Watt's to mppt

DIY
1

My situation:
3 panels of 440 watts and max 39.9V in series. (this is 1320 watts and 120V max.)
2x of these (so 6 panels total)
These 2 series [strings] each go to their own MPPT 150/45 (so 2 units in total) to be able to charge at 90 amps (everything is 12 volt).
With this, I charge 4 paralleled batteries (4x 300Ah LiFePo4 - 12 volt)

QUESTION:
Is my reasoning correct, and is this safe?

  • I’m feeding my MPPTs with a lot of watts to get through the darker days better; the excess watts from the panels will be “limited” by the MPPT.

  • Can I also send TOO MANY watts to the MPPT which could potentially cause damage??? I feel like I’m currently going way over the specified 650 watts (with 1320).

If this is possible, then I want to add another 2 x 3 panels and 2x MPPTs, what is your opinion on this idea?

Thanks in advance, Hendrik

2

The MPPTs have 2 hard limits, input voltage, max 150V and input short circuit current limit, max 50A. You have 1320W at about 120V so about 11A, maybe more if max power point voltage is lower but still well inside the 50A. All that happens on a very sunny day is the controller will increase the panel voltage to limit the current and power to 650W or thereabouts. You should be OK with this set up.

3

Thank you for the clarification, this will help me :+1:

4

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