Alright lads, I have fully assembled the circuit using a fourth relay in place of the XAC for now. Please see the most painful-to-watch circuit test video ever from a very nervous Aussie boi.
Feel free to like and subscribe 
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Nice work mate, Im looking forward to seeing your final assembly with the xAC.
Also interested to see the Total current draw when idle.
Here is a rough “guide” for you to consider if you dont use your car for a week or so.
- Here’s a rough guide and why I am suggesting this.
A “normal” expectation for most cars, with no power mitigation, would be approximately 2-3 weeks (depending on the age and type of vehicle, the battery and condition, accessories etc.)
Your battery in your car is a 60Ah battery
Normal Parasitic draw of vehicle is approximately 60mA
The xAC V2 is also 60mA Idle (100mA Operating ( Theoretical ))
So you can half what time you would usually expect to be able to leave you car without starting or driving and the battery being OK to start, Therefore = 1 -1.5 weeks
Quick calc, not including your relays ?
Then you probably want to include A safety margin of approx 20-25% ( so you can still start your car, and not fuck your battery )
Basically
You might need some power mitigation strategies if your car ever sits unused for a Week or more.
#Rough Guide/ suggestion, feel free to ignore or do your own calcs
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Just to expand, if you were wondering…
For example, if you were leaving you car idle for a long period of time
- Maybe Isolating the Negative terminal, ( switch / Breaker etc ) it will only discharge at approx 5% per month…You might want to check what your car does with no power eg. One of my cars automatically unlocks
- A solar trickle charger. Check that the cigarette lighter plug will charge the battery (blah blah,circuit protection blah diode blah, whatever…it may not work, so you may need to go direct to battery) But remember to disconnect before you start your car ( add a switch, if you have gone direct)
- add a momentary switch, (or similar)that only powers your circuit when pressed, this is not as clean, as you have to press when you scan in, but it removes all the other mitigation options needs…
Anyway, just some more STUFF for you to think about
Love the video! I’m slightly confused about the inclusion of an extra relay though. You should be able to actuate the circuit by pretending to be the switch inside the XAC, which touches the COM terminal of the bistable relay to the positive post of your battery for 1 second durations.
Seconded.
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@Pilgrimsmaster Thanks for the advice regarding power draw. Next time I’m at work I’ll pop the multimeter on it with the XAC system connected and check the parasitic draw rate just to make sure it doesn’t kill the battery in a few days. It’s very rare the car sits undriven for anymore than a couple days though, so I think I’d be more likely to go with an isolator terminal for the battery.
@AbbottSmith Looking back at the diagram now, I see what you mean. I think my brain went to “The XAC has an onboard relay so I should use the spare relay on the module to represent that”. Let’s just write that one off as a brain fart 
Glad you guys like it though and I look forward to showing off the final version!
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Hey I hope the project is going well. Some information about the XAC v2 was recently posted in a different topic that I was unaware of, and I think is important to know if you do not already.
Since I’m unsure of the XAC v2’s default position for the S3 jumper, you will need to either:
1.Remove the S3 jumper completely, preventing the chance of the XAC v2 shorting the power supply to ground.
Or
2.Simplify the wiring diagram by using the S3 jumper properly, which effectively replaces the wire connected to the XAC v2’s COM terminal.
Hey, thanks for the info! I’ve installed it all in the car and will post photos soon. I did work this out very quickly when I connected 12v to it and a diode started smoking. Thankfully nothing else broke and I removed the S3 jumper.
It’s being a bit temperamental though, only unlocking after holding the chip to the sensor for an extended period of time, but I’m thinking changing the delay will fix that. It’s almost like the 4 channel relay board is going to sleep or something.
Anyway, I’ll post everything soon once I’m not so flat out at work.
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It should be connecting the COM pin to ground out of the box. But always check first, the board has markings on the back that should make this relatively easy.
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