Solar The Solar Panel Thread

[mikerezny]

Hi @mikerezny , congratulations. I dips my lid to your greater knowledge!! You are a great asset to have on a forum like this. I too like the KISS principal and try to explain things simply for those who have limited electric knowledge. When I was in a car club, there were members who could rebuild all engines and feel/notice bearing/journals that were out of round by only 10 thou. But mention car electrics, they immediately shied away calling it "white man magic" because they could not actually see the electric currents and voltages. To each his own in expertise!!!

Hi @Boots in Action,
knowledge, experience, and wisdom come in many, many different forms and comes out in the strangest of places. I am always pleasantly surprised at how it surfaces. For instance, when I first joined, I would never have thought that I would get so much information from this forum from so many different people.

cheers
Mike

 

[mikerezny]

Thanks @G Daddy for clarifying that about Blocking diodes . If that is what @mikerezny is referring to, then it will be an easy fix to insert a Schottky diode in the output line of one of the panels that connects in series with the other panel. More great information. Another good reason for being on this forum - knowledgeable and friendly members! Cheers

Hi @Boots in Action,
First step is to look inside the terminal block of each solar panel. They often already have blocking diodes. If they are there look at the marking and google it to see if they are Schotky diodes and how they are wired.

Referring to the diagram from a few posts back, for panels connected in series, you need a bypass diode across each panel. For panels connected in parallel you need a blocking diode in series with each panel. That is my understanding.

I hope this helps.

cheers
Mike

 

[Boots in Action]

Hi @G Daddy,
thanks, that is really useful information.

Since we like to park in shade, I spend more time then I would like, shifting the solar panel around because of a tiny shadow drifting onto the panel resulting in zero output.So I would be interested in replacing my panel with one of the ones you mentioned.

You have just reminded me that I need to go buy some more cable to extend the radius around my van so I can get the panel further away and into less shaded areas.

cheers
Mike

Hi @mikerezny , when I was at the Caravan Show in Brisbane last year, I came across 10 metres of twin 4mm sq cable that is used for solar panels for buildings etc. It was from a marine supply place just south of Brisbane. Only cost me $40.00 too, which was better value than what I had previously bought on EBAY for about $29.00, from someone in Bairndale Vic. It was only 5 metres long and nowhere near as thick in the copper conductor as the one I bought at the Show, probably only 2mm sq cabling. Practically NIL voltage drop on the current cable I have been using for the last 18 months. Had Anderson plugs on both ends too, probably a Show Special!!

 

[Boots in Action]

Hi @Boots in Action,
First step is to look inside the terminal block of each solar panel. They often already have blocking diodes. If they are there look at the marking and google it to see if they are Schotky diodes and how they are wired.

Referring to the diagram from a few posts back, for panels connected in series, you need a bypass diode across each panel. For panels connected in parallel you need a blocking diode in series with each panel. That is my understanding.

I hope this helps.

cheers
Mike

Thanks again Mike. Will have a good look and see what has to be done tomorrow..

 

[G Daddy]

An interesting video on series - parallel and shading

 

[Dobbie]

You guys lost me a couple of pages ago!

Good to see the in depth discussion ....but it's too deep for my simple mind.

I had occasion to check the SOC on our batteries yesterday....had one small panel hooked up to trickle charge while we finish the cleaning ....and found the panel was giving no input at all.

Scratch the head time. Found one of the leads to the Anderson plug had parted company from the regulator....and it's an mppt.

That's the extent of my concentration level these days.

 

[Drover]

This is getting way too complicated and is really violating the KISS principle which I try to adhere to.

I think your KISS and my KISS have varied levels......lol,lol..........................

Had a better look over all the posts here and actually what might be an anomaly, the readings really do give a real world view, you tech heads are swinging back to the bench top perspective, I must admit while I can hands on build stuff the technical side of "Green Steam" does take me a bit of serious study to get on top of it, many years (45) since I did stuff with colour codes and diodes......

This is my controller seems to work well and gives a readout on volts, solar and load, only a pWM but don't have a MPPT to compare with it but it is better than the cheapies....

 

[Boots in Action]

Hi @Boots in Action,
knowledge, experience, and wisdom come in many, many different forms and comes out in the strangest of places. I am always pleasantly surprised at how it surfaces. For instance, when I first joined, I would never have thought that I would get so much information from this forum from so many different people.

cheers
Mike

Amen to that!!

 

[mikerezny]

I think your KISS and my KISS have varied levels......lol,lol..........................

Hi @Drover,
my attempt at implementing KISS is to gather all the information I need. With electronics, that is quite easy for me. Then I start filtering it and simplifying it.

