panel wiring of uneven numbers and wattage

jimskau

Got myself a new problem, and as usual I come crawling home to the safe womb of this forum for help - usually works :-D
A man has 5 X 12Volt 110 W + 2 X 12Volt 85 W panels. He wants to make use of ALL of them.
He has a MPPT charger (60 Amp ) able to take 24, 36 or 48 Volt nominal voltage.
The uneven number of panels is the first obstacle. Could I wire, say the two 85W panels in parallel (12V). Then wire the exit of that string in series with 1 x 12V 110W, making a string of 24Volt?
Second problem is the uneven wattage of the strings. The remaining panels would have to be paired in serial, giving two additional strings of 24 V each. Then the three strings would be wired parallel to the MPPT, but....
One string is 280 Watt and the two others 220 Watts.
Dunno... just don't know :?
Honours due to you guys, no matter the outcome.
Jim

niel

Re: panel wiring of uneven numbers and wattage

jim,
you have 2 options here. the first is to obtain another 110w pv that all pvs could be used in series at 24v. this would be the 2 85w pvs in series for 24v and these would be paralleled to 3 sets of 110w pvs in series for 24v. if another pv isn't available or for any reason out of the question, then you could parallel the 2 85w pvs and place in series with one of the 110w pvs at a loss. the remaining 4 pvs will be series/parallel for 24v. the odd string loss will show in the current as the weakest of the 2 series sections (in this case the 110w will produce less current than the paralleled 85w pvs making the whole string of the current rating of the 110w pv) will be the current you will realize, but it is workable with a loss of current. in short it will like 3 sets of 2 110w pvs in series.

crewzer

Re: panel wiring of uneven numbers and wattage

Jim,

Tell us more about "the man's" PV modules... what brand(s), what model numbers, and the key specs (Voc, Vmp, Isc, Imp), if you have 'em. Also, what battery voltage is he targeting? 12 V? 24 V? Does it matter?

Also, can you look insider the connection box on one of the 110 W modules and figure out how it's wired? Specifically, some "12 V" modules are actually two "6 V" modules wired in series using a jumper in the connection box...

More later,
Jim / crewzer

mike95490

Re: panel wiring of uneven numbers and wattage

jimskau wrote:

He has a MPPT charger (60 Amp ) able to take 24, 36 or 48 Volt nominal voltage.

What's the brand/model of the charger ?

jimskau

Re: panel wiring of uneven numbers and wattage

Well, The panels are a couple of 85W BP mono chrystalline. The others are mono chrystalline as well, but with no visual manufacturer labels on the back. I will be up the place later this week and have a closer look to find the specs. If not available I will try to do some readings of open circuit voltage per panel.
The MPPT charger looks to become an Apollo T-80. I was trying to implement a Blue Sky power booster, but the yolk won´t take less than 36 V . Pairing the number of panels in 3´s completely messes up the possibility of utilizing all panels. I think you are right Neil, to get another 110W panel to even up the score. If not, the best solution would be to keep the whole mess wired for 12 in parallel. The full cable run is fairly short, about 14 Meters from + to - .

crewzer

Re: panel wiring of uneven numbers and wattage

Well, The panels are a couple of 85W BP mono chrystalline. The others are mono chrystalline as well, but with no visual manufacturer labels on the back. I will be up the place later this week and have a closer look to find the specs. If not available I will try to do some readings of open circuit voltage per panel.

Jim,

Good idea on inspecting the modules and taking measurements.
Here’s a US link to specs for the BP 585 PV module (85 W).

http://www.bp.com/liveassets/bp_internet/solar/bp_solar_north_america/STAGING/local_assets/downloads_pdfs/pq/product_data_sheet_bp_585_03_3009_v3_en.pdf

Here’s a US link to specs for a 110 W BP polycrystalline module (derated from 120 W). Note that it’s “24 V” nominal.

http://www.bp.com/liveassets/bp_internet/solar/bp_solar_north_america/STAGING/local_assets/downloads_pdfs/pq/product_data_sheet_bp_sx_120_01_4004_v2_en.pdf

Here’s a link to a Shell 110 W monocrytalline module. Note that it too is “24 V” nominal

http://www.powerupco.com/panels/shell/Shell%20SM110-24P.pdf

Here’s a link to an old Siemens 110 W monocrytalline module. Note that it appears to be configurable for 12 V or 24 V.

http://abcsolar.com/pdf/sm110.pdf

If it turns out the 110 W modules can be wired for 24 V each, it’ll be pretty easy to build a “24 V” array from the 7 modules you have. We’ll see what we can do when we have more specific information.

HTH,
Jim / crewzer

jimskau

Re: panel wiring of uneven numbers and wattage

Thank´s Jim!

I will get the info down in a couple of days. Allow me to express my gratitude once again. It´s great to have guys like you, willing to put in the expertice for beginners like myself. :-)