03-10-2018, 06:22 PM
This is a followup to the thread about building an adapter to run a lithium battery in a tool that previously took nicads Adapter to use Lithium batteries in Nicad tools. I've been using it a bit, mostly in a 14.4 impactor building a side gate to the back yard. It worked great in that tool. However, when I initially plugged it into my Bosch 18v jigsaw, the motor kicked and then nothing. It has worked fine in all my drills as well as the reciprocating saw.
So today I decided to see what was going on with the jigsaw. I opened it up after a bit, got the motor out of the tool. I could barely turn the armature. I blew the dust out and used some brake cleaner to flush the armature. After a bit I got it to spin a bit, not really smooth, but it was moving. I was able to plug the trigger switch into an 18v nicad and the motor would spin up. It wasn't spinning as smoothly as I think it was designed to, and would at times hit a spot where it seemed to jam. I looked online and saw that a replacement motor is about 90 bucks, so that option is not an option.
I then decided to plug it into the adapter with the 18v lithium battery. It ran a bit then stopped. I twisted the armature a bit and tried again. Motor got really hot and started to smoke. Wires to the motor were warm, switch was hot. Not good.
[attachment=9024]
At this point I'm going to be a bit subjective and start to make some guesses as to what happened. This tool is geared down quite a bit. Since a lithium battery can dump way more current than a nicad, I think due to the mechanical resistance the motor has to turn, the excess current quickly overheated the motor windings causing it to bind since clearances seem to be very tight. Now why the recip saw works fine and this one has problems, I'm not sure.
At this point, the motor is smoked, shame since it is a really nice tool. I could replace it with another one (Ebay has one for 60 with free shipping) but it may end up the same. I can get a NIB lithium version saw for less than a 100 so I may go that route, since I now have two lithium batteries to use with it.
So today I decided to see what was going on with the jigsaw. I opened it up after a bit, got the motor out of the tool. I could barely turn the armature. I blew the dust out and used some brake cleaner to flush the armature. After a bit I got it to spin a bit, not really smooth, but it was moving. I was able to plug the trigger switch into an 18v nicad and the motor would spin up. It wasn't spinning as smoothly as I think it was designed to, and would at times hit a spot where it seemed to jam. I looked online and saw that a replacement motor is about 90 bucks, so that option is not an option.
I then decided to plug it into the adapter with the 18v lithium battery. It ran a bit then stopped. I twisted the armature a bit and tried again. Motor got really hot and started to smoke. Wires to the motor were warm, switch was hot. Not good.
[attachment=9024]
At this point I'm going to be a bit subjective and start to make some guesses as to what happened. This tool is geared down quite a bit. Since a lithium battery can dump way more current than a nicad, I think due to the mechanical resistance the motor has to turn, the excess current quickly overheated the motor windings causing it to bind since clearances seem to be very tight. Now why the recip saw works fine and this one has problems, I'm not sure.
At this point, the motor is smoked, shame since it is a really nice tool. I could replace it with another one (Ebay has one for 60 with free shipping) but it may end up the same. I can get a NIB lithium version saw for less than a 100 so I may go that route, since I now have two lithium batteries to use with it.
