bit of advice possibly before i call out the leckies.

[pathfinderstu]

Maybe one of you clever chaps can help here, background have 3 batteries I in front of the engine and two others under a bunk. they were installed into a 2006 beneteau. today was cruising along quite merrily when heard 3 short alarm bleeps from the switch board. turned out to be coming from the volt indictor which has two readings. one was fine and charging away as the engine was running at the time, the other was going into the red zone, I turned off the auto pilot and gps and alarm stopped but did not show charging on the voltage. so somehow that battery or batteries is not charging from the engine when its running.
I understand that it could be hundreds of things but maybe some one has had this before, maybe batteries is knackered...any way your thought s appreciated as always,

 

[prv]

How are the house batteries connected for charging?

Pete

 

[david_bagshaw]

Broken wire / joint
broken splitter diode,
failed battery

 

[Woodlouse]

Boats these days have charging systems whereby the starter battery is charged first, once that is back up to strength from starting the engine the charger is then switched to charging the domestic batteries.

If your alarm went off after turning off the autopilot and GPS that suggests it was the domestic batteries.

So I reckon the relay that switches the charge from the starter to the domestic batteries has failed.

 

[pathfinderstu]

How are the house batteries connected for charging?

Pete

sorry no idea.

 

[pathfinderstu]

Broken wire / joint
broken splitter diode,
failed battery

Thanks will look for broken stuff, diodes are beyond me. and will try charging with shore power if it takes a charge then presumably the batteries are still good.

 

[pathfinderstu]

Boats these days have charging systems whereby the starter battery is charged first, once that is back up to strength from starting the engine the charger is then switched to charging the domestic batteries.

If your alarm went off after turning off the autopilot and GPS that suggests it was the domestic batteries.

So I reckon the relay that switches the charge from the starter to the domestic batteries has failed.

That sounds logically interesting, will try and locate the relay and test it if I can figure out how to. Thanks.

 

[nigelmercier]

Boats these days have charging systems whereby the starter battery is charged first, once that is back up to strength from starting the engine the charger is then switched to charging the domestic batteries...

Will this old chestnut never die?

 

[Little Sam]

Of absolutely no help to the op , but in the long run maybe.

Build your own electric system. Then you know it by heart. That's what most of us old boat owners end up doing anyway so do it now then you'll get even more fun out of it.

 

[PilotWolf]

Will this old chestnut never die?

Not sure if you mean this isn't possible or the system is just ****.

We had it on the ambulances back in the late 1990/early 2000 - never worked properly, mainly due to the fact the vehicles didn't run long enough to charge all 3 batteries properly.

W.

 

[nigelmercier]

Boats these days have charging systems whereby the starter battery is charged first, once that is back up to strength from starting the engine the charger is then switched to charging the domestic batteries...

Will this old chestnut never die?

Not sure if you mean this isn't possible or the system is just ****.

Not that it isn't possible, but it isn't correct.

Neither diode splitters nor a VSR will fully charge one battery first before switching over to the other. With diodes, they just conduct when there is a charging current and charge both batteries. A VSR turns on as soon as the voltage rises above a set limit, normally within seconds.

 

[Talulah]

Also if the alternator is sensing a high voltage across the fully charged engine battery it will output virtually nothing to the domestic batteries even if they are flat. It depends how the system is wired up.

 

[davidej]

Boats these days have charging systems whereby the starter battery is charged first, once that is back up to strength from starting the engine the charger is then switched to charging the domestic batteries.

I think the chestnut he is referring to is the use of the word 'first'.

A VSR charges both batteries simultaneously, though of course the most discharged battery accepts the higher current

 

[nigelmercier]

I think the chestnut he is referring to is the use of the word 'first'.

A VSR charges both batteries simultaneously, though of course the most discharged battery accepts the higher current

Fully agree with your second sentence.

I disagreed with the whole section I quoted, with the exception of "Boats these days have charging systems"

Boats these days have charging systems whereby the starter battery is charged first, once that is back up to strength from starting the engine the charger is then switched to charging the domestic batteries...

The section in red is a myth.

 

[Champagne Murphy]

Um, could be really simple?? At risk of drawing a sharp response from the techs, Have you tried checking the fluid levels in the batteries?

 

[pathfinderstu]

Well the cure was pretty simple and thank you all gentlemen for you interesting replies.
I went down to the boat this morning armed with all your info, rechecked and found the problem was still there so started to look around the battery wiring where all the switches are next to the domestic batteries. no sign of any loose wires or anything obviously broken or out of place,
noticed a pair of fuses sticking out of some wires there, spade I think you call the type, one was five amp and the other ten pulled them out their sockets and to my surprise the five amp one was blown. replaced with new fuse, turned the engine on and everything was charging properly. to make sure all was ok gave the system a charge with shore power for 6 hours and rechecked all was fine, surprising what a five amp fuse can do, was very pleased as freed up my day and wallet was not expecting to get away that easily.
what blew the fuse you might rightly ask, all I can think of is had problems the week before with a badly connected windlass control.
anyway thanks again I will probably be back in the future with more old chestnuts, am sure.