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chrisgla avatar image
chrisgla asked

MPPT Online calculator different result to spreadsheet?

I'm looking for MPPT (either separate or Easysolar II GX 250/70) to use with 6 off JA Solar JAM60S10 -340/PR. I have an existing 6mm cable limiting me to 39 amps.

The online calculator gives me a result of MPPT 250/60 for 6 in series, or MPPT 150/35 for 3S2P.

But spreadsheet I added a custom module which is then not accepted and neither the Max PV V or current makes sense to me unless temperature is the impact (I'd expect 248.16V and 10.46A for serial?):-



Are 6 off these panels ok in series and any idea why spreadsheet fails?


Thanks!

MPPT Controllers
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5 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

The value for V temp coeff. must be negative and with only 2 decimal digits.

If I enter a value higher 0 or with more than 2 decimal digits I get this (with Firefox):


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klim8skeptic avatar image
klim8skeptic answered ·

The spreadsheet is correct! 273.226v @ -10c.


The online tool is broken.


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Lasse avatar image
Lasse answered ·

@M.Lange is correct, the system should have given an error when you tried to add a positive value to the V. temp. coeff. [%/C] apparently this is was not the case. It is a problem that occurs with Chrome, not with Firefox, this will be fixed in the next release.

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JohnC avatar image JohnC ♦ commented ·

It happens with FF too. I tested this earlier, but by the time I nailed it down the question was already answered.

A little thin red line around that box under certain circumstances, but it happily shows the incorrect result.

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klim8skeptic avatar image klim8skeptic ♦ commented ·

"the system should have given an error when you tried to add a positive value to the V. temp. coeff. [%/C] "

To further this, temps below STC will have a positive temp coefficient effect on the Voc. It should not matter if you add a - #, or a number greater than zero.

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chrisgla avatar image
chrisgla answered ·

Thank you for fixing this, both the online and spreadsheet tools are really useful tools!

Looking forward to receiving my Multiplus ii 5k, Cerberus and CAN MPPT. I work in Smart Grid and the Modbus functionality with Victron quality and support will let me try a few innovative ideas....

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Warwick Bruce Chapman avatar image
Warwick Bruce Chapman answered ·

I have been able to reproduce this.

For Canadian 365's, web suggests a 150/60 is fine but Excel says current will be limited:

Another example for Canadian 415's, web suggests 150/45 is fine but Excel says current will be limited:


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