Amount of solar needed?

[MtB]

On 29/05/2017 at 23:33, efanton said:

 

Finally,  would there be a problem (apart from the initial expense) from having too big a solar array?  Could too much power damage you battery banks?

 

No, and no.

[Paul C]

17 minutes ago, efanton said:

question from a newbie.

 

Is there not a meter that can be fitted to tell exactly how much power has been drained from your battery bank each day?

Would that be a difficulty thing to wire in to an existing set up, and if not how much would it cost roughly?

Surely if you were able to keep a record of how much power was taken from your battery bank each day or week then  deciding how much solar you need or how often you are going to need to run your engine (or separate generator) would be simple.

Finally,  would there be a problem (apart from the initial expense) from having too big a solar array?  Could too much power damage you battery banks?

This charging of battery banks,  how big your banks should be, etc etc, seem to be a regular topic on the forum. 

 

There's a lot of merit in having both an amp-hour counter AND a smartgauge AND the knowledge/understanding to be able to interpret the readings in a scientific way - for example the Victron tail current requirement which "resets" the meter to 100% charged, is somewhat erroneous, its worth knowing why and what to actually set it to, rather than blindly changing the values based on an internet forum thread.

Such a gauge - which combines the smartgauge and an amp-hour counter; and has additional algorithms to provide info such as battery health - exists - it is the Merlin Datacell II - however it costs a lot (if you need to ask, you can't afford it!).

[MtB]

On 29/05/2017 at 23:33, efanton said:

 

This charging of battery banks,  how big your banks should be, etc etc, seem to be a regular topic on the forum. 

 

Yes, and you ought to spend a couple of days reading and understanding them!

[Paul C]

Too big a solar installation might simply not fit onto the roof of a narrowboat; or fit, but with some of the panels behind the centre point (ie behind the centre attachment for the centreline) and thus be prone to damage from the rope inadvertently catching a panel and tearing it off (possibly in a lock, for example).

Or it might fit but not allow other items on the roof, for example you'd lose some potential storage space or something like that.

And of course, it would be a needless cost.

[efanton]

4 minutes ago, Mike the Boilerman said:

 

Yes, and you ought to spend a couple of days reading and understanding them!

And I am slowly but surely going through all the old posts on the forum.  (and that wont take days it will take weeks)

 

[efanton]

32 minutes ago, Paul C said:

Too big a solar installation might simply not fit onto the roof of a narrowboat; or fit, but with some of the panels behind the centre point (ie behind the centre attachment for the centreline) and thus be prone to damage from the rope inadvertently catching a panel and tearing it off (possibly in a lock, for example).

Or it might fit but not allow other items on the roof, for example you'd lose some potential storage space or something like that.

And of course, it would be a needless cost.

The question was would a solar installation cause problems by 'overcharging' and you have answered that by saying no.

Obviously no one is deliberately going to install a solar array bigger then they need,  but I might be tempted to install an array that produces slightly more then I estimate I will need if I know this will have no detrimental effect on their battery banks or electrical system.

 

[MtB]

On 30/05/2017 at 00:41, efanton said:

 

Obviously no one is deliberately going to install a solar array bigger then they need, 

 

In saying this, you demonstrate a fundamental misunderstanding of the nature of solar.

The output varies by a ratio of about 20:1 over the seasons in my personal experience. So how big an array do I 'need'?

[efanton]

6 hours ago, Mike the Boilerman said:

 

In saying this, you demonstrate a fundamental misunderstanding of the nature of solar.

The output varies by a ratio of about 20:1 over the seasons in my personal experience. So how big an array do I 'need'?

are you naturally a pedant, or is it you put great effort into belittling people you assume to have less knowledge than yourself?

While I have never owned a narrow boat I do have a reasonable knowledge of solar but in this case very little to none in managing battery banks (have owned a few (fishing)boats before and built large scale model aircraft).  I am very well aware that the power output of an array will vary massively depending on time of year, cloud cover , which way the panels are tilted or pointed as well as the actual quality of panel bought

Having said that I dont think anyone  on a narrow boat expects solar to be their only source of power, if its turns out that way some of the time then that's a bonus.  As I see it you ensure you have the capability of providing all your power needs without solar (engine, generator or shore power) , and then the solar simply supplements or reduces the overall costs.  Anything beyond that is a big bonus. 

