Array with different panel voltages

fergusson

i have been at this for 28 years and there is always a new question 
i have a 12 volt system dumb I know changing soon
some panels are 21volts and some are 26 volts is it ok to mix them ?
or are some canceling out others?
 Thank you 

icarus

They are not “canceling” each other out, but like battery voltage, they will seek the lowest voltage in the string.  I assume your “Papal” voltage is not some devine inspiration?

tony

BB.

What kind of charge controller? PWM would be fine... The Vmp-26 volt panels will produce a few Watts less.

Are you taking about Voc or Vmp for the panels?

Bill

fergusson

I have some very old controllers
and I don’t know what VOC or VOM is
i am happy they aren’t canceling out I was told they were 
im just not getting the Amps that I should out of each array I have three
80 Amps 50 Amps and 60 Amps
they aren’t putting that out
thank you for you very prompt answers
tri star controlers 

jonr

It depends on details, but you might be losing 10% of the watts of the 26V panels or 5% of total watts (as compared to the case of all panels being the same voltage).

fergusson

I loosing a lot more than that
ive been at this for quite a while it seems like I know nothing
thank you

Estragon

Have you tried checking to see if there are specific panel(s) underproducing? 

Generally, you should get ~75% of rated amps in full sun with proper tilt, and enough of a load to use the current.  With 190a total, that's ~140-150a of load.  What is your load (eg if battery charging, what size bank in amp-hours, and what type batteries (eg flooded lead acid,))?

A clamp-on DC amp meter is handy for debugging problems like this.  Absent that, you could try covering individual panels with a tarp or whatever and watch output to get a rough idea.  

BB.

We really do need to know details... All panels connected in parallel to the controller(s)?

As Estragon suggested, you can cover one panel at a time and see how the system responds (batteries should need charging, or you have some loads connected, such as an electric heater, so the controller is outputting its maximum current.

Also, can you tell us the voltage at the Vpanel input of the controller(s) and the Vbatt output voltage?

And, for better/easier debugging of any DC power system, getting a DC Current Clamp Meter (Digital multi-meter) will help a lot--Very nice to have if you are going to work with DC (and AC) power systems very often.

A decent DC/AC Current Clamp DMM is around $100 (USD) and you can find ones that are "good enough" for $50 or less:

https://www.amazon.com/gp/product/B019CY4FB4 ($100)
https://www.amazon.com/gp/product/B07546L9RT ($50)

-Bill

BB.

I should add there are AC only Current Camp DMMs (with DC voltage measurement capabilities). These are perfectly good meters...

However, they cannot measure DC current and are not useful for our DC needs.

Be careful when reading the product descriptions... They can be a bit confusing at times.

-Bill

littleharbor2

Look in the specs and you need to see a DC current rating along with an Ac rating. If no DC rating move on.

fergusson

Well guys we don’t need to worry any longer the house burned down yesterday 
because I bought a cheap controller it started the fire

mike_s

In parallel, with a PWM controller, you're not losing anything. They're all running at battery voltage. A mix of panel voltages doesn't change that.

Parallel, with MPPT, some won't be running at peak efficiency.

Series, with MPPT, it's the difference in I(mp) current that matters, not voltage.

Sorry about the house. I hope you're joking.

mike95490

fergusson said:

Well guys we don’t need to worry any longer the house burned down yesterday 
because I bought a cheap controller it started the fire

Oh boy, I hope that's just a figure of speech or a joke.   It's also a reason to have the power gear NOT in the main house.