Figure 5

Pros: 

• Optimized use of both starting and deep cycle battery types with sensitive electronic loads isolated from the starting circuit.  
• Extreme simplicity!   Heavy Duty Switches are NOT needed!   Zero!     None!    Zip!   Minimal wiring needs.   Alternator protection device NOT needed!
• External solenoids NOT required.   Can be used with 300+ Amp alternator!
• Low Cost!   Utilizes the low cost BIC-75150.   And with heavy duty switches costing as much as $30.00 to $90.00 each, consider your savings by eliminating up to 3 of these.   Save about $25.00 for an alternator protection device.   Save money by reducing the amount of wiring required.   Save labor dollars by simplifying installation.
• Easy, simple to understand, installation!   Eliminate all the hole drilling for those switches.
• Your house battery and loads will be automatically isolated from your starting battery.  Electronic devices sensitive to voltage dropouts during starting will not be affected (unless manually combined during starting.)
• Your starting battery need not be deep cycle.
• Simple automatic operation!   Virtually free of human intervention.  No hassle, worry free.
• Simple manual parallel combination via a remote micro-switch.    From a remote console, you can use very small wire running a long distance to switch the batteries in parallel.  
• The Hellroaring BIC-75300 and BIC-75150 limits inrush currents when switching.   No arcing to wear out the device!
• Achieve full charge for both batteries.  No diode voltage drop effect when ON!   Very low ON resistance (less than 0.008 ohms!)

Cons:

• If your starting battery fails, you can not immediately crank with  your house battery.  However, you may be able to transfer sufficient charge from the house battery to the starting battery by manually combining them for at least 15 minutes.  This is good practice for a deep cycle battery anyway. Keep in mind that it will not fail due to house loads.