Need to know details on hooking up 17V panels

6 Posts
Jun 18, 2009 10:08 pm
Need to know details on hooking up 17V panels


I just recently purchased a bunch of old solar panels and am kinda confused on the system configuration.  My trouble is, their rated @ 17V.  That's not a number that I see relate to any batteries, so if anyone can help figure out what kinda of battery(s) I need to get, it would be much appreciated.

Here's the panels link:

I know their old, but I got them sooooooo cheap, I couldn't NOT but them!

While your at it, if there's any good recommendations to which charge controller, inverter, and cabling I'd be happy to take them as well!

Thank you so much in advance for answering what seems to be a fairly simple question!!!
« Last Edit: Jun 18, 2009 10:10 pm by Mike Nork »
578 Posts
Jun 19, 2009 10:50 am
Re: Need to know details on hooking up 17V panels

read this,

let us know if you have any questions after.

you are going to need to know what you are trying to do, and you will have to do a loads list to define your needs.

altE staff

"Making Renewable Do-able"

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
578 Posts
Jun 19, 2009 10:58 am
Re: Need to know details on hooking up 17V panels

if you are just getting started:

for free info, forum is good, but i would just take my time and read articles and watch videos in the university section.  there are tons of free articles for those patient enough to read and absorb it.

keep reading and learning BEFORE buying if at all possible.

i would also suggest this book for those starting and wanting a practical guide.

altE staff

"Making Renewable Do-able"

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
Jun 20, 2009 03:52 am
Re: Need to know details on hooking up 17V panels

I agree with Jame's point of view Mike.

I would like to add that, photovoltaics are not toys to be trifled with. They can produce a serious amount of electricity that, if not conducted properly, can cause a fire.
The NEC - National Electrical Code is an institution (for lack of a better word) of the NFPA - National Fire Protection Association.

That "bunch of old solar panels" you mention, if "wired" together a certain way, might have the potential to weld steel together. It all depends really on just how many a "bunch" is and what the specifications are. All of the PV modules ratings, not just volts, is the first thing an electrician would look at. He or she would need to know all of those ratings before any calculations could be made for sizing the electrical components for the rest of the system.
Wire size is typically based on the expected amperage to be conducted over them but * it can also be based on such things as voltage drop over the length of the wire, as well as the type of insulating jacket it has and the location where it is intended to used.

There should be a label on the back of your PV modules that shows several "ratings" at a STC. - Standard Test Condition.
One in particular is the Isc or Impedance short circuited or in a more familiar term, Amperage short circuited. UL - Underwriters Laboratories, requires an additional 125% be added to this Isc rating. The NEC requires an additional 125% to that. So if a PV modules has an Isc rating of 4.75 amps for example, 156% of that amperage must be added back to that amperage and that is where calculations for wire size, based on amperage, starts for a PV source circuit. 125% x 125% = 156%
4.75 x 156% = 7.41 So, based on that example of Isc 4.75, 7.41 amps is used to start calculations for wire size, based on amperage, not just the Isc of 4.75 or the lesser rating Impp. This just scratches the surface! Believe it or not, ambient temperatures can take a part in these calculations. 
Now, perhaps, you can begin to see why electrical contractors require an Electrical Contractors License and why permits must be issued followed up by inspections from the; city, county, or state which ever one holds jurisdiction over the location of a proposed job?
In particular,

I can only guess but it would seem to me that this would make getting a "sweet" price on the PV modules even "sweeter."
6 Posts
Jun 20, 2009 06:13 pm
Re: Need to know details on hooking up 17V panels

Dear James AND Thomas,


I actually have been researching this for a fair amount of time, and my interest is just increasing exponentially.  First, let it be known that I am still a novice at this.  Also, I am learning.  Lastly, I am doing what is order (studying, researching, investing time and money) to actually get into the solar industry.  I want to be the guy that comes to your house and hooks up your system for you.  That's what I'm doing here, and I feel like I've struck a GOLD MINE with Alt+E.  No joke. 