So in the end, my practical KISS is a 105Ah GEL battery, Setec unit, a $50 40W portable solar panel, $6 three-stage solar charger, and that $12 gizmo that measures battery volts, amps into the battery, and accumulated charge, but a reasonable understanding of what all the bits do. I would guess that this is about as close to KISS as one can get.

Whilst I understand the electronics, and bits and pieces of the mechanicals, I really take my hat off to those with the skills to do magic with metal and lathes and welders and grinders etc. Absolutely out of my depth in that area.

cheers
Mike

 

[mikerezny]

An interesting video on series - parallel and shading

Hi @G Daddy,
really informative video. Thanks for sharing the link.

cheers
Mike

 

[Dobbie]

and me!

I'm absolutely hopeless at anything metal...welding, cutting and so forth ...and so fifth.

but it's fun trying to make sense of what's within my limited range and that includes solar for our needs.

as I've said, I'm now very satisfied that our solar needs are now met and that I have a reasonable chance of sorting it out if it's not. We do carry a multimeter, a voltmeter, spare cable and various Anderson plug adaptors...just cos I hate not using the sun to keep the second car battery fully charged as well.

For the record....we now have 160 solar on roof, a very efficient 120 flexible portable panel and a rather heavier (but foldable) 120 panel that's just for backup. At home, we use an old (probably 10 years old...battered and very well used) 120 panel to keep the two 125 AGM batteries charged as the van lives in the shed.

We started with a spreadsheet to determine power needs ...the new fridges were the unknowns there so previous requirements had to be adjusted. We then used that spreadsheet to calculate the solar charging range from what we had.

We can now put away the calculations and just get on with life, but I'm pleased we did it yet again.

So, for us, it's just a matter of determining capacity, needs and charging potential to make sure all things work when off grid and that's up to a month at times.

I applaud you knowledgable guys who are continuing the fun of discovery and confirmation of principles.

Have you read Collyn Rivers book on solar? I haven't seen it around lately ...but it's good common sense, from memory.

 

[mikerezny]

We started with a spreadsheet to determine power needs ...the new fridges were the unknowns there so previous requirements had to be adjusted. We then used that spreadsheet to calculate the solar charging range from what we had.

Hi @Dobbie,
are any of your fridges 2-way?

If so, in all the information you gathered, for those 2-way fridges, did you happen to make a note of the current draw when the compressor was running and when it was not AND the total Ah used by the fridges over a 24 hour period?

It would be very interesting to know the duty cycle since some manufactures only quote the power usage when the compressor is running and that is obviously not what the actual Ah usage is over a 24 hour period.

cheers
Mike

 

[Dobbie]

hi Mike.

I'm trying to find the spreadsheet I used as it has the cycling we researched....but it was on my previous pc and, like all good things, it died....but I'll try.

It may be an earlier version, but the principles are the same.

Solar Battery Calculator estimate.zip

hope this works!!!

 

[Boots in Action]

An interesting video on series - parallel and shading

Thanks @G Daddy for the referral to this video. Certainly good to know how different connections of panels is affected by Shading or partial shading. Looks like I will be changing connections to get the best out of panels when shading becomes an issue. I will keep details of this video with me in the van so I can refer to it as necessary. So much info available to use!!!!

 

[Boots in Action]

You guys lost me a couple of pages ago!

Good to see the in depth discussion ....but it's too deep for my simple mind.

I had occasion to check the SOC on our batteries yesterday....had one small panel hooked up to trickle charge while we finish the cleaning ....and found the panel was giving no input at all.

Scratch the head time. Found one of the leads to the Anderson plug had parted company from the regulator....and it's an mppt.

That's the extent of my concentration level these days.

Nothing like a broken wire to stop every thing and cause one grief!! It is usually the simple things that are hardest to find also!!

 

[Dobbie]

It seems that technology has defeated me, once again.

That's about the best I can do at the moment but, in answer to your question, the main Thetford fridge has a constant 12v draw for the stupid electronic panel so that's 15amps daily.

The Waeco cycles on and off at 2.7 amps for about a total of 10 hours.....so 24 amps per day. From my observation, that's about right.

Below is the copy of the spreadsheet that has lost all the columns and settings ....you might be able to decipher some of it while I try to sort out why the zip for the Excel spreadsheet doesn't seem to work!

but it's a beautiful balmy 25deg here again today so my gardening might just get preference over sorting this out.

Apologies for the confused techno stuff!




