Solar....how much wattage is enough

[magictime]

Well I've learned something anyway! Thanks all who have helped to clarify that point.

[Horace42]

27 minutes ago, magictime said:

Well I've learned something anyway! Thanks all who have helped to clarify that point.

....and me. Thanks as well.

[WotEver]

5 hours ago, Mike the Boilerman said:

 

And in poor light conditions e.g. winter, it is better to string your panels together in series as this adds together the (low) voltage each panel is giving, and sometimes you'll get more output than if they are in series. 

Which is exactly the point that I made yesterday which was contradicted by another poster.  

[Alan de Enfield]

5 minutes ago, WotEver said:

Which is exactly the point that I made yesterday which was contradicted by another poster.  

You can lead a .......................

 

 

 

 

 

 

 

Edited May 20, 2018 by Alan de Enfield

[WotEver]

5 hours ago, reg said:

 I can see his logic from his point of view and for his method of installation. 

Unfortunately for him and anyone else reading such drivel he doesn’t make that distinction. He states as a categorical fact “Be aware that in 12V or low voltage applications, AMPS are key not watts” which is totally incorrect for any mppt installation. I would imagine that the vast majority of installations use an mppt controller. 

 

WATTS are a measurement of power and it is that power that is converted into stored energy within the battery. 

[reg]

1 hour ago, WotEver said:

Unfortunately for him and anyone else reading such drivel he doesn’t make that distinction. He states as a categorical fact “Be aware that in 12V or low voltage applications, AMPS are key not watts” which is totally incorrect for any mppt installation. I would imagine that the vast majority of installations use an mppt controller. 

 

WATTS are a measurement of power and it is that power that is converted into stored energy within the battery.  

Oh yeah fully agree that what he was saying was incorrect and in an earlier post I think I said that. In the post you quote I was trying to work what I thought he wanted to say. 

I think whole flaw with his argument is that it appears to say that that the Amps going into the controller are the important thing whilst the opposite, to me at least, is true in that it is the amps the controller puts out that are important thing and in winter any amps is better than zero amps. 

My important criteria is having a charging voltage from the controller, his appears to be that getting high amps into the controller is more important. On that I believe he is fundamentaly wrong. 

 

 

 

 

Edited May 20, 2018 by reg

[cuthound]

47 minutes ago, reg said:

Oh yeah fully agree that what he was saying was incorrect and in an earlier post I think I said that. In the post you quote I was trying to work what I thought he wanted to say. 

I think whole flaw with his argument is that it appears to say that that the Amps going into the controller are the important thing whilst the opposite, to me at least, is true in that it is the amps the controller puts out that are important thing and in winter any amps is better than zero amps. 

My important criteria is having a charging voltage from the controller, his appears to be that getting high amps into the controller is more important. On that I believe he is fundamentaly wrong. 

 

 

 

 

 

I agree. Otherwise battery manufacturers would recommend charging currents, rather than the charging voltages they actually recommend. 

[reg]

23 minutes ago, cuthound said:

 

I agree. Otherwise battery manufacturers would recommend charging currents, rather than the charging voltages they actually recommend. 

I think it was Tony B who made the point that his arguments may of held up for PWM controllers but they don't hold up now that he is using mppt controllers.

Could be some residual PWM knowledge has tainted his thoughts or, again as TB also said, its simply that the information needs to be updated to reflect his current usage of mppt controllers. 

 

Off topic:but my keyboard seems to think that Tony Blair made the same comments as TB which amused my simple mind. 

(but I forgive it as it just said I have a splendid mind and not a simple on, little does (it's does not Die you ***** keyboard) it know) 

 

Edited May 20, 2018 by reg

[Clodi]

I too want to thank all who have shared their knowledge.

 Matt&Jo I too am actually looking to install solar + batteries, monitors etc so will let you know if I find any bargains. It's all a bit of a nightmare as so many people will tell you their views and it's hard to find consensus (sometimes).

Whatever I end up with I'll be posting on the forums for opinions before I part with my limited dosh.

[Guest]

I've got 350w of panels on my roof and it's plenty to power my (more or less defunct) fridge, LED lights and water pump. I don't tend to run a lot of appliances to be honest, most of them run off batteries which I charge up at work. I still have needless anxiety about running out of power, which I haven't done yet.

 

I'm currently charging up my Bluetooth speaker via a mains adapter and I'm trying to assure myself that I've got more than enough power to do so. I've got 5 x 120ah batteries, so I have plenty in reserve.

[MtB]

41 minutes ago, welly said:

I'm currently charging up my Bluetooth speaker via a mains adapter and I'm trying to assure myself that I've got more than enough power to do so. I've got 5 x 120ah batteries, so I have plenty in reserve.

 

The power consumption of your fridge dwarfs everything else you list. Your bluetooth speaker battery capacity is probably about 1AH for example, so it will use 2AH out of your 600AH battery capacity to fully charge it from totally flat (which it won't be) assuming a charge efficiency of 50%.

[Guest]

1 minute ago, Mike the Boilerman said:

 

The power consumption of your fridge dwarfs everything else you list. Your bluetooth speaker battery capacity is probably about 1AH for example, so it will use 2AH out of your 600AH battery capacity to fully charge it from totally flat (which it won't be) assuming a charge efficiency of 50%.

I think I calculated the fridge to be about 40ah a day. Might have been less. The speaker is definitely the least of my worries, not that I should have any. My power audit worked out to be around 60ah a day.

[Johny London]

On 19/05/2018 at 12:38, Nightwatch said:

Cheack lowenergysupermarket. (Whatever). 

I have 'finally' got some cable and connectors from Bimble. Took ages to get here and blow me, one of the connectors is broken. Superbly packed so may have been broken before despatch.

 

Bimble okay, but indeed not the best experience I have had.

 

martyn

Www.lowenergysupermarket.com

I don't recommend these - when I got mine one was smashed in transit - no problem got it replaced, but after trouble shooting after fitting them up, I found that one had never had its wires connected in the connection box on the back of the panel - so they cannot be testing them at all before sending out. Also, the output from 2x150w is never more than 11a in full sun.

[Richard10002]

1 hour ago, Johny London said:

I don't recommend these - when I got mine one was smashed in transit - no problem got it replaced, but after trouble shooting after fitting them up, I found that one had never had its wires connected in the connection box on the back of the panel - so they cannot be testing them at all before sending out. Also, the output from 2x150w is never more than 11a in full sun.

With 490W I am delighted with 20A in the sun that we've had this past few weeks

[Matt&Jo]

Well im on the hunt for solar options at crick even if i dont buy it there i want to come away knowing what i want and need.....problem is i cant do a power audit untill i collect the beast on the 13th of next month.....

[Richard10002]

32 minutes ago, Matt&Jo said:

Well im on the hunt for solar options at crick even if i dont buy it there i want to come away knowing what i want and need.....problem is i cant do a power audit untill i collect the beast on the 13th of next month.....

It would be reasonably safe to assume that if you aren't profligate with power, nor do you skimp unnecessarily, you will use between about 70Ah and 120Ah per day. I think I use about 100Ah per day and am finding that 2 x 245W panels, one of which is flat, and one of which is angled a bit in a North South direction, fill me up during the day. This has been the case on most days since about Mid April, and I haven't run the generator for a few weeks.

 

Between October and March, inclusive, Solar came nowhere near fulfilling my needs, and I used the generator as if there was no solar.

[MtB]

10 hours ago, Matt&Jo said:

Well im on the hunt for solar options at crick even if i dont buy it there i want to come away knowing what i want and need.....problem is i cant do a power audit untill i collect the beast on the 13th of next month.....

 

The power audit won’t help you much given solar output fluctuates between zero and max according to season, i.e. virtually zero in mid winter when you need it most and full output on hot summer days when you need it least.

 

 

Edited May 25, 2018 by Mike the Boilerman

[Dr Bob]

10 hours ago, Richard10002 said:

It would be reasonably safe to assume that if you aren't profligate with power, nor do you skimp unnecessarily, you will use between about 70Ah and 120Ah per day. I think I use about 100Ah per day and am finding that 2 x 245W panels, one of which is flat, and one of which is angled a bit in a North South direction, fill me up during the day. This has been the case on most days since about Mid April, and I haven't run the generator for a few weeks.

 

Between October and March, inclusive, Solar came nowhere near fulfilling my needs, and I used the generator as if there was no solar.

