Using leisure batteries only

[theoldsalt]

I don't have a dedicated engine start battery, just a couple of cheap leisure batteries that supply the domestics and are coupled together (via 1,2,both switch) for engine starting. They have lasted years and give plenty of current for engine starting. I therefore never have to move the 1,2,both switch when the engine is running. Yes the nav. instruments do sometimes drop out due to voltage drop but it's easy to press the on buttons again if necessary.

 

[Amulet]

For many years I have had 2 general purpose batteries on a 1-2-both switch. I have a tiny engine and any one of the batteries can start it (I can also start it by hand in extremis). I never have the batteries switched both, but I of course have the option in dire circumstances. I run the domestics on one battery and reserve the other for starting. They are fully charged after any night in a marina, and then on trips starting on an odd date I select battery 1 and reserve battery 2. Starting on an even date... you guessed it. That means that I know both are functional. I have battery monitors on both, and, contrary to normal practice, even put the starter current through the battery monitors. It has all worked fine for about 6 years, with no battery renewal. The Sterling shore charger has separate circuits for each battery, meaning that the one not in use gets topped up too. The engine alternator likewise charges both through a regulator intended for a wind generator.

 

[William_H]

As said the whole question of battery management depends on your sailing style and habits. If I were doing any long periods of sailing or long periods of camping using current without engine running then I would want an isolated battery for engine starting. If I was discharging the only battery available for engine start (multiple batteries in parallel are really just one battery in this context) I would be constantly worrying about reserving enough battery capacity for the engine start.
Considering that a common failure mode for a lead acid battery is a steady decline in usable capacity the risk would get worse over time. (years)
A single battery like your car but used with an on off switch is the simplest most foolproof battery system. But you have to husband your battery capcity resources. Which often would result is a grumpy nervous captain. An isolated engine start and domestic battery system releives the captain of that worry. So i would go for isolted systems if I had a diesel which I could not hand crank start. The differnce with my car is that I do not run any services with engine not running so no risk of battery discharge.
To have a sytem with possibility of isolating the batteries and not using them isolated just means the skipper has not yet been stuck with flat batteries and no engine start capbility. It will happen.
good luck olewill

 

[geem]

+1

Much depends on boat use, whether day sailing or living aboard for extended periods. We have 2 house banks totalling 480AH plus a dedicated engine battery. Prefer 1,2,both switching as nothing to fail which can't be fixed on the spot.

I agree. We have 480 AH at 24v (960AH at 12v) and two 110 AH batteries for engine start/windlass. They are kept separate by a 1,2 both switch. Also, we have a 320w of solar and a duogen that both have separate charging regulators that supply both banks of batteries. It's a live aboard set up with little to go wrong.

 

[KellysEye]

>The reason for splitting start from service power is volt drop and noise when running the starter motor, this was, and still does, cause drop out of navigation equipment or memory.


Agree in addition the start battery should be a Cold Cranking Amp battery not a house battery, it isn't designed for starting.

 

[cryan]

>The reason for splitting start from service power is volt drop and noise when running the starter motor, this was, and still does, cause drop out of navigation equipment or memory.


Agree in addition the start battery should be a Cold Cranking Amp battery not a house battery, it isn't designed for starting.

Very often the only difference between a starter battery and a leisure battery is the sticky label on the side and the price. All so called leisure batteries will have a cold cranking rating.

http://www.sterling-power.com/support-faq-2.htm

 

[Amulet]

>The reason for splitting start from service power is volt drop and noise when running the starter motor, this was, and still does, cause drop out of navigation equipment or memory.


Agree in addition the start battery should be a Cold Cranking Amp battery not a house battery, it isn't designed for starting.

If you are determined to operate by rules of thumb rather than doing the maths then I suppose this is a reasonable view. I can read the spec of my battery, measure the cranking amps, and work out that a general purpose battery can do the job. I certainly wouldn't want an oh-so-clever swiss-roll starter battery on my boat.

I guess some boats are much more carefully specced than mine. If I had nav equipment that couldn't cope with a transient dropout in power I'd wonder whether I wanted the damned stuff on my boat. I used to sometimes have to reset the gps signal to one of the computers after starting the engine - about 30 sec work. I was aware that I'd been a bit optimistic about the unshielded signal cable, and replacing it made the problem go away. If you want a cost effective solution you have to apply some thought - if you're not willing to do so then I guess you're obliged to buy the batteries on the basis of the labels on them and pay the price. Two general purpose batteries have both been able to start the engine and keep the beer cold for seven years, but I guess I'm just a klutz living dangerously.

 

[boatmike]

I don't think you are missing anything but I have the smartbank/smartgauge fitted and have fitted a digital ammeter to show charge/discharge too. I like the automatic function and readout of battery state and feel confident that whatever I do I will never flatten my engine start battery that is always charged as a priority. My situation is different from yours though as I have 2 stonking great 200 HP Volvos to start and also run AC off an inverter whan en-route drawing 65amps replaced by running 2 90 amp alternators so the opportunity to flatten batteries inadvertently is quite high without real time monitoring. In your case I would still fit smartbank/smartgauge but understand that you might think it unjustified if you can always start them from an emergency power pack or portable genny. I guess it depends what else you run. If you have high draw equipment like Radar you need to be very careful, but if you don't maybe you can get away with it. I once sailed across to Cherbourg in my catamaran with radar running and the offending switch on "both" by mistake. When I got there my engines wouldn't start. Interesting sailing a 37ft cat on to a pontoon................
edit: I now have an Aquastar Mobo. I don't have twin 200HP engines in a sailing cat

 

[KellysEye]

> the start battery should be a Cold Cranking Amp battery not a house battery, it isn't designed for starting.

A CCA battery will last longer than a house battery used for starting, as said above it isn't designed for starting.

 

[Amulet]

... a house battery used for starting...

7 years and counting. Still does well on a capacity test. This is not magic. There is no magical property of a CCA battery. it just has thinner plates with more surface area. I'm not even convinced that, if a battery with fat plates designed for deep discharge will start your engine, that it does it any harm to do so. Can someone please explain? I can understand that it might not be able to start your engine due to lack of plate surface area, in which case you need a more cranky battery I agree.

And, lest there be any confusion, it will of course quickly destroy a cranking battery if you deep discharge it.

 

[vyv_cox]

Very often the only difference between a starter battery and a leisure battery is the sticky label on the side and the price. All so called leisure batteries will have a cold cranking rating.

http://www.sterling-power.com/support-faq-2.htm

I understand that one of the principal differences is that a leisure battery is taller to allow for a deeper space beneath the plates. On various batteries I have bought the additional height of leisure ones always seems to be the case. When lead sulphate falls off as a result of deep cycling it doesn't short out the plates.

Better leisure batteries have fewer, thicker plates than starter batteries, which allows them to deliver low currents for a longer time, whereas starter batteries can deliver higher currents in a very short time. The question then is whether a small yacht auxiliary engine in summer requires a large current when compared with a big car diesel engine in the depths of winter.

Recently some combination batteries have been introduced, notably by Bosch, that claim good performance for both starting and deep cycling. I have several of them and they seem to be lasting well, but I cannot find the way in which they differ from other types. They are tall, which suggests the void beneath, so maybe they have more plates as well? Anyone know?

 

[alahol2]

One other point that has kept me using leisure batteries for starting is that I am unsure just what angle of heel a 'standard' car battery would cope with. We do occasionally get to some fairly alarming angles. The 'sealed' batteries seem to cope OK.