Assumptions Daily Usage Fridge Lights Radio DVD TV Other Day/Night Usage
Battery Average amps 2.0 1.0 3.0 1.2 Day Night
Battery capacity (amphours,AH) 250 Approx hours per day 8.0 3.0 3.0 6.0 Fridge 75% 25%
Minimum allowable SOC 50% Approx total Watt Hours 192 36 0 0 108 86 Lights 0% 100%
Remaining capacity at minimum SOC (AH) 50 Approx total Amp Hours 18 3 0 0 10 8 Radio, DVD, TV 10% 100%
Initial state (incl system losses) Other 50% 50%
State of charge (SOC) is 80%
Available capacity at min. SOC (AH) 50 Battery state of charge (at 27 degrees C)
Solar Panels Wet standard or wet low maintenance Data taken from table on this web site http://www.uuhome.de/william.darden/
Nominal capacity (Watts) 120 Rest voltage 12.65 12.45 12.24 12.06 11.89
Panel efficiency 70% SOC 100% 75% 50% 25% 0%
Actual output ( Watts) 84 Wet "maintenance free" or AGM/Gell cell
Rest voltage 12.80 12.60 12.40 12.00 11.80
Estimated system losses 10% SOC 100% 75% 50% 25% 0%

Assumed Sun Hours per day 8.0 8.0 5.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0

Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 Day 9 Day 10 Day 11 Day 12 Day 13 Day 14
Day Available power - sufficient, insufficient, none
Battery state of charge at start of day 71% 75% 80% 77% 81% 85% 89% 91% 91% 91% 91% 91% 91% 75%
Battery power (AH) 178 189 199 192 202 213 223 228 228 228 228 228 228 188
Available power (AH) at minimum SOC 128 139 149 142 152 163 173 178 178 178 178 178 178 138
Solar panel output (AH) 56 56 35 56 56 56 56 56 56 56 56 56 0 0
Total available power(AH) 184 195 184 198 208 219 229 234 234 234 234 234 178 138
Drawdown (AH)
Fridge 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3
Lights -0.0 -0.0 -0.0 -0.0 -0.0 -0.0 -0.0 -0.0 -0.0 -0.0 -0.0 -0.0 -0.0 -0.0
Radio, DVD, TV 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
Other 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0
Total drawdown 18 18 18 18 18 18 18 18 18 18 18 18 18 18
Shortfall (AH) 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Surplus solar power to battery (AH) 32 32 14 32 32 32 32 32 32 32 32 32 0 0
Available battery power (AH) 161 171 164 174 185 195 200 200 200 200 200 200 160 120
Night
Battery SOC 80% 84% 88% 85% 90% 94% 98% 100% 100% 100% 100% 100% 100% 84% 68%
Battery power (AH) 200 211 221 214 224 235 245 250 250 250 250 250 250 210 170
Available power (AH) at minimum SOC 150 161 171 164 174 185 195 200 200 200 200 200 200 160 120
Drawdown (AH)
Fridge 4.4 4.4 4.4 4.4 4.4 4.4 4.4 4.4 4.4 4.4 4.4 4.4 4.4 4.4 4.4
Lights 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3
Radio, DVD, TV 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0
Other 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0
Total drawdown 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22
Shortfall (AH) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Battery power at end of day (AH) 128 139 149 142 152 163 173 178 178 178 178 178 178 138 98
Battery SOC at end of day 71% 75% 80% 77% 81% 85% 89% 91% 91% 91% 91% 91% 91% 75% 59%

Summary
Power available (AH)
Battery 150 128 139 149 142 152 163 173 178 178 178 178 178 178 138
Solar 0 56 56 35 56 56 56 56 56 56 56 56 56 0 0
Total 150 184 195 184 198 208 219 229 234 234 234 234 234 178 138
Power required (AH) 22 39 39 39 39 39 39 39 39 39 39 39 39 39 39
Shortfall (AH) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

 

[mikerezny]

It seems that technology has defeated me, once again.

Hi @Dobbie,
many thanks for the zip files.
I was able to download it, extract the spreadsheet, and view it without any problems

cheers
Mike

 

[G Daddy]

Here's a link to Maxium new technology article
https://www.google.com.au/search?q=...t=firefox-b&gfe_rd=cr&ei=6xeAWao-6tzzB8DGs9AJ
And below a clip from the article

 

[mikerezny]

Hi,
I just pulled the cover off the terminal block of my 40W solar panel. There are no diodes.

Also did some testing of my panel in the shade. The panel has one string of series cells. If I completely block out any one cell, the output of the entire panel goes to zero. Partially blocking out many cells just reduces the output.

cheers
Mike

 

[G Daddy]

Article on panel angle