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Solar panel output


LucyCath
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Absolute newbie here so be gentle. I have just bought a cruiser that I want to equip with solar panels. The boat already has one very small one that says its drawing 12v when I looked today. How many solar panels and how much wattage should I be looking at getting to power a liveaboard lifestyle of: phone charging, WiFi router, laptop use, sewing machine, fridge, electric oven and small projector. Just looking for an estimate. Ive been looking at 350w panels but not sure how many would do the job. Thanks! 

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3 minutes ago, LucyCath said:

Ive been looking at 350w panels but not sure how many would do the job. Thanks! 

The first thing to realis is that for 5 months of the year you are going to get virtually nothing out of solar panels, so you do need to  plan to have a second source of electricity generation.

 

When you say 'cruiser' do you mean a fibreglass motor cruiser, or a cruiser stern steel narrowboat.

 

If it is a fibreglass cruiser it is unlikely that you will be able to get enough solar 'on the roof' to even keep you going in Summer.

 

You will certainly not be able to run an elctric oven and a fridge.

 

I think you firstly need to do a power audit of the equipment you want on board, you can then look to see how much you can generate and then find out how to 'match the two numbers' - BUT, the 1st move is to dump the idea of an electic oven.

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9 minutes ago, LucyCath said:

How many solar panels and how much wattage should I be looking at getting to power a liveaboard lifestyle of: phone charging, WiFi router, laptop use, sewing machine, fridge, electric oven and small projector.

 

Much more solar than can physically fit on your boat and a shorepower mains hookup is the only correct answer.

 

You need to do a "power audit" - search the forum for this phrase for more details.

 

Is the sewing machine used all day every day or just now and again for an hour or so?  As Alan says, the electric oven is worrying on it's own, and the projector might be depending on how big it is.

 

Don't forget to add your lights and water pump(s) to your usage!

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Solar output is of course reduced in winter and certainly cannot be relied upon.  Right now during the shortest days I get about one third of my maximum output (around 300w out of an 860w array) in strong unobstructed sun if the boat is positioned east-west with panels tilted south.  Still useful, but not much given how short the days are.  If you want to spend any time on your boat outside a marina solar is a no-brainer, the more the merrier. 

 

As the others imply gas hobs or stove tops are a more efficient means of cooking, so unless you have deep pockets and there is some reason why you are determined to be all electric this is a much better option.  If you have high power needs in the winter away from shore power a portable generator may be a more convenient solution... mostly because they are easier to maintain than your engine and provide a largely bulletproof power source for when things go wrong.  Just don't moor near me if you get one. 

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10 hours ago, LucyCath said:

Absolute newbie here so be gentle. I have just bought a cruiser that I want to equip with solar panels.

Oops!  As gently as I can, may I suggest that this sort of research should come before buying the boat?  Too late for you to avoid disappointment, because what your hoping to do is not achievable, but maybe it might help others avoid making the same completely avoidable error. :(

 

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12 hours ago, LucyCath said:

Absolute newbie here so be gentle. I have just bought a cruiser that I want to equip with solar panels. The boat already has one very small one that says its drawing 12v when I looked today. How many solar panels and how much wattage should I be looking at getting to power a liveaboard lifestyle of: phone charging, WiFi router, laptop use, sewing machine, fridge, electric oven and small projector. Just looking for an estimate. Ive been looking at 350w panels but not sure how many would do the job. Thanks! 

If by electric oven you mean an electric cooker with an electric hob then even on shore power most marina supplies would not be enough to power it without overloading.  To do what you want in summer you would need as many panels as a house.  In winter, it can’t be done by solar.  
 

Added - Forget to mention that you would also need a massive amount of batteries to run that lot after dark.

Edited by Chewbacka
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Solar panels do not "draw 12v" that's bunkum. They need to produce a voltage in excess of the battery voltage so that a current flows into the batteries. It is current that charges, not voltage.

 

You will not run an electric oven on solar in winter with the area restriction of a boat.

You will not run all those appliances simultaneously either.

 

Search threads on here about a power audit, you have much to learn and understand.  Being as gentle as possible but your lack of knowledge is going to make life on a boat difficult for you.

