What is "overcharging" a NiMH battery?

[ballester]

I saw in Thomas Distribiuting customer reviews that a man both a new 204F charger and it overcharge his batteries... and he has to return the gadget...
I guess it doesn't give more power to the batteries, so, if you can explain me what happent to this man, because I have one of those chargers

Thanks for your time and help

Jorge

[kelly]

Found some information Jorge.

http://www.greenbatteries.com/documents/Ba...Charger_FAQ.htm

[ballester]

QUOTE(kelly @ Jun 5 2003, 2:40 PM)

Found some information Jorge.

http://www.greenbatteries.com/documents/Ba...Charger_FAQ.htm

 Thanks a lot kelly

My concern is because I bought 2 sets of Powerex 2200... and I really can't believe how long they last. I have one set in my new Olympus C-400Z and after 31/2 128MB cards with the LCD ON all the time, downloading all 3 cards with the power of the camera, using tha flash maybe half to the shots and using a lot of the noise reduction... they are still runnig...
I bought them because my 2 sets of 1800 NiMH (one Powerex, the other Nexel) just gave me enough power for about one card and a bit more (sometimes) with the LCD ON and downloading from the camera tha 128MB card...
I supposed that (using a Kindergarden logic) that the new ones will gave me about 20-25% more power... but no 300%...
I'm thrill, and I hope this is for real, and my original question were because of my desbelief, and heared that the batteries could be "overcharged" I thought (?) that the charger could overload the batteries, givind them more power (I don't see how... but), and damagin them on short terms...

I know that he best thing to do is to see what happens with the other set and with the one is in after they have been recharged, but I'm really impressed...

Thanks for hearing me again

Jorge

[Al]

Lots of great information there, Kelly.

Jorge, I use a lot of NiMH batteries to run my RC cars.  You would need a peak charger, one that senses the peak charge and shuts off.  Seems the charger in question just keeps charging and charging and charging.  I wouldn't know if they make peak chargers for the batteries that your using.  You can monitor the batteries by feel, when they start to get warm, then it is just about fully charged.  If they are sustained warm for a long time or get hot you have over charged them and it's life expectancy can and will be shortened.  Also, fast or rapid charging will shorten lifespan too, but not as fast as overheating them.

Edited to add.... After taking a look at your charger online, it is a peak charger.  It seems to be overcharging your peak charge time.  Everything else seems great.  You can discharge your batteries too.  It's not a great idea to trickle charge you batteries once they are fully charged, it will keep your batteries at peak, but it will also keep feeding a charge to them which will eventually shorten the batteries life.

[Bill]

ballester.
By far the best chargers are ones that have some form of thermal devise intergraded in there design.
This fraud thread gives a quick explanation.
Basically a thermal coupler identifies when the charge in question has reached close to its capacity and shuts the charging down.
More elaborate ones actually will 'know' when the charge is depleting while sitting on standby in the charger and turn to a trickle mode of some sort.

These thermal couplers are NOT very expensive for the manufactures to include in there chargers.
I really,really do not understand why this isn't a mandatory with all chargers?

Examples. Do you have any brand of cordless drill? 99.999% of the chargers that come with those cordless drills stop the charge of the battery when it reaches close to full.
Cordless landline telephones have a thermal devise (pending the brand and model) or a thermal which switches to the trickle mode.
Many household appliances. Same.

Why they don't include these in chargers like cameras,cells etc etc as mandatory,I'm at a loss?
You can rule out the cost factor.Demand is there hundred fold.
Back of my mind keeps shouting political politics in the industry.
-Hey! We can't do that! Then my cousin Rufus will get cut off from his monthly cut!-