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nick1965
nick1965

Posted: Sat Dec 25, 2010 12:46pm

Post Subject: Electricity

Hi, I am very confused and recieving all sorts of conflicting advice regarding converting 12volts to 240v. The boat is 40' and I would only intend to use 240v for use of telivision and sound system, possibly the fridge in the Summer, Presently there are three batteries including the starter battery. Is it best to, as recommended to to install an additional battery, invertor and second alternator. How long would I need to run the engine per day to keep up the charge. I have then been told that idling the engine, being diesel is very bad for it. Is that true? Are there any other optons other than getting a generator? I will if strictly neccasary but notice other people site them well away from the boat. Is that just for reasons of noise? Hope you can help. Regards, Nick Phillips

Tony-B
Tony-B

Posted: Sat Dec 25, 2010 4:58pm

Post Subject: Electricity

Yes there is a far better, but more expensive option and that is to run a 12v boat. You can get 12v TVs, 12v fridges and car radios with CD/MP3 players are also 12v. If you go down the inverter route you must plan to use 20% more electricity than you would with a 12v system because despite what the vendors say you would be very foolish to assume the inverter will be more than about 80% efficient. However a SMALL inverter for phone and camera battery charging is fine, its the large ones where problems start. No one can answer the battery questions until you take some time and do a power audit and charging calculation. You will find samples http://www.tb-training.co.uk/Poweraudit.htm. (all on one line) It is true that idling a diesel does it no favourers but you should not be idling it until after an hour or so has passed, you should be running it at the speed that gives maximum charge and that will be loading the engine similarly to the prop on normal canal boating. There is one make of engien who will not honour the warranty if you idle for more than about 20 minutes but most makes do not mention it. The alternatives are wind generators or solar panels but without a lot more information about how you intend to use your boat I can not say more. The bottom line is to do all you can to minimise electrical consumption. A "Honda" type suitcase generator is not noisy and most are probably used chained up to the boat (they are "desirable"). Tony Brooks

nick1965
nick1965

Posted: Thu Dec 30, 2010 4:07pm

Post Subject: Electricity

Dear Tony, Thanks for the advice I shall follow that. One last question, I intend to moor up in a maina, now if I buy these 12v appliances am I still able to charge using their power? I was thinking that they only supply 240v and that can not be used to power and charge at 12v. Best reagards and thanks once again as I am a lot clearer about this. Nick Phillips Nic

Tony-B
Tony-B

Posted: Thu Dec 30, 2010 7:40pm

Post Subject: Electricity

I will now make it less clear. If this is a holiday boat mooring in a marina with a mains shoreline then as long as you buy a multistage battery charger and leave it running 24/7 your batteries will usually be fully charged and when you are in the marina the charger will supply your 12V load up to its maximum output. As long as you can get the batteries fully charged every few weeks you could go down the mains equipment and inverter route but I am sure this would require at least one more domestic battery and perhaps an alternator upgrade but whatever you do we can not address those two things until you have worked through the power use and charging calculations I pointed you towards. If you send me your results I will be able to comment further. Now you can get inverters that also contain a battery charger but I would prefer to have separate units so you do not loose both the battery charger and the inverter output if one part fails. If you go down the inverter route the only way to be sure the audio-visual equipment will work as it should is to buy a pure sine wave inverter - these tend to be more expensive. The important thing is if you have access to a shoreline then buy and use a multistage charger. It will probably give you one or two years more battery life (as long as you have done those calculations and acted accordingly!) Tony Brooks

nick1965
nick1965

Posted: Fri Jan 07, 2011 2:26pm

Post Subject: Electricity

Dear Tony, Thanks for the advice, sorry not to have replied earlier Ive been on holiday. On the subject of generators, if the appliances 12 v do I have to have 12v gearator? Do I need an appliance to charge the batteries as someone has told me? Who say, other than a marine engineer be able to fit all this and advise me. I am rather limited about the choice of engineers in this part of the world which is Bath and the last one I used gave me very bad advice that I know know to be very untrue. Thanks once again, Best regards, Nick

Tony-B
Tony-B

Posted: Fri Jan 07, 2011 9:26pm

Post Subject: Electricity

Do not even think about trying to use the 12v output some generators have to charge batteries. Buy a proper mains multistage battery charger and use that. IF you are happy with a transportable generator I can see no reason why a reasonably competent DIYer could not fit the battery charger but I am not going to say someone I do not know could fit a proper on-board marine generator. I must caution about the dangers of petrol generators on boats. I note that you have not sent the results of the calculations I advised in my first reply so nothing I say can be any more than guesswork. Matching generators and chargers involves something called the Power Factor so if you do decide to buy a generator and mains charger get the supplier to advise you on the largest charger the generator will drive without problems. I your inverter is a combi-unit then it will have a charger built into it (see answer above) so in that case you will not need a separate charger but make sure your generator has a suitable output to drive it. Tony Brooks

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