Batteries on a little boat

[Antc]

Hello all
In the process of the winter refit and I have had some old 110ah leisure battery in which now will only stay charged for about 10minits
Will a 80ah battery last the 15 hours that the Round Isle of wight race may last running VHF, stero, nav lights, instruments etc?
Is there anything better than a leisure battery for boats?

I have no engine to start (its an outboard) so it only runs utilities

Further more it has 3 charging inputs a solar panel which has an overcharge and over discharge protector as the utilities are connected to this. it also has a mains charger and the outboard has an alternator which are connected strait to the battery, is this ok


Any help will be much appreciated

[Joakim]

Originally Posted by Antc

Will a 80ah battery last the 15 hours that the Round Isle of wight race may last running VHF, stero, nav lights, instruments etc?
Is there anything better than a leisure battery for boats?

That is impossible to know, with that little information. Why do you need a stereo during a race? How much is the consumption of your VHF and instruments and especially nav lights and how many hours do you use nav lights. Especially nav lights can have a huge range of consumption. LED tricolor can be about 0.5 A while in the worst case you have three separate lights 2 A each, thus 6 A.

In my boat VHF is about 0.5 A, instruments 0.5 A, nav lights 1.5 A and a cool box 0.5 A, thus daytime about 1.5 A and nighttime about 3 A in total. So 25-45 Ah in 15 hours and thus 80 Ah is enough. Actually I have a 100 Ah battery and it has been OK without any charging in a 24 hour race.

Yes there are better batteries called AGM batteries. They last more cycles, but are much more expensive as well and not as cost effective in typical boat use.

[Submarine Tom]

You'll need a deep cycle battery which is already designed for your purpose.

You'll need to minimize your load, that is, reduce your current draw.

You could use a hand held radio, LED lights.

Install a switch (or disconnect) your instrument illumination lights and use a headlamp to see those gauges at night.

Remove the stereo.

What are the "etc"?

-Tom

[Antc]

The etc is internal lights, handheld VHF charger, handheld gps charge, rairly used. I'm not sure how much the main VHF uses and my nav lights are a tri light.
Is it as simple as finding out the amps that everything uses and multiplying it by there usage time to get the AH, and as long as that doesn't go over the battery capacity I'm ok?
Are gel filled leisure battery's much better?

[Antc]

Oh and the stereo is just for forecasts and cursing it doesn't get used much

[Joakim]

Originally Posted by Antc

Is it as simple as finding out the amps that everything uses and multiplying it by there usage time to get the AH, and as long as that doesn't go over the battery capacity I'm ok?

Yes and no. It's OK to count the Ah that way, but you need a clearly bigger battery capacity, since your battery is probably not 100% when you start and you don't want to have it 0% ever actually you shouldn't go below 30% if you want the battery to last long. Thus you will need a battery that is about twice the counted Ah.

[gonzo]

Gel batteries can be completely discharged without damage. They also have more charge/discharge cycles than a lead/acid battery. How are you using the stereo for forecasts? It only a 24 hour race, so you can figure out the forecast in advance with internet information.

[Antc]

It doesn't get used much it's just on standby most of the time but it isn't able to be isolated at the mo so it still has a small drain. Which is why I included it.
Thankyou all this has been most helpful

[Crag Cay]

If you're talking about THE round the island race, you have to be going very slowly to need nav lights. Even if you're based in the Hamble it's light by the time you leave for the start and it's still light 18 hours later. I've only ever used lights if I go into Cowes afterwards and then cross back over the Solent at closing time.

I don't think I've ever kept a listening watch on VHF either. It's so busy and chaotic round about you that you'll learn nothing helpful listening to the radio. I think a decent, well charged 100Ah leisure battery will be ample together with a handheld VHF, spare AA batteries and a couple of good waterproof torches.

That's certainly more than most of the small keel boat classes will be carrying. The leading Sonatas will have one small motorcycle battery (new for the Scottish Series overnight race several years ago and not charged since), a decent depth sounder for Ryde sands and the cheapest handheld VHF going! Spend your money of Bruce's Island and Solent Hazard books, tide guides, and OS maps with all the information compiled on to them.