Solar panels: How many Ah/day can you expect?

[Grace and Favour]

Slightly but I will give it a go anyway.

 

Where is the best place to buy solar panels. We are considering installing a smallish, say 100 watt, system to NC to help keep the batteries topped up whilst we are away from our mooring and out cruising. On the odd occasion we do stay somewhere for a few days any extra power we can stick back into the batteries without running the engine or knackering the batteries would be a bonus.

 

This would involve some custom stainless steel fabrication but we can factor that in if the cost of the panel isnt too prohibitive.

 

Any suggestions glady recieved.

 

I guess that part of the equation may be how much can you let your panel weigh before it alters the trim of NC?

 

Have you considered one of the ultra-thin, ultra-light panels that one glues to the boat and that you can walk on (if necessary) - - - I understand a favourite of sailboats

[Naughty Cal]

I guess that part of the equation may be how much can you let your panel weigh before it alters the trim of NC?

 

Have you considered one of the ultra-thin, ultra-light panels that one glues to the boat and that you can walk on (if necessary) - - - I understand a favourite of sailboats

 

We dont want the walk on ones they dont look very attractive and the only place we would have for them is on the coach roof.

 

Trim shouldnt be an issue with a 100 watt panel (average weight seems to be around 7.5kg) as we plan to mount it on the radar arch with a bit of custom fabrication and will be able to install it centrally to keep the trim level. These boats can have radar domes mounted up there which weigh considerably more than a small solar panel

[lewisericeric]

Sorry to revive this post, but say, for example, I have one of these 240w solar panels connected to my 330ah battery bank. What sort of charge on the bats would i be getting. I really dont understand all this chat about ah per hour and daily accumulations etc.

 

I know, that when i have the engine on, my batts when off shoreline, charge by about 1% every 20-30minutes.

 

Im guessing that solar panels will do nothing of the sort in that timeframe. But could i expect say, a five percent charge per day depending on what im using, weather, etc et c etc!!

[Ex- Member]

Sorry to revive this post, but say, for example, I have one of these 240w solar panels connected to my 330ah battery bank. What sort of charge on the bats would i be getting. I really dont understand all this chat about ah per hour and daily accumulations etc.

 

I know, that when i have the engine on, my batts when off shoreline, charge by about 1% every 20-30minutes.

 

Im guessing that solar panels will do nothing of the sort in that timeframe. But could i expect say, a five percent charge per day depending on what im using, weather, etc et c etc!!

 

 

hi Lewis

 

My understanding is a 240 watt panel would at best in direct sunlight produce 20 amps. however a fixed solar panel even on a bright sunny day would be lucky to average 10 amps IMO so in a 10 hour day of good light or sunshine the panel in theory should give you around 100 amps.

 

If your batteries are only charging at 1% for 20 minutes I would say that's not good from an engine alternator, although you might have 20 batteries

 

 

[lewisericeric]

Hi Julian

 

I have only three batts. However when i say that they're charging only one percent every twenty mins or so, that is with appliances on the boat still on, like 240v freezer, chargers etc. if everything is off including invertor, its probably five to ten mins max that it would charge one percent.

 

When you say that it would give me a max of one hundred amps, what does this mean in terms of battery charging and how many percent in a day i should expect? i know its variable, because of the loads ill be drawing off them etc, but just rougly. i have three batteries, 110ah each plus the starter battery

 

Aaaah i see youve just sent me a private message as well good to hear from you and see you back on the forum ;0

Edited March 28, 2012 by lewisericeric

[Nickhlx]

Sorry to revive this post, but say, for example, I have one of these 240w solar panels connected to my 330ah battery bank. What sort of charge on the bats would i be getting. I really dont understand all this chat about ah per hour and daily accumulations etc.

 

I know, that when i have the engine on, my batts when off shoreline, charge by about 1% every 20-30minutes.

 

Im guessing that solar panels will do nothing of the sort in that timeframe. But could i expect say, a five percent charge per day depending on what im using, weather, etc et c etc!!

 

 

 

 

To help you gauge what a 240Wp panel will give, our 3.92 kWp array has been producing over 20 kWh/day for several days recently.. ( 102 kWh in last 5 days) This scales to approx 1.2 kWh for a 240 Wp panel / array although that would assume you also have a MPPT controller taking best advantage of the panel's capability. At 14 volts this would equate to around 85ah and assuming battery charging efficiency of perhaps 80%, around 65 aH into the battery bank - This would certainly run a typical boat fridge and more.

