# How many amps does a cordless drill use?



## BatteryCharger (Dec 28, 2005)

I have an old Craftsman Versapak 7.2v cordless drill that I haven't used in probably 5 years. The original 1.2ah NiCd batteries bit the dust years ago. Being 7.2v, it would be a perfect candidate for a new li-ion pack.

Does anybody know roughly how many amps a small drill like this uses? I'd measure it myself but I don't have any 7.2v source to hook it up to right now. I'm just wondering if regular ~2000mah lithium ion batteries will work, or if I'll have to get some of the high discharge lithium polymer batteries...


----------



## BentHeadTX (Dec 28, 2005)

Usually, cordless drills pull a huge amounts of power from the cells--an area were NiCads deliver. 

One thing you can do is see what wattage the drill motor is rated and do the calculation. If the motor is 20 watts or less you should be able to get away with using Lithium Polymers. Normally cordless drills have much more powerful motors so the amp draw comes a concern when using LiPos or LiIons.

I have been using a Milwaukee 28V Lithium-Ion drill for the last few weeks and it's 28V 3.0Ah pack can punch 50 to 100 amps! Very special cells though, maybe sometime in 2006 you can get bare cells to build a pack with. The warning is the batteries are $129 each so it will not be a cheap way to do it. I would just rebuild the packs with NiCads since you have a charger and you know it will work. 

The Milwaukee 28V LithiumIon packs have changed my view on the current abilities of rechargable lithium batteries--the Milwaukee special type and the upcoming A123 systems Lithium-Ions should create a revolution in batterys for personal transportion, power tools and maybe trickle down to flashlights. 

Imagine a Surefire DARPA with A123 systems 7.2V 3.0Ah Lithium-Ion packs


----------



## CNC Dan (Dec 28, 2005)

BatteryCharger said:


> I have an old Craftsman Versapak 7.2v cordless drill that I haven't used in probably 5 years. The original 1.2ah NiCd batteries bit the dust years ago. Being 7.2v, it would be a perfect candidate for a new li-ion pack.



I'm not familiar with the versa-pak system, but most full size cordless drills can draw over 20 amps. My old sears 12v drill was a bit weaker than todays drills and it pulled just under 20 amps. I gutted a dead pack and added a cord to it so I could use it with some some of the SLAs that I had arround. I started with a 10 amp fuse and kept increasing it untill it didn't blow under load.


----------



## gadget_lover (Dec 29, 2005)

The old versapack based drills were pretty weak, but if all you needed was to drill a few holes it was a handy thing to have around. I wonder if they have a wattage rating stamped on the tool somewhere? You could then calculate the amps requirement.

I've considered rebuilding a few of the power packs using quick charge NiMH cells. My versapack based tools include a real handy 3 inch circular trim saw that I've wanted to use once or twice a year.


----------



## BatteryCharger (Dec 29, 2005)

Yes, this is a very low power drill. I seem to remember it having trouble driving some 3" deck screws. Even so, it's more than enough for small screws or drilling small holes. I had it open a few days ago and didn't notice any markings on the motor, though I didn't look at the bottom side of it.

I just can't imagine a 1.2ah NiCd battery with mid '90s technology could put out more than about 3 amps for any useful length of time...am I wrong?


----------



## MoonRise (Dec 30, 2005)

The VersaPak batteries are 3.6 V each, the drill sounds like it uses two batteries to get the 7.2 V.

You can get a new VersaPak 3.6V battery, with NiMH cells inside, at Home Depot for $17 each. Go to their website and search for "versapak".

A NiCad cell can put out some pretty good amps, especially once you get bigger in size than a AA cell. A NiCad AA can put out a 'flash amps' of somewhere in the high single-digits/low-teens of amps.

But all that is just the max current capability of the cell, you would need to find out what the max current draw of the motor is. AFAIK, small drill motors that use rechargeable batteries usually don't list the current draw on the product nameplate, while corded devices or devices that can/will be wired to AC power will have the electrical specs (voltage, current, phases, etc) listed on the nameplate.

Your call as to just buying two new batteries or trying to rebuild the existing 'tubes'.


----------



## snakebite (Dec 30, 2005)

forget rebuilding versapak sticks.
they are crimped together at the contact end.they are dirt cheap at walmart.
got a few nicd out of the closeout aisle for $2 ea.
they use 4/5 sc cells to complicate things further.
many li-ion cells can deliver high current now but the mosfets on the protection unit is the weak spot.


----------

