We plan on placing a +12VDC AC adaptor (110-220AC, which will plug into an outlet) in parallel with a battery connector using a "Y" connector, so that the user can operate our device using either a battery, or the wall adaptor. ONLY EITHER the battery or the wall adaptor will be hooked up at any time.
Here is the adaptor we will use:
However, will the impedance of the AC adaptor (when it's not plugged in) be sufficiently high enough to make the current draw on the battery insignificant?
Because if the adaptor looks anything like the following:
Then I'm not worried about the half-wave rectifying diode, but rather the shunt Zener diode which is only 8.2V.
I'm hoping that the current draw going into the adaptor will be insignificant, so that i can wire it in parallel to the battery connector, without having to hassle with putting a relay or switch in there.
Maybe i can just solder in a series diode in-line with the AC adaptor....