James, I have been going through all these articles for some time and knew that the information that I needed was already in type, right here.  I'll admit, I took the lazy way out on this one and looked towards to these forums for the answer to be posted because I know you and the people that use this site have a lot more time invested than I do, and knew that someone would be able to point me right where I needed to be.  I was right, so good... and thank you again for doing my leg work!  The article you posted was a perfect explanation.

My intentions with all this is as such:  I followed a suggestion that if you are trying to get your hands on some cheap panels, to call around to companies that do the service work (where I will eventually be working) and ask them for any off-spec, or damaged, or blemished panels that they cannot use and are looking to get out of the way for cheap.  It was some of the soundest advice I ever took.  The first place that I called had 31 panels in their warehouse (nothing wrong with them at all, they just could no longer use them for installs) for literally $0.50/watt.  I needed to commit to buy them all, which is why I hesitated at first, but then after thinking about for a few months, I realized that I should just get them all, keep a few and sell the rest for money to buy the rest of the system components.  Not a bad idea, eh?  It's working.  Within 3-4 hours of posting them on ebay, I sold one and many more are expressing interest.  So far, so good.

What ever the panels were, I figured I could FIND a use for them (I have a computer with powered studio monitor speakers and an electronic drumset that I'm aiming to be able to power, at least for a few hours out the day, if that's all I can do).  I don't have experience with solar panels, and I wanted some, so my determination (and research) is currently providing me with a means of success.

From the money I will make from such a good discount, I;m going to try to get not only the rest of the system, but also, take some educational classes here in Florida for a week and at the end, they offer to take the NABSEP exam.  If I can eventually pass (I've got A LOOOOOOOOOOOOOOT of reading to do!) then I was told from the owner of the company I bought all these used panels from that he would hire me on the spot.  Call me ambitious, I know... but I call myself motivated to get this and to start doing whatever I can do to help the world's energy start.  Humble beginnings... 

Thomas, thank you so much for your reply and your insight.  This is why I came to this site... because I know people like you are out there and willing to help people like me.  That's what it's all about!  I appreciate your concern, and assure you that I will respect these panels with the respect they deserve.  I wish I knew every single detail I needed to know before messing with this stuff, but I don't, or else I'd already be selling and installing these panels professionally.  It's the old chicken-before-the-egg deal.  Like, getting a credit (card) when your young, just starting out - you gotta have it first before you can get it! 

I've got some educational material from a guy based out of Miami, here in Florida, that writes books and designs programs and classes to help teach all about what I need to learn.  His name is Mike Holt.  Check him out.  I got a 2008 copy of the NEC and (essentially) a training guide to help turn this mystical information into something I can learn and understand, and (eventually) master- the kind of thing that you and James have already expressed to me that you know! 

I'm sorry for being so long-winded, I just wanted to explain myself a little more to you and express my gratitude towards ALL who are in this together doing this!  You are all my brothers and sisters, who I have yet to meet!


6 Posts
Jun 20, 2009 06:35 pm
Re: Need to know details on hooking up 17V panels

Oh yeah... sooooo after all that... I just wanted to RECONFIRMED what I learned from you:

My system voltage should be 12V, correct?

That means:

1.) I need to buy a 12V inverter.
2.) I need to buy batteries that will get me to a 12V system voltage (I understand there are all different combinations I can use to get there, but that is what I'm shooting for, correct?)
3.) I don't NEED to, but I WANT to get an MPPT Solar Charge Controller for this system.

Now, I know you cannot possible give me any kind of real suggestion of which of these items I should buy without knowing my load calculations, but would you be able to point my in the right direction as to what companies, brands, etc. are reliable and that you or people you know have good experiences with?  That's all what I'm looking for now.

Since I know you're going to ask, this is what I've come up with so far for loads:

- ONE desktop computer with a 300W power supply.
- ONE Samsung 172N computer monitor, rated @ 40W.
- TWO powered speakers, each 100W (Alesis Active MKII are the speaker brand).
- ONE electronic drum set module, rated only at about 18W (Roland TD-9).

