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Solar....how much wattage is enough


Matt&Jo

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Hi all, so i have not carried out an audit of my power to work this out as i dont fully own the boat yet but is there a kinda rule on how much is a good benchmark for a liveaboard... 400w of solar???

 

I want to get thing rolling asap as we collect her a week and a half after the survey all being well....i want to start looking into costing this stuff and sourcing it so advise away if you would be so very kind 

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without a power audit (everyones usage varies) it is impossible to answer without getting wildly conflicting answers.

although not a liveaboard I do just fine on 140w, others struggle with 2kw

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Get a controller big enough to accomodate your growing needs, or keep adding controllers as you add panels.

 

1000W easily covers our needs flat mounted from April-Oct, and we could probably get away with 500W.

 

All depends upon your requirements

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I have read that most people who don't particularly skimp on the use of power, and who don't go over the top with it, use between about 70Ah and 100Ah per day.

 

500W at 50% efficiency for about 8 hours a day provides about 140Ah per day, so probably enough for most people between early April to late September.

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So 4-500w is aboot right then....to start with. Would it be faor to say that the standard tilt brackets you can get for about £50 are a reasonable choice for most? Ive got an evening of solar hunting....any recommended sellers please do shout out. Im after reasonable cost and proven reliability

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Bear in mind no matter how much solar you get, it more or less stops working completely in the three winter months, in my personal experience with several installations.

 

Edit to add:

 

So no matter how much solar you have, you'll need to be able to replicate its performance with fossil fuel in those three winter months when your leccy demand is highest.

 

 

 

 

Edited by Mike the Boilerman
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Apart from monetary budget the next most important budget seems to be roof space. I've got 590w in total and cannot really increase on that as being single handed I need to have some clear roof space for locking. 

Rusties advice on controllers is well worth taking re allowing for future expansion. 

Only advice I would give is to get high voltage, low amp mono panels and match them with a genuine Mppt controller. 

400w seems a decent starting point to see how you get on but as Mike has pointed out in winter you mostly be getting nothing but a trickle from them. Rest of the year you wouldn't want to be without them 

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I can offer a slightly different view for if you mostly cruise rather than moor for longer periods.  The first phase of charging to get back to 80% goes in fairly quickly - the batteries will take a high current at first, diminishing as they fill.  After that, the charging current tapers off and it takes a long time to achieve a 100% charge.  A decent cruise with reasonable alternator ought to fill your batteries, but even a fairly short cruise will get you quite a way up the percentage fill, with a tank of hot water as a bonus. After a short cruise, or a hour or so engine run alongside, you'll only need maybe a 10 or 20 amp capability to finish the job - so a couple of hundred watts could cope if used to "top off".  Same caveat applies about the shorter, darker days though.  Still, it might work quite well for much of the time and could very well easily cope with many a leisure boater's needs.  Not right for everyone, but another idea to consider.

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We are pretty typical using 100-120 Ahrs a day and last summer managed with 200watts but this was on top of 4 hrs cruising per day. Over winter we added 300 watts more and it makes a big difference in summer with us not needing to cruise each day. Also a big difference when it is not very sunny. Really glad we added the extra to get us to 500W.

Pretty useless in the winter though. 

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12 minutes ago, WotEver said:

Totally illegal if true. Trading Standards would be interested. 

 

Was certainly true last time I bought from them. In fact every time.

Copy N paste from their shopping cart checkout:

 

Checkout

Discounts: (automatically applied)
Card Payments / Paypal - 2.5% off
Bank Transfer / Cash - 5% off
Buy Now Pay Later - 0% for 4 months with Paypal Credit

 

Perhaps they would argue giving a discount for card payment smaller than the discount given for bank transfer or cash is different from adding a charge to pay by card. I can't imagine they haven't considered the issue!

 

 

Edited by Mike the Boilerman
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8 minutes ago, Mike the Boilerman said:

 

Was certainly true last time I bought from them. In fact every time.

Copy N paste from their shopping cart checkout:

 

Checkout

Discounts: (automatically applied)
Card Payments / Paypal - 2.5% off
Bank Transfer / Cash - 5% off
Buy Now Pay Later - 0% for 4 months with Paypal Credit

 

Perhaps they would argue giving a discount for card payment smaller than the discount given for bank transfer or cash is different from adding a charge to pay by card. I can't imagine they haven't considered the issue!

Oooh, that’s a clever (?) way around it. I wonder what TS would make of it?

 

Tony

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5 minutes ago, WotEver said:

Oooh, that’s a clever (?) way around it. I wonder what TS would make of it?

 

Tony

 

I'm pretty sure TS would hve ruled it illegal. No matter how you wrap it up, for the past many years we card merchants have not been allowed to charge different prices depending on payment method.

 

I've a sneaky feeling however this changed recently and the rules became more complex (quelle surprise), but I didn't pay attention because it is my policy to charge the same whatever payment method the customer chooses. 

Edited by Mike the Boilerman
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24 minutes ago, Mike the Boilerman said:

 

I'm pretty sure TS would hve ruled it illegal. No matter how you wrap it up, for the past many years we card merchants have not been allowed to charge different prices depending on payment method.

 

I've a sneaky feeling however this changed recently and the rules became more complex (quelle surprise), but I didn't pay attention because it is my policy to charge the same whatever payment method the customer chooses. 

Wot?  Even cash, nudge nudge, wink wink, know what I mean? ?

 

You're no fun, Mike!

 

George

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37 minutes ago, Mike the Boilerman said:

 

I'm pretty sure TS would hve ruled it illegal. No matter how you wrap it up, for the past many years we card merchants have not been allowed to charge different prices depending on payment method.

 

I've a sneaky feeling however this changed recently and the rules became more complex (quelle surprise), but I didn't pay attention because it is my policy to charge the same whatever payment method the customer chooses. 

A bit of Googling suggests that ‘discount for cash/bacs’ is quite a widespread model used to cover the ‘no surcharge’ rule. 

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8 minutes ago, WotEver said:

A bit of Googling suggests that ‘discount for cash/bacs’ is quite a widespread model used to cover the ‘no surcharge’ rule. 

To me it looks like the retailer is kinda of back street and box it and ship it cheap so customer service will be low priority.  Me personally wouldn’t order anything over the Internet or anything that needs delivered worth hundreds with anything other than a credit card.

Edited by Robbo
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15 minutes ago, Robbo said:

To me it looks like the retailer is kinda of back street and box it and ship it cheap so customer service will be low priority.  Me personally wouldn’t order anything over the Internet or anything that needs delivered worth hundreds with anything other than a credit card.

Agreed on both points. 

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