Backup Battery Relay Wiring?

• Isolate the backup battery to prevent draining it if I leave my lights on, and
• trigger the alarm when main power is cut.

Maybe its me and its way to late, im not sure.

But it seems to me that the last 2 relays are backwards. It looks to me that if you lose voltage all together from your 1st relay than your 30 and 87a on the second are going to have continuity, thats where your negative should be, not on 87. Because the way its wired now, it looks like it passes ground when its energized. 

Then on your 3rd relay (charging relay) when you have ign hot, your 87 and 30 are going to have continuity which from the looks of it, thats not what you want. You only want the battery to charge while you the ign on. So I would change constant from 87a to 87. Let me know what you think

Not too late at all, I've had no replies yet...   :-)

OK, good calls.  I've got a new diagram here.

Relays 1 and 2 are to set the alarm off when the main vehicle battery is disconnected.  I made changes to Relay 1after I read your comments - constant +12V energizes the coil, and keeps the circuit open (continuity between 30 and 87, with no connection on 87).  When the +12V is gone, such as when the battery is disconnected, terminals 87a and 30 will have continuity, passing +12V from the backup battery from terminal 30 on relay 1 to terminal 85 on relay 2.  This will energize relay 2's coil, completing the circuit from terminal 87 to 30, which is ground, which should cause the (-) trigger of the alarm to set off the alarm.

I also changed relay 3 - when the ignition is on, it passes current to terminal 85, energizing the coil and applying +12V to terminal 30, which should recharge the battery.  When the ignition is off, it will de-energize the coil, isolating the back-up battery from the vehicle power.

How's that?