are the batteries ni-cad or lithium-ion ??
as a general rule of thumb, ni-cads tend to accumilate "memory" and thus start to supply less "useable charge" to the user. (you know..... if you use them but don`t dis-charge them completely before charging again).
lithium-ion batteries were origonally developed for uses such as laptops and mobile phones, but are now becoming ever increasingly used instead of ni-cads. They don`t develope "memory" and generally last longer in-terms of charge retension than ni-cads. (I don`t think that they can supply the sample current capacity though???? i.e. per unit weight, but I`m not sure).
anyhow for a pro workshop (being used every day), and being treated well (not being thrown about, generally looked after) 2 years is quite good life-time and you should probably look at getting some replacements. (I know for a fact that site-work means considerably less life-time!!!!!).
symptoms for a bad battery would include:
1) not holding charge properly (i.e. go flat very quickly)
2) excessive heat generated (by-product of electro-chemical reaction that supplies the current)
3) loss of power in the drill i.e. less torque
4) shortened charging times
a little tip is not to leave batteries charged if they aren`t going to be used for a while (i.e. more than a week). I have been told that this can effect the charge storage of a battery.
If the batteries in your case are ni-cads, try discharing them COMPLETELY i.e. running down completely flat, you may need to get a car-bulb and connect it across the terminal of the battery to do this to ensure that it is COMPLETELY flat (check it with a multi meter). Then charge it (on slow charge if available) and repeat a few times.
charge-discharge-charge-discharge being careful to completely discharge the battery.
SOMETIMES this can unlock the charge "memory" of the battery (an old cam-corder trick)
hope this helps!!
8)
