Battery charging question

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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.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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In my original reply I said "provide individual current limit resistors and charge them in parallel", meaning that the battery/resistor combinations were in parallel.
The current remains constant providing the supply voltage is high enough that the battery voltage change is insignificant. Let's say that the cell voltage ranges from 0.5 to 1.2V, choose a supply voltage of 15V and a 220R series resistor. Initial charge current = 66mA, final charge current is 63mA. I would have thought this was constant enough to keep a NiCd or NiMH happy. If you want it more constant you simply choose a higher voltage, naturally the power dissipated in the resistor increases with voltage.
Dave S
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Personally I have a conditioning charger that discharges and then charges the cells separatly - takes 4 cells at once. This is to reduce the memory effect of nicads. For devices that have there own chargers I still occasionally remove the cells and put the in the conditioner for a couple of cycles.
On 2 Dec 2003 23:57:15 -0800, snipped-for-privacy@mailinator.com (Oldskoolskater) wrote:

Lawrence
usenet at lklyne dt co dt uk
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applications, with an extremely regular charge/discharge cycle). The term memory effect was stolen from this phenomenon to describe the reducing capacity of over charged, abused cells.
The only use for a discharge is for a timer based charging system (NiCad or NiMh), so you are sure each cell is flat (but not too flat - also damaging) so you don't try and cram a full charge in an already half full cell.
A smart charger that charges each cell individually is the way to go. Costs about 30, and won't fry your batteries like a set time charger.
Also of note, new NiMh cells will get fried if you do a full charge on the first few charges, they take a few cycles to get conditioned. A smart charger will switch off earlier if the cell is ready. I have a friend who took his smart charger back to the shop because of this, and swapped it for a timer based charger because he said it charged them better. If only there were an RSPCA for batteries.
Bob
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dead NiCds.

really *are* intelligent chargers. Unless they actually mention that they're 'delta V' or similar how is one to tell?
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snipped-for-privacy@isbd.co.uk wrote:

course but only occurs in very specific (and thus rare) conditions. It occurs when NiCds are recharged at regular intervals by exactly the same amount. It was noticed (as previous poster said) when NiCds in a satellite were recharged *very* regularly by solar cells. The amount of discharge was always the same and recharging occurred at exactly the same (sunrise) time. After, I believe, some hundreds of cycles like this the NiCds lost capacity.
The chances of repeating this regularity in a domestic situation are miniscule.
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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
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Oldskoolskater wrote:

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
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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.
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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
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IMM wrote:

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

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110? hang on I'll me coat.
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IMM wrote:

usually with 4 batteries, and should charge them in 1-2 hours.
Bob
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intelligent charger?
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snipped-for-privacy@isbd.co.uk writes:

Give it an IQ test.
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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
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On 2 Dec 2003 23:57:15 -0800, snipped-for-privacy@mailinator.com (Oldskoolskater) wrote:

Don't charge batteries, charge individual cells.
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