Any better?  What do you think?
6 Posts
Jun 20, 2009 06:42 pm
Re: Need to know details on hooking up 17V panels

ON second thought... I'm still up-in-air about the MPPT charge controller.  I don't know exactly what I'm talking about yet with that.  All I know is that money is NOT the issue here with me, and I do NOT want my frustration to come from cheap quality components.  Got me?
6 Posts
Jun 20, 2009 06:57 pm
Re: Need to know details on hooking up 17V panels

For the battery, a quick look led me to:

Am I getting warmer with this one?
Jun 21, 2009 04:40 pm
Re: Need to know details on hooking up 17V panels

Oh yeah... sooooo after all that... I just wanted to RECONFIRMED what I learned from you:

My system voltage should be 12V, correct?

I cannot confirm the you have a 12 volt nominal PV module from what I have read from your posts here. A PV modules nominal voltage can be derived from the Vmpp or Vmp - Volts at maximum power, (not to be confused with the Voc - Volts open circuit which is a higher rating than Vmp) which is typically found on a label on the back of PV modules. But even if its Voc is 17 volts, chances are it is a 12 volt nominal PV module but the Vmp will be much lower if it is. Possibly something in the 14 volt range. If it is this way it would not perform as well in a hot climate as it would in a cooler climate. It would be great if you could come up with the power curve chart for this particular PV module.

Here is a specification (cut) sheet on a modern day, brand name PV module.
Take a look under the electrical characteristics heading at "current/voltage characteristics" "at various cell temperatures" and you can see how, as cell temperature goes up voltage goes down. One reason why most new PV moduels have a higher Vmp and Voc than older ones
Let me stress here that I am not saying this what you have. The point is, without specifications of your particular PV module I cannot tell for sure that it is 12 volts nominal. It all depends on weather the 17 volts you mentioned earlier is Voc or Vmp.

MPPT - Multiple Point Power Tracking charge controllers are a good investment especially if the PV source circuit has an exceptionally long wire run, and or the PV array is on a tracker and "sees" the sun from first thing in the morning to last thing in the evening.
PWM - Pulse Width Modulated charge controllers work very well otherwise.

Another good "tool" I use is this. The number of hours of equivalent full rated charge from a PV module per day. Man, somebody needs to come up with a shorter name for that or an acronym or something. This site -
gives a very good indication of that under various circumstances. Just follow the instructions.

There is another "tool" you have probably heard of, its Ohm's law? You need one other thing to go with the wattages you gave and thats time. How long of time will these wattages be drawing power from the PV/battery/inverter system over a 24 hour period?

I would have to say that best investment I made concerning PV power was a subscription to Homepower magazine.

578 Posts
Jun 22, 2009 10:33 am
Re: Need to know details on hooking up 17V panels

yes, you do have a 12v nominal module.  notice the 36 cells in series, 17vmp, and 21 voc.

no, you dont have to have a 12v system.  you may wire your array and or battery bank in several different ways.

no, i would not recommend using expensive surrettes as your first RE battery bank.  they are fantastic batteries, but as many teens get a "beater" car for their first ride, i often suggest that folks get simple local golf cart batteries for their first endeavor, and spend the money they save on better battery monitoring and safety gear, and still come out ahead.

yes, mike holt publishes great stuff, however, last i checked, he does not make a guide that covers article 690 (pv).  i currently keep understanding the nec volume 1, and illustrated guide to raceway and junction box calcs on my desk.

as for the code, i would recommend picking up the nec handbook, (the light blue hardcover), as this version has illustrations, photos, and notes that better explain the cryptic code speak.

i agree with mr schmidt, a subscription to home power would be good, and if they still offer it, get the upgrade with the dvd of every issue ever.  i would start at 1999, and read one issue every few days until you get to the present.

finish your loads list, and come up with a number for watt hours per day.  then we can give you more concrete help.  if possible, use a kill a watt meter instead of guessing.

if your pants are that on fire to get in the industry check on classes that offer the nabcep entry level certificate of knowledge test.  employers often use this as a benchmark of interest and dedication when screening applicants.  we have classes here, but there are other places as well such as sei, real goods, mrea, and more that offer quality training.

good luck,

altE staff

"Making Renewable Do-able"

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
6 Posts
Jun 27, 2009 09:27 am
Re: Need to know details on hooking up 17V panels

Thank you both for your help.

