ex Raggie needs advice - battery charging

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pappaecho

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My present ketch has a wind generator, which charges the battery banks and also from the engine -without problems...
In my search for a mobo, I have so far inspected 3 boats for sale, all with twin diesel engines, and none has started on both engines because one or more batteries were flat

So my questions is, what system do you use to ensure that the output from two alternators are directed either to the approriate engine starter battery, or to the common domestic bank, and is the system intelligent?
 
pappaecho said:
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So my questions is, what system do you use to ensure that the output from two alternators are directed either to the approriate engine starter battery, or to the common domestic bank, and is the system intelligent?
Click to expand...

It depends on the boat builder.

You can have port and starboard engine batteries and a service bank, with both alternators charging all battery banks, with emergency link start for flat a engine battery.

You can have one engine with it's own dedicated start battery, and the other engine has a larger bank for engine start / service loads, with emergency link start.

You can have one engine charging a common starter bank for both engines, the other alternator charging a service bank.

Those are the main ones, depending on system used, they can be intelligent, or quite thick.

Brian
 
Your obviously finding sloppy boat owners. Most Mobos will be in marinas and on shore power. So no reason for not starting. If it's on a buoy, the owner is probably hard up and not done much maintainance either.

My charger seems fairly intelegent as it apears to work. Just one battery looks after starting. But if you think about it, if it can start one engine, it can more easly start two.

Mobos tend not to have wind generators, dunno why. Perhaps looks daft.

I have two options for none starting, which has only happened twice in 12 years.

One jump lead across to the domestic side. The negative is already conected.

Or switch on the trusty Honda and make a bit more elactricery.
 
Sorry to hijack a thread - will start another willingly if requested(!) - but was glad this thread appeared as am looking at present to 'design' my battery/charging circuits. Twin engine - thought of two batteries/two alternators so completely independant. Two additional leisure batteries for lighting etc. 240v hookup on marina to IDEALLY ensure that all batteries are 100% charged when I jump it on it for a jolly. Also have a 5.5hp Honda genny to go onboard for 240V whilst offshore if needed. ALSO wanted to put 2 x solar panes on roof of cockpit for additional charging.... The problem I have is the switching of the charging circuits to ensure that all are charged as needed and not boiled dry. Unless I have missed something obvious.......
 
Alot of twin engined boats have one engine starting battery for both engines, and a separate domestic which is charged with either a VSR or splitter diodes. A VSR has zero volts drop while the diodes have about 1.2v drop though this can be compensated using the sense wire of an advanced regulator fitted to the alternator on the output side of the diode.

Mark
www.boatdoctorni.com
 
I could be being completely foolish BUT I a having a new fueltank fabricated - split down the centre so that I will end up with two different (but the same(?!?!)) engines, two seperate fuel tanks, completely independent batteries etc per engine for (vitually) complete dependantcy. Does this mean the charging to look after all this is going to get silly complicated? Incidentally my generator could provide 240v to a 12v battery charger if needed whilst offshore incase of a problem.
 
mil1194 said:
I could be being completely foolish BUT I a having a new fueltank fabricated - split down the centre so that I will end up with two different (but the same(?!?!)) engines, two seperate fuel tanks, completely independent batteries etc per engine for (vitually) complete dependantcy. Does this mean the charging to look after all this is going to get silly complicated? Incidentally my generator could provide 240v to a 12v battery charger if needed whilst offshore incase of a problem.
Click to expand...

Two choices, each alternator connected to all three banks via a diode, or each alternator charging it's own battery and the domestic bank, via a diode. If needs be, each alternator could utilise an advanced alternator regulator. Not hard at all.

Personally, i would use a single batter to start the engines and a bank for domestic use. Each alternator would charge both banks via diodes. The isolator switch would be a Blue Sea Dual Circuit Plus. One click on/off for both banks, with the option to "combine" the banks in case of a flat battery.
 
Paul Gooch's suggestion seems to make a lot of sense. The only questions are the diodes which are mentioned. I guess they must be fairly hefty, the sort used as blocking diodes on alternators, not the 4147s used in low voltage work. Anybosy know source?
 
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