 

However, earlier this month we were getting less than half this per day - during March is when it really takes off though, producing more than double that of February, and an average of around 3 times the Wp figure in kWh, with April - September around 4 times the Wp figure. It tapers down to the weakest months of December/January, with November/February a bit better.

 

Over last year, the array produced 3534 kWh, which I though quite remarkable...

 

Nick

[Ex- Member]

Hi Julian

 

I have only three batts. However when i say that they're charging only one percent every twenty mins or so, that is with appliances on the boat still on, like 240v freezer, chargers etc. if everything is off including invertor, its probably five to ten mins max that it would charge one percent.

 

When you say that it would give me a max of one hundred amps, what does this mean in terms of battery charging and how many percent in a day i should expect? i know its variable, because of the loads ill be drawing off them etc, but just rougly. i have three batteries, 110ah each.

 

Aaaah i see youve just sent me a private message as well good to hear from you and see you back on the forum ;0

 

Hi Lewis cheers, I miss private messages too lol

 

Your battery bank is 330 amps so 100 amps is replacing almost 1/3 of your battery banks capacity. Of course if you're using power at the same time then that solar energy is is being absorbed by what ever you're using. For instance if you're using 50 amps an hour then the surplus added to your battery is 50 amps. That's how I read it mind, the boffins will no doubt correct me if I'm wrong. I suspect there certain losses to account for during the charge process.

 

It is a tricky subject, I think you've had advice on wiring your batteries correctly and checking the water levels in them regularly. I'm planning on 2 x 240 watt panels in to a new battery bank I've ordered totalling 928 amps I reckon on average we'll be using around 150 amps per day and we're hoping to get at least 20 amps from the solar panels. So on a good ten hour day we might get 200 amps meaning we won't have to run the engine for additional power.

 

I would do an audit of your usage. You have to write down every appliance 12 and 240 volt. Work out how long you'll use each appliance daily. Than work out the amps each appliance uses. For instance a 12 volt TV thats rated 24 watts = 2 amps. If you have the TV on 10 hours a day then your TV daily usage is 20 amps for TV. Do this with every appliance. Water pumps and the like that are used for short periods daily I add together and work out at 10 minutes a day, this should be about right unless you shower 3 times a day.

 

When you get to an average daily amps figure I would fit enough solar panels to well cover it. Remember watts are divided by 12 to get Amps. You might already know all this as I haven't been around And I'm assuming you're 12 volt.

 

Hope all's going well with the build

 

Don't panic though 12 volt electrics is probably the most difficult thing to get your head around.

 

To help you gauge what a 240Wp panel will give, our 3.92 kWp array has been producing over 20 kWh/day for several days recently.. ( 102 kWh in last 5 days) This scales to approx 1.2 kWh for a 240 Wp panel / array although that would assume you also have a MPPT controller taking best advantage of the panel's capability. At 14 volts this would equate to around 85ah and assuming battery charging efficiency of perhaps 80%, around 65 aH into the battery bank - This would certainly run a typical boat fridge and more.

 

However, earlier this month we were getting less than half this per day - during March is when it really takes off though, producing more than double that of February, and an average of around 3 times the Wp figure in kWh, with April - September around 4 times the Wp figure. It tapers down to the weakest months of December/January, with November/February a bit better.

 

Over last year, the array produced 3534 kWh, which I though quite remarkable...

 

Nick

 

Hi Nick that's some great figures especially if from fixed panels. I wonder how much engine time it would take to produce the same amount of power you,ve achieved thus far with solar. Fuel cost wear and tear etc I would imagine you've gone some way in recovering the original cost of the panels.

 

 

 

Edited March 28, 2012 by Julynian

[Nickhlx]

Hi Lewis cheers, I miss private messages too lol

 

Your battery bank is 330 amps so 100 amps is replacing almost 1/3 of your battery banks capacity. Of course if you're using power at the same time then that solar energy is is being absorbed by what ever you're using. For instance if you're using 50 amps an hour then the surplus added to your battery is 50 amps. That's how I read it mind, the boffins will no doubt correct me if I'm wrong. I suspect there certain losses to account for during the charge process.

 

It is a tricky subject, I think you've had advice on wiring your batteries correctly and checking the water levels in them regularly. I'm planning on 2 x 240 watt panels in to a new battery bank I've ordered totalling 928 amps I reckon on average we'll be using around 150 amps per day and we're hoping to get at least 20 amps from the solar panels. So on a good ten hour day we might get 200 amps meaning we won't have to run the engine for additional power.

