question

mike-deau avatar image
mike-deau asked

MPPT Solar Choice: 1, 2 or 4 MPPT controllers

I know this is asked all the time, but I need a bit of clarification.


I am adding 4x Panasonic 340 W panels to my van. I have run the calculator and I think I know my options. Any option will communicate to a cerbo and will provide power to 4x tesla model s modules in parallel at ~24v.

I am slightly concerned with shading. System performance is more important than cost.

Would I be better served with option:

1) Qty 1 SmartSolar 150/70. Panels in a 2x2 configuration.

2) Qty 2 SmartSolar 150/35. 2 series panels on each MPPT.

3) Qty 4 SmartSolar 75/15. 1 Panel on each MPPT.


I am leaning towards option 3 for the following reasons.

A) If each panel had it's own MPPT, then partial shading will be less of an issue. Is this true?

B) This is also the lowest cost option? Might be equal once I have to get cables for each MPPT.

C) I can use a powered USB hub on the cerbo to communicate with all of these MPPT controllers and create a "singular" solar module in software.

D) I get 4 more software accessible relays? Can I get at these from the cerbo and touch gx?


The only downsides I see are wiring complexity and extra MPPTs to package.


Thanks in advance!


Mike




MPPT SmartSolarSolar Panel
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1 Answer
Vance Mitchell avatar image
Vance Mitchell answered ·

If they are the Hit+ modules you will have to watch the temperatures where you are using them.

according to this spec sheet Panasonic Hit+ 340/335 they will exceed the max voltage to the controllers if the temperature drops below 7°C.

Try entering the panel specs into Victron MPPT Calculator once you add the V temp coefficient and your possible temperature range you might have to consider the following options;

1) Qty 1 SmartSolar 250/60. Panels in a 2x2 configuration.

2) Qty 2 SmartSolar 250/60. 2 series panels on each MPPT.

3) Qty 4 SmartSolar 100/15. 1 Panel on each MPPT.

This is of course if I chose the correct panel to input.

option 3 seems like it could be a good solution as it will ensure that shading on one panel won't affect the output from the other 3 but you will have increased self consumption and more space required for the controllers.

I'm unsure on if you can control the load outputs from a remote device (I'm thinking not possible)

You can create a smart network between the devices without a cerbo or GX device where each controller will show its own output and a network total output in the victron connect app.

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mike-deau avatar image mike-deau commented ·

Thanks for pointing the temperature coefficients! I must have typed them in wrong when I ran the numbers and am not experienced enough to have thought of it as a problem.


I agree with your options as the correct ones. The only ones that make sense to consider are 1 and 3.


I think that if there is no reason not to do so, I will go with 1 MPPT per panel, option 3.


According to this paper:

https://ecee.colorado.edu/~rwe/references/MacAlpine_PV_PELS2013.pdf


It says that in moderate shading the array with produce 3-16% more power. In heavy shading, it will produce 34-42% more power! I will most likely be BLMing it in the forest and will appreciate this power bump.


Thanks for the other answers as well. I am going with a cerbo to have quick access to all the information regardless, hopefully it will play nice with the smart network.


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Vance Mitchell avatar image Vance Mitchell mike-deau commented ·

Once you connect a cerbo it will network through that and ignore any smart network.

The cerbo is a much nicer option anyway and you won't have to setup the smart network.

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mike-deau avatar image mike-deau Vance Mitchell commented ·

Thanks Vance!


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Related Resources

MPPT product page

VictronConnect manual

PWM or MPPT

MPPT calculator

MPPT codes

Additional resources still need to be added for this topic