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13 hours ago, LucyCath said:

Absolute newbie here so be gentle. I have just bought a cruiser that I want to equip with solar panels. The boat already has one very small one that says its drawing 12v when I looked today. How many solar panels and how much wattage should I be looking at getting to power a liveaboard lifestyle of: phone charging, WiFi router, laptop use, sewing machine, fridge, electric oven and small projector. Just looking for an estimate. Ive been looking at 350w panels but not sure how many would do the job. Thanks! 

On the red bit. As @Tracy D'arth said they do not draw 12V but might produce anything up to about 36 volts and that will destroy your batteries let alone the boat's 12V equipment so you need a controller sized to handle the amps and volts the panels can produce. We need to know what is telling you 12V because in boat terms 12V is an almost totally discharged battery AND is nowhere near enough to even start charging a battery. You ned an absolute minimum of about 13.6 volts for charging and ideally around 14 volts with a well charged battery.

 

If that 12V is on the solar controller then the panel is doing absolutely nothing of much use. If its on a voltmeter with nice coloured bands on it then its unlikely to be accurate enough to be telling much more that if the batteries are likely to be charging or not.  If its a digital meter showing decimal places than its good but we then ask how many battery banks do you have and which one is it measuring. If its the engine battery (assuming two banks) then the battery may be too discharged t start it. if its the domestic bank and you want lights for a few hours tonight stop all use of electricity and work out how you are going to get the batteries recharged ASAP - even if it does man running the engine at maybe 1200 to 1500 rpm for the rest of the day. An hour after you stop it pray the voltmeter shows around 12.7 volts half an hour after stopping.

 

I agree with all that what must seem like very negative posts to you about your expectations. Its simply not realistic or in my view even possible. You have much to learn so for a start I would suggest that you spend some time studying and understanding both sets of course notes on my website (tb-training.co.uk). Start with the electrical ones and ask me or the forum to clarify anything you don't understand.

 

What sort of fridge is this? If you are very lucky it will be a three way gas, mains electricity, 12v one and if so NEVER run it on 12v unless you instead to destroy your batteries in days or less., use the gas option. It may well be a 12v compressor fridge and if so during the winter may I suggest you find a cool area outside and in the shade to store your perishables so you don't use the fridge. That sort of fridge uses all of a typical 110Ah battery's worth of electricity per day and more to the point you need to put it all and more back into the battery the next day. (This sentence is an over simplification but the message is correct). Cook on gas, just like almost all other boaters. I doubt there are more than a handful of all electric cruisers on the UK waterways and any that are will almost certainly have a hefty built in generator.

 

You will also need an inverter to convert your 12V DC to mains voltage AC and in inexperienced hands inverters encourage excess electricity use.

 

In an ideal world you will need some kind of battery monitoring so you don't destroy batteries every very few weeks.

 

Anyway, welcome to the forum and the wonderful world of boating.

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  • 4 months later...
On 22/12/2020 at 23:38, Ex Brummie said:

Obviously we have given the OP too much to think about, or there is insufficient to charge her equipment so she can reply.

Ha ha. Nice one. I have been following this with interest, being about to embark on the solar-power odyssey myself.

 

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1 minute ago, Rob Stuthridge said:

Er...I only joined a week ago! This thread is 'new to me', so bite me.

Welcome to the forum Rob. I won't be taking up the offer biting you as I'm sure you'll quickly see my post was purely in jest. Again, welcome aboard - I hope you enjoy the forum. :)

 

 

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12 minutes ago, Sea Dog said:

Welcome to the forum Rob. I won't be taking up the offer biting you as I'm sure you'll quickly see my post was purely in jest. Again, welcome aboard - I hope you enjoy the forum. :)

 

 

Ha ha...sorry Sea Dog, married to a Yank, so 'bite me' is always meant in jest also! Thanks for the welcome. I'm a NB-info sponge right now, currently in the process of finalising a boat purchase for the first time...tomorrow should be the day, hopefully, when she belongs to us. This forum is absolutely golden with so much experience and great information, even the older stuff. ?

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4 minutes ago, Rob Stuthridge said:

Ha ha...sorry Sea Dog, married to a Yank, so 'bite me' is always meant in jest also! Thanks for the welcome. I'm a NB-info sponge right now, currently in the process of finalising a boat purchase for the first time...tomorrow should be the day, hopefully, when she belongs to us. This forum is absolutely golden with so much experience and great information, even the older stuff. ?

Exciting times Rob - I hope you, your yank and your new boat have many wonderful, happy times together! ;)

 

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