Check this thread
Powering UPS from inverter.
Excuse the colors it looked better till paint saved it in 256 color bitmap It was not my fault I did not read the box the computer did it I tell you.
Not sure if this would work or not, let me know what you think, it would be nice if it did work wouldn't it :-D the only thing I see wrong for it is the ground to the ACC wire, where would this go?
A complicated and expensive way to do something simple. And how are you going to start the computer?
By the time you buy all those parts you could have afforded an Opus.
I have the inverter, I can pick up a UPS for about $80 and a relay is $20 at the most expensive normally they are $7
Ok this is what you done wrong :
Your relay is switching the negative side of the battery to your inverter. Try to stick to standard by switching the positive side instead.
The ACC put out a +12V, I see you connected this to the relay coil. You must therefore connect the other end of the coil to GROUND.
Your circuit would just turn your inverter on controlled by the ACC line. Remember when you crank the ACC line do get cut off.
I agree with Ricky in that you need to ground the other side of your coil. However switching ground (even though "unstandard") will work fine, and is actually done more than many think. Most window motor control, car door locks etc switch ground. This is because keyless entry decoders create a closure to ground when activated and float when not activated.
Even with that going for you, you're still hosed.
This would work to turn off the computer ONLY if you set the UPS to shut down the computer when line voltage was lost.
However, this wouldn't start the computer unless you found a way to get the UPS to auto-start the computer when line voltage was re-applied.
Then the question remains as to how long a UPS will run switched on, with the computer switched off (still drawing power as we know power supplies still draw current even when their off) without line power to keep the battery charged.
Nice try though...
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