Battery charging question

[Dave Plowman]

I'd hope so too given just how cheap electronics are. I'm referring to the PPro etc drills of a couple of years ago.

[The Natural Philosopher]

You sure it isn't a delta peak already?

Ther are chips available that do all teh stuff you need.

HOWEVER a trip to the local model shop will net you a charger that will generally do from 4-7 cells at usually about 3A, with built in delta peak, for next to bugger all - about 25 quid from memory.

e.g.

and have a look see.

Ideal for sub C nicads,

[Oldskoolskater]

Right then Gents....

To clarify: The batteries in question are 4 AA Nimhs - identical as they were in the light when I bought it. Option 1 - Charge the batteries in the light which comes with a trickle charger Option 2 - Take the batteries out of the light and put them in one of those chargers that take 4 AA's and plugs into a socket, covering most of it.

I assume that the external charger charges in parallel. Just wondering which is the best way to go?

Cheers

Steve

[ma005724]

this functionality?

Positive.

Do you have any suggestions for specific chips that I can search for?

I know I could buy a new charger but I fancy trying to cobble something together just for the hell of it.

Regards,

Andy.

[Bob Smith]

Trickle charging will kill the batteries eventually. And they will be charged in series, as a pack, the weakest battery getting hottest, and getting even weaker.

Better idea, if it is a smart charger. A manual or timer charger will fry your batteries.

Each battery would be charged individually.

Bob

[IMM]

While on batteries, what is the best method to see who much charge a battery can take, and how much change is actually in it.

[Bob Smith]

You could weigh it, and calculate how many electrons are in it :-)

To see how much charge it can take, you charge it. The voltage of the cell increases as it is charged. Eventually, it reaches a point where the voltage decreases (called negative delta V), and then it is time to stop charging. Another clue would be to monitor the temperature of the battery. If it gets warm, you are frying it (boiling off the electrolyte)

To see how much charge is left, the only true way is to discharge them! (hindsight being 20/20) A NiMh gives a pretty flat discharge curve, and falls off suddenly when it is nearly flat. The only warning you get is a "nearly flat" warning when the as the cell voltage starts falling off.

Modern lithium polymer batteries are hard to charge, so they have a chip built into the pack that counts charge and discharge, and it tells the charger when to stop. A handy side effect is that sometimes they have a handy charge indicator graph on the side that comes on when you press a button.

Bob

[The Natural Philosopher]

functionality?

NiMh, NiCd and even Li-ion.

[The Natural Philosopher]

Buy and expensive charger/disharfges as used by model enthusiasts, which will do all that automatically.

Schulze Chamaleon 6-330d springs to mind as one of the best...abiout 110 quid

[Toby]

There's the MAX712 IC used here:

the esteemed Mr Parry has this:

[usenet]

If you ask nicely they'll send you free samples, I have two of their NICd/NiMh charger chips that I got just for the asking.

[IMM]

£110? hang on I'll me coat.

[Andy Dingley]

Don't charge batteries, charge individual cells.

[Bob Smith]

An ordinary intelligent charger for 4 x AA or 4 xAAA is about 30 quid, usually with 4 batteries, and should charge them in 1-2 hours.

Bob

[usenet]

... and as I asked before, how do you *tell* that it's really an intelligent charger?

[Huge]

Give it an IQ test.

[Bob Smith]

The description should mention "smart" or "intelligent". Watch out though, I saw one advertised as a "smart silver charger", which I assume is in relation to its aesthetics. Other giveaways are "negative delta V" or "delta V". "Individual cell monitoring" should be a smart one too.

Anything mentioning a timer is a no-no. Anything under £20 is probably a dumb charger.

Bob