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samuil avatar image
samuil asked

Question about solar set up - MPPT/PWM??

Hi,

Please could you advise on what solar charge controller system I should run on my set up.


I currently use a 12v - 120Ah AGM Deep cycle battery(https://www.batteryworld.com.au/C12-120XDA-Century-AGM-Battery) and a 100w solar panel (https://au.renogy.com/renogy-100-watt-12-volt-monocrystalline-solar-panel-compact-design/).

I would like to keep system on permanently (24/7) and have the benefits of the Victron Remote Management Portal (VRM). I have looked at both your Blue solar PWM and your BlueSolar MPPT 75/15.


From my research I can see that the PWM does not offer me any access to VRM is this true?


The Bluesolar MPPT would be in my opinion better than the smartsolar version as we would not be using any Bluetooth on the charge controller, but instead we are thinking to connect directly to our onboard computer which already has internet access using this cable https://www.victronenergy.com/accessories/ve-direct-to-usb-interface#high-quality-photos (raspberry pi4+). Is this something that is possible? Or do we need a GX system in order to access our solar charge controller remotely?


We are hoping to just use a BlueSolar MPPT 75/15 with a VE.Direct to USB interface, connecting to our raspberry pi4 (which always has internet) giving us the accessibility of Victron Remote Management Portal (VRM) is this possible?

BlueSolar PWM
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4 Answers
klim8skeptic avatar image
klim8skeptic answered ·

No one can count?

The panel linked is a 33 cell panel. Renogy 100w panel.

Not suited for a Victron mppt.


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samuil avatar image samuil commented ·

Hi, sorry I’m new to solar panel game, can you please tell me why a 33 cell panel won't work with the solar charge controller? I did just read the specification that it mentions 36 cells minimum. What adverse affects would this have? I already will be moving to a 36 cell panel as a result of the spec, but just for learning purposes I was hoping to get insight on why.


Thanks again.

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klim8skeptic avatar image
klim8skeptic answered ·

As per the Mppt manual, you need a panel with 36 cells (or more) for reliable start-up and charging.

2 of those panels in series would be a good match for your 75-15, and be under the PV voltage maximum of 75v.

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Paul B avatar image
Paul B answered ·

Only use MPPT the PMW is NOT the way to go these days as you basically loose 20% efficiency from your solar if you use PMW


MPPT allows for much higher string voltages and thus is by far a better unit


PMW brings the string voltage down to battery voltage so you loose a LOT of solar output using PMW

OC = Open Cuirct

WV working voltage

IE a solar sell is rated at OC 48volts and a WV of 40volts and amps output is 10 this is then a 400 watt panel

so a MPPT takes PV in at 40v and the 10 amps in

and outputs at battery voltage

Say 12 volts and 33 amps into your battery this is still 400watts ie 12 x 33 =396 (*close enough)

A PMW PV in however drops the panel to 12 v (Battery voltage) but still only takes 10 amps this is then 12 x 10 or 120watts


you loose 276 watts in this example

so in the above example using the same panel the below is the result

MPPT gives 12 volts 33 amps or 396 watts

PMW gives 12 volts 10 amps or 120 watts


Note a solar panel is a constant current device it will supply in this example 10 amps all the time then in full sunlight and NO MORE, However the voltage can be any figure upto the WV being 40Volts

MPPT multi power point tracking - tracks the best PV voltage to get the MAXimun output from the panel


Hope this helps explain the differences as a general overview



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Paul B avatar image Paul B commented ·

note that the panel you are looking at (https://au.renogy.com/renogy-100-watt-12-volt-monocrystalline-solar-panel-compact-design/).

They do not show you the panel specs and just say its a 12v panel this is really very incorrect in my opinion.

yes it says 12 volts HOWEVER its output or 100watts would be rated at 18V and 5.5v

18 x 5.5 is 100watts

using PWM its 12v x 5.5 amps or 66 watts is the max you would get

ONLY use MPPT

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samuil avatar image samuil Paul B commented ·

Hi Paul and thanks for your reply.


Given the lack of specs provided I am cautious of using the panel I have mentioned, do you know of any quality panel providers in Australia, we are looking to charge the 120A battery as previously mentioned. (I predict we wouldn't be needing anything above a 100W panel).


Cheers!

Samuil

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wkirby avatar image
wkirby answered ·

Like Paul said, the MPPT would be the better choice with that panel.

To answer some of your other questions.
Yes, the Bluesolar model would be perfect for you. You can use the VE.Direct-USB cable connected to a computer to perform the initial setup and then use the same cable connected to your RaspberryPi.
You do not need a GX device. Once you have installed the VenusOS image on your RaspberryPi it will be the GX device and will have full access to VRM.
Here is the information for installing VenusOS image on a RaspberryPi: https://github.com/victronenergy/venus/wiki/raspberrypi-install-venus-image

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samuil avatar image samuil commented ·
Hi that sounds great thank you.


Quickly, do you know if it would be possible to use the raspberrianOS instead of the VenusOS or will the VRM only be usable through the VenusOS?


Thank you!

Samuil

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wkirby avatar image wkirby ♦♦ samuil commented ·
You need to use VenusOS.
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samuil avatar image samuil wkirby ♦♦ commented ·
Okay I see thank you
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