battery charge time

This is actually slightly computer related. I am setting up several computers. The electrical outlets are under the table. The tables are permanently mounted to the wall. I am having to drill holes through the table to plug in the computers.

I know that this is pretty far off the usual topics, but maybe someone can take pity on me. I have a cordless drill with an 18 volt battery. The charger says: Input 120 V AC ~ 60 Hz Output 22 V DC, 500 mA.

So, how long do I have to leave the battery on the charger, or is the time required impossible to determine given the details? I'd rather not leave my equipment here over night.

I am pretty stupid when it comes to electrical formulas and conversions.

Almost all of the newer battery operated tools come with a 'quick charger' that takes 3-5 hours tops.

Take it home, charge it while you sleep.

Yes, as CCT says. You have to know the battery rating and the actual charge current to calculate charging time. The 500mA rating is the charger pack's maximum output, although for common arrangements, you could probably take it as the charge rate. If the battery pack has an Ampere/Hour rating you could assume a charging time based on the 500mA - eg if the battery has 2.5AH (2500mAH) label, 5 hours (nominal) charging time.

Ok. Thanks to both of you for the replies. I just want to be cautious not to shorten my battery life. I know that newer rechargeable batteries are less susceptible to the memory effect for short charging, but I want to make sure that I get a full charge, just the same.

The newer batteries require FULL discharge during early use before re-charging to allow their 'memory' (gawd I hate this new tech crap) to ensure they fully charge the next time.


I suggest, if it isn't fully discharged, and you don't have a spare battery that you alternate, to BUY A SPARE BATTERY THAT YOU ALTERNATE!


I don't mean this nastilly, but you can either kill the one or alternate the two.

:)