OK, so my solyndra panels will not fit on the RV in any configuration I want to live with, so they will go on the patio and run some other loads at the house.
I have been looking at panels, and three Kyrocera 140W KD140SX-UFBS panels seem to be a good fit in the rooftop envelopes I have. So the question is:
Series @ 6.33 Isc and 66.3 Voc
or
Parallel @ 18.99 Isc and 22.1 Voc?
End output is basically the same at 29.2A to the battery bank, but the Series setup allows me to run smaller (read cheaper) wire. Voltage is higher, current is lower. To me, a series arrangement is a no brainer, but is it?
66VDC does not bother me...
This will be a 12V system with 2 GC2's possibly adding two more GC2's when these crap out.
Well thats tough. Parallel is to close in voltage for my comfort. I guess as long as shading is not an issue I would go Series
Putting them in series also means that you will not need a combiner and circuit breakers.
Part of the decision should be based on the distance between the array and the controller.
The best arguments for putting them in parallel is that there is a small increase in efficiency, and that you could use lower voltage DC breakers, fuses, switches, etc.
Generally, I am not too concerned about a fraction of a percent of efficiency... the exception being when you are using the controller at its limits. If you spend a lot of time drawing 30 amps from the Kid, then you should lean towards lower input voltage. But as halfcrazy points out, there's not much headroom.
What I would really like to see is 4 of those 12 volt panels (100-110 watts each) connected in series/parallel. 8)
--vtMaps
Since I posted this, I have been looking at other panel sizes. Larger wattage panels give better bang for the buck and lower weight due to less frame material overall, but I run into "things" on the roof. This is one instance where my Carrier Low Profile 15K heat pump is a problem as it is longer and wider than the usual RV AC units. My roof is also curved...
4X100W is also a good fit for me as I can put three of them on the right side and the fourth on the left side and not have it shaded by the other three if I tilt them. It also helps balance the weight somewhat as the Left side of my coach is a bit heavier due to the genset location. (I have a Honda EV4010 for the heat pump when camping in the desert in the summer) Cost and weight go up a bit with four, and there are more roof penetrations for the mounting rails. I really want to get as close to 500W as possible, however.
The controller will probably be mounted high on the wall near the front of the trailer so it is as close to the battery bank on the tongue as possible, but still be able to use it without sticking my head in a compartment hatch. Wiring will come through it's own penetration sealed under a sealed electrical box instead of the usual through the refer vent to prevent dripping. No matter how much you work to put drip loops in wiring, 70MPH and road vibrations will probably work against me.
Just where do people mount the Kid controllers on RV's anyway? Sure would be better to have a controller and a separate control panel that could be remote mounted anywhere. I guess it doesn't really matter as I will have less than 30A and can upsize the charge wires a few gauges, although I have about 200' of 10-3 find strand cable made in Japan, that really holds up in weather. I have an extension cord made out of the stuff and it has stood in the sun for years with a gate sliding over it almost daily...
2 x2 was my first thought too. No combiner CBs needed just one disconnect, less wire than 3 and less loss also. Closer to final V of b. bank so less heat losses in downconversion. can you find some 140 or 150W pv's??
Yeah, looking at the Grape 135 mono's as they are longer and narrower so I can actually fit 4.
I could squeeze 5 Grape 100's or three Kyocera 140's/Grape 160's.
Starting to look like I have a lot of options.
Any thoughts on the Grape's? Not much out there, Homeowner Depot carries them.
Quote from: ZoNiE on July 28, 2014, 06:03:26 PM
Any thoughts on the Grape's? Not much out there, Homeowner Depot carries them.
Some Grapes are or were positive ground. They didn't work too well with a conventional negative ground.
--vtMaps
The minute you go over 2 wires going to the CC you will need a combiner box with CBs to protect your investment... so 2 x 2s or 2 x 3s ( s = series) etc...
OK, I am now looking at some other options.
A local dealer/contractor here has some leftovers from larger jobs. I presume they buy them by the pallet, and end up with extras, but not enough to do a full job.
I can fit two 240W Sunpower panels, (three will fit, but 480W is about my target for Watts and Weight) but are these positive ground? They are 19-series, 19% efficient. I really want to use these, and at $160 each for new, and no shipping, a really good price.
Then there are some Kyrocera 140's, and some used Alps 123's. I can fit four of each of these, but it is not ideal.
Is the positive ground an issue with the Kid?
