conflicting information about solar install?
- Thread starter centerline
- Start date
The outboard panels and the ones over the cockpit fold down or over in seconds for docking, which I very rarely ever do.
The panels might have some effect but I believe my main issue was not having a higher 2nd reef point for the main for the wind speeds at the time. Martin at Somerset Sails has added one since then but I haven't been back out. At the time the boat was exceeding 7 kts. Not saying the panels might not effect things but I feel I'll now be able to trim the boat better in the future. I'm not sure what caused the rudder bracket to crack and finally break, but the rudder has always been very neutral and not required excessive force. I had been running for a number of days at the time with fairly heavy following seas. I'm about ready to fix the rudder issue and will reinforce it some. I have read over the years of other Macs rounding up in the right conditions that don't have panels.
One thing you can count on is that I'm a cruiser and that is how the boat is setup. The panels aren't coming off
. In the 3 months while in the Bahamas I never once had to run the gen-set or the outboard to charge the batteries and I have a large fridge, CPAP machine and a lot of computer usage. There was one period of very heavy cloud cover for 3 days as a tropical storm was building in the Bahamas and I was on anchor and still the batteries never went under about 60%. I can live with some performance issues in order to have the electrical power I have on long trips.
Sumner, not that a couple amps should matter one way or another in an adequate system, but help me find out (or show me) where my math is wrong....
by using the panel rating of 140 watts divided by 12 (volts) = 11.6 amps. OR... the same formula divided by 14.3 volts = 9.79 amps....
what figures should I be using?.... so I can come up with the same maximum output of 8amps per panel as you show....
I was using the theoretical maximum of (both panels, parallel) 23amps at a total run of 25ft, to arrive at the need for a 5ga wire, for less than a 3% drop....
I do agree that it is very unlikely that either panel (or the system) would ever put out its maximum potential, but for the sake of design, I want it installed like it could if it wanted to
your panels should have a maximum power point amp spec - no need to guess by voltage (plus the maximum power voltage will change with temp a fair amount - current not so much). Or use the short circuit current spec which will be just a little higher than the MPP current spec.
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I got the 8 amps (actually 7.91 A) here....
https://www.altestore.com/store/solar-panels/kyocera-kd140gx-lfbs-140w-12v-solar-panel-p10189/
Which I figured might be the panels you bought.
They arrive at the 140 watts by taking the output voltage of 17.7 X 7.91 amps (17.7 X 7.91 = 140 watts). This also illustrates why the panel is no longer 140 watts if using a PWM controller as it just connects the panels 7.91 amps to the 12 volt battery and if its voltage is say 12.5 volts then you have 7.91 amps X 12.5 volts for 98.9 watts. This is where the MPPT controller shines as it can increase the amps the battery sees above 7.91. It is still 10% to 15% under what a straight conversion would probably be but better than the PWM controller,
Sumner
==============================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...http://purplesagetradingpost.com/sumner/endeavour-main/endeavour-index.html
Mac Trips to Utah, Idaho, Canada, Florida, Bahamas
Thanks... it helps know what numbers to use.
short circuit current is 8.68 amps per panel.
...current at load is 7.91 amps
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I got the KD140SX-UFBS panels... I think I got a decent deal @ $230ea... and $203 for the bluesky 2512iX-HV controller...
thanks everyone for all the help....
I used the panel's short ckt amperage of 8-9 amps(IIRC) to determine a 12-ga wire from each panel to he controller. I placed my controller in the nav panel so I can see the lights. I also have the remote monitor in the nav panel. From this nav pnl location I used maybe 2 feet of wire to tap into the two battery leads that feed the breaker panel. That wire was bigger than what I would have use to get the MPPT controller output to the batteries. I mounted two terminal posts to tap into those two cables. I also have a panel-mounted ckt brkr to cut off the MPPT output to the 12-volt breaker panel.
The MPPT changes WHATEVER the input is to 12+ or so to feed the batteries, and THAT is where you'd consider the percentage loss, so you have the max charge going to the batts. Remember solar panel output is a higher voltage run than the usual battery to equipment run. In parallel, my 2 panels put out about 20/21 volts(IIRC). Panels in series, a bit more than 40v (IIRC). I have a switch to go from series to parallel or to take one or both panel off line to the MPPT. (P.S... "IIRC" means it's too freaking nasty to go to the boat to check the figures.)
