# Parallel panels slightly diff Voltage



## KyleP (Dec 14, 2018)

Hello all, bear with me and read completly.

Ive done research and I know that putting panels with different voltages together isnt advised. BUT every time I find an exemple, its with really big differences.

So
I have 5x 48w panels = 3.02A 15.9V rated ( 3.35a 19.8V max)
but 1x 100w panel = 5.9A 17V rated ( 6.5a 21.6V max)

I run a 12v system ( 12v Charge Ctrl ) so i got them all In parallel

Questions;
1 - Its not 18v with 36v OR 12 with 24v ( double the V diff ). We re talking about 1.1V. In my case, Is it as bad as everybody says on the internet ??

2 - The real reason of my post is that I am thinking about buying an other Panel to the lot; 1x 90w 5.17A 17.4V rated ( 5.58a 22.58v max)
--- which would make a 1.5V difference with my 5x 15.9V. I am scared its going to draw down the New 17.4 making it see too many Amps and
wearing it down faster

3 - I feel limited to that one panel because all others are around 18v rated making 2.1v higher, which scares me. Should I worry ?

4 - am I wrong to think that the charge control being PWM so my understanding was that it limited the panels to what was needed thus making okay to
mix my voltage a bit???

Thank you all for your help!!


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## backwoodsman7 (Mar 22, 2007)

They'll be fine. You might lose a little efficiency, but it won't hurt anything.


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## wy_white_wolf (Oct 14, 2004)

KyleP said:


> Hello all, bear with me and read completly.
> 
> Ive done research and I know that putting panels with different voltages together isnt advised. BUT every time I find an exemple, its with really big differences.
> 
> ...


1. The lower voltage pulls the 100watt panel down to the lower voltage. So instead of 100 watts (5.9x17) it only producing 93.8 watts (5.9x15.9). No big deal on your system. Really doesn't matter anyway with question 4.

2. about the same as question 1. It gets pulled down to 82watts. Really doesn't matter anyway with question 4.

3. No after reading question 4.

4. PWM charge controllers mean amps out equals amps in and voltage out is what is needed by the batteries for charging plus system losses. So with that all your panels are limited to @14.4 (what's the max charge voltage of the CC?) plus line loss of half a volt or so. It's all a matter of what loss is acceptable to you. If you accept the loss from the PWM then the losses on 1, 2, or 3. don't matter as you would loss them anyway.

If you want something to be concerned about on your system it would be the low production time loss from being limited by the 15.9 volts. High sun angle from early morning/late afternoon and slight haziness can make it hard fore the 15.9 panels to reach high enough voltage to produce anything. That will pull all panels down. That happens weather you add more panels or not.

If you want to get that production back for the 100w panel and any others you might add put them on a separate charge controller. It won't get you back any loss being limited from the 14.4 volts of the PWM but it with get back the low production time loss for them when they can reach voltage and the 48 watts can't reach voltage.

WWW


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## Gary in ohio (May 11, 2002)

How did you damage a device with different panel voltages. THat should have all been isolated with the battery.


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## MichaelK! (Oct 22, 2010)

Question for Allyara, were these DC appliances or AC appliances that got damaged? If AC, I'm guessing that this was a very small 12V system, and the inverter browned out from low input voltage. The link you provided for the voltage stabilizers appears to be concerned with AC brownouts, which makes me think the inverter couldn't supply enough voltage to properly run the devices.

To answer Kyle's question, the typical variance that is easily tolerated is ±5% of voltage. One way to get around this, and actually increase your power is to switch from an PMW controller to a MPPT controller. You can then wire panels in series such that different strings of panels put out the same voltage. You get the added benefit of lower power loss through voltage drop. The MPPT controller will take the raw panel string high voltage and transform it down to the battery voltage, thereby increasing the charging amps at the same time.


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