The roof is rubber over Wood, with nothing metal except the radio and TV antennas. The TV antenna is nowhere near where these will go, and the radio Antenna will be replaced with a rubber one anyway.
any advice on the SunPowers?
Pulled the Trigger on three KC130GT black panels today. It's a little less than I can fit, but the price was right, they were local, and 390W was pretty close to my 400W goal. I could have had a fourth panel, but then I'd be over on total Wattage on the Kid and I'd have to remove the TV antenna from the roof of my trailer to squeeze the fourth panel in, as my Rooftop AC unit is wider than normal being a Carrier Low Profile.
Ok here is what I have:
Two panels will be mounted on one side, end to end, and the other across from them.
I can wire in series or parallel just as easily, so wire runs do not matter.
Since I have an odd number of panels @ 20V / 8A each, it is also not an issue wire size-wise. I will be running #10 regardless, as I have 100's of feet of good cable already.
(note, volts/amps are rounded)
So, 60VDC into the Kid @ 8A for 12V output @ 24A
Or, 20VDC into the Kid @ 24A for 12V output @ 24A
Sure, I will need three breakers for Parallel, instead of one for series, but they are cheap. It's also more wire weight, but that's negligible.
Efficiency wise, is 60VDC to 12V charge really a problem?
Negative ground?
Zonie,
In your case parallel would better for two reasons ......the charge controller will be more efficient at a 1.4 to 1 conversion ratio than it will be at 5 to 1 conversion........more work to do....more heat..less efficient and with your RV you will be much more likely to have of shading issues. Parallel configurations will be less affected as only the shaded panel will have a power loss where if you are all in series all panels in the string will be down to the same power as the shaded panel.
td
Negatve Ground, Yes.
Quote from: tecnodave on September 06, 2014, 02:04:43 PM
Zonie,
In your case parallel would better for two reasons ......the charge controller will be more efficient at a 1.4 to 1 conversion ratio than it will be at 5 to 1 conversion........more work to do....more heat..less efficient and with your RV you will be much more likely to have of shading issues. Parallel configurations will be less affected as only the shaded panel will have a power loss where if you are all in series all panels in the string will be down to the same power as the shaded panel.
td
Good point, and that is what I was looking for. I had considered the conversion ratio, but NOT the shading issue, which will probably be an issue.
Parallel it is!
Zonie,
I have tried the setup I have suggested , it is a bit close in voltage , but the kid does pretty good at low voltage input and getting every available watt. I am using L-16 and GC-2 battery format and I do equalization at 15.6 to 16.0 volts for my 12 volt systems but with a p.v. Output V@pmax rating of 18.7, sometimes I cannot finish an EQ due to low light levels. My preferred system would have a 34 volt string voltage for 12 volt system ( two 36 cell or one 72 cell panel ) and 68 volt. ( two 72 cell panels in series ) for my 24 volt systems, because I live in the coastal pea soup fog belt and need to scramble for every watt. I have done 105 volt and 140 volt strings but all controllers will run hotter doing this, the kid is no exception, heat produced is power lost, and heat is one of the killers of electronic gear.
If you can possibly squeeze one more panel in there and run two strings it would be worth doing but real estate on a motorhome is difficult. Modern 6 inch cell panels are just too big. Most of my good panels are 5 inch cells at about 32 X 64 inches for the panels. The Eoplly panels work well for an RV.
td
I was hoping to find some slightly smaller 100W panels to do just that, have four, in two parallel strings, or two larger 200W-ish panels with higher Voltage, But the only ones that seem to be available locally are the positive grounded ones. This being a Trailer, well, that was a non-starter. The old 100W siemens panels are loooong gone.
I could conceivably put a fourth panel, either as a loose mount, or hinged with the single one where it would only deploy when I am camping, so those two would be "off" leaving the two others to work alone when the trailer is sitting in my driveway for weeks on end. I could still get the fourth matching panel from the guy...
Another thing is, at 520W, the array is "excessive" on the Kid calculator (1.3), so I decided not to do that.
Then, I had also considered a 65W panel from the same series, to add to the lone panel, as there is room to do that, but then I would have a lower voltage on one string. I'm a bit anal about matching things, and, that one panel currently would cost 2X what My 130's cost.
I have a good way to run the three to a junction box in an upper cabinet, and install the three 10A pushbutton Breakers I am using, and then a 30A PB breaker for the run to the Kid. (I have tons of these things already for free).
http://www.alliedelec.com/search/productdetail.aspx?SKU=70128888 (http://www.alliedelec.com/search/productdetail.aspx?SKU=70128888)
Quote from: ZoNiE on September 07, 2014, 01:38:36 PMAnother thing is, at 520W, the array is "excessive" on the Kid calculator (1.3), so I decided not to do that.
