Wiring panels together

4 Posts
Oct 31, 2005 09:10 pm
Wiring panels together

I have two solar panels, both 12v, a 20W and a 102W.  I need to connect them to an inverter that requires 24v DC energy.  I assume if I wire them in-line (that is negative of one panel to the inverter, positive of that panel to the negative of the other, and the positive of that panel to the inverter) it would produce 24v DC for my needs?  My only concern was I wasn't sure if both panels have to be the same size - does it matter that they are different?

Thanks!

 
10 Posts
Nov 1, 2005 06:57 am
Re: Wiring panels together

If you connect them in series, yes they will produce 24v, BUT at only 20W power or just 1.67A.
You'll be wasting 82W from the 102W panel. I'm afraid I can't think of a way to connect your panels since they are not same power!  

Brian

 
4 Posts
Nov 5, 2005 09:00 pm
Re: Wiring panels together

Thanks for your help.  I have another related question.

I am trying to wire these panels to a Trace Microsine MS100, which is a small scale utility intertie inverter.  The Microsine requires a 24v input and uses MPPT.  Would it be acceptable to just wire the 102W, 12v panel with the 12 to 24 volt DC converter availible from Altenergystore?  I would assume that wouldn't bother the MPPT function of the inverter?

Thanks!

Ross

 
Nov 6, 2005 02:00 pm
Re: Wiring panels together

Its a bad idea to wire PV modules in series that are not identical. They have to be identical in every way.
Can I assume that the 102 module is not convertable to 24 volts nominal? If yes then your best option, for efficencies sake, would be to purchase a second one identical to it as well as a charge controller such as the Sunsaver Ss-10l 10a, 24v Pwm. Charge a 24 volt nominal battery such as two 8a31 Agm 105 Amp Hour Sealed batteries in series and then power your inverter from the battery.
In this way a minimum of power is wasted and it gives you stored power for use at night or low sunlight levels.
Two -102 watt PV modules in series should give you about 34 amp hours per day of equivilent full rated charge. This depends on several factors of course. If whatever you are powering from that 100 watt inverter consumes 100 watts you shoud be able to use it for upto 8 hours from one days charge. A fully charged battery should allow it to be powered for upto approximatly 18 days without sunlight.
But then your usage may not warrant all of this, so think of the possibilties for other electric needs and or desires. 24 volt lighting maybe? So much depends on how you use the power.
Or you could just get a 12 volt microsine inverter? Some places take trade in's.
 
351 Posts
Nov 6, 2005 05:18 pm
Re: Wiring panels together

What are you attempting to do ?  A little guerrilla solar perhaps ?  Or do you want a real solar installation ?

You have a real �orphan� collection of mis-matched parts. The best recommendation would be to try selling the individual pieces to people that want them, and then start over from the beginning with components that match.

The MS100 lost it�s UL rating in 1999 with the new IEEE anti-islanding changes.  This is probably the reason that Trace no longer handles it.  It is still available as the OK4U from the Dutch manufacturer. It is grid tie only (no batteries) and only made as a 24Vdc unit.

You did not say which 12/24 converter you are talking about, but the odds are it would keep the MPPT from functioning, as well as costing you some watts as a parasitic load.

The simplest way of hooking it up would be to buy the matching 102w solar panel and wire the 2 panels in series. This would give you the maximum output that the MS100 can handle (100w).  If you are in a good sun region, you might average half a kilowatt hour per day. As an example, at 13 cents a kwh, that�s 6.5 cents a day, so any more money that you invest in this system is going to have a long payback.  

 
462 Posts
Nov 7, 2005 12:25 pm
Re: Wiring panels together

rnizlek, how about wiring the panels in parallel? Then it would be 12 Volts at around 7-8 amps. Wire them to a battery with a proper controller then wire the controller output to a 12-24 volt converter then into your inverter. Also check your inverter to see if you can switch it to 12 V.
 
4 Posts
Nov 9, 2005 05:11 pm
Re: Wiring panels together

Here's the general idea of what I'm trying to do:

I have a 102W panel wired to a 35 amp hour battery through a Morningstart Sunsaver 10 charge controller in my college dorm room.

During my vacation break, I want to take the panel home, but I don't want to bring back all the wiring, charge controller, battery, etc.

So I happened to acquire a Trace Microsine.  What I figured I could do is bring the 102W panel and my old 20W back and do something of a guerilla solar installation for the month I'll be home.  Ever paying the costs back is not an issue, the costs for all the equipment was paid for by profits I made be selling some extra Microsines I found on eBay.

Apparently, the idea of wiring the panels together isn't going to work, but I contacted Solar Controllers, Inc, and they recommended a pump controller they said they had used for a similar purpose and would hold the voltage at around the MPPT tracking point.

So it seems that I have a solution to the problem, I'm going to order their product and hopefully that will take care of the issue.

Thanks to everyone for their help.

 

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