Convert 20v DC to 12v DC?

[TMG51]

How can I step 20v DC down to 12v DC?

I have a rechargeable Bluetooth speaker which I charge in my van and would also like to be able to power from one of my 20v DeWalt tool batteries. Is this feasible or more trouble than its worth?

 

[highdesertranger]

you could try an old Dodge coil resistor it drops 12v to 9v. if it doesn't burn out it should drop 20v to 15v. then there are the Chevy heat/AC resistor it has 2 step downs can't recall the amount of drop of the top of my head. both of these options will be cheap. on both of these the excess voltage will be turned into heat. highdesertranger

 

[blars]

You want a "buck" DC-DC converter. Readily available on ebay for cheap if you aren't in a hurry. (Shipping from china can take a month or more.) Specs tend to be very optomistic, most "3A" ones need a heatsink to run over 1A. The connectors may cost more and be harder to find.

 

[DwelledLongAgo]

Maybe with something like this?

uxcell DC 24V 36V 48V 60V (20V~72V) Step-Down to DC 12V 10A 120W Waterproof Car Power Supply Module Voltage Converter Regulator Transformer

 

[ZoNiE]

DC-DC converter, as stated above. However, if the current draw is low, you may get by with a simple 7805 voltage regulator screwed to an aluminum plate as a heat sink. they are easy to wire. Three pins. One input, one output, one common ground (center and the base).
Radio Shack carries them. The wiring diagram is on the back of the package

You can use a barrier strip to wire it. without soldering.

.

 

[SternWake]

https://www.amazon.com/DROK-Regulat...1971&sr=1-1-spons&keywords=drok+voltage&psc=1

https://www.amazon.com/DROK-Adjusta...8&qid=1477011971&sr=1-3&keywords=drok+voltage

I had a 2 amp version for a 1.3 amp fan which did not like battery charging voltages, So I limited it to 11v. 

11 volts was very stable even if battery voltage was swinging wildly.

There was 1 volt overhead so if battery dropped to 11.99v, then output voltage was 10.99v.