question

honu avatar image
honu asked

Mppt calculator wrong/unprecise ?

Hello all,

I'm using the mppt calculator (online) and running into a problem.

My PV are :

Voc : 41V

Vmpp : 34V

Isc : 12.2A

Impp : 11.6A

I got 2 strings of 5 panels.

Still the calculator do not show me the rs450 and i suppose it's because it accept 20A max on each mppt. And maybe this is where the problem come from, rs450 accept 30A on each mppt if you do not inverse polarity. Would better to still display the mppt, maybe with a red flag and showing which parameter is out of line.

If i'm wrong, can someone explain to me why my panel configuration could not be accepted by a rs450/100 ?

Thanks



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2 Answers
Alexandra avatar image
Alexandra answered ·

@Honu

Because while they allow the 30A connections is it not recommended. So logically it is not recommended as a solution. Following on from that thought, a 'mistake' cannot be claimed under warranty using ignorance as an excuse.

I get genuinely surprised at the number of people that ignore little warning triangles.

If you now choose to connect up to the 30A it is now your responsibility.

You may as well use both trackers anyway if you only have two strings.

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honu avatar image honu commented ·

What are you talking about, victron say that it support 30A max.. period, you are talking for nothing and i certainly not need someone like you to waste even more of my time.

You got no argument or intelligent idea to add to the matter just starting bashing someone for no reason.

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Alexandra avatar image Alexandra ♦ honu commented ·

Supported? No - it is allowed.

Definitely not recommended.

So it follows that as an option in the recommendation will not appear. Because most people will stick to what is more correct to keep on the warranty good side.

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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Click on "Export" in the upper right and share the link here.

Maybe some filters are wrong? Did you select 48V battery voltage? Did you add the 2nd string

The max Isc for the RS 450 is 20A not 30A! Where did you get that from?
The max operational input current is 18A!

You can't use two of your strings on one tracker, you need to add a 2nd tracker for the 2nd string.

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Alexandra avatar image Alexandra ♦ commented ·
They do "allow" an absolute maximum of 30 A. In the PV array config it is mentioned. Just not recommended.
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Matthias Lange - DE avatar image Matthias Lange - DE ♦ Alexandra ♦ commented ·
OK, found it in the manual.

But I think it's the best to stick to the datasheet.
That's what the MPPT calculator is doing, it uses the safe values from the datasheet not the "out-of-warranty" values from the manual.

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honu avatar image honu Matthias Lange - DE ♦ commented ·

Reason i say that the calculator should show the result for mppt that are near the limit, the 30% over paneling is not good enough.

My system is clearly under 30A, meaning that i'm within specs (if i do not swap polarities and even then i would need to swap polarities at the worst moment which is highly improbable).

The calculator should show the rs450 as a possible solution WITH a warning: The input current can be higher then 20A, swapping polarities under more then 30A will destroy the mppt.

Cause how it's done today, it can be hard to understand why a device disappear from the recommended list.

My system remove the rs450 cause as you said, 2xImpp = 22A is over the 20A but still far under the 30A. Connecting arrays early or late in the day and the risk is null.

I think the calculator should be smarter and give elements to the users to make their choices, displaying all devices with each time the reason it got a red flag = do not use it. There is not that much charge controllers in the victron lineup for this to be a problem.

Many users know what they are doing and those can't really take an advantage of the calculator.

It's not really a problem since 90% of victron mppt are bad devices in the way that they are not serviceable and i find this unacceptable, none of my client is using one of those devices, only SRNE or even Epever cause they can be repaired.


Not serviceable is the reason I got an rs450/100 connected to this array for a year and a half. The 2 rs are the only devices that are serviceable in the victron mppt lineup. Note that EVEN fuses are not accessible in the others mppt but this is an other problem.

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