ChrisKaye
regular
Reged: 26/08/2004
Posts: 547
Loc: Wiltshire
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Only had this new (to me ) boat 6months or so so still finding my way around it all.
Currently when unplugged from shorepower my batteries (2 in the domestic bank) only last for around 4 hours with just the fridge on, radio and a couple of internal lights (standard 12V halogen downlighters) on. I've had the batteries checked and the bloke says the batteries hold their charge OK
I have a generator fitted to the boat from new which charges the batteries and I wondered if the domestic battery bank was deliberatly a smaller size due to having a generator fitted.
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Wiggo
regular
Reged: 10/09/2003
Posts: 3405
Loc: (State, Country, etc.)
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Umm, yer man's wrong - they're shagged. The fridge should use about 1-4Ah, the radio uses next to nothing and two halogen bulbs use about 2Ah between them.
If you had a pair of 100Ah domestics, they should last at least 20 hours and possibly twice that.
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The nicest thing about not planning is that failure comes as a complete surprise, and is not preceded by a period of worry and doubt.
Nereid Charter
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ChrisKaye
regular
Reged: 26/08/2004
Posts: 547
Loc: Wiltshire
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Thank you Wiggo for the eloquent technical description of the current state of my batteries. To be fair to the bloke, he told me he's more mechanical than electrical and I was hoping this was the case instead of having to get an expensive marine electrician in
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Wiggo
regular
Reged: 10/09/2003
Posts: 3405
Loc: (State, Country, etc.)
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Never been afraid to call a spade a manually operated excavating appliance...
If you really want to know if they're OK, get a £5 'turkey baster' hygrometer from Halfrauds and test them yourself. It only takes a few minutes.
What you need to do is work out how much current everything draws. A fridge can draw about 4 or 5 amps when it's running, but it might only be on 20-25% of the time, so it averages about an amp. If you know the power consumption, just divide by 12 to get the number of amps something needs, so your 10W halogen lights use just under an amp.
Now work out the energy use: just multiply the current by the number of hours you will run it. Fridge for 5 hours = 5Ah, two lights for 1 hour = 2Ah etc and that will tell you how long your battery should last. Bear in mind that you will rarely be able to use more than 40% of your batteries' stated capacity, so if you have 100Ah of domestics, expect to be able to use 40Ah or 40 hours of fridge and nothing else.
Incidentally, fridges are difficult to work out, because they use more power if you keep opening them to take beer out...
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The nicest thing about not planning is that failure comes as a complete surprise, and is not preceded by a period of worry and doubt.
Nereid Charter
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S28
regular
Reged: 19/09/2002
Posts: 4115
Loc: South Coast
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Batteries are cheap. I chuck 'em away after 5 years.
dv.
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Hurricane
regular
Reged: 11/11/2005
Posts: 1606
Loc: Sant Carles de la Rąpita
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Quote:
Incidentally, fridges are difficult to work out, because they use more power if you keep opening them to take beer out...
Solution - ration the beer.
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blueglass
regular
Reged: 27/04/2003
Posts: 744
Loc: Greece (boat) Shropshire (home...
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I have 2 x 110 AH deep cycle batteries for my domestics and yes I get much longer than that. with the fridge turned down a notch or two they will last 24 hours. With normal fridge use + lights, stereo, water pumps etc about 18 hours or so. 4 hours is way out.
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mikehibb
regular
Reged: 23/09/2007
Posts: 425
Loc: Turkey Azerbaijan and Georgia
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Quote:
Quote:
Incidentally, fridges are difficult to work out, because they use more power if you keep opening them to take beer out...
Solution - ration the beer.
I can assure you that my passengers/crew would all chip in to buy a bigger battery bank rather than think about that un-repeatable phrase.
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gwylan
regular
Reged: 31/05/2007
Posts: 272
Loc: Portishead, on tour
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Wiggo has grasped the technical niceties of the situation.
Also make sure you keep the fridge full to capacity with beer - that way once it is cold it uses less energy to keep the contents cool.
Fridge uses 5A, works about 25% of the time so uses about 30AH per day - 100AH battery should last 3 days, if you get over 2 days [ 48 hours] with the lights, water pump and everything else you are doing well
If you are feeling keen you can make sure that there is a good airflow around the back of the fridge. We achieved this with a cheap but quiet computer fan, from Maplin, and saw a comfortable increase in efficiency
The rest is too tiresome and technical to deal with. Replace the batteries and have another beer....
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The pessimist complains about the wind;
the optimists expects it to change;
the realist adjusts the sails
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Wiggo
regular
Reged: 10/09/2003
Posts: 3405
Loc: (State, Country, etc.)
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Mike, I'd like you to go away and think carefully about what you just said. Then you can come back and apologise to all the nice people on the forum you just upset.
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The nicest thing about not planning is that failure comes as a complete surprise, and is not preceded by a period of worry and doubt.
Nereid Charter
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