Batteries

Hawkflier

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After many years crewing, but a 17 year gap in owning a yacht I hope that I am just about to again be an owner.I have lots to get back up to speed upon but the first issue I would like to ask about is the issue of marine batteries.
Currently the yacht I hope to be buying has 2 batteries (not sure what they are) I presume one for the engine and the other for domestic use. They are totally past it and need replacing. I am considering replacing the 2 with a 3 battery set up (1 engine & 2 domestic). There is some work that needs doing that requires the main saloon to be stripped back, so while it is being done I can use the opportunity to change the battery box etc.
What should I be looking for in terms of battery ratings and types? I know that I want deep cycle but to be honest I am not sure what that refers to. Yes any responses really do have to be at a basic level!
The yacht will eventually have all her electronic navigation aids updated (integrated system.. will be asking about that soon enough) and it is intended that we will do some long distance cruising with her eventually (she is 38feet).

Any advice etc would be greatly appreciated
Cheers me dears!
 

sarabande

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OK...

Step 1. Put together a decent forecast of your likely power usage pattern. You might use a daily pattern, or a weekly one if you are cruising.

As a rough guide, on a busy 24 hours, you might use 80 to 100 amp-hours, but that figure might vary enormously.

Step 2. Decide on how you are going to replace all those Ahrs. Will the boat be charged up fully on a marina ? Solar/wind power ? Recharge batteries using engine, or generator ?

Step 3. Decide on battery type. Another rough guess would suggest 2x110Ahr for the domestics, and 1-110Ahr for the engine, though if you are likely to use e.g. a fridge a lot, the domestic capacity might need increasing. There are charging advantages to using a 'standard' battery so that cycle life can be consistent. You can use very expensive marine batteries with a potential life of 5+ years if looked after, or buy lorry batteries, and throw them away after two or three years. Your wallet chooses.

FWIW, a 'leisure' battery seems to be the best compromise for domestics, with an starter-type battery (more CCA than a leisure battery) for the engine (surprise). There is a difference in the way they are made which reflects the way that power is taken out of them.


Battery University has a very good 'teaching' site:-

http://batteryuniversity.com/

which covers all sorts of usage conditions, types, charging, storage, etc.
 

macd

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This link gives good basic info on lead-acid batteries.
www.xs4all.nl/~erkooi/YL/battery.html

If you do a search you'll also find many, many threads on the subject on this forum.

If there's room, your idea of going for a 2-domestic/1-starter makes complete sense.
A bog-stock automotive starter battery will do for the latter. It won't need a huge capacity (or huge physical size), but should comfortably exceed the engine manufacturer's spec. CCA (cold cranking amps) is the important figure for this. My own battery is specc'd to start a 2-litre diesel Transit, so it copes comfortably with a 1 litre Beta.

Options for domestic batteries are huge and can be baffling. So-called deep-cycle batteries have thicker plates and sturdier construction, better able to withstand repeated 'cycles' (i.e. number of deep discharge/recharges). Traction batteries (as fitted to golf carts, electric fork-lift trucks etc) are the most robust; 'leisure' batteries rather less so. If you live aboard and routinely cycle the batteries quite deeply, it may be worth paying for the more expensive option, but many boats get by on fairly cheap kit.

At least as important as a sound battery choice is the charging regulation. A standard alternator regulator (or cheap mains charger) will never fully charge your batteries, which will do them no good in the long run. 'Smart' regulators (or 'smart' battery chargers, usually called 3- or 4-stage chargers) overcome this problem. Again, a search will throw up heaps of relevant threads.
Good luck.
 

Hawkflier

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Marine Batteries

Many thanks for your advice.

I will need to do an evaluation of the power demands of the yacht, although this is a little difficult as she is currently in Eire and my access will be in short bursts to get her ready to come back to the UK for the repair/refurbishment program that we have in mind for her.
I will also be changing the 'demand' as I upgrade electrical equipment etc.
But your advice and the links have been invaluable.

Many thanks.

Can you recommend a good (decent priced) supplier on the West coast of Ireland near Knock?

Cheers me dears!
 

Quandary

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Your Sigma 38 has two 110ah. batteries in a good secure grp battery box just behind the main bulkhead, so a relatively short run if you intend to fit a windlass. There is plenty of space for a dedicated starter battery beside the engine to stbd. below the aft cabin bunk but you will want to make a secure box for it. Only a very compact battery could be fitted in the engine bay and it gets very warm in there.
On ours we stuck with the standard 2 battery arrangement ( 1-2 both switch)with the only mod. being the fitting of an Ardverc (highly recommended) to better manage the alternator output and a 3 stage shore power charger which was a bit unreliable. The switch was kept at 'both' when the engine was started and running but always switched to a single battery as soon as it went off. We usually used a different battery as the domestic each year and then changed them both together. The biggest load was the windlass but this was always used with the engine running. We were (still are) very frugal users and liked to keep the batteries close to full capacity, only running the frig. when the engine was on or on shore power. The frig in the Sigma is not that well insulated and tends to be greedy so it helps to keep it full and closed. The boat came with gel batteries but these were replaced with ordinary lead acid lorry batteries at half the cost, we got 5-7 years life from these. If you are going over to the boat by car I suspect it will be cheaper to take batteries from the UK these days, or buy them in Enniskillen, but they will be available from any battery shop or motor factor in Sligo. Once you get the boat home it will be worth investing in an Ardverc and a good shore power system with 3 stage charger, mine in Navix but these are very expensive and you can get non boaty ones for less than half the price.
 

Hawkflier

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Thanks J.

It is all an upward learning curve.
I should know if the sale is going through tomorrow or Tuesday but I am hopeful. Then it will be full steam ahead so to speak!

I hear what you say about keeping the 2 battery arrangement. However, as there are going to be some serious work undertaken if I am to install a third battery now is the time, although for the delivery home I will just replace the two existing one for domestic (deep cycle) and the other for engine start.

I don't suppose you know the dimensions of the battery box?
Cheers
 

Tranona

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Have just been through this exercise and my set up is common. I* engine start battery a conventional lead acid aroud 85Ah, but if I was replacing this would probably go for a smaller Red Flash. 2*135 Ah deep cycle lead acid for house (cost just over £300). This fits my battery box perfectly. Charged by engine alternator and VSR and switched by a BEP Marine switch cluster. Each bank individually switched but can be paralleled and the VSR splits the charge automatically. This is on a 37 footer with all the usual electronic goodies except radar.
 

Quandary

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Thanks J.

I don't suppose you know the dimensions of the battery box?
Cheers

I only know it is a neat fit for two standard? 105 a/hr batteries; at a guess I would say between 450mm. and 500mm. sq. by about 250mm. deep (Though it is not quite square) From memory I modified the retaining strap securing arrangement to make it more accessible but this was ten years ago. I am not advocating staying with just two batteries for ever but it should work for getting the boat home, you may find it easier to purchase marine bits like the Ardverc etc. in England than in Sligo.
Note, if you want to keep the boat in class (for possible resale) the position of the main battery bank like most heavy items is controlled by the one design rule.
 
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