Advice re battery chargers

[pelicanpete]

Could anyone out there please advise on what sort of battery charger and/or set-up I may need?
I have no knowledge of these specialised marine devices and, before buying, would appreciate the 'experts' knowledge and comments.

On my 31 ft motor cruiser I have a fridge, navaids, incl radar and low wattage (10w) halogen interior lights, etc. I have no idea of the total power consumption of all this stuff.

My desire is, when in a marina and on shorepower, to run the fridge full time, have all the interior lights on (at night), the 12v hi-fi, keep a cooling fan running (for my wife!) and have the battery bank (3 batteries , 2 house + 1 engine) kept fully charged.

Thanks, in advance to knowledgable forum-dwellers.

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[Anthony]

Hi,

I would suggest you go and start at the begining by calculating your electricity needs. Without it any of us would just be stabing in the dark, e.g. is it a big or small fridge, how many halogen lights, 2, 5 , 10? there is a lot of variation there

Idealy use an ammeter to measure how much current each item draws, the fridge is a little more tricky as it will switch itself on and off.

I would then suggest you review how much battery power you have, its really easy to kill batteries by draining them to low (<50% or rated capacity). you may find that you need more, and its better to figure that out before you buy a charger, then have to replace it later.

Once you have those numbers we, or the charger manufactueres wouyld be much better positioned to advise you, but basically I would suggest an intelligent multistage charger, the actual capacity would depend on your findings.

If you really dont want to do that, and just want to suck it and see then I would suggest a stirling 20 as a minimium, prob a 30, but thats only a guess without any reall decent info to go on.

Anthony

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[paddywackcocker]

add up your consumers, 6x10watt lamps devided by the volts (12) gives you your amps consumed = 5amps. W/v=A. Can use it the other way if your drawing 5Amps from a 12V source and are powering 6 lamps 5x12=60/6=10W

I would be inclined to allow 12 amps continous for the frigde as to allow a saftey margin and the beers extra cold, but should have values written on side of Motor
You could put in a regulated 12v power suply so as to run all domestics when on shore power and just have a battery charger of mid range quality to keep batterys in top charge.

<hr width=100% size=1>Sorry for the spilling

 

[Guest]

Wattage ....

OK - find all the data panels / instruction books on the items you can .... they will tell you a) voltage supply required, b) amps / milliamps supply will have to provide, c) kilowatts / watts that appliance / item consumes.

Now for each voltage set .... ie all items with 12-15V requirement and separately all items that are 220 - 240V requirement - complete the following 4 steps for each voltage set ... 12V and 240V.

1) If it says watts / kilowatts - add them up into watts .... (kilowatt = 1000 watts). 2) For all the items that they do not say watts - then take the voltage supply and multiply by the amps required= watts then add 10% for start-ups / safety.
3) Add all watts together and now add another 10%. This gives total power requirement of your system ......
4) Now divide this total by the voltage supply - this will give the ampage requirement for each voltage set ..... 12V or 240V respectively.

Now toddle off to your local electrical / Caravan store such as Maplins etc. and they will pass across counter the charger / article suited to that rating ..... even Les Smiths / Halfords !!


<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[Guest]

12V convertor ....

As with Paddywackcocker ..... I prefer the 12V transformer run from the mains with engine / battery charger purely for batterys.
A suitable relay in line to auto switch between them is fine - or go for the ZIG panel in your Caravan shop .... a masterful piece of kit - bit pricey, but worth it.

Marine kit .... is it really worth it ? Put the word Marine in front of the name and wow - count the cost !! Caravan shops often sell same article with its original / other brand name on .... get my drift ...... fogive the pun !!


<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[Rick]

Agree with Patrick / Nigel, but a couple of points.
1. If the electric fridge uses the Danfoss BD35F or BD50F, get a shore power rectifier, as they run the compressor at high speed suppying 24 volts instead of 12 - faster cooling and less running time.
2. While mraine generally means more cost, in the case of chargers it may well be justified - cheap units often pair the mains and DC earth together, asking for an underwater corrosion problem. If you're buying a three stage unit, then this is unlikely to be the case even if not a marine variant.

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[MainlySteam]

And adding to your good point 2 is that if the mains and DC are not isolated in the charger by means of an isolating transformer then reversed polarity mains puts 230 v directly onto ones DC system.

Also, if the boat is one with an isolated DC system ie DC negative is not bonded to AC earth, then the isolation and its benefits will be lost and, as you infer, any galvanic isolator will also be bypassed if the boat is one without an isolated DC system.

John

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[silverseal]

For what it is worth, I have a 30 ft boat which uses 24 volt starting for the Ford Engine, but charges 12 volts .... In addition I have a another 110amp deep cycle battery, which powers lights, fridge, autopilot, radio etc. the previous owner had the boat in a marina and charged the batteries from 240 volts every few weeks. I use a 15watt solar panel, which charges all three batteries, and the levels are usually between 12.8 and 13.1 volts, when we go away. The battery which powers the boats lights etc, is often below 11 volts due to the fridge,after a trip but quickly recovers, when the solar panel is reconnected. The panel costs about £150, and we are about 1 mile away from the nearest mains power

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[pelicanpete]

Thank you one and all! Appreciate the advice.

<hr width=100% size=1>It's more important to be liked
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[MAURICE]

Hi
I have a Bavaria 34 with the same gadgets as indicated. My boat is in Spain so the fridge and fan are used most of the time
I use a sterling 20 which keeps my batteries well topped up

regards

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