2 19VDC laptop chargers in series

[jason701802]

Originally Posted by Ether

Even though they're isolated (so there's no leakage path), I still wonder:

1) These chargers are designed to source current, not sink it.

2) They're probably switching technology.

3) If one's switched "on" while the other's switched "off", then the "off" one sees the "on" one trying to push current through it. That's where I think Eric's earlier comment may come into play. Wish I knew more about this kind of stuff.

Isolated switching power supplies (which A/C supplied switching power supplies usually are) can easily be and are regularly hooked in series. The supply will never be sinking current, current will always be going out the (+) terminal and in the (-) terminal. To be safe, reverse biased diodes should be connected to each output so that if one power supply comes on more quickly, it will not apply reverse voltage to the other. See here: http://www.acopian.com/acopianPowerS...y.aspx?nsId=17

Originally Posted by jwallace15

Adding them in parallel will double the amperage.

While this is true for linear power supplies, it is not true for switching power supplies unless they are specifically designed for it. Because the output voltage of a switching power supply is actively controlled, any minute differences in output voltage will result in the supplies fighting each other. It will work for supplies that are well matched, but because they will use some current fighting each other, the available current will be less than combined rating and should only be done temporarily when there are no other options.