FYI series panels and shading

[hemsteadc]

Series vs. Parallel is a common topic of discussion which often ends up with the caveat "If one panel in series string goes, the whole thing goes."  That may be true for *some* installations, but here is how mine behave.  

Pictured below is the shading on 2 of 6 series-connected various brands of 125w-135w panels:

And this is what the controller says:

So, 57.2 x 5.6 = 320w (IN)

This is normal (full sun) about 20 minutes later:

Input =84.8 x 6.6= 560w.
Output is 53.4 x 10.3= 550w.  Not bad efficiency for 560w IN.

Output shaded = 53 x 6 = 318
Output not shaded = 53.4 x 10.3 =550

(550 -318)/550= 42% loss, with 2 panels in partial shade.

Looks like those two shaded ones (Kyocera) have diodes.  Thank heaven for that!

[jcussen]

I had the same results, have 3 in series, some loss but not near as bad as some predicted when partial shading. Are you running a 48 volt battery bank?

[hemsteadc]

36 minutes ago, jcussen said:

 Are you running a 48 volt battery bank?

Yes I am.  Relion 48v 100ah pack.

[jcussen]

13 minutes ago, hemsteadc said:

Yes I am.  Relion 48v 100ah pack.

Very nice. Looks like Outback charge controller, does it charge batteries directly?

[hemsteadc]

2 hours ago, jcussen said:

 does it charge batteries directly?

Not sure what you mean by directly. 

[jcussen]

14 minutes ago, hemsteadc said:

Not sure what you mean by directly. 

Do the batteries have a built in BMS [battery management], or does the charge controller control the charge and voltage to the batteries.

[hemsteadc]

Yes, it has BMS, and the controller is hooked to the battery just like any 'normal' battery.  I set the charge voltage for the specified 58.5 bulk and 55.2 float.

I have 2- 48v 15a shore chargers specially modified to produce only the above two voltages. 

[jcussen]

Nice setup, how do you handle your 12 volt house loads?

[noteven]

Shading with solar panels, Saskatchewan style:

https://youtu.be/3nKCH-whO2A

[hemsteadc]

43 minutes ago, jcussen said:

Nice setup, how do you handle your 12 volt house loads?

Victron DC/DC converter, 300w.

[GlennWest]

6 hours ago, hemsteadc said:

Victron DC/DC converter, 300w.

Will that converter operate hydraulic slides and leveling jacks?

[oldjohnt]

 Hemstead, wow good info thanks for the data and details. Sounds like your system, configured as is, works great Congratulations !!!! 

 As an engineer this topic is like so many technical concerns I dealt with over the years, THERE ARE TRADE OFFS. In series voltage increases so current down to the controller decreases which can (BUT subject to conductor size) lessen voltage drop concerns. In correct parallel voltage is equivalent but current down to the controller increases. Although there are many variables and subject to the methods, configurations and equipment used, parallel wiring can, in some situations, be advantageous if some of the panels are shaded . I would prefer all panels be of the same design, type, rating, voltage and even age when using multiple units, although, sure all sorts of engineering correct combinations still work fine, no problem...

 Soooooooooooooo different configurations and different roof real estate and the systems and methods used can dictate whether series or parallel or a combination is best on a particular RV.

 Study your roof real estate and potential shading and research your equipment and then make an informed decision of what's best for YOUR RV which may or may not be the same as another persons.   For my RV roof given panel locations and AC and roof vents and other factors I chose parallel wiring (3 now soon to be four panels 1 KW) but that doesn't mean it's best for some other RV.    

Yall take care, best wishes n God Bless

John T

[hemsteadc]

5 hours ago, GlennWest said:

Will that converter operate hydraulic slides and leveling jacks?

I don't know, I have electric slides and jacks.

[hemsteadc]

A fellow on the 'other board' pointed out my voltage is low, so I went up there and checked 'em. Not a fun job.

Here are some voltage readings starting with the 1st panel in the string to the last:

Kyocera 17
Kyocera 17
BP   15
BP 15
off brand 17
Old Kyocera roughly 2!  Yes, 2. 

Now, I couldn't lower the panels all the way down and still keep the voltmeter probes on the connection, so these measurements are close but not 100% accurate.  The Outback controller says about 90 volts.  So we have (3x 17) + (2 x 15) = 81v, so the Old Kyocera (OK) must be around 9 volts.  Incoming amperage is 6.6, so the OK is still able to pass amps, or I'd be dead in the water.

It's a little difficult to tell if the BPs were more like 14 or 15.. if 14 that would put the OK at around 11v.

Anyway, things are a bit sick.  If I do any replacement it will be the OK panel.  I might be able to live with the under-performing BPs.