Mix and Match PV panels

hillbilly

Pardon the newbie question here, as I think it's probably been addressed, but I couldn't quite find a solid answer by searching. I know that in mixing pv panels it's best to keep the voltages consistant between parallel panels, but I'm wondering if that is just to keep losses down due to lower voltage panels pulling the higher ones down, or if this is also hard on the panels themselves (or the charge controller for that matter)?
Likewise for running panels in serries with different amp outputs... would this be harmfull to the panels or just wastefull in terms of lost overall watts?
thanks,

crewzer

Re: Mix and Match PV panels

Check this thread: http://forum.solar-electric.com/showthread.php?t=2181

HTH,
Jim / crewzer

mike95490

Re: Mix and Match PV panels

excerpt:

crewzer wrote: »

As indicated, adding panels to an existing array, or reconfiguring an array, requires that you pay close attention to two basic rules:

One is that the PV modules wired in series have substantially the same Imp specs. (amps)

The other rule is that the PV strings wired in parallel have substantially the same Vmp specs. (volts)

Deviation will only waste power, and not likely to burn anything up.

hillbilly

Re: Mix and Match PV panels

Thanks, I had read a few posts like those indicated, but never any mention of anything but the power loss issues... had always wondered. I ask as I just inherited a VERY OLD pv array of 10 Solarex modules that I can't seem to find any specs on... they seem to have a pretty low output, but the price was right :-) and I figure that I would rather not spend any money on a seperate charge controller. I am hoping to just wire that array parallel with the other two strings that I have and let the MX sort it out... just didn't think it was worth the trouble if it might stress any of the existing panels or my charge controller.
Cheers...

rplarry

Re: Mix and Match PV panels

Hillbilly
I did what you are proposing, and I actually lost about 50 watts. I then rewired the array and got another charge controller to handle the extra panels and then I gained watts. Your system will probably react differently, but my experience was less than desirable.
Larry

niel

Re: Mix and Match PV panels

hillbilly,
does this help? keep in mind these are no longer being made as solarex was, i believe, taken over by bp solar long ago.
http://www.solarex-solar.com/

hillbilly

Re: Mix and Match PV panels

Thanks everyone,
Niel, I had looked at that page, but my panels are either not labeled correctly (all they have is a tiny metal tab with the numbers HE51G), or, more likely, they are sooooo old that no one has any intrest in keeping specs posted on them. I tried connecting them to my MX60 the other day, with my array disconnected. I hoped to be able to see just what kind of power output they might have.
First of all, total hassle to just do a quick wire job to test them out as the J-boxes had no easy connection point without a plug in addapter (only a few of these were still in usable condition)... anyways in the end I was just able to connect four of them in series, and the total output was around 70watts, in fairly strong sun, good tilt angle, cold temps and the batteries around 85% SOC. The MX60 read that the PV voltage was at about 44 volts (a bit low I thought), but I realize that there are too many variables to reach any hard conclusions from this little test.
Since my exsisting array has two strings, each with a VMP of about 60V, I thought that I might need to wire these solarex panels into two strings of five. My logic would be that the losses would be minimal from these panels compared to pulling the voltage down on my exsisting array with it's combined IMP of about 13Amps... (I can totally see how one could loose 50watts or so very easily here)
Unless I am missing something here, the way I see it the new panels would be able to opperate at a VMP of roughly 60 volts (pulled down by my exsisting array), with a current of at least 1amp possibly as high as 2amps or more amps. Thus I don't see myself loosing any watts, but gaining another 100watts or so. I could gain a few more watts by using another charge controller, but I am not sure that the $ would be all that well spent... not sure that I would even want to invest much money in wire for this array, as they are pretty old and worn looking... not sure how much longer they'll continue to put out much juice...
Thanks again for all the help, this forum is GREAT!

niel

Re: Mix and Match PV panels

you may need to check the voltages of each panel individually with a dvm. a good meter will be able to test the short circuit current of each pv up to about 10 amps too. i'm guessing, but the model number may indicate no more than about 50w or so.

icarus

Re: Mix and Match PV panels

Niel,

A question that has been lurking for months. Why the lack of Caps in all you posts?

Inquiring minds want to know!

Tony

niel

Re: Mix and Match PV panels

not many are really wondering, but it's a bad habit i got into in trying to post somewhat on a faster pace at some points. i'm not a fast typer and getting rid of the caps saves me some time and still gets my meaning out there. i have tried using caps elsewhere and it/i goofed up and slowed me down. using all caps creates enemies as i had found out early on elsewhere and not all punctuation went right with it anyway so all small it became.

icarus

Re: Mix and Match PV panels

The only inquiring minds are my own. Thanks

T

creakndale

Re: Mix and Match PV panels

A coworkers high school aged son was in the habbit of not using any capitalization in his technical email correspondence with me regarding video editing, projectors, HDTV, etc. When I asked him why, his reasons were, I quote:
1, i chat online way too much.
2, i got too used to microsoft word correcting everything for me.

I mentioned to him that I found it quite demanding to read his emails without proper capitalization. A few emails later I noticed he was using capitalization. When I asked why the change he said, by coincidence, his girl friend had recently mentioned his lack-of capitalization "trademark". Oh, the power of women.

H2SO4_guy

Re: Mix and Match PV panels

Neil and company,

Post anyway you wish, as I am here for shared knowledge, NOT grammar. We have a common bond, and the information is wonderful. I for one appreciate all of your help, and effort you put into this, as do many others.

Skip

nigtomdaw

Re: Mix and Match PV panels

Content is King........I'm poor at English, but since half the correct spelling I screw up on is highlighted because the USA version is different to proper English (hard hat on) complicated by the fact I bought a new LT with Vista and the OP Sys language is in Spanish + Keyboard (I try my best but it gets lost in translation English to English...... with a Espana key board I screw up regulary

Icarus I know you needed to ask and your reply was cool and I don't doubt that you and I are better off for content rather than Eng Lang points.

icarus

Re: Mix and Match PV panels

I have no problem with the posting style. I was just curios. I have much more trouble figuring out the "text generations" use of letters to convey whole thoughts. I have figured out lol, imho. Other than that it is beyond me. I guess there is a good use for teenagers after all.

As has been said, the content is what counts, and the real smart guys here are head and shoulders above most forums that I sometimes read. Keep up the good work all.

Icarus

niel

Re: Mix and Match PV panels

now if the question of my using all small letters is over and done with, can we get back to the real subjects that matter?