Fairline battery conundrum...

[Nauti Fox]

This is the arrangement on our Fairline 43-45.
I'm still trying to get my head round the battery setup, with all the batteries isolated (so each battery is disconnected and then tried on their own) the port starts the port engine only, starboard one starts starboard engine and domestics, centre battery starboard engine and domestics.
The port and starboard batteries are linked together in parallel.
The centre battery is linked with the negative only ( as far as I can see)
There is also a battery connect relay which I can't find but is probably under the battery box.
I have only a limited knowledge of boat electrics and I don't want to muck things up, but it doesn't look right to me and I'm looking for advice, would it be best finding a marine electrician?

Looking aft

 

[PaulRainbow]

Some of that just sounds wrong.

A common arrangement for a boat such as yours would be to have the port battery start the port engine, the other batteries (wired as a bank) would start the starboard engine and then run the domestics. All of the negatives should be connected together, from one battery to the next, taking the engine start from the relative battery/bank and the domestic supply from the domestic bank (opposite where the positive is connected). There should not be a parallel connection on the positive side of the banks, as this means that all batteries are combined into a single bank. You mention a relay, this could be a VSR, which may be closed and giving you a false result, in that the banks are only combined when charging.

Personally, i would wire things differently. I would fit a hefty engine starting battery, capable of starting both engines, this doesn't actually need to be enormous. This would then obviously start both engines, but not be connected to the domestic bank. The domestic batteries then only get used for house circuits.

Each alternator would be connected to a Victron FET based isolator, which would then be connected to both battery banks. This means that both banks are always isolated from one another, but each alternator will charge all batteries. You could, for instance run one engine to charge all batteries. Additionally, once the engine batteries are recharged after starting (doesn't take long) both alternators will be charging the domestic bank.

A third switch would be fitted for emergency use, in the event of a flat engine battery or failure of a battery. No relays would be used in such an installation.

You can adopt such a arrangement, or just tidy up the existing setup, with varying degrees of the above (for instance, you can keep the setup i described in paragraph one, but adopt the improved charging system with the FET based isolators.

I have to say though, the wiring in your picture is a mess and those batteries look old. The negative wiring would be much neater with single cable connections at the batteries, connected to a busbar. The positives are in dire need of a tidy up, there are far too many unfused connections there.

 

[Nauti Fox]

Thanks Paul, I'll be in touch.

 

[GregOddity]

What Paul said ^^
That battery bank needs fuses and proper BUS bars with single cables at first glance.

 

[matthewriches]

That's certainly an interesting photo. Like most boats, stuff gets "added" and "added".

 

[matthewriches]

Good to meet you today to sort your shore power issues out! And a good day to get the beamer out for a ride. I have most of the other stuff we discussed in stock so will do round 2 soon then you'll be electrically sound

Not sure if I have your email address? I need to forward you marina info. Happy to speak with them direct if you like, as maybe they'd want a full periodic on their install to address all the issues?


Speak soon,
Matt