What is the maximum time for charging batteries for digital camera?

I'm not sure what you're trying to learn but let鈥檚 see what I can do about answering your question anyway.

First of all the maximum time depends on the charger. It can take as little as fifteen minutes with a fast charger and NiMH AA batteries to as long as sixteen hours. Some chargers are designed to charge very fast, others provide a trickle charge only. Now that doesn鈥檛 mean you should buy a fast charger, in fact sometimes it鈥檚 better to have both extremes. The fast chargers tend to really stress the batteries and often you鈥檒l find that after fifteen minutes the batteries are very hot. The slow chargers don鈥檛 stress the batteries and thereby extend battery life making it possible to recharge the batteries more often in the longer term. What I usually do is keep a set of batteries charging slowly and I use the fast charger only if I need an instant charge, something that doesn鈥檛 happen too often.

How long batteries can be left in the charger after they鈥檙e charged is another question. NiMH batteries shouldn鈥檛 be left in a charger beyond their charging time. This too can stress the batteries and shorten their life. However that depends on the charger. Trickle chargers (the ones that take up to sixteen hours) have such a minimal effect on the batteries that you can forget them for a day or two without damage. In addition, many chargers are smart, that is, they will turn themselves off when the batteries reach a full charge and will turn on only when the battery has discharged a little. When it comes to smart chargers you can leave the batteries in them until you happen to remember to take them out. That鈥檚 one reason I own a trickle charger, so I don鈥檛 always have to remember to remove the batteries at the end of the charge.

So that鈥檚 the story with the NiMH batteries. Similar rules tend to apply to the lithium ion batteries as well. If you have a smart charger you don鈥檛 have to worry about removing them quickly, if you have a regular charger I鈥檇 not leave them in the charger more than a day. One difference though is that heat doesn鈥檛 tend to damage the lithium ion batteries as much so fast chargers don鈥檛 usually hurt their longevity.

The rules for nicads are more stringent. They must be removed from the charger when they鈥檙e finished, even a day in the charger is not usually good. And they should be charged only when they have run down whereas the others can be topped up any time. Fast chargers for nicads aren鈥檛 usually recommended either. But this point is academic, you really shouldn鈥檛 be using nicads any more anyway. They hold a lot less power than the other types and they do not last as long either.

I hope this answers your question.

1-6 hours depending on batteries being used(aa-6 hrs./litium-1hr.)

It will depend upon the capacity of the batteries and the power of the charger. There's no one right answer.

For example, AA NiMH batteries may take as short as 15 minutes to charge or as long as over 15 hours, depending upon the batteries and charger.

Lithium rechargeable batteries can typically be charged within an hour or so.

NiMH AA's should not be overcharged,as the heat damages them. You can try to compute the maximum charge by taking the capacity and dividing it by the amperage of the charger, but that's a crude measurement. Advanced chargers actually measure the battery temperature and voltage, cutting off the current or reducing it when the batteries are fully charged. Advanced chargers will often "trickle charge" their batteries--providing just enough current to keep them from self discharging. You shouldn't leave NiMH batteries on indefinite trickle charge.

A fully discharged Nikon EN-EL3e Lithium-Ion battery takes just over two hours using the Nikon MH-18a quick charger.

That said, when it comes to long lasting batteries, this experience may have been a record or it may be the result of good power management.

In a nine and a half week period, while on assignment in the Caribbean, my Nikon D100 w/MB-D100 (contained two Li-ion batteries) only had to be charged twice.

I shot over 12 GB of large, fine JPEG images downloading using a card reader attached to my notebook computer. I did not use the LCD screen except when there was difficult lighting (rare in the islands) and turned off the camera after nearly every shot.

My D200's are not that miserly with batteries. It may have a lot to do with the larger MP count, larger LCD screen and other energy using features on the camera, although I can shoot a couple of full days (a few hundred shots a day) without needing to recharge the batteries. With the MD-D200 when one battery is exhausted, I can take it out and recharge it and use the battery that is left in the battery pack.