# CORDLESS DRILL RE-POWERING ??????????



## Madman (Jan 5, 2008)

I have a Milwaukee 2.4 cordless drill, the type that looks like a straight piece of pipe but folds to form a more traditional style handle, that I have a question about re-powering. The batteries have ceased to be of service, and the drill is not worth the expense of new ones. As mentioned, the batteries are 2.4 volts DC. So if I were to power the drill with my LGB power pack, and turn the throttle up to as close to 2.4 volts as possible, the motor should turn. Such is not the case. I get a barely audible hum. I know the drill is OK. So what's the problem?


----------



## dbodnar (Jan 2, 2008)

Dan - without putting a meter on the thing my best would be that the power supply is not able to provide sufficient current to turn the motor & gears. Those batteries can supply several amps at start-up / your power supply probably cannot. 

Try it with two fresh AA or C or D cells and see what happens. 

dave


----------



## Madman (Jan 5, 2008)

Incredible! I wired it to two D cells, and it performs better than the original NiCad battery. The LGB power pack is rated at 1 Amp. I can't believe that two D cells have more amperage or power. But seeing is believing. 
Thanks Dave.


----------



## RimfireJim (Mar 25, 2009)

Posted By Madman on 18 Aug 2010 08:28 PM 
Incredible! I wired it to two D cells, and it performs better than the original NiCad battery. The LGB power pack is rated at 1 Amp. I can't believe that two D cells have more amperage or power. But seeing is believing. 
Thanks Dave. 

According to Eveready's technical data sheet for Energizer alkaline D cells (here), 1 Amp is at the upper limit of practicality, or maybe beyond. I suspect 1) the screwdriver isn't drawing 1 Amp no-load, and 2) something is goofy trying to power it from the LGB pack.


----------



## krs (Feb 29, 2008)

Posted By RimfireJim on 18 Aug 2010 08:53 PM 

According to Eveready's technical data sheet for Energizer alkaline D cells (here), 1 Amp is at the upper limit of practicality, or maybe beyond. I suspect 1) the screwdriver isn't drawing 1 Amp no-load, and 2) something is goofy trying to power it from the LGB pack.



I'm not sure how you came to the "1 amp upper limit" conclusion.

With a 150 - 300 milliohm internal resistance that D cell can deliver 5 to 10 amps into a short circuit for a brief period of time, a lot more than a basic LGB power pack.


----------



## John J (Dec 29, 2007)

I have a Ridgid 18 volt cordless drill I use the batteries for my trains. I hooked up a Amp meter between the cordless drill and the batteries. It draws 5 to 6 amps NO LOAD CONDITION. 

Two SD-45s up on blocks draw 3 amps. 

Why am I telling you this? I have no idea


----------



## dbodnar (Jan 2, 2008)

Gentlemen - another trick I have used to activate motors from power drills with large (Darlington or Mosfet) transistors is to put a high wattage, low resistance resistor in series with one of the motor's leads. You will have to experiment with exact values as it is dependent on the specific motor. I have used 1 ohm / 10 watt up to 10 ohm / 10 watt resistors with success with different drills.

The reason that they draw so much current is that most power drills and power screwdrivers have planetary gear systems that generate lots of friction when they move.

I used such a gear system from an old power drill to change the tilt on a rotating 48" diameter train table that I put together for the ECLSTS a few years ago. See: 

Tilt-a-Whirl Train 

dave


----------



## RimfireJim (Mar 25, 2009)

Posted By John J on 19 Aug 2010 08:12 AM 

Why am I telling you this? I have no idea 
Now that is one of the most refreshing bits of pure honesty I've seen on a forum in a long time!


----------



## RimfireJim (Mar 25, 2009)

Posted By krs on 18 Aug 2010 10:58 PM 
Posted By RimfireJim on 18 Aug 2010 08:53 PM 

According to Eveready's technical data sheet for Energizer alkaline D cells (here), 1 Amp is at the upper limit of practicality, or maybe beyond. I suspect 1) the screwdriver isn't drawing 1 Amp no-load, and 2) something is goofy trying to power it from the LGB pack.



I'm not sure how you came to the "1 amp upper limit" conclusion.

With a 150 - 300 milliohm internal resistance that D cell can deliver 5 to 10 amps into a short circuit for a brief period of time, a lot more than a basic LGB power pack.