 

I would do an audit of your usage. You have to write down every appliance 12 and 240 volt. Work out how long you'll use each appliance daily. Than work out the amps each appliance uses. For instance a 12 volt TV thats rated 24 watts = 2 amps. If you have the TV on 10 hours a day then your TV daily usage is 20 amps for TV. Do this with every appliance. Water pumps and the like that are used for short periods daily I add together and work out at 10 minutes a day, this should be about right unless you shower 3 times a day.

 

When you get to an average daily amps figure I would fit enough solar panels to well cover it. Remember watts are divided by 12 to get Amps. You might already know all this as I haven't been around And I'm assuming you're 12 volt.

 

Hope all's going well with the build

 

Don't panic though 12 volt electrics is probably the most difficult thing to get your head around.

 

 

 

Hi Nick that's some great figures especially if from fixed panels. I wonder how much engine time it would take to produce the same amount of power you,ve achieved thus far with solar. Fuel cost wear and tear etc I would imagine you've gone some way in recovering the original cost of the panels.

 

 

 

 

 

Hi,

Yes - fortunately we are on the original tariff but the main reason we went for it was that unusually we are heavy users of electricity in the summer months during the day ( pump) so we actually use most of the generation ourselves - It is likely we will break even after about 6 years ( in about 4.5 years time). Our grid consumption has more than halved compared to prior to the installation from around 25 kWh / day to (recent days) around 8 kWh/day, mainly from the solar but also from managing consumption ( do washing / dishwasher during the middle part of the day) Oh - and the kids left home

 

Nick

 

 

[Ally]

We have just fitted 2x 135W panels, flat mounted, and expected nothing this month. However, in the unusually sunny weather we have had this week, we were getting up to 12.8A out of them....happy enough with that for March!

[Tony Brooks]

We have just fitted 2x 135W panels, flat mounted, and expected nothing this month. However, in the unusually sunny weather we have had this week, we were getting up to 12.8A out of them....happy enough with that for March!

 

 

These figures seem to tally with the output of my 60watt, flat mounted panel with PCM controller.

[lewisericeric]

Thanks Julian - good info there.

 

However, what sort of MPPT controller would you choose? There's anything from ten amp ones to eighty amp ones.

 

What would be best to have if you had, say, 2 x 240watt solar panels

[Nickhlx]

Thanks Julian - good info there.

 

However, what sort of MPPT controller would you choose? There's anything from ten amp ones to eighty amp ones.

 

What would be best to have if you had, say, 2 x 240watt solar panels

 

With 480 Wp available ( at least potentially) the controllers would ideally be able to handle the around 40 amps input this suggests. However several factors will likely ensure the peak will rarely if ever be met. These include the orientation and elevation of the panels, the time of day and time of year, the ambient temp and the operating temperature of the panels. I would ensure that a suitably large MPPT controller was used so that it was not working near its limit on the best days, and so cooler. It may be that one day you may want to add another panel.

 

It would also be essential to select one to suit the series or parallel voltages that the panels work at and that this is comfortably within its operating window. It is also possible to get controllers with more than one input. The pros and cons of this are that with two inputs you can have the panels orientated differently, so that the output is lower but longer which is what the battery bank might be needing. The potential () downside is that in winter with lower outputs, the system might be more efficient with them in series for a higher output voltage feeding into one input. This may not be needed if you don't cruise in the November to February months though...

 

So the choice of controller will be influenced by how you use the boat year round...

 

Nick

[Ex- Member]

Thanks Julian - good info there.

 

However, what sort of MPPT controller would you choose? There's anything from ten amp ones to eighty amp ones.

 

What would be best to have if you had, say, 2 x 240watt solar panels

 

40 amps would suffice

 

 

Hi again Lewis, you need to think ahead, personally I'll be using a controller that's way above what I'm intending to fit regards solar panel. I'll kick off with 480 watts divided by 12 = 40 amps

 

However I might want or need to fit panels in the future so if I got a 40 amp controller now I would have to up it to add more panels.

 

This might mean buying an additional controller to cope(unsure if you can run 2) or replacing the existing controller with a higher amperage to cope.

 

I think the general consensus is to use MPPT controllers although I really don't know much about them. However a trusted member did recommend an excellent controller called Outback which I looked into, very expensive but claims to improve solar collection by 10 to 30 %

 

I liked the read up on it and the member who recommended it has fitted them, so I plan on using an outback 80amp this will allow me to double my solar array in future and not worring about additional controller or costs. This unit is expensive but pretty much top of the range, they're are many MPPT controllers cheaper, so it's quite a decision to make. But this product impressed me. I'll just have to find the wonga

 

http://www.electrica...om/product/1852

 

It does do a lot of extra stuff you don't get with a standard controller, worth a good read.