Mine is maxed out at 405 watts (3 x 135, series), currently. That is 1.0. But, I don't get anywhere near that. Mine is closer to 325 watts, usually?
With system losses, you won't be anywhere near that high. Instead, you will probably be right at 1.0.
you could add some voltage drop by using undersized wire...
Zone,
Those breakers are rated for DC but only 50 volts but breakers are worth the trouble when krap happens.
I think that you should not try to match up mismatched panels.....things get too complicated. Three panels should be fine, I used old Siemens 55 watt panels for years but prices are falling and I am getting new panels for 33 to 75 cents a watt.....some old stock that has outdated MC-3 connectors....some odd ball.....some off brand but I stick with 72 cell panels so all will have same voltage.
On the current limit on the kid......I have 1020 watts in at 70 volt strings and can produce 30 amps at 31.5 volts .....942 watts out......kid got a bit warm at 53 deg. C. so my current limit is set down to 25 amps (found in battery menu) to protect my equipment. The current limiter is very active and is able to protect the kid from too much power. I have just received a second kid and plan to team them up with even more panels. Running at that high a power level is taxing on the equipment.....my goal is never to exceed 80% max power and run at more like 66 % of maximum power.
My motorhome is rarely driven......it's used as a mountain cabin.....solar panels mount on a rack made up from awning arms and mounts. It's 7 feet wide and a bit over 16 feet long, folds down flat on roof and tilts up to 35 degrees....has 6 Sharp 170 watt 72 cell polycrystalline panels for 24 volt system , plus 8 Siemens 55 watt 36 cell monocrystalline panels for 12 volt system . Air conditioner was in the way and was removed...I need to park east or west as rack will tilt either way.....Sun must be off side of motorhome.....
td
EF, and TD, I was thinking about that. Will I Really get 520W. No, probably not.
My TT will eventually be a starter mountain cabin.
Prolly should get that 4th panel.
BTW, my panels have MC3's. came with 12Ft extensions for 18' total each line. Nice.
Also Nice to know the Kid will protect itself.
The CB's are 28VDC rated, btw.
Thanks for all the real world info folks. Just what I need.
Thing about solar power is: once you have some you want more.... and will use more...
ZoNie,
I have three 230's attached to a Kid in 12V for now. It makes better power on cloudy days like today(240watts), and in full sun, it makes 415 watts (30 amps). Yes I am waisting some power, but the Kid has no problem with the extra on sunny days. I'll check the temp on the next full sun day I am out there. I am running an 12V 65 CFM fan 24/7 to keep everything cool, so that is going to reduce the temps some.
I like having the extra power on cloudy days, and autumn is just around the corner.
My next Kid is going 24V and six panels. I'll report as things go.
Quote from: Westbranch on September 07, 2014, 08:55:39 PMThing about solar power is: once you have some you want more.... and will use more...
It's worse than drugs I tell ya! Worse than drugs!! I need my fix!
Over paneling is not a bad thing......just watch the current and temps. I was getting 130 watts out of 1020 watts of panels in yesterday morning through heavy fog. When the fog broke at 1:30 I was way behind in getting full charge so set current limit up to 30 amps and turned diversion off and saw 800-900 for early afternoon..... Floating by 5:30.....could not have done that without the big array. Tracer booster controller has been removed to make room for kid number two. I might just push things a bit and add 1050 watts of Eoplly 72 cell panels and experiment with bully mode or follow me.
My portable home is now fully powered by Kid's and the Classic powers a 40 foot high cube shipping container portable workshop
5 years ago I had some ancient Siemens 30 cell panels, a sun saver and a D-8 truck battery....now three MidNite controllers , 9 other brand cc's and about 70 panels, 4 battery stacks
My real nickname is tecnojunkie ....according to the other side! I don't really have a defense on that!
td
Quote from: Westbranch on September 07, 2014, 08:55:39 PM
Thing about solar power is: once you have some you want more.... and will use more...
Yup.
Quote from: Free Energy Freak on September 07, 2014, 10:08:56 PM
It's worse than drugs I tell ya! Worse than drugs!! I need my fix!
And Yup.
