How to test the dual battery system?
The TRUE isolator is a sophisticated programmed voltage sensitive relay. Although the programming is sophisticated and complex the operation is basically simple. It functions by sensing the voltage available in your electrical circuit and connects (closes) or disconnects (opens) according to programmed threshold and timing factors. It is not connected to your ignition and does not turn on and off with your keyed ignition.
Once you have followed the instructions and the installation is complete you should start your vehicle and observe the isolator. After a short period of time, usually less than 2 minutes, the electrical system will reach 13.4 volts or higher and the TRUE isolator will illuminate signaling that the circuit is closed and both batteries are connected together and being serviced by the vehicle charging system.
Once illumination occurs you can verify the unit further by shutting the engine off thus removing the charging source. When the voltage level in the system drops to a standard resting level of 12.9 volts or below the TRUE isolator switch will turn off, indicated by the blue LED shutting off.
It may be necessary to turn on some of the accessories or headlights of the vehicle for a couple of minutes to bring the batteries to the correct resting level more expeditiously. It is okay to turn the key on but do not start the vehicle when verifying this step.
Note that there are variable timing mechanisms and thresholds involved in the function of this isolator so it will not turn off or on immediately at the thresholds it may take several seconds for this to occur.
It is not uncommon for batteries, especially new ones, to hold a false surface charge that could linger for several hours and keep the TRUE isolator engaged. This surface charge will dissipate quickly when the accessories are engaged in bringing the system level to a natural resting level allowing the TRUE isolator to disengage. It does not hurt the isolator to stay illuminated.
Once you have observed that the TRUE isolator opens and closes automatically, as described above, you have verified the installation is correct and can feel confident that your primary battery is now fully protected from accessory related discharge.