Solar Output

Submitted: Sunday, May 18, 2014 at 13:57
ThreadID: 107827 Views:2865 Replies:4 FollowUps:7
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I would like to know how many amps a particular amount of solar panels put out per hour.

I realize there are many variables but would like a rough indication.

Ok, so this is my setup.

Dmax has a 120 ah in the tub, along with a Redarc BCDC 1240 (40amp), on the canopy roof, I have a Redarc 150W solar panel. This is wired into the BCDC and also has an Anderson plug so I can plug it into the camper when needed.

The camper has a 120 ah battery along with a Redarc BMS unit, the camper has two 65W solar panels fitted to the roof that tilt. I have had an extra Anderson plug fitted to the draw bar and wired into the BMS unit.

I also have a portable 120W solar panel, I have had Anderson plugs fitted to it so I can bypass the regulator when needed.

So if I wanted to charge the camper battery, I already have the 2 x 65W panels, I can also plug in my 120W portable via an Anderson plug that is wired into the BMS unit. I can also plug in the 150W panel that is the on canopy via the same Anderson plug using a double adapter.

The cables for the portable and 150W are 6 b&s.

So this would give me a total of 400W of solar, roughly how many amps would this give me per hour on a regular sunny day?

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Reply By: Robin Miller - Sunday, May 18, 2014 at 14:16

Sunday, May 18, 2014 at 14:16
Amps is an instanteous measurement Evaredy and it varies with how strong the sun is.

You probably want to know how many amp hours per day ends up back into the battery.

This depends on how many sunny hours at your location and strength of the sun for those hours which can also vary during the year.

Your 400w of potential solar power probably delivers around 20 amps peak current hence 20AH for every hour of good strong sunlight shining on them.
Robin Miller

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Reply By: The Bantam - Sunday, May 18, 2014 at 15:33

Sunday, May 18, 2014 at 15:33
As you long is a piece of string.

The output of solar pannels varies wildly depending on the time of year and the prevailing solar radiation in that location.

If you are in allice springs in summer with a clear day...your pannels are probably capable of delivering their rated output

If you are in tasmania in the depths of winter..even on a clear day you may only get 20% of the rated output and then only an hour either side of solar mid day.

in the higher lattitudes...kimberly, Darwin Cairns you may get 10 hours hell may be 12 of good usefull electricity making sunshine on a clear day in summer...back to Tassy in winter and that 20% mignt last 2 hours and youy may be lucky enough to be getting some usefull of charge out to 6 hours.

A wise man will be generous in his design of a solar system.

If you are realy interested in getting your head arround this off and buy one of Ray Rivers' books on solar. they are easy to read and give you some realy good information like solar radiation maps.

you will bless the day.

AnswerID: 532695

Follow Up By: MEMBER - Darian, SA - Sunday, May 18, 2014 at 15:36

Sunday, May 18, 2014 at 15:36
Collyn Rivers ?
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Follow Up By: Bob Y. - Qld - Monday, May 19, 2014 at 13:45

Monday, May 19, 2014 at 13:45
"Ray Rivers".......sounds like name of a blues or jazz singer :-)


Seen it all, Done it all.
Can't remember most of it.

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Follow Up By: The Bantam - Monday, May 19, 2014 at 21:37

Monday, May 19, 2014 at 21:37
just to save confusion

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Reply By: MEMBER - Darian, SA - Sunday, May 18, 2014 at 15:52

Sunday, May 18, 2014 at 15:52
Keep in mind that panel watt ratings are nominal (ideal conditions...cold and sunny). When you really need the power in warmer weather, 70% of the nominal is a probable max output from what will be extremely hot wafers under the glass.
AnswerID: 532697

Follow Up By: Ross M - Sunday, May 18, 2014 at 18:29

Sunday, May 18, 2014 at 18:29
Darian is correct, hot summer = less than full output in Alice cos they are "OT. Iwoud go with the ONLY 70% factor.

A cool full sun day in Autumn or Spring will beat any hot summer day every time.
My house system will at least make 2KW more in a cooler/shorter daylight period in early autumn and Late spring than a long hot day in summer.

Panels are panels.
FollowupID: 816000

Follow Up By: Shaker - Tuesday, May 20, 2014 at 08:56

Tuesday, May 20, 2014 at 08:56
When we had our system installed, they said Adelaide was the most solar efficient city. We are in Victoria.

FollowupID: 816103

Reply By: evaredy - Monday, May 19, 2014 at 11:23

Monday, May 19, 2014 at 11:23
Thanks for the replies.

I wouldn't have thought the panel would produce more when it was cooler.
AnswerID: 532752

Follow Up By: RolaSolar - Friday, May 30, 2014 at 01:33

Friday, May 30, 2014 at 01:33
This is referred to as the temperature coefficient. All solar panels power output starts to degrade as the temperature of the solar panel goes over 25 degree C. This is because most solar panel manufacturers test the solar power output at a panel temperature of 25 degree C.

If the outside air temperature is 25 degree C, the solar panel could be as high as 50 degree C. By using the max power temperature coefficient on the solar panels spec sheet the losses can be calculated.

For Example:
A typical crystalline solar panel max power temperature coefficient is approx 0.4% / degree C. For this example for every degree that the solar panel is above 25 degree C the solar panel will have a power lose of 0.4%.
So even at a cool 25 degree C day the solar panel would be around 50 degree C, giving you a power lose of 10%. So on a typical hot summer day at 40 degree C the power lose would be closer to 20%. So on the hotter days all solar panel will produce less solar power than usual.

Amorphous modules generally have a temperature coefficient of approx 0.2% / degree C which is half of a typical crystalline solar panel.

In Australia this is an important factor to consider but most resellers either don't have this information or even don't know what your talking about. It's even common not to find it listed on the solar panel spec sheet.

Regards Dave G
FollowupID: 816776

Follow Up By: evaredy - Friday, May 30, 2014 at 13:12

Friday, May 30, 2014 at 13:12
Thanks very much for the explanation, it really does get you thinking.
At least now I have some understanding of how it works.
FollowupID: 816820

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