Why do I have TWO 3-position Battery Switches?

[Clivevon]

PS. I'm talking about sailing boats - not motor boats.

[rslifkin]

Originally Posted by Clivevon

PS. I'm talking about sailing boats - not motor boats.

Your concepts apply to both. Starting power should always be treated as critical, so the electrical system shouldn't require any manual intervention to ensure there's always a fully charged battery ready to start the engine(s) if needed.

[Clivevon]

Your shore power charger needs to be at least 10% of the size of your battery banks. I use the old (but smart) 20 amp charger for the engine battery plus a smart 50 amp charger for the 440 amp domestic bank. The alternator - I forget offhand but its at least 100 amp or maybe 120 amp for the combined 550 amp batteries.

[raahell]

Originally Posted by Kamen

What purpose does the service switch serve? Why not simply combine the two house batteries?

The logic is that if one of my 4 house batteries would fail completely (I guess this does happen), having the 4 batteries split into two mini-banks allows me to isolate the pair that has the bad battery and continue to run the boat with the good pair.

There seems to be a division between owners that like the house bank in 2 pairs, while others abhor the idea. redundancy makes sense but perhaps there is a cost in terms of the arrangement being improperly used and shorter battery life.

I definitely have to better understand how the charging side is set up. I'll get back to you with that information as I get it.

If anyone has a simplified system that they really like and are willing to share a wiring diagram that would be really helpful.

[mitiempo]

Originally Posted by raahell

The logic is that if one of my 4 house batteries would fail completely (I guess this does happen), having the 4 batteries split into two mini-banks allows me to isolate the pair that has the bad battery and continue to run the boat with the good pair.

There seems to be a division between owners that like the house bank in 2 pairs, while others abhor the idea. redundancy makes sense but perhaps there is a cost in terms of the arrangement being improperly used and shorter battery life.

You have posted that you have 4 12 volt batteries in 2 pairs. If you really are worried about redundancy you should have each battery on its own switch. That means 4 switches for the house bank.

I have never thought that it was necessary to split a house bank so never have.

As I posted a simple switch for house and another for start does it. All charging to the house bank (in a single engine boat) and a combiner like the Victron Cyrix between the banks to take care of the start battery automatically.

On a twin engine boat (typically a powerboat) one alt to the start battery and one alt to the house bank with the same Cyrix combiner between the banks. When the start battery is at over 13 volts the Cyrix combines so both alts can feed the house bank.

Simple is always better.

[Kamen]

Originally Posted by raahell

The logic is that if one of my 4 house batteries would fail completely (I guess this does happen), having the 4 batteries split into two mini-banks allows me to isolate the pair that has the bad battery and continue to run the boat with the good pair.

Interesting. What happens if the bad battery remains connected to the bank?

[RSB333]

Combine the two separate house banks into one and ditch the second switch.
RSB333