Most likely, your controller will specify how large of a connector can be fitted onto it's lugs/screws. That should limit the size of wire you can use. I put two sets of terminals on each screw.... .... there is only one set of connections at the controller to connect the load to, so if there is something im missing about how it should properly be installed, I need it explained/spelled out to me so that i can understand the reasoning behind it
Most likely, your controller will specify how large of a connector can be fitted onto it's lugs/screws. That should limit the size of wire you can use. From the series/parallel switches I ran only 2 wires to the controller.... .... there is only one set of connections at the controller to connect the load to, so if there is something im missing about how it should properly be installed, I need it explained/spelled out to me so that i can understand the reasoning behind it
Try and keep the VD to a bare minimum if you want the best performance. The MPPT needs to see the most voltage it can in order to give the most boost during bulk mode. Higher voltage on the controller input means more "boost" on the output. If you are dropping 3% and the panels heat up to 120F then your boost output will be hindered even more as panel voltage drops as temp increase and MPPT controllers count on the excess voltage on the imput side to create more current on the output side..
Even a 3% voltage drop at 14.4V = less than 14.0V at the battery terminals. Voltage drop also serves to shorten your actual time spent at the correct absorption voltage because the time clock (egg-timer) starts when the controller sees the absorption voltage regardless of what the batteries are seeing.
Far and away the most critical aspect of any charge controller is proper programming. For this, with the Blue Sky, you'll need an IPN-Pro remote or the UCM (universal communication module). The stock factory voltages 14.2V absorption & 13.2V float, are murder on many batteries and wind up chronically under charging and leading to sulfation, especially in PSOC use. They also have an absorption time 2 hours that is almost always far too short to keep the batteries healthy.
Even with the wiring squared away you really need to set the controller up properly or it is really all for naught..
FWIW you will only find wire in 4GA, 6GA, 8GA, 10GA etc. Sizes 5GA 7GA etc. are not wire you'll find available..
Centerline, I think you misunderstood my post, above. Here's a more detailed explanation:
Your panels each have about an 8A max current (though, if your literature for the panels shows something different, use that). If wired in series, the currents add, so you wire for a 16A current run to the controller at 15 ft away...so according to this calculator:
http://www.freesunpower.com/wire_calc.php
You would need 9 ga (realistically 8 ga) wire for a 3% drop. Wired in series, if one of the panels gets shaded some, it kills the output for both.
Edit 4/10: The above is incorrect but I left it for posterity. See Sumner's correction below. Bottom line is voltage adds on series circuit, current remains the same. So voltage is 24v and current is 8A, and wiring is smaller for the same % voltage drop, not larger...Doh!!
If wired in parallel, each panel has still has an 8A max current, but the wiring from each panel to the controller has to only carry 8 A, so you can get away with 12 ga wire. Now realistically, the calculator I found and linked only has a 12v assumption for voltage, not the 17 or so that the panels can put out, so you might want to find a more accurate calculator (but maybe since that's a solar site, they've already taken that into consideration). Anyhow, that gets you to the controller. If you wire in parallel, and one panel gets partially shaded, it only kills the output of the one panel, not both.
Now from the controller to the batteries... Your controller has a max current output of 25A, from the info I found, so I'll use that.
I'll try another calculator just for some variety The blue sky one is a good one here:
http://circuitwizard.bluesea.com/
One thing to note with this calculator, is they want you to input the total current run out and back. This is different than the solar calculator I used above, but accomplishes the same thing. So if I put 12v, 25A and 20 ft (out and back), I get 8 ga wire for that run. By wiring for the max of your controller, you have some room to add panels, if you ever need to. Again, if you can find a calculator that allows you to input the expected max voltage that your controller can output at the 25 A max current (instead of the 12v default on the blue sky calculator), your calculations would be better...you might need a slightly larger wire. I would err to the side of larger to keep the voltage drop well below 3% anyway.
