Can you explain how the 12VDC system is laid out?

[pgflrob]

We did a survey and sea trail on a 1996 37 Sundancer today.


Something came up that totally confused me. This is not my first boat or my first Sea Ray. When we went to start it the port engine fired right up, but the starboard would not. The captain hit the parallel switch on the console and it still did not start. The captain and the surveyor changed two batteries (starboard "house" AND "starter").


I asked why and really did not understand what they are saying. They said the starboard and port have two batteries (each a house and a starter) - four in total plus the generator. But they said the house is split and some 12VDC circuits run off the starboard battery bank and some off the port battery bank which is odd but makes sense.


But they also said the house drains the starter batteries. That just does not make sense to me. Why would the house and the starter battery be basically in parallel all the time?


Can you explain how the 12VDC system is laid out? How can I isolate the starter batteries from the house batteries?

 

[alnav]

I don't think Sea Ray makes a distinction between "starter" and "house" on any of its larger models like some boats do; I know they don't on mine. The same battery type (deep cycle) is typically used for all and each respective side feeds both house loads and engine start. This actually simplifies the layout and selection of batteries but results in a lesser amount of cranking amps as opposed to what you are used to while providing some redunancy when there is more than one battery per side.

 

[Air O'Nautical]

It maybe the same as mine..

Bank #1 is two batts. for the the starboard engine AND all house systems.
If drained it can be paralleled with the #2 bank to jump start yourself.

Bank #2 is one batt. for the port engine.
This only feeds the port starter motor so, should be charged up and available to jump the #1 bank if necessary.

Bank #3 is for the generator starting only.

I have three banks and four batterys in all.

Your maybe the same.

 

[Hwillcockson]

I have 1997 370DA and my battery setup is similar to Air O'Nautical's above, except I have two batteries in parallel for the port engine with five batteries total.

House loads run off of the two starboard batteries only.

Port batteries provide power to the port starter only and can be used to jump the starboard bank if needed via the emergency start (parallel) switch.

Single battery for generator start.

In your case the starboard (house) battery bank must have been completely drained and maybe shorted within the batteries.

 

[fwebster]

It isn't a screwy design once you understand what is going on. Whether or not one bank supplies some or all of the 12VDC need is strictly dependent upon the current demand for the various 12VDC components and their amp draw. The larger the boat, the more likely both banks have "house" duties. For example, I have 2 water pumps, 2 complete vacuflush systems, 2 stereo systems, electric servos for window vents, etc. so I must leave both battery banks online all the time since the load is split between both sides.

I had a 390EC for a number of years that was wired with one side as the house side. The major difference in every day use is that I could turn off the non-house battery switch on the 390 and have 2 batteries fully charged and ready to go after a day on the hook. If I ran down the house bank, I could cross feed the banks and immediately crank up both engines. I cannot do that on the 450 because both sides provide house current.

ANd, I agree with the previous post.......someone left a battery switch on and the convertor off, or you have a bad battery in the bank that was dead.