One battery or two?

lesweeks

lesweeks

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What little evidence there is suggests that the boat I'm restoring had just one battery charged by the engine. The electrics consisted of nav lights, log, sounder, pump, compass, VHF and possibly one or two internal lights to suplement the oil lamps. My intention is to keep the oil lamps, replace all of the filament bulbs (inside & out) with LED units and have the same basic instuments etc. but with a digital, DSC, radio. Will I manage with just one battery? If so is there a dual purpose type that would do the job?
 
Depends on how much usage you are going to make of the electrics, and what charging capacity you have. Single batteries used to be the norm, but with increasing electric usage and generally bigger engines, two banks, dedicated engine start and domestic bank, usually with split charging and a paralleling option have become the norm.

If you are going to stick to one, then go for what is termed a Leisure battery as this is a compromise that has sufficient crank for the engine, but capacity to take domestic demands.
 
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Sailorman has a point. If you cant start the engine by hand get two with a 1-2-off switch. Saved my bacon once and that is enough.

[/ QUOTE ]I agree with Roach, I can't start my engine by hand and adding a 2nd battery and a 1-2-both switch was one of my first improvements. I have a dedicated engine battery and an 85Ah service battery which is sufficent for an overnight sail with nav lights, VHF for 8 hours and autohelm for about half the time.
 
As I see it, the 'redback spider-in-the-woodpile' is the bilge pump. If it is teamed up with a float switch [as they usually are] and you get a leak devoping while you are absent [which is most of the time] then your battery can be flattened very quickly. Unfortunately, the leak continues to flow. I write from bitter experience here. If your budget can stand it, two batteries are better than one.
Peter.
 
further factors to consider are; the rate of charge that is available? and how long that charge is likely to be available at any one time?
Is an electric bilge pump really necessary? or at least one with a float activation? depending upon how long your away from your boat, and not able to pump out.

What might help is tot up the total maximum load that is likely to be drawn with all ancillaries working. This give a good guide as to AH of battery required, or bank of batteries.

The down side of multiple battery systems is that if one battery becomes less efficient, and it is associated with another. Then the weaker battery wil start to degrade the other.
Seperate charging and use circuits can be acheived, but tis down to how far you want to go with the other devices required to keep the electrics going, and of course budget etc.

But judging by you loads that you've mentioned, one for starting the engine only, and the other for the electronics. Theres nothing worse than the battery dieing on its arse, when the Brittany ferry is bearing down on you, and wind suddenly drops/forums/images/graemlins/grin.gif
 
Thanks guys.
It was always my intention to have two batteries, but with recent threads regarding LED's etc. and the thought of possibly saving space, I thought I'd pose the question.
Brittany ferries are big aren't they!
 
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Thanks guys.
It was always my intention to have two batteries, but with recent threads regarding LED's etc. and the thought of possibly saving space, I thought I'd pose the question.
Brittany ferries are big aren't they!

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Just a tad, and a lot bigger than the old Townsend Torrensen's used to be /forums/images/graemlins/laugh.gif
 
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Thanks guys.
It was always my intention to have two batteries, but with recent threads regarding LED's etc. and the thought of possibly saving space, I thought I'd pose the question.
Brittany ferries are big aren't they!

[/ QUOTE ]

And, more to the point, FAST
 
If you have the space I don't think you can better the system we had 40 years ago - two batteries, two engine-driven generators on separate belts. One battery strictly for engine starting only. Everything else run off the second battery.
That way each could be of the optimum specification for the job, and it didn't matter running the lighting battery down till the lights dimmed.
 
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