Buy a new drill ! :) Regards, Steve Maroney Business Computer Support, LLC -----Original Message----- From: veegee Sender: piclist-bounces@mit.edu Date: Sun, 24 Feb 2013 20:03:05=20 To: PICLIST Reply-To: "Microcontroller discussion list - Public." Subject: [EE] Driving an 18V drill at 24V Hi all, I have an old 18V battery powered drill which is missing its battery pack. I'm pretty sure the motor is a DC brushed motor, judging by the sparks and smell of ozone. I haven't opened it (or any other drill, for that matter) up yet to determine the trigger-switch mechanism, but it seems to be two-speed. Since battery packs are outrageously expensive, I'm thinking of using two cheap 12V AGM lead-acid batteries in series to power this thing. Very cheap, available anywhere, dead-simple maintenance, very high surge current, decently sized. Question: is it okay to build a simple PWM motor controller and drive this thing at 24V, with a reduced max duty cycle to prevent burning out the motor? Since it's a simple DC brushless motor, I'm assuming that it should be safe as long as the average power is kept below its max power at 18V. Suggestions? --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .