Solar....how much wattage is enough

[MtB]

5 minutes ago, Johny London said:

Sorry missed this - ok today in full sun (at 1pm) I'm getting 29v/5.9a or 13.4v/12.4a - seems low to me.

 

How many panels, what size, and are they flat on the roof or tilted to the sun?

 

I have one 100w panel on this boat tilted to face the sun and in bright sun I was getting 5.5A today at midday.

 

This is with a PWM controller.

 

 

 

 

 

Edited June 3, 2018 by Mike the Boilerman
spleeong

[Johny London]

2x150w, flat mounted. Surely 300w is about 25a, less some for the fact they are not perfectly aligned, I would have hoped to see nearly 20a. I do realise that my batteries are knackered, and might not be able to take that much charge but I checked when the fridge was cycling on (which is 8a?) and it was the same. They seem more like 100w panels to me.

[MtB]

3 minutes ago, Johny London said:

Surely 300w is about 25a,

 

We discussed this in depth earlier in this thread IIRC. 

 

Firstly, its 21A at 14.4v charging voltage. Secondly I doubt you are on the equator at midday with sun directly overhead, the conditions for peak output when you might, just, get 298W. 

 

At 50% reduction for grubby atmosphere here and yours lying flat, I think 12A about right in full sun.

[Johny London]

Thank you - in that case I may well go for another pair. Would it be possible to have the second pair in parallel with the first pair (each pair is series wired) into one controller? That way I'm not going to over voltage it. I believe any excess current (so if it is a 20a controller) is just lost? I'm not sure if this would work with different panel pairs, if at all!

[Horace42]

21 hours ago, Johny London said:

2x150w, flat mounted. Surely 300w is about 25a, less some for the fact they are not perfectly aligned, I would have hoped to see nearly 20a. I do realise that my batteries are knackered, and might not be able to take that much charge but I checked when the fridge was cycling on (which is 8a?) and it was the same. They seem more like 100w panels to me.

8A for a fridge?? - My fridge pulls 3A at 12V when cycling in the warm whether. Works a treat.

I know for a fact.  There is an ammeter in the circuit.

Edited June 4, 2018 by Horace42
added ammeter.

[Horace42]

On 02/06/2018 at 12:11, Nightwatch said:

Correct me if I'm wrong,I think, not sure though, this thread has gone off topic?

It's been off topic since my first contribution.

[Robbo]

40 minutes ago, Horace42 said:

8A for a fridge?? - My fridge pulls 3A at 12V when cycling in the warm whether. Works a treat.

I know for a fact.  There is an ammeter in the circuit.

Amps means nothing tho long term.   It’s Ah’s that really matter.

[MtB]

1 hour ago, Horace42 said:

My fridge pulls 3A at 12V when cycling in the warm whether.

 

You have a fridge that can ride a bike?? Fantastic!!!!

 

[Horace42]

5 hours ago, Mike the Boilerman said:

 

You have a fridge that can ride a bike?? Fantastic!!!!

 

Well spotted - I made that comment during a bad spell of whether.

 

 

[Matt&Jo]

I love this forum.... you guys are so quick witted and informative.....love it ?

[Nightwatch]

Not just Guys Matt, the girlies are catching up.

Edited June 6, 2018 by Nightwatch