Help with Alternator/Start Isolation Switch

[Matwill]

Hi Guys,

I have just replaced both of my batteries, house and starter,

Originally the shore power charged the house battery and a vsr charged the starter battery, the original set up looked a bit messy but it was straight forward once I could identify the wires.




In the new battery install - I made the start battery the primary charging source for the alternator and the shore power and I ran a dc/dc charger to charge the house battery

when i tested the shore power it all worked as intended with the dc/dc charger charging the house - the shore power charges the batteries even if the isolation switches are on or off.



The problem I am now having is the alternator is not charging and the house battery has a 5 amp parasitic draw. I am assuming the answers are in the isolation switch, i was hoping someone could help with how I should change this setup so that the switches work with the new batteries

I have asked a number of electricians in my area to come and have a look but they are all busy

 

[Tranona]

That is an odd way of doing it. The house battery is the one that needs the charge most - the engine battery only needs a few minutes after the engine starts. The usual way is to use the VSR from the alternator to both banks. It will give priority the start and then the house. Mains charger to the house for the same reason - that is the one which needs charge, then possibly a trickle charge to the start, although if you switch each bank independently and have a parallel switch you could connect the house to the engine in an emergency. The b2b is useful if you have a third battery such as for a bow thruster to avoid running heavy cabls through the boat.

 

[Boater Sam]

Crazy way to do it. Find the 5 A draw first, it could be the alternator.

 

[Matwill]

The reason i need to do it this way is because the house battery is now a lifepo4 and im using the AGM and the dc/dc charger to regulate the power coming from the alternator. If i connected the alternator directly to the lifepo4 it would burn out.

 

[Boater Sam]

Ah, but you neglected to tell us that vital piece of information. You still need to find the lost 5A though.