How long does the battery hold a chaarge when not in use?

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I bought one of the ebay travel wall chargers, and had been keeping my spare battery in the cradle of the charger in my camera bag. I was surprised today when I put it in the camera to find that it was completely dead. I had put the fully charged battery in the bag a little more than two weeks ago. Is is possible that keeping it in the cradle of the charger is somehow depleting the charge? Or is two+ weeks simply too long to expect the battery to keep a charge?
 
battery are self discharging, rate depends technology.
Li-ion (most common today) are about 10% per week, but will definitely not discharge totally. (will probably stay at nominal voltage for months)
If you leave any battery on a device , even off, the circuit will be still probably closed enough to discharge batterey slowly, and even worse, totally.
This will likely kill the battery very fast.
since old technology (Nicad) was known for memory effect, it was advised to store them empty.
With li-ion and other technology is it advised to store them fully charged, or leave them on a live charger.
deep discharge of any battery is always good time to time, but never under nominal voltage.
L-ion element are 3.6V (or multiple 7.2, 14.4) but once charged, it is a bit more (4.2, 8.4, 16.8).
 
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It is true that the Li-ion battery will be discharging into the charger, but it will unlikely be damaged as there is a safety circuit inside, which prevents over discharge. It puts the battery to sleep by disconnecting the cells from the battery contacts. Just recharge it, and see if it works.
 
This explains my aftermarket batteries sucking, I charge them, leave them on the charger for 2 or 3 weeks, then pop them in the camera and get about 1/2 the run time I get out of the stock battery freshly charged. I shoulda known this from years of R/C cars
 
Self discharge rate is affected by temperature. Some people leave them in a fridge, or if you have the time to let them thaw before use the freezer
 
nosys70 said:
since old technology (Nicad) was known for memory effect, it was advised to store them empty.
Click to expand...
I'm trying to find a University study I read years ago that the Ni-Cad memory effect was only on the very first cells made and was a myth for years.
nosys70 said:
With li-ion and other technology is it advised to store them fully charged, or leave them on a live charger.
deep discharge of any battery is always good time to time, but never under nominal voltage.
L-ion element are 3.6V (or multiple 7.2, 14.4) but once charged, it is a bit more (4.2, 8.4, 16.8).
Click to expand...

The same study said Lion Cell has a definite number of cycles. Meaning 1 full drain is equal to 2 half drains. Over time they can lose the ability to charge fully. The best way to keep Lion Cells at full strength is to buy twice what you need and only drain half. The worst thing you can do is deep discharge every time.

Also not mentioned was NiMH which some where around 5% a day.

My personal routine is to charge the day/night before a gig.
 
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