Do conventional/commercial AC to DC adapters have floating grounds?

Question

That is, could I stack two 12V DC adapters and get 24V DC?

Answer 1

Charles B: No the current capability doesn't change. It's like batteries in series. If the batteries can provide 1 Amp (for a while) the pair of them in series can provide 1 Amp (for a while). The voltage of the pair is the sum of the individual batteries. The voltage is important. Example: your computer's power supply has a 5V output for the chips that need 5V power. If the power supply has the ability to provide enough current, the current will be whatever the 5V circuits demand.

Randy G: the outputs of the 2 adapters would be stacked.

supastremph: Yes they typically do. (Wasn't always the case. I nearly welded the telescoping antenna of a portable radio to the faucet when I took the radio into the bathroom with me. The antenna became hot - 110V - because of the polarity with which I plugged it into the AC outlet. Fried the radio. Could have fried me. So you better double check the ones you have.)

Don't use this rig to charge a 24 V battery. There are so many different technologies of batteries now. Each has its own requirements for proper charging. But if you're planning to power a 24V circuit with it, that should work. Provided the current is adequate. For instance, if both are rated 12 VDC @ 1 Amp, the stacked adapters will be able to provide 24 VDC @ any current level up to 1 Amp.

Answer 2

Most, but not all, have isolated outputs. There's no fundamental reason for the output of a DC supply to be grounded. Read the specs on isolation.

If they are regulated supplies, be sure there's a resistive and capacitive load across each, or you could get some strange feedback resonances.

If they are the cheap wall-wart adapters, the only way to find out is by experimenting and measuring and taking your chances.

Answer 3

Ok, wow I actually went over this recently. Yes, you CAN easily turn 12 v DC into 24V DC, but that wouldn't do anything. What would happen is your current, pretty much the speed of electricity, would be cut in half, and the power output would be about the same. So, yes, you can do it, but, why would you want to? Its not really the properties of voltage that we want, since voltage is potential. We need current, and power.

Answer 4

How would you stack them? You could not feed the DC OUTPUT of on AC/DC adapter into the INPUT of another AC/DC adapter (it expects to have AC as its input, not DC).

===edit===

Here is how to build your own 24 volt DC power supply that runs off of 120 volts AC.

===edit2===

I forgot to add, if you feed DC voltage into the AC input side of a power supply (like the DC output of a first AC/DC converter into the AC input of a second AC/DC converter), then your first AC/DC converter will probably burn itself out, since the primary side of the transformer in a typical AC/DC converter will seem like a straight wire (i.e.: no load) to the first converter.

Sounds like a good way to start a fire.