Battery wiring

[derekh]

While checking the boat (beneteau Antares 1080) I noticed something which I think is strange with the original wiring of the batteries. There are three batteries as would be expected but two are wired in parallel. Not much start protection. Is this normal or just poor design ? What is the ideal wiring charge configuration?
Thanks for advice.
Derek

 

[Tranona]

Quite normal. Those two are your house bank and effectively one battery with double capacity.

 

[nigelmercier]

You probably have two in parallel for the domestic supply, and a seperate one for the engine.

 

[VicS]

You probably have two in parallel for the domestic supply, and a seperate one for the engine.

Twin engines ITYWF

Large bank supplies domestics and may start one engine. If so then the other engine is started from the separate battery

 

[PaulRainbow]

Definitely twin engines. I'm sure she would have been turned out with the pair of batteries doubling up as domestics and one engine starting, with the single battery starting the other engine. Common arrangement on Bennies and Jeanneau's of this size. Typically wired as separate circuits through a red 12v+ isolator for each bank, plus a 12v neg isolator (no idea why that should be). Not sure if there is an emergency switch to start an engine from the other bank in the event of a flat battery.

No my favourite wiring setup, but not a total disaster. I'd rather the single battery started both engines, for two reasons.

1) Obviously the domestic systems could deplete the batteries.
2) Starting an engine from the domestic circuit can play havoc with electronics, especially if the battery is partially discharged.

I would use the single battery to start both engines. If there isn't a switch for emergency starting, fit one. If she does have the two red and one black isolators i'd remove the negatives from the black switch and wire that as the emergency start switch, suitably marked of course.

I'm not sure how the split charging will be wired, if it has any. As a minimum i'd have one engine charge the domestic bank, while the other charges the engine battery and the domestic bank via a split charge system. I'd go for the Sterling Pro Split R.

That does leave a small issue in that if the alternator charging the engine battery failed there would be no charge going into the engine bank. Turning on the emergency start switch would rectify this though. Or, a second Pro Split could be fitted (probably a bit over the top though).

 

[derekh]

Hi Paul,
you are exactly right regarding the negative isolation and the emergency switch which parallels all battery banks. My thoughts would be to have three separate batteries or battery banks which would isolate domestic from running. domestic being charged through a split charge relay and the shore power charger being replaced with a dedicated 3 out put charger. My main concern which you mentioned is the navigation resets when the engine is started which concerns me.
Many thanks
Derek

 

[PaulRainbow]

Hi Paul,
you are exactly right regarding the negative isolation and the emergency switch which parallels all battery banks. My thoughts would be to have three separate batteries or battery banks which would isolate domestic from running. domestic being charged through a split charge relay and the shore power charger being replaced with a dedicated 3 out put charger. My main concern which you mentioned is the navigation resets when the engine is started which concerns me.
Many thanks
Derek

That also sounds like a good plan Derek. If you fit a 3rd (single) battery and leave the two paralleled batteries as domestics i'd fit split charging systems on both starter batteries. That way, once the engine batteries have quickly charged you get all the alternator output from both engines into the domestic bank. You'll also need to fit a second emergency switch between the domestics and the new battery.