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Old 04-30-2019, 03:33 AM   #4
Senior Member
Oneilkeys's Avatar
Brand: Thor Motor Coach
Model: 2016 Axis 24.1
State: Florida
Posts: 2,256
THOR #1765
I’m not sure I understand your comment that the BIRD is wired directly to the Chassis battery. It is supposed to be wired to the ignition switch, so that the BIRD is only powered by the chassis battery when the ignition is on.

The following is from the BIRD instructions.
“When the ignition switch is turned on and the engine is running, the system senses the level of voltage on the chassis 12 volt system. When this voltage goes 13.1 volts for approximately 2.5 minutes, as happens when the engine is running normally (normal alternator output voltage of a cold engine is approximately 14.4 volts), it will close the isolator relay providing charging current to the battery. This delay allows a cold engine an opportunity to start and warm up before having the heavy load of a discharged coach battery placed on it.

If the voltage should fall 12 volts for more than about 1 minute, the relay will drop out to feed all the alternators available output to the chassis battery to keep the engine running. This might happen when the alternator is not able to supply sufficient current to all of the loads and charge the coach battery at the same time. When the chassis voltage goes 13.1volts again, the relay will again close in about 2.5 minutes to retry to charge the battery.”

So when you turn the key off, the BIRD is no longer connected to the chassis battery.

Also from the instructions:
“If the voltage should fall 12.6 volts for more than about 1 minute, the relay will drop out to prevent the coach loads from discharging the chassis battery.”

So the system is designed to separate the two banks when the voltage drops below 12.6v so that the chassis battery will not discharge into the coach battery or the other way around. There is no way that the BIRD can discharge the chassis battery once the ignition is turned off - if it is installed and working correctly.
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