Cold Cranking for 60hp

[spilt-my-tea]

Evening all
Got a technical question for you, what would be the recommended Cold Cranking ability of a battery to turn a 60hp on-board engine?


30ft motor sailor, liveaboard based on Skye. Currently planning to overhaul the electrics starting with the batteries, I'd like to get a dedicated battery for the engine and two deep cycle jobbies for the living bits/nav equip/lights etc etc

The deep cycle one's aren't hard to find or figure out capacity needed but the engine one has me stumped, just how much Cold Cranking welly is needed for a 60hp on-board engine?

Any and all answers are greatly appreciated

 

[Tranona]

Any battery that is recommended for a medium sized diesel car. Would guess the manufacturer's specification will say something between 5-600 CCA but may well express the requirement in AH around 70-80. For example a Bosch S3 for a Ford diesel of 1.6 or 2.0l is 640 CCA and 70AH. Engine start batteries have an easy life in a boat provided you have a charging system that ensures it is recharged first after the engine is started.

A domestic bank of two sounds a bit light for a liveaboard unless you are regularly on shorepower as realistically this will only give usable capacity at 50% discharge of between 100-120 AH. Presumably you have done a usage audit in order to calculate required capacity and charging regime.

 

[lw395]

There is no right answer to this.
Your starter will probably draw around 100A while cranking with a bit of a surge as it starts to turn. So 200CCA would probably be fine.
But, you want lots of margin to allow for when the battery is not new any more, isn't 100% charged etc.
As an example, my 2 litre car, battery fitted has 750CCA. I changed the battery this year, the 11 year old one which still just about started the car would only give about 90A on a cranking amps test, and that was at plus 10 degC, not a cold test. I changed it because it was starting to go flat if I didn't drive the car for a few days.

So fit something which is a balance beteween 'ample' and 'good value'. If you fit a bigger battery with more CCA, you might get longer life, provided you look after it.
Some people fit a fairly small cranking battery for space reasons, but if you have lots of space, a chunky battery doesn't cost much more.
In my view, the starter battery has to be relied on, so I'm fairly happy to change it before it really needs it. I'm not trying to optimise cost per year, I want to know the boat will start. So a bit of margin is good value. IMHO.
My motorbike has a 210A battery. That would start your boat, but how many times over how many years?

 

[oldmanofthehills]

Personally I go for 096 battery as used in small vans and cars as I can get them for under £80 and they have spare capacity, though I only have 25hp motor. They give about 75AH and 650A and fairly compact unless space a real issue. I have just replaced my big dying domestic leisure battery with a large standard van battery ( Halfords 334) as doesn't make much difference to life and gives good cranking current if I need it ever to start the motor via jump leads, and that's what was available on a Sunday in Weymouth when I stopped in harbour. As a live aboard battery life might be more of an issue for the OP and they might have time to get reasonable size leisure at a reasonable price.

 

[DavidMcMullan]

The Beta Marine engine manual for their Beta 60 recommends a 12 Volt, 94 Ah (620 CCA Minimum) battery capacity. This is a 55HP engine.

 

[sailorman]

I have 4 of these https://www.batterymegastore.co.uk/...e-batteries/boat-batteries/hankook-xv110.html

1 is engine start
3 domestic

never had issues, those domestic`s installed are 5 yrs old, the engine must be 9 yrs old

 

[spilt-my-tea]

Thanks so much for the informative answers, whilst I understand that there's never one answer, especially when you get within sight of anything to do with the sea, I now have a greater understanding thanks to the various contexts offered.
Books are great but some real-world context helps immeasurably.....as does a wee dram.

 

[Tranona]

The other thing to consider once you have decided on the capacity is the physical size, location and type of terminals. There is some sense in having all your batteries the same as sailorman, but much depends on where you are going to site them and the space you have available. My boat for example has 5 identical AGMs each 90AH, one for the engine located in the cockpit locker close to the engine, 3 under a bunk in the saloon near the distribution board for the house bank and one in the forecabin for the bow thruster.