how does a battery boost switch operate?

garym114 wrote:
Not all systems that connect the chassis and house batteries have a relay involved. Some operate a regular battery solenoid that connects the two battery systems.

People are using Relay and Solenoid as the same item. Battery Boost---It takes a COACH battery system fully charged to activate the Battery Boost. If your Coach batteries are dead or below 11.5 volts the system will NOT activate. And if it does close the solenoid nothing will happen because the Coach batteries are below 12 volts. Remember, IF the CHASSIS batteries are fully dead, the Battery boost may not work on a Diesel Motorhome. THE AMP DRAW for a Diesel battery system is to great for some boost solenoids to transfer enough amps to start the engine. The dead chassis battery will "draw" some of the current that is needed to the starter. GAS engines will usually start with a dead Chassis battery and using the Boost. Doug