Optimal Panel arrangement into a Classic 150...

[TomW]

Well, folks, I am awaiting a major solar upgrade with several bits "in the pipeline" but not here.

I have a Classic 150 hung on the wall temporarily and feeding it with my 4 Kyocera KC130GT panels on a 24 volt system.

The KC130's are rated:

Maximum Power Voltage V 17.6

Maximum Power Current A 7.39

Short Circuit Current A  8.21

I currently have them wired 2 pairs in series in parallel.

I am showing an input voltage hovering around 34 volts in full sun on 40 F days. I am only seeing about 400 watts give or take from these panels which is not exactly pushing the 520 watt rating I was hoping to get close to. I am pushing this into a 24 volt ~1300 AH system at approximately 26 volts right now.

Would I get better output if I wired all 4 in series for ~75 volts in to the Classic?

I have been operating under the perhaps mistaken theory that the lower the difference between input and battery volts the better MPPT performance I would see.

Any ideas?

Thanks for any info.

Tom

[Vic]

Hi Tom,

Normally,  you could expect to get about 80% of the STC rating of PV modules,  in moderate temps,  near Solar Noon and with roughly correct tilt angle on the PVs.  So,  I would say that you are doing fine.

And,  given the choice between strings of two,  vs a string of four,  I'd choose the 2X2  config as you have it.  There is a tradeoff of the higher current of 2X2 vs 4X1 vs CC efficiency,  but if PV input run is not long,  and the wire of reasonable size for this run,  think that you are about as good as you will see.  You can see more power with COLD temps,  and some wind.  Some do see more than STC ratings with reflections from snow or perhaps water at times.
YMMV,  Good Luck,  Vic

[TomW]

Vic;

Thanks for posting the info and your time to do so.

Funny thing is, I regularly saw around 450 watts from these direct connected, wired the same as now. Which was supposed to be not optimal with Grid Tie type panels and less than ideal voltage matching? Maybe the Doc Wattson was not indicating actual wattage when they were directly connected? My current figures are from the Classic itself and the Doc is not in circuit on these panels.

My elevation is pretty much dead on, the array tracks within + - 10 degrees and that info I posted was @ noon and tracking pretty much dead on.

I guess I expected to easily beat the direct connected performance which was a tad over that commonly cited 80% value?

Thanks again.

Tom

[mtdoc]

Could it be that you were not seeing full output because you were not in the Bulk stage of charging?   What is your absorb voltage?  If in absorb (or float) you will not see full panel output. 

[TomW]

Could it be that you were not seeing full output because you were not in the Bulk stage of charging?   What is your absorb voltage?  If in absorb (or float) you will not see full panel output.

mtdoc;

It said bulk on the display (I think), I am not near it to see what it says now. I have not tweaked the settings because it will be retasked when the new panels arrive and I just wanted to run it awhile while I waited. I did not get a printed manual with this lightly used unit and, frankly, I am not making much headway with the pdf online. I do better with hard copies reading that type thing.

Been doing RE for a long time but new to MPPT and the Classic.

My system is never static. Always either using power from 100 to 1000 watts or charging while using power.

Time to check the manual a bit closer to see what might need to be tweaked.

I am up to my eyes in my real RE resource, firewood. Cutting and splitting every day with tunnel vision on the full woodshed goal.

This is when it was full with 30 cords a couple years ago:



Thanks for the comment.

Tom

[mtdoc]

Nice woodshed!

Right now I have 3 cords sitting in pile covered with tarps -waiting for the weather to improve so I can stack them.    My much smaller woodshed is already full

[Halfcrazy]

Tom
2 of those in series is close to to low a voltage for MPPT. You can try to go to Tweaks and enable LoMAX and you could also try Legacy.

Ryan

[TomW]

Nice woodshed!

Right now I have 3 cords sitting in pile covered with tarps -waiting for the weather to improve so I can stack them.    My much smaller woodshed is already full

mtdoc;

Thank you.

We own a nice tract of hardwood timber that gets logged regularly. The Loggers stockpile tops, culls and gnarly never make marketable trees where we can get at them easily. We hit firewood whenever we are up to it and the shed supply varies a lot based on firewood gathering activity. That shed holds enough for 7 years or so "normal" winters or 12 like last years warm one.

Firewood will get you through times of no money better than money will get you through no firewood. Especially if your sole source of heat is firewood! I dislike burning tires and railroad ties so I try to keep that shed full  .

Apologies for the topic drift to the regular readers seeking info . It is RE and carbon neutral, however!

Thanks

Tom

[TomW]

Tom
2 of those in series is close to to low a voltage for MPPT. You can try to go to Tweaks and enable LoMAX and you could also try Legacy.

Ryan

Ryan;

I went into tweaks and turned LMX off as it was on so see what shakes loose. Like I said, I have been lax on familiarizing myself with this beast but will eventually figure it out. It would be relatively trivial to rewire them all in series to get up around 70 to 75 volts pushing the electrons down the wire.

I didn't mention it before but this array is about 5 paces from the controller plus the inside path and up the pole they are mounted on much less than even 50 feet. I can't recall exactly but either #2 or #4 copper so plenty beefy for this I think?




Thanks.

Tom

[Vern Faulkner]

I didn't mention it before but this array is about 5 paces from the controller plus the inside path and up the pole they are mounted on much less than even 50 feet. I can't recall exactly but either #2 or #4 copper so plenty beefy for this I think?

I'm running 85 feet of #8 without any notable loss, two 240 panels, 37 Voc, in series. Your setup is overkill.

[TomW]

I'm running 85 feet of #8 without any notable loss, two 240 panels, 37 Voc, in series. Your setup is overkill.

It was what I had access to cheap at the surplus place nearby. When installed I had dreams of several times as much solar on the mount but it has not happened. The new solar upgrade is on another pole about 25 feet past the current setup and it will use #8 copper which I have leftover on the 1000 foot roll I bought to feed AC to the house from the inverters in the garage. I have enough cable and 2 trenched in conduit to run one pair of #8 per series string of 3 250 watt panels. More overkill but, again, I have it on hand so I will use it rather than sit on it in storage.

Thanks for the feedback.

Tom