Yes you might produce 20 times more solar power in the summer (not sure where you got that number), but any school child would and does realise that output will vary significantly.  You better get down of that soapbox, one day you will slip and fall.   Advice is very welcome but put downs or pedants arent. 

When deciding which panels and set up to buy for solar you dont calculate on the maximum theoretical output. having helped install solar systems on houses you factor in which direction the roof faces, the slope of the roof,  shade (tree, tall buildings etc), quality of the panel, and there are other factors as well.  certainly for the better brands of panels for use of homes most provide either a calculator or guidelines to help aid in deciding how many panels you need, or how much you can POTENTIALLY save for a given area of solar panels.  Obviously these calculators would be totally useless in relation to a narrowboat, as the roof will not be facing in a fixed direction while cruising, hedgerows, trees building and other obstacles will continuously vary, but many of the principals will be the same.  Its not an exact science simply because there are many variables. The best you can do is estimate by using averages (daylight hours, etc) and the recommendations by the manufacturer.

 

Quote

In saying this, you demonstrate a fundamental misunderstanding of the nature of solar

Not at all

but maybe , you demonstrate a fundamental misunderstanding of the person you are talking too. 

At the very least you should not assume everyone that might be new to this forum or new to  canal boats is not a complete idiot, and that  they might already have  skills and knowledge from their existing life that are relevant.

 

 

 

 

Edited May 30, 2017 by efanton

[rusty69]

4 hours ago, efanton said:

are you naturally a pedant, or is it you put great effort into belittling people you assume to have less knowledge than yourself?

While I have never owned a narrow boat I do have a reasonable knowledge of solar but in this case very little to none in managing battery banks (have owned a few (fishing)boats before and built large scale model aircraft).  I am very well aware that the power output of an array will vary massively depending on time of year, cloud cover , which way the panels are tilted or pointed as well as the actual quality of panel bought

Having said that I dont think anyone  on a narrow boat expects solar to be their only source of power, if its turns out that way some of the time then that's a bonus.  As I see it you ensure you have the capability of providing all your power needs without solar (engine, generator or shore power) , and then the solar simply supplements or reduces the overall costs.  Anything beyond that is a big bonus. 

Yes you might produce 20 times more solar power in the summer (not sure where you got that number), but any school child would and does realise that output will vary significantly.  You better get down of that soapbox, one day you will slip and fall.   Advice is very welcome but put downs or pedants arent. 

When deciding which panels and set up to buy for solar you dont calculate on the maximum theoretical output. having helped install solar systems on houses you factor in which direction the roof faces, the slope of the roof,  shade (tree, tall buildings etc), quality of the panel, and there are other factors as well.  certainly for the better brands of panels for use of homes most provide either a calculator or guidelines to help aid in deciding how many panels you need, or how much you can POTENTIALLY save for a given area of solar panels.  Obviously these calculators would be totally useless in relation to a narrowboat, as the roof will not be facing in a fixed direction while cruising, hedgerows, trees building and other obstacles will continuously vary, but many of the principals will be the same.  Its not an exact science simply because there are many variables. The best you can do is estimate by using averages (daylight hours, etc) and the recommendations by the manufacturer.

 

Not at all

but maybe , you demonstrate a fundamental misunderstanding of the person you are talking too. 

At the very least you should not assume everyone that might be new to this forum or new to  canal boats is not a complete idiot, and that  they might already have  skills and knowledge from their existing life that are relevant.

 

 

 

 

And breath........ 

[MtB]

On 30/05/2017 at 03:11, efanton said:

are you naturally a pedant, or is it you put great effort into belittling people you assume to have less knowledge than yourself?

