It would be difficult to precisely estimate how much charge is left in the battery and how long it should take to recharge it precisely. Smart chargers will back off the current when the batteries are fully charged so that they do not overheat. Doing it manually will be a guessing game.
Originally Posted by froze
My understanding...which is limited, is that if the battery takes for example 8 hours to fully charge and you don't have a timer but set the timer to shut off after 8 hours then how is that different then a charger with a built in timer that shuts it off after 8 hours? The temperture is the same regardless if the charger shuts it off or the timer does it after 8 hours. Supposely...note I said supposely, that the Cygolite company claims that their NiMh battery has more time latitude before damage can be done to the battery then other NiMh's which is why other companies use smart chargers. BUT I have sent Cygolite a E-mail concerning this problem and will see what they have to say and will share it with you all.