Quote from: tecnodave on September 06, 2014, 02:04:43 PM
Zonie,
In your case parallel would better for two reasons ......the charge controller will be more efficient at a 1.4 to 1 conversion ratio than it will be at 5 to 1 conversion........more work to do....more heat..less efficient and with your RV you will be much more likely to have of shading issues. Parallel configurations will be less affected as only the shaded panel will have a power loss where if you are all in series all panels in the string will be down to the same power as the shaded panel.
td
tecnodave, wow, that's something I hadn't read/heard before -- yes, I'm definitely a newbie so that's no big surprise. I have (4) 100w panels. I have them wired up in series. I thought MPPT worked better the higher the difference between the PV voltage and the battery bank voltage.
Maximum Power: 100W Maximum System Voltage: 600V DC (UL)
Optimum Operating Voltage (Vmp): 18.9V Open-Circuit Voltage (Voc): 22.5V
Optimum Operating Current (Imp): 5.29A Short-Circuit Current (Isc): 5.75A
My battery bank consists of (2) 125Ah 12v batteries wired in series to form norminal 24v bank. I was actually thinking of adding two more 100w panels, for a total of (6) panels in series. 22.5v x 6 = 135v, so still under the KIDS limit of 150v. According to your posting above, this is a bad idea? I would prefer not to deal with parallel setup as I prefer not to deal with combiner boxes.
BTW, I haven't been able to get more than just over 300w from my (4) 100W panels. :'(
I used 10AWG wires from PV panels to the KID, less than 40 ft. Should be more than sufficient for 5.75A though, right?
Ho NKOTB,
Personally, think that running 113 Vmp string voltage on a 24 V bank is a bit much ... Have not read all of your posts to try to guess just where you are located, to better estimate just how cold your PV environment might be ... But with a 600 STC Watt array and the envisioned HIGH string voltage, think that the KID will run HOT, and probably reduce its output current to try to keep cool.
Have you tried the KID String Sizer (?):
http://www.midnitesolar.com/sizingTool_kid/index.php
That might help you determine the best string arrangement.
And, as you probably know, the STC power specs are for PV cells that are at 25 degrees C. When PVs are exposed to the sun, they become warm/hot. This reduces the output voltage and therefore the output power. Normally one would estimate that in full sun, midday, with the PVs oriented at right angles to the sun that one would produce about 75% of the STC rating. On hot days, a bit less, and a bit more on cold days. So your 300 W output is right in there.
My opinions, Have Fun, Vic
Quote from: New KID On The Block on October 06, 2014, 10:08:00 PMI thought MPPT worked better the higher the difference between the PV voltage and the battery bank voltage.
I run double the battery bank voltage, on my PV array. As TD previously stated, the more the controller has to downconvert, the more inefficient it will be.
Quote from: New KID On The Block on October 06, 2014, 10:08:00 PMBTW, I haven't been able to get more than just over 300w from my (4) 100W panels. :'(
75%, not bad.
Quote from: Vic on October 06, 2014, 10:55:22 PM
Ho NKOTB,
Personally, think that running 113 Vmp string voltage on a 24 V bank is a bit much ... Have not read all of your posts to try to guess just where you are located, to better estimate just how cold your PV environment might be ... But with a 600 STC Watt array and the envisioned HIGH string voltage, think that the KID will run HOT, and probably reduce its output current to try to keep cool.
Have you tried the KID String Sizer (?):
http://www.midnitesolar.com/sizingTool_kid/index.php
That might help you determine the best string arrangement.
And, as you probably know, the STC power specs are for PV cells that are at 25 degrees C. When PVs are exposed to the sun, they become warm/hot. This reduces the output voltage and therefore the output power. Normally one would estimate that in full sun, midday, with the PVs oriented at right angles to the sun that one would produce about 75% of the STC rating. On hot days, a bit less, and a bit more on cold days. So your 300 W output is right in there.
My opinions, Have Fun, Vic
Thanks for replying
Vic.
I live in sunny Silicon Valley -- south part of greater San Francisco Bay Area. ;) My environment is not cold at all. I think you have a good point about both the KID and solar panels running hot. Hmm.. So if I want to add more solar panels to my rig, my realistic option would have to be series-parallel string of panels?
Well I'm glad to read that my ~300W of power production is about right. I took a photo of today's best reading: 306W. ;D
That's the best I've achieved so far.
Yes, I have used that KID String Sizer tool before but I'll go take a look at it again. Thanks.