While I have never owned a narrow boat I do have a reasonable knowledge of solar but in this case very little to none in managing battery banks (have owned a few (fishing)boats before and built large scale model aircraft).  I am very well aware that the power output of an array will vary massively depending on time of year, cloud cover , which way the panels are tilted or pointed as well as the actual quality of panel bought

Having said that I dont think anyone  on a narrow boat expects solar to be their only source of power, if its turns out that way some of the time then that's a bonus.  As I see it you ensure you have the capability of providing all your power needs without solar (engine, generator or shore power) , and then the solar simply supplements or reduces the overall costs.  Anything beyond that is a big bonus. 

Yes you might produce 20 times more solar power in the summer (not sure where you got that number), but any school child would and does realise that output will vary significantly.  You better get down of that soapbox, one day you will slip and fall.   Advice is very welcome but put downs or pedants arent. 

When deciding which panels and set up to buy for solar you dont calculate on the maximum theoretical output. having helped install solar systems on houses you factor in which direction the roof faces, the slope of the roof,  shade (tree, tall buildings etc), quality of the panel, and there are other factors as well.  certainly for the better brands of panels for use of homes most provide either a calculator or guidelines to help aid in deciding how many panels you need, or how much you can POTENTIALLY save for a given area of solar panels.  Obviously these calculators would be totally useless in relation to a narrowboat, as the roof will not be facing in a fixed direction while cruising, hedgerows, trees building and other obstacles will continuously vary, but many of the principals will be the same.  Its not an exact science simply because there are many variables. The best you can do is estimate by using averages (daylight hours, etc) and the recommendations by the manufacturer.

 

Not at all

but maybe , you demonstrate a fundamental misunderstanding of the person you are talking too. 

At the very least you should not assume everyone that might be new to this forum or new to  canal boats is not a complete idiot, and that  they might already have  skills and knowledge from their existing life that are relevant.

 

 

What a curious response. Far more loaded with assumptions about people than any of mine. 

I thought my comment which irritated you so much was perfectly reasonable given the assumptive comment of yours to which I was responding.

Edited May 30, 2017 by Mike the Boilerman

[Richard10002]

7 minutes ago, Mike the Boilerman said:

 

What a curious response. I thought my comment which irritated you so much was perfectly reasonable given the comment of yours to which I was responding.

+1 not necessarily the content, but the manner in which it is presented.

[efanton]

2 hours ago, Richard10002 said:

+1 not necessarily the content, but the manner in which it is presented.

 

I said

Quote

Obviously no one is deliberately going to install a solar array bigger then they need,  but I might be tempted to install an array that produces slightly more than I estimate I will need if I know this will have no detrimental effect on their battery banks or electrical system.

but you cherry picked just

Quote

Obviously no one is deliberately going to install a solar array bigger then they need

and then went on to say

Quote

you demonstrate a fundamental misunderstanding of the nature of solar

 

What fundamental misunderstanding are you referring too then?

Edited May 30, 2017 by efanton

[Paul C]

The truth is, most people don't know their future power requirements to any amount of accuracy. And a good proportion don't know their CURRENT power usage either.

 

[system 4-50]

12 hours ago, Mike the Boilerman said:

 

In saying this, you demonstrate a fundamental misunderstanding of the nature of solar.

The output varies by a ratio of about 20:1 over the seasons in my personal experience. So how big an array do I 'need'?

Methinks he will need to get a lawyer to frame the small print required to get his post sufficiently precise to avoid your candour?

[Paul C]

12 hours ago, efanton said:

The question was would a solar installation cause problems by 'overcharging' and you have answered that by saying no.

Obviously no one is deliberately going to install a solar array bigger then they need,  but I might be tempted to install an array that produces slightly more then I estimate I will need if I know this will have no detrimental effect on their battery banks or electrical system.

 

I really can't see the point in arguing on the internet about the various unknowns or variables.

Suffice to say, there is a huge variation in the power output of solar through the year, due to a combination of: shorter days; weaker sunshine (since the sun's rays pass through a greater amount of atmosphere due to the angle, in winter); and greater cloud cover. And even then, figures like 20:1 are an average - some winter days, there's basically SFA solar power generated.

