Maximun current and MPPT controler

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jordaanp asked Feb 20, '21

Maximun current and MPPT controler

Good day all,

Apologies if this has been asked and answered already. I have been searching for a couple of days now and not been able to find the answer yet.

I am in the process of upgrading and installing new batteries as well as a larger solar array on my boat.

I have bought 3* 220ah Victron deep cycle gel batteries.

My solar so far consists of two 365W panels with a Voc of 41.13V and Vmp of 33.96. the current ratings are 11.30 lsc to 10.75lmp per panel.

My plan is to connect these in series. I will be adding some more solar to these, probably 2 150W panels at a later stage.

According to the information I have been given and my calculations, the max carging current for the batteries will be 44A.

My question is this:

I have been advised to get the 150/85 MPPT controler for this as it can take up to 1200W for a 12V system. Is this really needed if I need to limit the charging current to 44A. Will a smaller MPPT better/worse for the charging of the batterie bank? or will it make no difference?

Kind thank you in advance.

Pieter Jordaan

MPPT SmartSolar solar mppt charging

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Answer 1 · 2021-02-20T15:20:58Z

Matthias Lange - DE answered · Feb 20, 2021 at 03:20 PM

1. You should not mix different panels at one MPPT, so you will need a second one for the 150W panels.

2. The two 365W panels will give you 50-60A of charging current. 730W / 12V = 60A

So I would suggest you a 150/60 for the two 365W and a 100/20 or 100/30 for the two 150W.

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seb71 commented · Feb 20, 2021 at 03:53 PM

For a boat, maybe even using one small MPPT per each PV panel.

If only one panel is shaded (by some structure on the boat), it won't drag down the energy production of the other panels (as it happens with series panels).

Also, each panel can have a different orientation in this case.

And greater redundancy.

Just make sure that the voltage of the panel is big enough to be used alone.

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Answer 2 · 2021-02-21T19:48:01Z

marc-de-montreal answered · Feb 21, 2021 at 07:48 PM

hi, if all panels are around 40voc, they can all be in parallel on one mppt with the max power available if some shadow happen.. (2 x 365w) + (2 x 150w) = 1030w total and divided by 12vbatt = 86amp.. so 100amp mppt is good with no much stress.. but yes, you can split your system as you want (to have 2 mppt give a chance to have some power if one of them fail one day in a journey).. it’s a nice problem to think about!! ..Marc

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Answer 3 · 2021-02-22T09:18:59Z

jordaanp answered · Feb 22, 2021 at 09:18 AM

Thank you all so far for the advice. I really appreciate it. Space is a bit of a problem on the boat with inverters, mains battery charges and various other pieces of equipment to install as well.

If you mix two sets of solar panels and not use two different MPPT's to charge the batteries, does this mean I am going to lose a lot of power from the larger array?

Best

Pieter

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seb71 commented · Feb 22, 2021 at 09:26 AM

If you mix two sets of solar panels and not use two different MPPT's to charge the batteries

Don't do that. If you must use a single solar charger, then get identical PV panels. And make sure they are all installed in the same plane (same orientation and same angle).

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