Charging ahead

[Elissaar]

Dear All

I would appreciate poeple's views on the choice of battery for domestic use on a sailing boat - yes this post is about batteries I'm afraid. I have been looking at previous posts but not sure they answer my question.

The background: Elissaar's batteries for domestic are 2 x 55 Ah lead acids. Although she has shore power, the current drain with the cabin lights on alone can be as high as 8 Amps. Simple maths suggests that these batteries are a bit small. I want to change them to 75 or preferable 85 AMps (the storage areas will limit the size of battery), what type should I go for? I presume I should use deep cycle leisure batteries but what type (lead acid, AGM or gel) budget is not exactly limitless but I really dont want to have to change them every 3 years either (some batteries seem to last years). Adding the fridge increases consumption alot but this is switched off at sea.

These lead acid batteries are probably 4 years old and dont really hold charge well anyway so they are due for a change. They have had a shortened life I think because they have gone flat rather too often in the past partly because of limited capacity.

Advice would be more than welcome.

Kind regards

Simon

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[john_morris_uk]

If I indicate some guidelines, perhaps you can decide which way to go? Also a search of posts will find lots of discussion on the subject.

1. Add up all the Amphours you will need between charging. Be strict and accurate!
2. Assume that with a good intelligent charging system you will only get to about 85 or 90% charged batteries.
3. If you want long battery life don't allow them to discharge below 40-50-% very often (if ever)
4. Use the correct type of battery - Gels are expensive and IMHO not worth the money - you also can't charge them as quickly. I suggest deep discharge leisure batteries or traction batteries are the way to go for domestics.
5. Make sure that they are charged properly - what goes out must be put back in plus 15% or so for inefficiency of the charge/discharge cycle.

From 1 above you will see why so many owners get twitched about lights being left on when you are at anchor. (We have over 400Ah of domestic battery bank in our new boat plus a seperate engine cranking battery, but we do live aboard sometimes.)

If you can't find the room for the Ah the calculations indicate, you will be discharging the batteries more than they can realistically cope with and this will shorten the battery life.

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[willothewisp]

Go for carbon fibre batteries (Elecsol). I know I'm going to. My 6 or 7 year old lead acid batteries are due for replacement, and the carbon fibre ones are claimed to be undamaged when deeply discharged, which normally shortens the life of a battery. Also, if possible, fit a three stage charger. Definitely saves your batteries.
For full info download "electricity on board"from the victron site (www.victronenergy.com)
Good luck


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[andyball]

well, a couple of well known smart-regulator manufacturers reckon cheapo lead-acid is the best thing for most people.

Elecsol sound amazing....web based research suggests they're great unless you need the warranty upheld (allegedly !).

many people buy cheap leisure batteries & accept they won't last long, probably flash-harry batteries are more economical long term? but not everyone wants to put their own money on it.

Locally you can buy two 85AH leisure types for under £60, or ,say £500+ for two optima 55AH . Likely you'll get more usable capacity from the optimas, but how badly do you want it?.

If it was my money, & I wanted to try something better than cheapies, I'd probably try elecsol too; they're not that pricey....almost too cheap to believe the claims made?.

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[anabel]

A good rule-of-thumb is to have an alternator capable of delivering about 1/5 the amphere hour capacity of the batteries is has to charge. This means the max AmpH capacity of your batterys will be decided by the output of your alternator.

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[charles_reed]

Batteries

Best IMHO are traction or industrial batteries allied to a smart regulator and pulse charger

My last domestic battery was changed after 12 years - only because 1 cell was slow in recovering after fast discharge.

Gel batteries need no maintenance but are slow to re-charge, Pb/Ca give you less capacity for a given case-size, are lethargic in giving up their power and require about 3 times as long as Pb/H2SO4 batteries to recharge, but stand very deep-cycle discharge with relative equanimity.
Carbon-fibre batteries have been around for a long time, the makers make great claims but IMHO they are unproven.
Deep-cycle leisure batteries are close to being a cynical rip-off by the manufacturers, again IMHO.
Look for golf-cart or similar 9-plate batteries for your minute case-size.

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