I based it on the service life graph, which maxed out at 1000mA with a corresponding voltage drop to 1.2V and service life of 1 hr. That's what I meant by "practicality". I'm sure you're right about the higher current capacity for brief periods (I thought about doing the calc using the internal resistance, but my brain was already fried from a day at work) - that's why they work for powering the ignitors used for model rockets, which are about a 1 Ohm load. What I couldn't tell from the OP's info is how long he ran the screwdriver on the D cells.

I believe the screwdriver has sub-c Ni-Cd batteries, which have an internal resistance of less than 10 mOhm, so it could very well be that the load is well above 1 Amp.


----------



## Greg Elmassian (Jan 3, 2008)

Yep, the "service life" on the battery (that is how long you can use it before you recharge it) is much shorter than what you would expect from disposable batteries. Therefore the current you draw can be pretty darn high. 

Put a 1 ohm load on a D cell and see how much current you draw! 

Remember that motors also are not a nice constant current source, when you first start them, they are in "locked rotor" mode, and for a brief period, draw a much larger amount of current, they really do look like a short circuit for a while. 

All of this goes hand in hand with what was observed, an anemic LGB transformer which cannot handle high surge currents, vs. a battery which will deliver gobs of amps into a low resistance load. 

Regards, Greg


----------



## rmcintir (Apr 24, 2009)

Posted By John J on 19 Aug 2010 08:12 AM 
I have a Ridgid 18 volt cordless drill I use the batteries for my trains. I hooked up a Amp meter between the cordless drill and the batteries. It draws 5 to 6 amps NO LOAD CONDITION. 

Two SD-45s up on blocks draw 3 amps. 

Why am I telling you this? I have no idea 
An SD-45 at full stall (4 motors) draws right at 9 amps.

I have no idea why I did this (could have damaged the loco). Actually I did some brutal testing of my receiver.


----------



## krs (Feb 29, 2008)

Posted By rmcintir on 02 Sep 2010 06:08 PM 

An SD-45 at full stall (4 motors) draws right at 9 amps.

I have no idea why I did this (could have damaged the loco). Actually I did some brutal testing of my receiver. 



At what voltage?

The stall current is voltage dependant. 


And if you don't want to take the risk of damaging the loco (a stall for a short period of time, a coupole of seconds, shouldn't be a problem) you can also get pretty close 
to the stall current value by measuring the DC resistance of the motor and then calculating the current.

We did that with about a dozen engines a few years ago and measured stall was within 10% of calculated stall.
The rick is to get an accurate resistance measurement which is not easy because the resistance of the motor is so low.


----------



## rmcintir (Apr 24, 2009)

Posted By krs on 02 Sep 2010 06:39 PM 
Posted By rmcintir on 02 Sep 2010 06:08 PM 

An SD-45 at full stall (4 motors) draws right at 9 amps.

I have no idea why I did this (could have damaged the loco). Actually I did some brutal testing of my receiver. 



At what voltage?

The stall current is voltage dependant. 


And if you don't want to take the risk of damaging the loco (a stall for a short period of time, a coupole of seconds, shouldn't be a problem) you can also get pretty close 
to the stall current value by measuring the DC resistance of the motor and then calculating the current.

We did that with about a dozen engines a few years ago and measured stall was within 10% of calculated stall.
The rick is to get an accurate resistance measurement which is not easy because the resistance of the motor is so low. 


V = IR


Actually it was at 18.5 volts. No damage to the drive line. Only did this a few times in testing (really dumb). Since there are 4 motors it's a bit tough to measure total the impedance with out individually measuring the motors. I only wanted to verify that my motor controller could (easily) handle the current draw. I tend to overbuild things, with a heat sink it can do 30 amps, 14 amps continuous without... In real life with a few bricks on top pushing a wall wall it would still have wheel slip and therefore never reach this insane amperage.


Did you post the results of your engine tests? Would be interesting to see. I no longer perform "stupid train tricks"  Too much risk of damage.


----------



## Ron Hill (Sep 25, 2008)

So ya'll are telling me that I can take my Craftsman 18V cordless battery, hook it up to my train engineer, run the antenna out the top of the car and it will power the thing? Cool! 
Ron


----------

