mixed panels Q.

[gww]

What would happen if I hooked up a 30 volt 7.6 amp panel in series with a 9 volt 3.6 amp panel.
Thanks
gww

[gww]

Referring to my above question;  I believe I will get 39 volts and 3.6 amps.  Is this right?   If I took 10- 9 volt 3.6 amp panels and hooked them in series and three 30 volt and 7.6 amp panels in series and then pareleled these two series conections would I end up with 90 volts and 11.2 amps?  If the total volts per series was 10 volts different from each other how would this affect each other connected in parelel with each other?  I have bought panels and homemade panels and I am trying to understand how they affect each other.  I am hoping to only run one line from my panels to my batteries.
Any help is apretiated.
Thanks
gww

[mettleramiel]

Yup, you got it right. You shouldn't have any problems hooking them all up like this, other than a whole bunch of short wires everywhere

[gww]

Mettleramial
Thank you.  Could you possibly comment on if my series connections were 90v in parrallel with an 80v series would the amps get through?  This would be to an outback mx 60 charge controller.
again thank you
gww

[Yyrkoon]

gww, You do realize that using the 30V panel by its self would give you more power output potential ? Mixing panels like this will cut your power potential in half.

As for your most recent question there. If both arrays are hooked into the same terminal on the controller. Most likely no. If there are dual input on the controller. Then possibly, but only if the charge controller has two separate converter circuits. Which I am thinking is unlikely. After briefly reading the online user manual. It seems that this charger can take in an input of 20v-125v. So you could string more panels in series to get a more desirable out come. *ONLY IF* your panels are rated to handle 125v series voltage or higher.

If you're going to be mixing panels like in your original question . . . you may want to consider matching panels, and making separate arrays.  Then using separate charge controllers for every separate array. Even if you use inexpensive trace / Xantrex PWM charge controllers the outcome would be more efficient.

[gww]

Yyrkoon
I have 2000 watts home made panels made in 30 watt increments (size of glass)  with evergreen 3.6 amp cells.  I just bought 6 235 watt mx panels.  I have a 48 volt system.  I have to put all panels about 150+ feet away from my house due to trees.  I read on the outback forum that the mx 60 controller is more efficient if you have at least 60-90 volts.  The contoller will take up to 150 volts but goes into self protect at 140 volts.  Placing the mx panels in series of three and then matching as close as possibly with my homemade panels is about my only option.  I was trying to max out the controller as I will also have tubines going to the batteries with anouther controller with a dump load. 

I know that certain electrical combos cancel each other so I am trying to understand how it works.  like does 80 volts take away from a 90 volt series I run in parellel.  I really think I can match the volts as long as the amps come through but would like to know the effects of things on each other.  If I had a wind tubine that put out 50 volts and one that put out 20 volts and run in parelel to 48 volt battery bank what amps or volts would make it to the batteries?
Thanks
gww

[Yyrkoon]

[EDIT]

Ok gww according to my buddy here what I said above is wrong.

His explanation to me was that Solar panels are strange critters, and sometime they do not behave the way you think they might.

He also says that if you add an 80v string to a 90v string on a charge controller. The charge controller would probably drop to 80v, and take current from both strings. I think you could test this easily enough couldnt you ? Then he says that if you run odd panels in series. The current may / may not be the lowest panel current for output. Lastly, he explained that mixing panels is still not a good idea.

Yeah so my bad, I had never seen this phenomena before personally. Have always matched panels to run in series.  Id be interested in knowing how the 80v and 90v string in parallel behave output wise. The math says you'll lose 70W(ish), but I know that does not always work out like that.  So, give it a try

[mab]

Referring to my above question;  I believe I will get 39 volts and 3.6 amps.  Is this right?

Yes, more or less.

If I took 10- 9 volt 3.6 amp panels and hooked them in series and three 30 volt and 7.6 amp panels in series and then pareleled these two series conections would I end up with 90 volts and 11.2 amps?  If the total volts per series was 10 volts different from each other how would this affect each other connected in parelel with each other?  I have bought panels and homemade panels and I am trying to understand how they affect each other.  I am hoping to only run one line from my panels to my batteries.
Any help is apretiated.
Thanks
gww

So each series string is made from panels with the same amp rating, but the two strings have different Voltages (80 & 90)? That should be fine.

Connecting an 80v array in parallel with a 90V to your MPPT; it should find a combined Vmp somewhere between 80 & 90 V (assuming your voltages are Vmp). I would think they would be operating close enough to Vmp that you won't gain much by having a 2nd MPPT.

