temporary Power supply suggestion

Thread Starter


Joined Feb 2, 2018
I have a 110V two cycle generator I use for camping and I want to turn it off remotely at night without going out in the cold and hitting the kill button. I bought a 12vdc RF wireless Remote Control relay switch to use to short the coil and kill the generator engine and a small 12vdc transformer to provide the 12vdc power.

The problem is that when I trigger the remote kill, the remote relay locks closed and the generator starts to die, but so does the 110VAC, and subsequently the 12Vdc, and then the remote relay loses power, opens, and the generator continues running. I need a temporary power supply which will keep the remote relay working for 15 - 30 seconds after the 110 VAC is killed. I could simply hook up a battery, but the generator sits for months without running and the battery would be dead every time I try to use it.

I also do not want to carry around a big 12 volt battery for only such a small task. I am thinking there might be a way to use a capacitor as a temporary power supply. The generator runs for hours prior to killing it at night so there is plenty of time to charge a capacitor. I also guess I could get a small rechargeable 12 VDC battery (the relay will supposedly run off a A23 Battery), like for a remote garage door opener, and simply charge it up every time, but charging and completely discharge those batteries is not suppose to be good practice. Any suggestions on a solution?

The 12Vdc remote relay I have can be found on Amazon as "
O'plaza ®Dc 12V 10A Relay RF Wireless Remote Control Receiver Momentary Switch (12V 1 Channel)", but I have no idea how much current it draws.


Joined Jan 29, 2010
That 12Vdc relay requires 30mA to 35mA to operate.
You should add a few more mA's for the electronics, say 50mA total

Thread Starter


Joined Feb 2, 2018
Well I figured out a solution. Not sure how it will work in the long run. I found a 9Vdc rechargeable battery and wired it in parallel to the 12 VDC power supply. When the generator turns on, the 12 VDC power charges the 9 Volt battery and the 9 volt battery provides enough power to keep the relay functioning when the generator is turning off. I will have to see how long the 9V battery lasts being on a 12v circuit. I would have been cleaner to figure out how to wire a capacitor in parallel to provide temporary power, but ran out of time. I did try a 1000 uF capacitor in parallel, but it drained really fast once the power was off and I activated the relay. I am thinking the mechanical relay takes quite a bit of power.


Joined Oct 29, 2013
You can get what's called a latching relay, which takes only a pulse to turn on or off and then it stays in that state until you give it a pulse in the other direction.


Joined Feb 8, 2018
You can get what's called a latching relay, which takes only a pulse to turn on or off and then it stays in that state until you give it a pulse in the other direction.
That makes for an "interesting" problem when it comes time to restart the generator.

You could make a manually resettable latching relay of sorts out of a mouse trap and a small solenoid.


Joined Mar 14, 2008
A way to avoid a battery--
Connect the the kill contacts to the NC relay contacts in series with a toggle switch.
Open the toggle switch to start the generator.
Now with power from the generator available, push the remote to operate the relay and open the contact.
Close the toggle switch.
Now when you toggle the relay off to close the NC contacts and stop the generator, the loss of power will have no effect.
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Joined Nov 22, 2017
Use AGASTAT 7000 Series, Industrial Electropneumatic Timing Relay:
Instant Transfer (Auxiliary Switch
Code L, maximum of 1 per relay.)
1. Energizing coil transfers main and
auxiliary switches instantly.
2. De-energizing coil resets auxiliary
switch and begins time delay.
3. Main switch transfers after total
preset delay.
Auxiliary switch is factory adjusted to
give instant transfer operation. Two-step
timing may be set at the factory to cus-
tomer specification up to a 3:2 ratio



Joined Jan 23, 2018
The agastat relay is bigger and heavier than the 12 volt battery..Also more expensive.
The solution by Crutschow will work very well. Another solution would be an extension cable to bring the kill switch inside the tent, alongside the power cord you already have. Simple and reliable andprobably lighter to carry.