View Full Version : SMPS (battery charger) voltage output question

01-10-2012, 11:44 PM
Hello Everyone

I have a couple of questions pertaining to a DeWalt 7.2V - 14.4V one hour charger. With no load except that of a multi-meter, this battery charger has an output of 48VDC. I cannot imagine pumping 48V into a 7.2V battery, so I would also imagine that this output voltage will drop significantly when a load is applied. Is this assumption correct?

I would like to use this power supply (battery charger) to power up a motor, but I do not want to exceed 24V. Is there any possibility that the output of the charger will drop down to 24V or below?

Thanks in advance for any and all responses.


01-11-2012, 12:00 AM
Do you have some more specs for the charger by any chance?

I would be almost certain the voltage will drop when you connect the battery.

I suspect if it is switch mode, and it is a 1 hour fast charger, it will be doing things like sensing the voltage regularly and looking for the peak that you get when a battery is fully charged. So it would get very confused if you tried to power a load like a motor.

Of course, you could use the charger to charge the batteries, and then use the batteries to power the motor...

01-11-2012, 12:43 AM
Hey there Dr_Acula, I hope life has been treating you well.

It appears this charger has been recalled because it was causing batteries to burst and causing injuries. The automatic shutoff was not working properly. A VERY BAD THING for an unsuspecting construction worker. Glad it wasn't me that got injured.

Anyhow the specs are very limited and the owners manual is useless. On the charger it states:

Input: 120VAC 60Hz 2.0A
Output: 2.8A DC

There is a label on this which states the output at the charging is 120VAC. Hmmm....

I think I will attempt to hook up a smaller motor and test the voltage while it runs, if it runs that is :)

Additionally, I am looking for a cord and plug solution for a cordless DeWalt drill motor. You'll know why when you see the new machine. I hope this works, because I have modified the charger housing and I think it will look nice on the new machine. If not, then I just might build a linear supply and stick it this housing.

Thanks for your response.


01-11-2012, 01:02 AM

You were correct. It runs for a second or two and then shuts down, then it starts again and then it shuts down, just like a loop.