Starter battery

poter

poter

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Still going south currently in Corsica for winter
www.fairhead.com
I have two 100AHr on board a 35' yacht which do both starting and domestic.
The engine is a Volvo 2003t 43hp.
I have a 50 watt solar panel, & shore power with a charger.

So what extra battery do I need, if I am to have a dedicated battery for just engine starting & the two existing are used just for domestic power.
How do I wire up this lot & what additional kit do I need?
battery monitoring & or mangement, VSR etc?

There seems to be a big difference in battery prices, what would you guys recommend?

Any wiring diagrammes on line?
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poter
 
I would be inclined to suggest you do nothing. Is the present system not adeqate? It is all very well to say the leisure batteries are not made for starting but a big battery is good for starting even if it is not made for it. You need to retain one 100AH charged for engine start at all times. A small battery however needs to be designed for starting if it is to survive.
Younmight benefit by a VSR to automate your charging of 2 batteries while using only one.
If you feel you don't have enough domestic capacity then sure an engine start battery would be the way to add to capacity by making both 100AH batteries available for domestic use. ie can be discharged while retaining engine start capability from dedicated battery.

connect the engine start battery to the engine alternaor circuit. Isolate all your domestic loads and connect to the 1,2,both switch (if you have one). Fit a VSR with 2 outputs so that the engine battery /alternator will charge both 100AH batteries with engine runninng. You should provide a jump start lead or switch so that the leisure batteries can be used for emergency engine start.
Any more additions to the system like battery amnagement, solar charging, wind generator, shore power charger are all discretionary if you have the urge to spend money and think you need them.

You need to understand all the detail of your system and why you need it so. Any wiring diagram will then become obvious from your understanding.

good lkuck olewill
 
On my last boat I had two 120ah house and an 80ah cranking for my 4cylinder Beta. Charged via a diode splitter, the start battery didnt go through a selector switch - it was 'always on' just fused - then utlised the 1,2,both switch, in order that I could use the start battery for house, house batteries for start or link the start and house for some extra oomph.

I had a 50w solar panel, an aerogen4 and an Adverc smart charger. Never once required shore power.

Adverc are very helpful - I'd second the suggestion to look at their web or pick up the phone - they are very helpful.
 
Alternative battery strategies

1. Get a starter battery, if space is an issue you can buy some very expensive, tiny cranking batteries that will work upside down, or underwater. However, a bog standard small diesel engine car battery should have the CCA rating required for your engine.

2. Go for identical batteries throughout. As my original batteries gave up I have fitted 130Ah truck batteries - spec'ced for tail lift operations. When I get round to doing what you are doing, I will fit the same as a starter battery too (and parallel the existing 2 for domestic), they are cheap (about 50p / Ah from a truck factors), they are happy to take a deep discharge as well as start an engine (a 6 litre truck engine actually). In fact they will start a yacht engine like yours AFTER a deep dicharge.

Added benefit is built in redundancy, dependent upon your wiring arrangements, all batteries fit all spaces and will perform all duties if required to do so.

Cheapest wiring regime would be same as you have at the moment, just parallel the existing together on circuit 2, and wire the new to circuit 1.

Best wiring regime would be a 2-way Voltage Sensetive Relay. With shorepower connected to domestic bank, once charged it will then connect to starter battery to charge that. Engine alternator to starter battery, once charged VSR will switch in the domestic bank to charge that. As either bank loses charge below a certain level, the two banks will be separated.
 
Re: Alternative battery strategies

If you fit the solar panel to the engine battery, it will keep this charged. As there is no load on the engine, it will always be charged, and the relay will then almost immediatley charge the domestic bank. If the VSR has built in link start, you cover your back-up starting without the need for additional cabling.

Brian
 
Without major surgery on what youy have already ...

a) Purchase your extra battery - if to use as start battery only - then a Heavy Duty Diesel Car / Van battery is fine.
b) Parellel the two existing batterys on one side of your battery changeover switch - effectively doubling domestic capacity and still staying 12v for charging / power supply.
c) Connect now spare cables to new battery and use as start battery.

The advantage here is that you still have possibility to change over from domestic to starter bank and vice versa ... you have possibility to also have both banks connected at same time for charging both from engine etc.

I am not a supporter of boost / "battery management systems" as I have seen burnt out systems and fried batterys ... but thats IMHO.
 
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