I decided to spend some extra time working on the schematic, so here it is! Totaling 5 relays including the Dangerous Things XAC.
Most “latching” relays I come across do not maintain their state after power is lost. These latching relays use a small flip flop circuit (usually activated by a button) connected to a standard relay coil. This means if the power is cut, this latching relay will default to the Normally Closed circuit, not remaining latched. I use this type of “latching” relay in the schematic above. (Edit: They are called Bistable Self-Locking relays) Also, the SPST Relays used in the schematic do not have a trigger in other words they need to actuate the instant 9v-12v is applied to them.
I feel like this video should accompany my schematic because I am not an electrical engineer.
I believe there is a way of removing one of the relays if you can determine whether the key fob’s buttons pulled the contacts on the circuit board high or low. Here is the schematic for that. Though I should mention this method should only be used by professionals as connecting the battery directly to the button contacts could be harmful to the key fob.
Edit: Forehead slap DPST Relays exist