I assume you are putting the MPPT at the battery end of the 150' line? that way you minimize cable loss.

m

[gww]

M
I believe I can match the voltage pretty well.  My homemade may be slightly higher or lower depending if I put nine or ten in series.  most of the homemade are 10.5 volts unloaded and the bought one that I checked was 34 volts unloaded.  I am figuring under load the bought, per it's tag, is 29 volts.  Homade is probly 7.5 to 9 volts under load although guessing alittle.  They are not the same amps though. If I run the same amp panels in series with each other and then parellel the series connections I hope all amps come through.
Thank you
gww

Thank you yrrkoon
gww

[Ontheronix]

What happens if there is only a slight offset?
For example,  a lead-acid battery who puts out 12V-13V in parallel to a PV solar panel with a dc-dc converter that outputs 12.8-13.2V (or a bit higher 13-14V) ?
(I have both, but hesitating to connect them)

[gww]

Ontheronix
I'm not sure I understand your question.  don't take it badly as I write more stuff that can't be understood then anybody.  are you saying you have a;
1.  battery
2.  solar panel
3.  dc to dc converter
              ?

Are you trying to charge the battery?
Use the battery and solar panel injunction to run something?
Can you tell us more of what you want to accomplish?
        gww

[Ontheronix]

This was my plan, but I just realise I made a mistake: the voltage of the panel drops under load (certainly without a MPPT controller), causing a big difference in voltage, and not the small one described below.

I'm charging the battery with a solar panel hooked up with a dc-dc controller to up the voltage a bit. When it's charged, I want to use the battery together with the solar panel to operate a computer because the solar panel doesn't put out enough power on its own. (On occasions it does, but most of the time not)
But ofcourse, the voltages are slightly offset, the panel puts out 12-14V unloaded, and the battery 12-13V.

Image  I had a MMPT, what would a slight offset of 2 voltage sources in parrallel cause, let's say we keep them seperated with 2 isolation diodes?

[gww]

Ontheronix
Where it has full member by my name it should say newby.  I'm not sure I am the guy that should answer your question.  Maby someone else will chime in.  I, if I have the stuff always just try it.  That doesn't mean that I don't ruin things sometimes.  I don't know how picky computers are.  Just a guess from nowhere,  I can't believe a volt or two one way or anouther would make that much difference as the batteries that laptops run on surely have a slight voltage differance from full charge to half charge.   Maby if I got this wrong someone will correct me.
Good luck
gww

[DamonHD]

1) Voltage has to drop (at least slightly) under load compared to Voc (open circuit) else you'd be getting no power out!

2) If you were very unlucky and/or the voltage difference between the strings was big and/or you had a poor MPPT controller which did not do a wide sweep and could get stuck in a rut, then one panel string might not be getting used.

Actually I have loads of different Voc/Vmp (all 12V nominal) panels in parallel, via blocking diodes, to one MPPT controller, and it seems to all work fine, so far as I can tell.

It is likely that the MPPT will discover that dropping the voltage to something where both panel strings can contribute delivers the most power overall.

Rgds

Damon

[gww]

ontheronix
I don't know if this helps.  I took a 17 volt 60 watt homemade panel and tried to run a trolling motor.  The trolling motor just bairly jumped with just the panel.  I hooked it to a little lawnmower battery and then hooked the trolling motor to the battery and fished about 3 times longer then the battery has lasted in the past.  I hooked it up a fallay knife and it would actually run the knife with a slight delay in starting.
Good luck
gww

PS
My wife hated the solar panel in the boat,  she said it took up too much room.  My dog didn't seem to mind as she walked all over it, got it dirty, and I'm suprized it put anything out.  not bad in a pinch if you are battery poor.

[gww]

damon
I missed that you post was probly for me or maby for both of us.  I had to read it a couple of times to get the gist of it.  Not what you wrote just what I understand.  Mostly it seems you are saying it will probly work fine.  The smallest string I will have will be about 300 watts and If I were to lose a whole string surely I will be able to notice a loss like that.  You did raise one question in my mind dealing with diodes. On the bought panels I don't know but on the homemade string I will have ten diodes though out the string, every 30 watts worth of panels.  When you buy or build panels and wire in series to create a string and then wire it in parrallel with other strings, do you also put a diode on each string prior to wiring paralel with other strings?
Thanks
gww

[DamonHD]

Hi,

Simplistically, yes, each string should have a blocking diode IMHO (to protect the string against backfeeding which can damage it), though some panels may already have such blocking diodes built in.

Be careful not to exceed the maximum reverse voltage of any such blocking diode, and assume that unless you take steps to avoid it that all blocking diodes in your PV system may see the full max array voltage at some point.

Rgds

Damon

[gww]

damon
Thank you
gww