using 12 volt battery with a 7.2 volt drill

 

Hello
Can I use a 12 volt battery with a 7.2 volt drill.  these are for basic
robotics we are trying to get into.  Also would a 12 volt battery power
a 14.4 or 18 volt drill.
Thanks
Mike

 



Mike wrote:


Google Groupie alert !

WTF makes you think you *could*  ?

Graham

 


with PWM limiting the current that should be OK. without it may not last long.


can't get any 12V drills cheaply ?

14.4 would probably be OK, 18 probably not.

Bye.
   Jasen

 



Yes you can but what would be the results?
DC motors of this type are quite tolerant of overvoltage and would spin a
little faster and get a little hotter, (more than just a little under load).
Providing less voltage will reduce the RPMs and torque.
Since you are beginning robotics, I would like to suggest that you get used
to following specifications.
Regards,
Tom

 


Mike wrote:

Hi, Mike.  I guess you could use a 12V battery for a 7.2V motor, if you
drop the extra volts.  The simplest way to do this would be to get a
string of five 1N5402 diodes, and put them in series between the
battery and the motor like this (view in fixed font or M$ Notepad):

|
|          5 X 1N5402
|
|      .-->|-->|-->|-->|-->|--.
|      |                      |
|     +|                     / \
|     ---                   ( M )
| 12V  -                     \_/
|      |                      |
|      |                      |
|      '----------------------'
|
|
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

This is OK for a small motor that's drawing less than 3 amps full load.
 Of course, you'd be wasting 5/12ths of your battery power as useless
heat.  And the diodes aren't going to regulate the motor voltage all
that well.

Speed and power of DC motors is dependent on input voltage.  So, your
14.4V and 18V motors will run, although the 18V one will be slow and
weak.

Better to think 'er over, and get the right parts for the job.  There
are plenty of DC motors available for robotics that are made for 12V
batteries.

Good luck
Chris