Edit: Here's a calculator that you can input any voltage you want, and calculate the percentage voltage drop after you get a basic idea of wire size needed using what I did above. You can then tweak the wire size to see its effect on voltage drop.
http://www.calculator.net/voltage-d...ance=15&distanceunit=feet&eres=8&x=68&y=12
Your panels each have about an 8A max current (though, if your literature for the panels shows something different, use that). If wired in series, the currents add, so you wire for a 16A current run to the controller at 15 ft away...so according to this calculator:
http://www.freesunpower.com/wire_calc.php
You would need 9 ga (realistically 8 ga) wire for a 3% drop. Wired in series, if one of the panels gets shaded some, it kills the output for both.
Edit 4/10: The above is incorrect but I left it for posterity. See Sumner's correction below. Bottom line is voltage adds on series circuit, current remains the same. So voltage is 24v and current is 8A, and wiring is smaller for the same % voltage drop, not larger...Doh!!
If wired in parallel, each panel has still has an 8A max current, but the wiring from each panel to the controller has to only carry 8 A, so you can get away with 12 ga wire. Now realistically, the calculator I found and linked only has a 12v assumption for voltage, not the 17 or so that the panels can put out, so you might want to find a more accurate calculator (but maybe since that's a solar site, they've already taken that into consideration). Anyhow, that gets you to the controller. If you wire in parallel, and one panel gets partially shaded, it only kills the output of the one panel, not both.
Now from the controller to the batteries... Your controller has a max current output of 25A, from the info I found, so I'll use that.
I'll try another calculator just for some variety The blue sky one is a good one here:
http://circuitwizard.bluesea.com/
One thing to note with this calculator, is they want you to input the total current run out and back. This is different than the solar calculator I used above, but accomplishes the same thing. So if I put 12v, 25A and 20 ft (out and back), I get 8 ga wire for that run. By wiring for the max of your controller, you have some room to add panels, if you ever need to. Again, if you can find a calculator that allows you to input the expected max voltage that your controller can output at the 25 A max current (instead of the 12v default on the blue sky calculator), your calculations would be better...you might need a slightly larger wire. I would err to the side of larger to keep the voltage drop well below 3% anyway.
Edit: Here's a calculator that you can input any voltage you want, and calculate the percentage voltage drop after you get a basic idea of wire size needed using what I did above. You can then tweak the wire size to see its effect on voltage drop.
http://www.calculator.net/voltage-d...ance=15&distanceunit=feet&eres=8&x=68&y=12
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If the panels are in series the voltage will double to a little over 35 volts and the current would still be 8 amps. In this case you have to use a MPPT controller that will work with voltages over 18 volts and not a PWM controller. If they are in parallel the voltage will be approximately 17.7 volts and the amperage will double for his panels to 16 amps.
It is important when using a calculator to know if it is figuring the run as out and back (in this case if the panel is 15 feet from the panel the run would be 30 feet) or figuring the run as one-way (15 feet). This one will do either...
http://boatstuff.awardspace.com/awgcalc.html
I usually compare a couple different ones to each other,
Sumner
======================================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...http://purplesagetradingpost.com/sumner/endeavour-main/endeavour-index.html
Mac Trips to Utah, Idaho, Canada, Florida, Bahamas
is this an acceptable way to connect the panels in a parallel circuit , or should they both have independent wires running to a junction block, then a single run to the controller?....
or would it be better to run independent legs from both panels all the way to the controller?....
these SX model panels have junction boxes on them, so im trying to minimize the addition of other connections if I can do it with what is already included...
or would it be better to run independent legs from both panels all the way to the controller?....
these SX model panels have junction boxes on them, so im trying to minimize the addition of other connections if I can do it with what is already included...
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With MPPT, you are "supposed" to match the maximum power point voltage of panels connected in parallel. Connecting in parallel forces the voltage of both panels to be identical. The controller finds the maximum power point voltage and if the panels are identical, both panels are producing maximum power. What you have shown produces the best matching of voltage on both panels so is a good idea..
However.. I am fairly sure that if you tried to measure any improvement by doing that, you probably could not.
I have just been messing with two very miss-matched panels in parallel with a MPPT controller. One is 10 watt, the other is 20 watt. You dont care about matching current at all since the current just gets summed. But the parallel connection forces the voltage to be the same on each panel. So the 20 watt panel list the nominal 25C Vmax = 16.4 volts and the 10 watt panel the Vmax = 17.3 volts (ie, 0.9 volts different).