 

 

Edited March 29, 2012 by Julynian

[Theo]

Thanks for all the input, chaps. That gives me enough to do some auditing and planning.

 

Nick

[lewisericeric]

Thanks again chaps and special thanks to Julian as always.

 

i just wasnt sure if using one at say 80amps would somehow use the energy from the panels inefficiently or somethign so thanks for that. Cost isn't an issue as I believe that if you're going to do something you've got to do it right. Like you say Julian, it will only cost more in future to have to upgrade the MPPT controller etc.

[Justme]

The 5 year warranty from Outback is well worth having too.

 

In most cases they send you out a new one first & you then use the packing to send the old one back.

[Ex- Member]

Thanks again chaps and special thanks to Julian as always.

 

i just wasnt sure if using one at say 80amps would somehow use the energy from the panels inefficiently or somethign so thanks for that. Cost isn't an issue as I believe that if you're going to do something you've got to do it right. Like you say Julian, it will only cost more in future to have to upgrade the MPPT controller etc.

 

Hi Lewis

 

A bigger output charge controller might use a tad more power if it did, It would be negligible though if at all.

 

Buying the most expensive equipment isn't always the best route to go from my experience, In this case and IMO the Outback I's a pretty sound investment though.

 

I believe that if you're going to do something you've got to do it right.

 

If you're going to be live aboard and CC'ing then even more so.

 

Forward thinking

Edited March 31, 2012 by Julynian

[lewisericeric]

Im now thinking of getting 4x 250w monochrystalline panels, but cannto find a suitable MPPT controller or other for them.

 

I worked out that realistically I'd need something at around 83Amps. The outback one would maybe cover that at 80amps but I dont really want to pay £600-700 for a controller.

 

Could I use a 30amp controller for each panel? Can you hook up to batteries using multiple MPPT controllers using something cheaper than the outback??

 

Any suggestions for good 30amp controllers if so?

 

Cheers lads n lasses

[arpeeuk]

My understanding is that you will be charging your batteries at a voltage somewhat nearer to 14v than 12v or they won't charge and so you will actually need your controllers to handle more life 70a. To me this means you could use a 20a controller for each panel.

 

As to using a controller for each panel, I think this is OK. As your batteries get to nearly charged it is likely that the individual controllers will sense the batter charge differently and go to float charge at different times until you end up with just one controller and panel finishing the absorption charge.

 

But I am know expert and I hope that others will be along to confirm this or put me straight.

 

Rik

 

 

Im now thinking of getting 4x 250w monochrystalline panels, but cannto find a suitable MPPT controller or other for them.

 

I worked out that realistically I'd need something at around 83Amps. The outback one would maybe cover that at 80amps but I dont really want to pay £600-700 for a controller.

 

Could I use a 30amp controller for each panel? Can you hook up to batteries using multiple MPPT controllers using something cheaper than the outback??

 

Any suggestions for good 30amp controllers if so?

 

Cheers lads n lasses

[Ex- Member]

Im now thinking of getting 4x 250w monochrystalline panels, but cannto find a suitable MPPT controller or other for them.

 

I worked out that realistically I'd need something at around 83Amps. The outback one would maybe cover that at 80amps but I dont really want to pay £600-700 for a controller.

 

Could I use a 30amp controller for each panel? Can you hook up to batteries using multiple MPPT controllers using something cheaper than the outback??

 

Any suggestions for good 30amp controllers if so?

 

Cheers lads n lasses

 

Hi Lewis

 

To use the larger size solar panels 240/250 watts you need to run them with quality MPPT controllers as these size panels operate around 30 volts. I've just found this out myself BTW

 

By buying a 30 amp controller for each panel is surely going to cost nearly as much as a 6 to £700.00 for an Outback or similar quality MPPT controller.

 

A cheap MPPT 30 amp controller costs around £100 + P&P and does not do all the Outback can do, so 4 are going to cost you over £400 then you have all the extra wiring and connectors to wire in 4 units as well as the additional time it would take to fit 4.

 

It might be wiser to get 1 x 80 amp outback and a 30amp cheaper model, but bear in mind also that 1000 watts of power from solar panels is maximum and in reality you'll very rarely get that output for any length of time. So an 80 amp Outback would probably suffice IMO The maths 1000 / 12 = 83 amps. also bear in mind the additional efficiency Outback claim using their controllers at up to 30% and a 5 year guarantee.

