh in mine with no problems and they have more life than most = Dry=20 | cells=20

Zinc - carbon perhaps, but *not* alkalines which have a shelf life of a few years.

--=20 Dave Fawthrop Some of my Hobbies: VDU Glasses=20

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[Newshound]

Assuming the camera has a viewfinder, you should get *much* more than 40 frames life by turning off the LCD screen when taking pictures.

[meow2222]

traditionally flash units had no current limiting resistor, using the battery's internal R to determine current. NiCds and NiMH have very low internal R, and using those will kill these flashes. If youre using them with flash and it survives, the flash must be designed to work with those too. However rechargeables should never be used in old camera flashes, which are not NiCd compatible.

NT

[AJH]

I don't know, I still don't understand why Nicad are not allowed so what are the characteristics of these compared with alkaline or Nimh?

AJH

[AJH]

OK I'll re use them in remotes.

This is the sort of thing I envisage, leave the alkaline cells in for instant, random use and buy some NiMH if it looks like it will get a lot of use. I'll need to consider a charger as mentioned by Dave to treat the NiMH gently as I'm in the bad habit of forgetting to stop charging.

AJH

[Jonathan Schneider]

Because if you grind up a NiCd battery and swallow it you could get ill.

Seriously though there's a lot of tosh talked about NiCd and the truth is they are about the most robust battery technology about. Characteristics similar to NiMH of course but more cycles and lower energy density and cost.

Jon

[AJH]

I've had a better read of the manual now and it suggests: "do not use AA size manganese or nickel cadmium batteries in your finepix because the heat created by the batteries could damage your camera or cause it not to work"

Which makes me wonder about the lithium ion one Adam pointed me to.

BTW I agree about nicad verses NiMH. My LA has just started a recycling scheme for discarded cells so at least I can avoid them getting incinerated.

AJH

[TimB]

Usage sounds about right based on mine - digicams drink battery. As far as re-use - remotes, clocks, in fact most things except digicams as long as you're not hugely concerned about lifetime. I've run my minidisc player for well over a weeks worth of commuting - around 20 hours use - on a single AA that the digicam claimed to be dead. New batteries give me around 40-50 hours use.

[PC Paul]

The heat generated by Nicads if they should happen to short is likely to damage just about anything in the vicinity. A single AA cell can easily vaporise a length of solder or make a length of wire glow red hot and melt the sheathing off it.

Nicads have a very low internal resistance, hence a very high disharge current. Li-Ion has about double that, NiMH has about 5 times. NiCads are much much more nasty when they short out.

They also tend to be used with less 'clever' chargers and get hotter when charging. I don't know if that's what they are worrying about?

[Mike Tomlinson]

In article , AJH writes

Wall clocks. This is how I use up my half-dead AA cells. They're usually good for at least a year.

[Roly]

If an alkaline cell is showing as discharged when it's reached 1.45V, you won't get very far with NiCads etc as they only start off with 1.2V per cell.

[Dave Fawthrop]

| AJH writes: |=20 | > I don't know, I still don't understand why Nicad are not allowed so | > what are the characteristics of these compared with alkaline or Nimh? |=20 | Because if you grind up a NiCd battery and swallow it you could get = ill.

Cadmium poisoning is very nasty

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[Dave Liquorice]

Your forgetting about internal cell resistance. Digi cameras take quite a current, alkalines have relatively high internal resistance. So a significant amount of voltage is dropped across the cells resistance hence the camera thinking them "flat". A NiCd has very low internal resistance and won't drop as much voltage.

It is worth remembering that NiCds start at 1.2v nominal rather than

1.5v but quite often it's not a problem.

[Dave Plowman (News)]

I'd guess the 1.45V is the open circuit volts. What matters is the voltage under load - or whether it can still supply the required current, as it were. That's the beauty of Ni-Cads - they can supply the same current throughout most of their cycle.

[AJH]

Is this a reason for them to get hotter in normal use?

I'm just going to have to try a few different types but atm cannot really see why nicads are expressly excluded.

AJH