question

As you pointed out elsewhere, Fronius have a paper from 2013 pointing out that East/West banks on a single Fronius MPPT are only marginally less productive than split on two MPPTs and the cost saving of the single MPPT outweighs the production benefit:

SE_TA_Efficient_East_West_orientated_PV_systems_with_one_MPP_Tracker_EN.pdf

However, this is for Fronius. The Victron team have yet to address this question to my knowledge and it should be determined first whether the Victron MPPT handles to two conflicting IV curves efficiently.

@warwick thank you, @Guy Stewart (Victron Community Manager) do you have a comment on this?

@warwick if i put the east side on a MPPT 150/45 what would i miss ? If it worked with both sides on same MPPT why is it a good idea to do this ? I didnt understand his reasonings about the MP2 1,5kw charger ? Is it because i can’t charge battery quick enough or ?

wUnless you are dirt poor in ghetto or 3rd world economy the need is better served with 2 separate controllers. Here is why...

1. You MUST have a controller that can handle the voltage of ALL your PV's at ANY given time of day -regardless of amps, the voltage (1st stage in MPPT controller) need to be met or you have limits and complete losses of anything else attached (at best)-negating any gains you hoped to have cutting costs here.

2. You MUST address the possible best solar condition or you will FRY your MPPT at some point -destroying it, and ALL initial cost savings you were attempting to reduce -to the sum of needing to have bought now THREE separate controllers; the 1st (now toast) and two new ones to avoid frying even more.

3. A MPPT (by anyone) large enough to handle all the above will be significantly more expensive than TWO smaller ones which, once you factor in the difference in prices works out to be very minimal in cost vs efficiency! Remember it's not the cost of one huge controller but only that cost vs two smaller ones adequately sized -because you STILL need to have the system PV size needs met.

So if you really can NOT afford that then you bought or got too many PV's and didn't budget -and hence design- correctly IMHO. It is a beginner"s mistake to invest in top notch or new PV's and run out of money when the most important thinga are (in order) - your battery system, monitors, wiring, fuses, controllers and inverters, and lastly the PV's!

I.E. Used grade-b panels can still harvest plenty of voltage and be obtained dirt cheap if you dig around in a modern culture (where you are) -which if you are efficiency and budget conscious might have been the better direction to go in. But since we all make mistakes and this is the most common one for solar (not budgeting correctly for a system's needs) then there are solutions.

A. Go with what you can afford to hook up with correctly sized controller and wiring -morning vs afternoon having best light will depend on your exact area and common weather patterns (where I used to live the clouds would roll in off the ocean in the afternoons most days of the year but where I am now the fog is common until noon so a morning array here is a luxury).

Now if it really is a matter of the budget and unforseen by anyone hurdles and you find you need to somehow finish a system bought or designed out of order then Traces/EPEVER (China) makes an excellent MPPT that can suffice efficiently when you can't afford to get the two MPPT's from Victron! The BN-series can handle the voltage and amps needs and be sized correctly without needing budget problems solved getting similar sized units from Victron.

I have used both and there are a lot of pros on the Tracer-BN series but the biggest con is it is not Victron networking -which is huge for me. The biggest plus is big lugs and higher amps per cost capable.

If this is just theoretical than budget and costs are irrelevant and you would be better served with a MPPT for every series of panels and huge single-roof sized panels that have super high voltage. So aim for THAT everytime!

:D