I agree, and with Mikes comments as well. A power audit is not going to help and it will be a while before you understand your power needs and they will change anyway in the winter. We use the same asRichard. 500W is a good number. Any more and you won't see the roof of your boat. We have 4 panels on our roof and for me that is the limit. You need to consider the look of the boat and be able to walk on the roof to do locks efficiently. Don't get too hung up on how many Watts. As I said earlier, one year of 200W told me it wasn't enough in summer. This year 500W is great and we get 25A+ from 4 tilting panels. 

We went for victron panels this year. Bit more expensive but picked them up from the supplier in Nuneaton and hence good back up if things go wrong.

[MtB]

1 minute ago, Dr Bob said:

I agree, and with Mikes comments as well. A power audit is not going to help and it will be a while before you understand your power needs and they will change anyway in the winter. We use the same asRichard. 500W is a good number. Any more and you won't see the roof of your boat. We have 4 panels on our roof and for me that is the limit. You need to consider the look of the boat and be able to walk on the roof to do locks efficiently. Don't get too hung up on how many Watts. As I said earlier, one year of 200W told me it wasn't enough in summer. This year 500W is great and we get 25A+ from 4 tilting panels. 

We went for victron panels this year. Bit more expensive but picked them up from the supplier in Nuneaton and hence good back up if things go wrong.

 

I too have about this number. 560W actually. It keeps my fridge, lights, lappy etc all running happily for 8-9 months of the year.

 

For the remainder of the time my virtually silent Whispergen charges my batteries at night. If ever you see a second hand Whispergen for sale, grab it!

[Ssscrudddy]

I have 660W (4x165W), wired 2 in series into 1 mmpt controller (giving 84V max from the panels, 24A max to the batteries at nominal 12V after the mppt controller has done it's thIng), & 2 controllers in parallel to the batts. So a total of 48A max to the batts under optimal conditions.

 

On a perfect winter's day without a cloud in the sky all day (18th Dec) I got enough solar to run my fridge-freezer for 8 hours (which is old & tired & never seems to turn off for more than 5 seconds)

 

The last few cloudless summer days I've been getting 30A at 12V, because that is the power I'm using & the batteries were already full & not draining (they probably could have done more).

 

Today at 9.45am, it's dark & grey & miserable & chucking it down, cloud cover so thick you cannot see in the sky where the sun is supposed to be. My 660W are putting out (each series of 84V max, I think from memory actually doing 23V 0.2A), giving me a whopping 0.8A at 12V to the batts (2 days ago it was doing 30A at the same time of day, not a cloud in the sky).

 

[Alan de Enfield]

How much wattage is enough ?

 

If you are a constant moorer and never run the engine 5Kw would be a good starting place.

If you cruise 4 or 5 hours a couple of times per week then 1kw is probably enough

If you cruise 4 or 5 hours every day then you don't need any solar.

 

Other scenarios are available, including the use of generators, wind power and hydrogen cells.

[Dr Bob]

14 minutes ago, Alan de Enfield said:

How much wattage is enough ?

 

If you are a constant moorer and never run the engine 5Kw would be a good starting place.

If you cruise 4 or 5 hours a couple of times per week then 1kw is probably enough

If you cruise 4 or 5 hours every day then you don't need any solar.

 

Other scenarios are available, including the use of generators, wind power and hydrogen cells.

...but cruising 2 hrs, 5 or 6 times a week, we need 500W. (in the summer)

[rusty69]

1 minute ago, Dr Bob said:

...but cruising 2 hrs, 5 or 6 times a week, we need 500W. (in the summer)

You need a hand cranked singer

[Dr Bob]

Just now, rusty69 said:

You need a hand cranked singer

...with reverse!

[Matt&Jo]

14 hours ago, Richard10002 said:

It would be reasonably safe to assume that if you aren't profligate with power, nor do you skimp unnecessarily, you will use between about 70Ah and 120Ah per day. I think I use about 100Ah per day and am finding that 2 x 245W panels, one of which is flat, and one of which is angled a bit in a North South direction, fill me up during the day. This has been the case on most days since about Mid April, and I haven't run the generator for a few weeks.

 

Between October and March, inclusive, Solar came nowhere near fulfilling my needs, and I used the generator as if there was no solar.

What size genny do you use?