Ok... what I would recommend is taking two of the 8Ds and forming a two-battery house bank with them. If you can fit them both under the Port Settee, that would make wiring a bit simpler. Leave the Starting 8D as the start bank.
To get maximum flexibility, I would recommend getting the additional hardware:
Then wire up the batteries as follows:
What this allows you to do is pretty neat. It allows you to isolate any one of the three 8D batteries and use it either for the starting bank as well as the house bank.
Normal Operation:
- Leave Perko #1 in the BOTH position
- Perko #2 in the #1 position
- Put the DCP in the ON position.
What this does is isolates the starting system to the starting battery (#3) and the house system to the house batteries (#1 & #2).
Dead House Battery
- Turn the Perko #1 switch to 1 or 2 to isolate the dead or damaged house battery.
- Perko #2 in the #1 position
- Put the DCP in the ON position.
Basically the same as the first setup, but only using one of the two house batteries as the house bank, isolating the other.
Dead House Battery Bank
If both house batteries are dead and you need to start the engine and run the house loads off the starting battery, do the following:
- Turn the Perko #1 Switch to OFF. This takes the dead house bank off-line.
- Put DCP in ON position
- Put the Perko #2 switch in the #1 position and start the engine with Battery #3.
- Once the engine is running, then turn the DCP switch to the "BOTH" position to run the house loads off of Battery #3.
This allows you to start the engine without any house loads on the starting battery and then add the house loads to the electrical system once the engine is running. The starting bank will charge via the DCP.
If the house bank is dead due to just overuse, rather than damaged batteries, you can then turn Perko #1 to the Both position to get the batteries to charge. Once Batteries #1/#2 have charged a while, you should be able to turn the DCP back to the "ON" position. The starting battery will continue to charge via the ACR.
Dead Start Battery
If the start battery #3 is completely dead or damaged, you can start the boat still by doing the following:
- Leave DCP in OFF position
- Turn Perko #1 to 1, 2 or both, depending on the state of charge and condition of batteries #1 and #2.
- Turn Perko #2 to the 2 position, which will connect the house bank to the starter motor.
- Start engine
- Turn DCP to ON position to connect HOUSE BANK to House Loads
- Turn Perko #2 back to position 1, if the starting bank is just dead, but not damaged.
This allows you to start the boat using the House Bank, either #1, #2 or both #1 & #2, then run the house loads on it once the engine has started. If the starting battery is just dead from overuse, it will start to charge via the ACR.
If it is damaged, you will want to disconnect the #3 battery before starting the engine.
All charging sources go to the house bank normally, but can be put on the starting bank in the case of a dead house bank by turning the DCP to BOTH. While this setup is a bit complicated, it does give you complete redundancy and the ability to isolate any of the three batteries, use any of the three batteries for house or starting loads, and keep all the batteries charged. The TWO RED LINES WITH ARROWHEADS are the common lines coming off the Perko switches.