Quote from: Free Energy Freak on October 07, 2014, 12:02:26 AM
Quote from: New KID On The Block on October 06, 2014, 10:08:00 PMI thought MPPT worked better the higher the difference between the PV voltage and the battery bank voltage.
I run double the battery bank voltage, on my PV array. As TD previously stated, the more the controller has to downconvert, the more inefficient it will be.
Quote from: New KID On The Block on October 06, 2014, 10:08:00 PMBTW, I haven't been able to get more than just over 300w from my (4) 100W panels. :'(
75%, not bad.
Thanks for commenting
FEF.
I'm starting to understand that down converting from high panel voltage to lower battery bank voltage will incur efficiency losses at the KID, but I'm also concerned about losses due to wiring (size and length) from PV panel to the KID. The way I'm thinking, I'll have less voltage drop on the cabling from the PV panels to my charge controller by having all 6 panels chained in series. All that voltage would only be putting out about 5.3A to the KID. Is the DC voltage down conversion at the KID losing that much more than my gain from the lower voltage drop of using higher voltage from panel to KID?
NKOTB: Just a heads up from someone who in 2005 thought as you are thinking now. I wired in series four 85w BP 380J polycrystaline 17.6Vmp panels on my SportsMobile Voyager roof with Thule tracks using a Xantrex XW MPPT 60 charge controller to 12v 250Ah UPG agm house battery.
Didn't work well. I have since learned that my array's output was severely reduced by series wiring vulnerability to shading. Now I am buying a new controller (probably Kid or Brat) and definitely re-wiring to parallel.
Whatever you do, please post your experience, so we can all learn.
Quote from: E350 on October 08, 2014, 11:24:46 AM
NKOTB: Just a heads up from someone who in 2005 thought as you are thinking now. I wired in series four 85w BP 380J polycrystaline 17.6Vmp panels on my SportsMobile Voyager roof with Thule tracks using a Xantrex XW MPPT 60 charge controller to 12v 250Ah UPG agm house battery.
Didn't work well. I have since learned that my array's output was severely reduced by series wiring vulnerability to shading. Now I am buying a new controller (probably Kid or Brat) and definitely re-wiring to parallel.
Whatever you do, please post your experience, so we can all learn.
Thanks for your input
E350.
Shading issue is actually one that I was already aware of and took into account when I started designing my system. My panels are on top of my house roof. There is only shade from a side chimney that affects my series of panels at the very end of day -- right at sunset just before the sun sets. I understand the shade issue with respect to series chain links. I can accept the tiny loss at the very end of day. It's not producing much watts at that time of the day even
with no shading whatsoever.
I'm sure you're well aware of the need for properly sized (read BIGGER) wire gauge cables for parallel hookup.
I'll update with my experience/observations if/when I purchase more panels to add to my system.
Oh, I misunderstood this was for a house, there was a mention of an "rv" earlier in the thread.
Also, thank you! I was not aware of the necessity for larger cables to wire in parallel. So, if you guys don't mind please tell me what the sizing requirements are.
This onion seems to peel forever...
Quote from: E350 on October 08, 2014, 06:48:43 PM
Also, thank you! I was not aware of the necessity for larger cables to wire in parallel. So, if you guys don't mind please tell me what the sizing requirements are.
There are two sizing issues: ampacity and voltage drop.
When you put solar panels in parallel (like in a combiner), the voltage stays the same, but the current is additive. The combined output (Imp) of your four panels is about 19.3 amps. The Isc is a bit higher.
Therefore the wire that runs from the combiner to the controller needs to have an ampacity greater than that.
Suppose you decide that 10 gauge has adequate ampacity to handle the Isc (about 20 amps). The next question is how long is the wire? If the 10 gauge wire was 20 ft long (one way), you would have a 4.5% voltage drop along that wire... too much! Increasing the wire size to 8 gauge would reduce the voltage drop to 2.8%.
--vtMaps
Quote from: E350 on October 08, 2014, 06:48:43 PM
Oh, I misunderstood this was for a house, there was a mention of an "rv" earlier in the thread.
Also, thank you! I was not aware of the necessity for larger cables to wire in parallel. So, if you guys don't mind please tell me what the sizing requirements are.
This onion seems to peel forever...
E350, the original poster ZoNiE was asking about a setup for his RV. You didn't misunderstand. :-) I happened along and interjected my question into this thread. I hope he doesn't mind.
You're welcome. It's important to properly size our cables, especially for 12V and hookups chained in parallel fashion. Good luck with your new/redesigned setup.