Just before noon the other day on a sunny day, I compared the output from the MPPT controller (Genasun GV5) for each panel individually and then summed. Here are the results:
20 watt panel only (towel over the 10 watt panel)
I = 1.37 amps
Vpanel = 15.3 volts
Vbattery = 12.75 volts
10 watt panel only (towel over the 20 watt panal)
I = .63 amps
Vpanel = 14.4 votls
Vbattery = 12.68 volts
10 watt plus 20 watt = 30 watt
I = 2.00 amps
Vpanel = 15.25 volts
V = 12.9 volts
So.. even through the panels are miss-matched for Vmax at both nominal temp and warm (where I tested them), the currents of the individual panels is equal to the sum of each panel when run individually. Apparently I either dont have or cant measure any penalty from the mismatch. Ie, 1.37 amps + .63 amps = 2.0 amps.
Interesting also that you can see how much the Vmp dropped with temp. The Vpanel in the data I gave is the maxium power voltage as found by the Genasun controller. The Vmp of the 10 watt panel was higher than the 20 watt panel for the 25C spec. However, at the temperature I tested them, the 20 watt panel had a higher Vmp.. This does not track well with the two panels - yet I cant see that Im loosing anything with this parallel setup.
And.. why I say the careful matching in your diagram just doesn't matter that much.
However.. I am fairly sure that if you tried to measure any improvement by doing that, you probably could not.
I have just been messing with two very miss-matched panels in parallel with a MPPT controller. One is 10 watt, the other is 20 watt. You dont care about matching current at all since the current just gets summed. But the parallel connection forces the voltage to be the same on each panel. So the 20 watt panel list the nominal 25C Vmax = 16.4 volts and the 10 watt panel the Vmax = 17.3 volts (ie, 0.9 volts different).
Just before noon the other day on a sunny day, I compared the output from the MPPT controller (Genasun GV5) for each panel individually and then summed. Here are the results:
20 watt panel only (towel over the 10 watt panel)
I = 1.37 amps
Vpanel = 15.3 volts
Vbattery = 12.75 volts
10 watt panel only (towel over the 20 watt panal)
I = .63 amps
Vpanel = 14.4 votls
Vbattery = 12.68 volts
10 watt plus 20 watt = 30 watt
I = 2.00 amps
Vpanel = 15.25 volts
V = 12.9 volts
So.. even through the panels are miss-matched for Vmax at both nominal temp and warm (where I tested them), the currents of the individual panels is equal to the sum of each panel when run individually. Apparently I either dont have or cant measure any penalty from the mismatch. Ie, 1.37 amps + .63 amps = 2.0 amps.
Interesting also that you can see how much the Vmp dropped with temp. The Vpanel in the data I gave is the maxium power voltage as found by the Genasun controller. The Vmp of the 10 watt panel was higher than the 20 watt panel for the 25C spec. However, at the temperature I tested them, the 20 watt panel had a higher Vmp.. This does not track well with the two panels - yet I cant see that Im loosing anything with this parallel setup.
And.. why I say the careful matching in your diagram just doesn't matter that much.
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Nice real world test Walt ,
Sumner
===============================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...http://purplesagetradingpost.com/sumner/endeavour-main/endeavour-index.html
Mac Trips to Utah, Idaho, Canada, Florida, Bahamas
,Sumner
===============================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...http://purplesagetradingpost.com/sumner/endeavour-main/endeavour-index.html
Mac Trips to Utah, Idaho, Canada, Florida, Bahamas
this is some enlightening information. the test results surprise me... only because I thought multiple panels connected in the same system needed to be nearly identical for them to all produce close to their design potential....
I would agree not many probably would try it... but Walt did, and gave us some surprising numbers... but in series, I think there would be a problem....
Sumner,
Thanks for clearing that up. I think I must have been brain deficient when I wrote that yesterday! I do know better, and proofed it twice! The beauty of having smarter people double checking you. (so wired in series= smaller wire for the same % voltage drop, the opposite of what I posted).
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