How many Hours is 680 mAh?

That 680 mAh means the battery will put out 680 milliamps for one hour. If you use less than 680 mA, it will last longer than an hour, if you use more, it will not last as long between charges. The only practical use for this info is as a basis for comparison between batteries.

mAh is not a measure of time, its is a measure of a battery's total capacity. The higher the number the more charge the battery can hold.

A 270mAH hour cell can in theory deliver:270mAH for 1 hour27mAH for 10 hours2.7mAH for 100 hours27A for 1/10 hour (=6mins)270A for 1/100 hour (=0.6mins = 36 sec)in theory, but in practice cells are not efficient at high curents and other things impose lower limits (like the thickness of metal in the cells internal construction/wiring.The amount of current a cell can deliver for 1 hour is known as the C rating.The standard charge current for most cells is usually 1/10th C which in your case is 27mA or 0.027A it's the same thing. It theory it should take 10 hours to charge your cell at 1/10th C but because the charge process is also inefficient it normally takes about 14 hours.Fast charging is usually defined as anything over about 1C or 2C eg 270mA (=0.27A) or 540mA (=0.54A) in your case.If your cells are designed for fast charging then you should be ok at 0.5A and possibly more.At 2C your cells should take about 1/2 hour to charge. At 3C its 1/3rd hour = 20mins etc

680mA for one hour. The number of hours depends on how much current you electronic device is going to draw.