 

Going the route of 4 MPPT controllers will in the long run undoubtedly cost you more IMHO

[Grace and Favour]

Hi Lewis

 

To use the larger size solar panels 240/250 watts you need to run them with quality MPPT controllers as these size panels operate around 30 volts. I've just found this out myself BTW

 

By buying a 30 amp controller for each panel is surely going to cost nearly as much as a 6 to £700.00 for an Outback or similar quality MPPT controller.

 

A cheap MPPT 30 amp controller costs around £100 + P&P and does not do all the Outback can do, so 4 are going to cost you over £400 then you have all the extra wiring and connectors to wire in 4 units as well as the additional time it would take to fit 4.

 

It might be wiser to get 1 x 80 amp outback and a 30amp cheaper model, but bear in mind also that 1000 watts of power from solar panels is maximum and in reality you'll very rarely get that output for any length of time. So an 80 amp Outback would probably suffice IMO The maths 1000 / 12 = 83 amps. also bear in mind the additional efficiency Outback claim using their controllers at up to 30% and a 5 year guarantee.

 

Going the route of 4 MPPT controllers will in the long run undoubtedly cost you more IMHO

 

I've researched Outback 80 prices - - the lowest I've found, delivered is £604.

[smileypete]

Im now thinking of getting 4x 250w monochrystalline panels, but cannto find a suitable MPPT controller or other for them.

 

I worked out that realistically I'd need something at around 83Amps. The outback one would maybe cover that at 80amps but I dont really want to pay £600-700 for a controller.

 

Could I use a 30amp controller for each panel? Can you hook up to batteries using multiple MPPT controllers using something cheaper than the outback??

 

Any suggestions for good 30amp controllers if so?

What are you going to do with 1kW of solar on a boat BTW? Seems a bit much.

 

Anyway for controllers maybe see what's on Ebay and do lots and lots of googling on the make/models. Has anyone tried them or are they sold by reputable dealers?

 

(A few of the cheapest MPPTs eg 'Wellsee' are not in fact MPPT! just a simple PWM. But tellingly they can't take a high panel voltage...)

 

No experience of this one, but seems pretty reasonable: (clicky)

 

cheers,

Pete.

[Ex- Member]

I've researched Outback 80 prices - - the lowest I've found, delivered is £604.

 

Try here

 

http://www.knowyourplanet.com/

 

You have to register as a member to make a purchase.

 

 

 

 

Your Total

£475.00

Sub-Total:

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£20.00

Zone Rates (Shipping to GB (1 x 8.00kg(s))):

<br class="clearBoth" style="clear: both; font-family: 'Lucida Grande', Verdana, Lucida, Helvetica, Arial, sans-serif; font-size: 11px; text-align: left; ">

£95.00

UK VAT @ 20%:

<br class="clearBoth" style="clear: both; font-family: 'Lucida Grande', Verdana, Lucida, Helvetica, Arial, sans-serif; font-size: 11px; text-align: left; ">

£590.00

Total:

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[Danny1234]

Hello

I've just been reading though the thread, .... thanks for all that

I'm looking to get some of this kit myself at some point in the near(ish) future .... (the shell needs building first though!)

 

I'll add the KnowYourPlanet to my bookmarks list, ....., there seems (fortunately) to now be a whole heap of companies offering various solutions/panels. But this can be a bit bewildering, ....

 

Recently come across this one

http://www.navitron.org.uk/

They seem 'good value', though I've not bought anything from them (you do so at your own risk, I can not accept any responsibility, ..... ect, ect, ..)

What they do have that seems to be worth a look/browse is a very active forum for such things

http://www.navitron.org.uk/forum/

 

Good luck with it all

 

Regards

Danny

[Nickhlx]

Hello

I've just been reading though the thread, .... thanks for all that

I'm looking to get some of this kit myself at some point in the near(ish) future .... (the shell needs building first though!)

 

I'll add the KnowYourPlanet to my bookmarks list, ....., there seems (fortunately) to now be a whole heap of companies offering various solutions/panels. But this can be a bit bewildering, ....

 

Recently come across this one

http://www.navitron.org.uk/

They seem 'good value', though I've not bought anything from them (you do so at your own risk, I can not accept any responsibility, ..... ect, ect, ..)

What they do have that seems to be worth a look/browse is a very active forum for such things

http://www.navitron.org.uk/forum/

 

Good luck with it all

 

Regards

Danny

 

Certainly I and many others here have been following the very good information and products available through Navitron - some of the best people in their field

are members of that forum..

 

Nick