I figured I'd get a real good battery because I'd like to see how one really performs.  That Surrette I was looking at... would it be able to safely be connected in parallel to the Xantex PowerPack?  I see some sort of similarity between the two in that both say 20 hours, but the Surrette also states the 357 Ah.  Why do they have two numbers on the Surrette, other than to confuse me?

I am definitely motivated to get into the industry.  I've actually already paid my registration fee to FSEC, down here in Florida for their PV Class, and after taking the class, I will be eligible to take the Entry-Level NABCEP exam.  Any advice (other than buy and read Photovoltaics: Design & Install Manual)Huh  And yes, when I asked the owner of the solar service company I bought my panels from how I could get a job either in the industry or with him, he said, "If you go get NABCEP Certified, I'll hire you on the spot."   Now, I wonder if he's talking about the Entry-Level, or the big-dog certification.  I need about 3-4 years experience to get that certification... I wonder if he knows that.

I just got the deluxe solar starter kit from Alt+E in the mail (with the 25 watt panel instead of the measly 6.5 watt it comes with), so now I have both the Design + Install Manual as well as the kill-a-watt.  FUN STUFF!

As for the 12V panels, I've deduced that they are, in fact, 12V nominal after going to the links you sent.

Which battery would you suggest that I can beat up, but still offer me plenty of capacity?  I'll have to swallow me ego and get something not quite as good, if that's the best idea.

Also, I took the advice, and got the subscription to Home Power.  Now I just need to READ READ READ.... EVERYTHING!

OK, but next post, I will have a finished loads list for y'all.

578 Posts
Jun 29, 2009 11:36 am
Re: Need to know details on hooking up 17V panels

the xantrex power pack is not really designed to be used as a permanent system.  for that reason i would not try to hook up outside batteries to a powerpack. 

the nabcep entry level certificate of knowledge is waaaaaaay different from the pv installer certification.

to have taken the nabcep entry level certificate test and passed it does not make that person nabcep certified.

you can find more info on nabcep here.

as for the battery, i would not try to rig up an outside battery to a portable powerpack, and when deciding on a permanent battery bank, i would not splurge on the first try.  surrette makes great batterys, folks new to off grid generally are not kind to their first battery bank.  i would suggest inexpensive golf cart batteries for starters.

altE staff

"Making Renewable Do-able"

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
351 Posts
Jun 29, 2009 12:35 pm
Re: Need to know details on hooking up 17V panels

The Xantrex power pack UL approval is as a portable (temporary) power inverter. It is for plug in use only. If you attempt to use it as a part of a permanent system, it would be a NEC code violation.

While I have never used it, it appears to be a half voltage scheme inverter. Assuming that it is, if you ever connect it to a standard 110V system with a neutral bonded to ground, you will either smoke the inverter or cause other severe equipment damage.

If you want to go beyond plug in use, look for a different inverter.

Jun 30, 2009 05:23 am
Re: Need to know details on hooking up 17V panels

I hope you do not take offense Mike but reading these posts in your thread is lot like seeing a little kid turned loose in a candy store.
I want to remind you that PV modules are all about electricity and if its not conducted properly it can cause serious damage, not just to yourself but there is always potential of harm to others.
Moderation, self control, common sense.
Common sense, there is a phrase that I think a lot of people have lost touch with its true meaning in the text for which it is intended. 
The NEC is, I think, more about possibilities than probabilities. Thats to say, the worst may not ever happen but it can happen, so prepare for it as though it will happen. Electricity can be a harsh mistress.
Gotta go!

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