Electronics > Beginners
Conversion of a beard trimmer from nimh to Li-ion
james_s:
Should be lots of different modules that will do that.
I would try just running the motor direct from the battery though, most small DC motors work nicely over quite a large voltage range. Otherwise look for a LiFePO4 cell, lower voltage than most Li-ion types.
6PTsocket:
A silicon diode has a typical forward drop of .7 volts. Two in series drops 1.4 volts.Not very elegant and wastes a little power. Just make sure you use diodes that can handle the current. The 1N4xxx series are only good for an amp. You'll have to look it up.
--- Quote from: downloaders on September 06, 2018, 12:32:40 pm ---So the step down module came, and guess what? I does not work. I should have measured the current. The module goes up to 500ma and When measured, the motor needs max 1.5A when i hold it down a bit like when cutting beard.
I couldn't find any step down module that could turn a 4.2 - 3.5V to 3V with 1.5A or more.
Does anybody know one that I could use, or some other way to bring the voltage down to 3v from 4.2 - 3.5V?
Thanks!!
--- End quote ---
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6PTsocket:
I apologize if I am hijacking the thread but I have a very similar situation. I have an old Iso tip soldering pencil. The power is a 2 cell NiCd sub C pack rated for maybe 1300mah. It has a 1 hr charger. There is a thermal switch mounted against the battery that trips when the temp rises at full charge. This was a common charge method with NiCds and cheaper than more sophisticated methods. The switch is bypassed with a resistor to maintain a trickle charge. Trickle charging is the death of NiCd's and the real reason for loss if capacity, not memory. The memory problem was corrected in the early days of NiCd production but the story stuck, according to Battery University.The battery is long dead. I can put in some 2Ah sub C's and charge with my smart charger that does no need any thermal sensing but as I use the iron so seldom, I thought I might want to use an 18650. The lithiums in my Bosch tools seem to stay charged forever. My concern is what to do with the extra 1.2 volts. I could use a couple of diodes and get close but that is wasteful and maybe too much heat inside the case. Unlike a motor, the soldering tips wjth built in element might not tolerate the extra voltage. If there is no good solution I will stick with better NiCds and my smart charger.
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