Rechargeable Batteries

[Terry W.]

I have recently purchased a new digital camera which uses re-chargeable batteries. I have not used rechargeables for 10 years and have the following questions:

The battery pack says charge for 16-20 hours. Will I damage them if they stay on charge for, say, 3 days or more ?

Is it advisable/necessary to use/discharge the batteries totally before recharging, or can I recharge them when they are half used. They used to say that rechargeables developed a "memory" - is that still true?

I've seen advertised charges that will recharge ordinary non-rechargeable batteries. Are these any good ?

Many thanks for your patience with a non-techie type and thanks in anticipation of your replies.

Terry W.

[Graham]

I used to make chargers that recharged ordinary batteries when I was a kid, they wern't all that successful as I remember, but the technique is called "dirty DC".

Googling that term seems to be useless, as an AC/DC tribute band uses the same name!

If you are interested, Googling "dirty DC" "zinc carbon" will give you the right info.

[Dave Fawthrop]

| |> I've seen advertised charges that will recharge ordinary non-rechargeable |> batteries. Are these any good ? | |I used to make chargers that recharged ordinary batteries when I was |a kid, they wern't all that successful as I remember, but the technique is |called "dirty DC". | |Googling that term seems to be useless, as an AC/DC tribute band |uses the same name! | |If you are interested, Googling | "dirty DC" "zinc carbon" |will give you the right info.

Google Advanced Search will do a better job. delete all hits with "Tribute" or "band". Lots more ways you can limit the search.

[Dave Plowman (News)]

That depends entirely on the charger - not battery. So you'd need to look at the instructions for that. If it obviously switches off after charging it should be ok.

It never was. It was a con to persuade you it was your fault batteries didn't last.

No. And rechargeables cost so little more anyway.

[EricP]

Probably, but it depends on the charger and battery type.

What sort of batteries are they?

Yes but only for a limited number of charges and not 100% capacity. Normally 10x > 15x for good alkaline batteries at 80% capacity.

[TheOldFellow]

What did happen was that a process called 'Dendritic Growth' occurred where a crystal-like thingy developed inside that shorted out the plates of the cell. I built a device to destroy them (found recently covered in dust!).

I don't think modern NICADs of NIMH rechargeables do it any more though.

R.

[Guy King]

The message from "Terry W." contains these words:

Since you can get 4xAA for £2 from Aldi (and they're OK - I've had loads and never a dud or low-capacity) why bother?

[Peter Crosland]

Wrong! It depends on both. You need to use a charger designed for the type of battery you wish to charge. For example Ni-Cad cells need a quite differnt charging patter than say Li-Ion ones.

Wrong! It was not a con at all, but has been repeatedly proven by experiment. Ni-Cad cells are particularly prone to this.

Wrong again!

They do work but not very well. Not a good choice really unless you are desparate.

Wrong! Unless of course you regard a price difference of at least 50% as being insignificant.

Peter Crosland

[The Natural Philosopher]

It all depends on the cell chemistry. Lithium batteries will not allow you to flatten them, and contain charge limiting circuitry anyway. And can only be charged with chargers designed for them.

Nickel cells can be flattened, but again its not good for them especially NiMh.

The can be trickled forever..they dump it all as heat anyway. .

[Dave Plowman (News)]

Wrong! It doesn't. ;-)

And how is this relevant? FWIW, there are battery chargers that cope automatically with both types and varying number of cells too - and switch off at the end of the charge cycle.

Wrong! It has not been 'proved' at all under normal use.

Have you missed something?

FFS, it is insignificant over the life of the battery. 'Recharging' alkaline batteries only partially works - and only even that for a few times. As opposed to hundreds of times for a Ni-Cad or NiMH.

[Peter Crosland]

I suggest you go away and do some proper research before spouting inaccuracies further Dave..

Peter Crosland

[The Natural Philosopher]

It does.

[Dave Plowman (News)]

You need to be more specific. I have two chargers that are designed to handle both Ni-Cad and NiMH - both of which may be left on indefinitely.

But the OP is presumably using the one supplied with the camera so that's a red herring.

As regards 'memory' with Ni-Cads I stick by my view. It was never a problem in normal use.

And if you think recharging alkaline batteries worth the effort or cost you're the one who needs to do some research.

[Dave Plowman (News)]

Lets be clear. Are you denying there are charges that auto sense between Ni-Cad and NiMH and shut off after use?

[Peter Crosland]

The problem with, and always has been, with Ni-Cad cells is that they do develope memory unless you discharge them fully and then recharge them. The problem with them is that people seldom do this and indeed often leave them on charge day after day.

Please point to the post where I said about alkaline cells.

[Guy King]

The message from "Dave Plowman (News)" contains these words:

My fast=charger's like that. Shove anything in it and a while later it's charged but leaving cells in for a week doesn't seem to have any adverse effects. They're hot at the end of the fast-charge cycle but cool right down to (as far as I can tell) ambient once it switches to trickle.

[tinnews]

If you read up on the "memory effect" you will find that it is very rare indeed. It only occurs when a NiCad is repeatedly charged and discharged in *exactly* the same way (i.e. both times and levels). It was discovered in NiCads used on satellites where the cycling was very regular indeed.

Thus "memory effect" is very, very unikely indeed to be seen in any domestic use of NiCad cells.

The only sensible reasons that I can think of for discharging before recharging are:-

To guarantee they are fully discharged before applying a full charge which would otherwise overcharge them. A good "intelligent" charger shouldn't need this.

To try and "even up" cells used in series so that all cells will start completely discharged when charging them. However charging cells in series is best avoided if you can. Discharging cells in series completely is a *very* bad idea because the weakest cells will get reverse charged towards the end of the discharge and this does them no good at all.

[manatbandq]

Well, obviously! We assume the OP has been provided with the charger appropriate to his cells, in which case all that matters is whether the charger is designed not to overcharge them.

Only under very particular circumstances such as spacecraft passing regularly between night and day where the batteries were regularly charged/discharged between the same points. It doesn't happen in normal domestic use. Just google "nasa nicad memory effect".

You have to look at the lifecycle of the cells. Even 100% difference would be insignificant when you take into account the number and effectiveness of recharge cycles possible with true rechargeables.

MBQ

[Guy King]

The message from [e-mail] contains these words:

Can happen with model aircraft - run at full pelt until the onboard electronics cut the power at a given voltage and then are recharged using expensive controlled chargers. Exactly the situation you describe.

[Dave Plowman (News)]

Not so - they have to be discharged to precisely the same point time and time again - very unlikely in most uses.

That is an entirely different matter. Many early chargers were crude in the extreme and would soon damage a battery by overcharging. But that's got nothing to do with memory effect. Makers of these cheap crude chargers might well imply it was, though.

You mentioned recharging non rechargeable batteries. I'd guess few use zinc carbon types these days. But these can't be recharged satisfactorily ether.