The most efficient way

[Takis]

Dear friends,

i own renogy Rover li 40amps mppt charge controller which has
Max input voltage 100v and Max input amps 50a.
i do also own 4 Canadian solar 330 solar panels same voltage and amperage.
Each panel gives at Max 45 volts and 9.5amps.

In order to get the most out of panels and controller, which is the most efficient way to set them up?
All panels in parallel giving at Max 45v and almost 40amps?
Or
Two pairs of two panels in series and finally two strings giving me at Max 90v and 20amps ?

[SunEagle]

Dear friends,

i own renogy Rover li 40amps mppt charge controller which has
Max input voltage 100v and Max input amps 50a.
i do also own 4 Canadian solar 330 solar panels same voltage and amperage.
Each panel gives at Max 45 volts and 9.5amps.

In order to get the most out of panels and controller, which is the most efficient way to set them up?
All panels in parallel giving at Max 45v and almost 40amps?
Or
Two pairs of two panels in series and finally two strings giving me at Max 90v and 20amps ?

When you say each panel has a Max 45v rating do you mean the Voc rating?

If that is so then to be safe wiring all 4 panels in parallel is probably the right thing to do because if the panels see low temperatures that 90V could exceed the max 100V max input rating of the CC.

[Takis]

Yes 24v with Voc 45.6.
But 45.6 is the maximum voltage, isn't it ?

I guess despite the safety reasons that the second set up is better?

[bcroe]

But 45.6 is the maximum voltage, isn't it ?

Panel Voc is specified at 25 deg C. It will increase from there as temps decrease.
My array picks up 60 volts (17%) mid winter. Bruce Roe

[SunEagle]

Yes 24v with Voc 45.6.
But 45.6 is the maximum voltage, isn't it ?

I guess despite the safety reasons that the second set up is better?

As bruce states when the panels get cold their output voltage goes up. If you exceed the max DC input voltage of that CC you could have a big issue.

[Mike90250]

What is your battery voltage ? Generally 1.5x peak battery charge voltage, is a good point for a MPPT controller which steps down voltage. Too low of voltage, and it may not start up MPPT function, too high and you loose efficiency with a wide down-conversion from 95V to a 12V battery.

[Takis]

My battery is 24v.
i guess I have an issue then.

I have 4 panels with Voc 45.6 and 9.53amps.
An mppt cc with Max input 100v and 50amps with output 24v/40amps.

Any suggestions for panels ordering?
A) all in parallel is almost 40 amps and 45v and safe. But is it efficient? Is it using mppt function?

B) two pairs in series and the pairs in parallel with voltage risk and damages

Is there any other way ?

Generally mppt needs more voltage or more amps?

Thank you all.

[Takis]

Too low of voltage, and it may not start up MPPT function, too high and you loose efficiency with a wide down-conversion from 95V to a 12V battery.

how to calculate the voltage threshold?

[littleharbor]

With a 100 Voc. max CC and a 24 volt battery bank your best bet would be to use 60 cell panels. With a typical Voc. of around 36 - 38 volts you can series wire two panels at a time without fear of smoking your controller.

[SunEagle]

My battery is 24v.
i guess I have an issue then.

I have 4 panels with Voc 45.6 and 9.53amps.
An mppt cc with Max input 100v and 50amps with output 24v/40amps.

Any suggestions for panels ordering?
A) all in parallel is almost 40 amps and 45v and safe. But is it efficient? Is it using mppt function?

B) two pairs in series and the pairs in parallel with voltage risk and damages

Is there any other way ?

Generally mppt needs more voltage or more amps?

Thank you all.

An MPPT type CC will work regardless of how you wire your panels. They work as efficiently as listed with Watts in = Watts out. The one upside to going with 2S2P wiring is that your wire is only handles 20A instead of the 40A with all four panels wired in parallel. The other upside is that with a higher voltage going to the CC you may not have to worry about the voltage drop exceeding 2%. With a 24V battery system, 45volts will work.

Depending on how cold it can get your panels can easily exceed that 45V rating by as much as a 25% increase. If you live down at the Equator I would not worry but if you live just about anywhere in the US you could experience freezing temps.

One option for you would be to replace the CC with a unit that has a higher max voltage input then 100V.

Or you can replace your panels with ones that have a lower Voc rating at around 36V.

[Takis]

I live in Greece (Athens) and the lowest temperature is minus 10 degrees Celsius (14F).

I've learned that the cc has overvoltage protection so I'll try both setups.
Charge controller is located 6 meters far from the panels so voltage drop is not issue.

Two last questions.
Is better to feed cc with extra volts or extra amps ?
For my 24v battery, 40 to 50 volts are enough for cc to activate mppt function?

Thank you all.

[SunEagle]

I live in Greece (Athens) and the lowest temperature is minus 10 degrees Celsius (14F).

I've learned that the cc has overvoltage protection so I'll try both setups.
Charge controller is located 6 meters far from the panels so voltage drop is not issue.

Two last questions.
Is better to feed cc with extra volts or extra amps ?
For my 24v battery, 40 to 50 volts are enough for cc to activate mppt function?

Thank you all.

In my opinion it is better to have a higher voltage and lower amps going to the CC.

[Mike90250]

What is the Vmp of your 45Voc panels ? You need about 30V to properly charge a 24V bank. You may just barely get by with all 4 panels in parallel, but you need heavy wire and could a simple PWM controller instead. 90Voc is too much to trust going into 100V charge controller, it's likely to fault on a cold morning, in my opinion