This large variation (even taking averages) also coincides with a variation in power requirement - typically higher in winter, due to darker days needing more lighting, greater time spent indoors rather than outside, etc etc. Don't be thinking there's less demand on a fridge - fridges are installed indoors, and indoor areas are heated, so there is not a large power difference summer-winter.

Given the above, the question "how much solar power do I need" is solvable for one or a limited time of the year, and if an answer is given it must be noted the assumptions its based on. A more practicable question would be "how much solar power do I need to provide useful power from (for example) March-October"; another way of phrasing it might be "if I install (for example) 400W of solar, what typical season will this be sufficient for, without additional engine running?". And if you consider a leisure usage where the boat is not used/occupied in the winter time, then it is possible that the solar installation will be useful all-year-round.

Its really a slightly separate subject, but the power requirement to trickle charge to prevent self-discharge is incredibly variable, depending on the condition of batteries. Batteries in good condition require very little power (to prevent self discharge) in the winter. In fact, a good battery should be able to go on for weeks/months thru the winter without any charging. It really is incredibly variable. Another factor is that really you want to prevent self-discharge of the engine/start battery too, as well as the leisure battery bank.

[efanton]

31 minutes ago, system 4-50 said:

Methinks he will need to get a lawyer to frame the small print required to get his post sufficiently precise to avoid your candour?

I am well aware of the unreliability of solar power.  I think most people are.  I agree many people might underestimate their power usage, especially if they have not had to rely on anything other than the national grid.  Obviously before installing a solar system a power usage audit is required first.  Even then your power usage will vary over the year, often using more power when less solar power is available.

But the point remains where have I demonstrated "a fundamental misunderstanding of the nature of solar".  Why use such a phrase if I had not stated my estimate of power usage and the solar array that I intend to use?  Of course the alternative is that they assumed without any evidence at all that I was unaware of the unreliability and variability of solar power.  Why jump to such conclusions unless you wish to be pedantic?

Edited May 30, 2017 by efanton

[Richard10002]

49 minutes ago, efanton said:

What fundamental misunderstanding are you referring too then?

No criticism nor misunderstanding of your content regarding solar power... I dont really understand it to the ultimate technical degree. I just think there are less assertive and argumentative ways of expressing yourself.

[efanton]

ok lads.  Lets drop it and mark it down to the inter-webs having the effect that what might be read might not be what was intended by what was written.

It was not my intention to hijack someone else's thread, apologies to the OP. 

[Tony Brooks]

May I suggest that as you have only been a member for less than a month (although you may have lurked for a longer time) that just perhaps you do not have the experience of how questioners word things on here and what they actually mean. Many have been here far longer than myself and I have been offering technical advice online since the early 2000s. Now this does not mean I know more than you or anyone else in a specific area but it does mean over those thousands of posts and correspondence I (and other well qualified and experienced members) do get an inkling for what the questioner needs to know rather than what they asked. I suppose to someone who does not have such experience this may get the impression that the people who reply think the questioner is an idiot or new to the forum or boating.

If the OP did have a good understanding of solar and boat electrics they would have either answered their own question or framed it in a very precise way. I submit the OP did neither and it was fair to try to help by trying to give the bets answer we can rather than just answer what looked like an unanswerable question to me.

I am far from clear how experience of specifying domestic solar directly transfers to boats that may or may not have tilting panel mount, rotating mounts, and travel the country. The panels may or may not be fully or partially shaded depending upon individual moorings.

[sharpness]

Thanks everyone for your technical contributions & advice. It seems it is an almost unanswerable question because everyones experience is so different & there are so many variables & opinions about those variables, usually the case with electrics it seems. I've got a few more ideas now & will have to decide which way to go.

Thanks

Steve

[WotEver]

38 minutes ago, sharpness said:

Thanks everyone for your technical contributions & advice. It seems it is an almost unanswerable question because everyones experience is so different & there are so many variables & opinions about those variables, usually the case with electrics it seems. I've got a few more ideas now & will have to decide which way to go.

Thanks

Steve

The simple answer, as you've probably gleaned from the various responses is... at least 100W but more if you can afford it and have the space. You can't have too much. 

[sharpness]

13 minutes ago, WotEver said:

The simple answer, as you've probably gleaned from the various responses is... at least 100W but more if you can afford it and have the space. You can't have too much. 

I think you're right Tony, I picked that up from your earlier response. I'll have a measure up & see where I get to. Thanks for your input.  Steve 

[smileypete]

One of these and a 100W '12V' panel will do useful bit of batt topping up, say about 20Ah/day in summer.

http://www.ebay.co.uk/itm/EPSolar-10A-LandStar-PWM-Solar-PV-Regulator-Charge-Controller-12V-24V-/282178038084

http://www.ebay.co.uk/itm/EPsolar-LandStar-LS1024B-PWM-Solar-Battery-Charge-Controller-10A-12-24V-/251654550694

That said fully charged sealed leisures should hold their charge fine for some months if properly isolated from any loads, question as said is whether they're fully charged on returning to the mooring.

Edited May 30, 2017 by smileypete

[efanton]

9 hours ago, Tony Brooks said:

May I suggest that as you have only been a member for less than a month (although you may have lurked for a longer time) that just perhaps you do not have the experience of how questioners word things on here and what they actually mean. Many have been here far longer than myself and I have been offering technical advice online since the early 2000s. Now this does not mean I know more than you or anyone else in a specific area but it does mean over those thousands of posts and correspondence I (and other well qualified and experienced members) do get an inkling for what the questioner needs to know rather than what they asked. I suppose to someone who does not have such experience this may get the impression that the people who reply think the questioner is an idiot or new to the forum or boating.

If the OP did have a good understanding of solar and boat electrics they would have either answered their own question or framed it in a very precise way. I submit the OP did neither and it was fair to try to help by trying to give the bets answer we can rather than just answer what looked like an unanswerable question to me.

I am far from clear how experience of specifying domestic solar directly transfers to boats that may or may not have tilting panel mount, rotating mounts, and travel the country. The panels may or may not be fully or partially shaded depending upon individual moorings.

Surely the more logical (and I am sure in general more appreciated)  approach would be to answer the question asked? If it is impossible to answer a question directly, then explain why.  there is no need to second guess what the OP really asked, nor make judgement on what you might think they know or do not know.  If the OP doesnt get the answer they were expecting then leave it up to them to re-frame the question.

Those that wish to learn more will ask more questions,  those that have the answer they need would I hope thank who ever answered their query.

 

 

I am on a couple of these forums (motorbikes and other interests), as well as being a moderator on two, and the same problems seems to happen time and time again,  people answering questions not asked, the more established members often treating new members differently (dont know why that happens but I am certain it does on nearly every forum I am on)  or appearing aggressive in the way they respond (might not be intentional, but then again sometimes its deliberately  done like that to not run foul of the mods).  There is a real risk, and I have seen this happen time and time again on other forums,  of new members being driven out or feeling not welcome on forums in general and that is a real shame. Forum are a great repository of information and apps, instant messengers, google+ etc that are slowly replacing forums will never be able to compete in  that respect.

Me, I'm quite a simple man.  I have no affectations of grandeur nor illusions to my fallibility.  If I need help I will ask,  if I offer help I offer it because I want to help not because a forum gives me a platform or a alternative to actually having a real life.  Life is only as complicated as you wish to make it, personally I prefer uncomplicated.

Edited May 30, 2017 by efanton

[Alan de Enfield]

6 hours ago, efanton said:

Surely the more logical (and I am sure in general more appreciated)  approach would be to answer the question asked?

If we take an example which in various guises appears on a very regular basis.

"My batteries are flat by morning"

"My low voltage alarm is going off by morning"

Q : Do I need to replace the batteries ?

In your world the answer is simply "yes", but in the Canal world where folks try and give constructive help, they suggest reasons why the batteries may be flat, and ways of avoiding (minimising) the liklehood of it happening again in the near future.

 

I would have thought the 'questioner' would be more appreciative of knowing 'why' and how to avoid it again, than just saying 'yes - go and pend another £500 but you will need to do it again in 6 weeks / 6 months as you havn't corrected the 'problem'.