question

There appears to be several problems with the MPPT calculator.
What it said was OK for my setup a while ago no longer appears, in fact if I mess about with the strings, it still won't show the 250/100 as being suitable.
Not sure I would trust it atm.

Try the excel version you can download. It will limit the output current, but is not ideal and looks like it by default oversizes irrespective of you deselecting the option.

The 250/70 at 48v can potentially produce 3360W (volts x amps)

Rememebr I am calculating at 25°C. So colder means higher production. Working with a 48v system as I dont know what yours is.

6x 310W is 1860W. (1860w @ 48v is 38.75amps. well under the 70a max)

6x 410W is 2460W. (2460w @ 48v is 51.25amps also well under the 70A max)

So yes you will protentially produce 600w more more on the same charge controller with the 410w on a 48v system.

Where did you get 89.13A from for interest?

The short circuit current is 50A so you cant put them all in parallel to the input. You need to make at least 3 strings of 2. But best is 6 in one string with will then only have the isc of one panel for the string.

My system Voltage is 24V and Absorbtion 28,6V Float 27,6V.

Eqzalizing is 30,6V.


My Solarpanels where bought in August 2018 and have currently up to 2170Wp at around 0°C.


However, in the summer I use the Relays with "High voltage" 28,8V to switch on my 200l Boiler using a 2x500W/24V Heating Element and up to 30°C environment temperature, it deliver without any compromise and additional cooling 67A.


Hence if I have 6x410Wp (2460Wp) in series, it output 89-92 Amperes.


It seems, that the MPPT calculator ignore my system Voltage and fix it to 48V. Maybe the programmer of the MPPT calculator should take a look into the code to find the error.


Also I would suggest, that the "Check Box: allow more then 130% over sizing" should be changed into a "Drop down box" or a "Radio List" with the options

1) no oversizing

2) allow 30% oversizing

3) allow more then 30% oversizing


And yes, with approximately 37,32V Voc I am realy at the limit, but I have now logged the Voc of my first system 3s2p 1860Wp and recalculated it to the new 6s 2460Wp and up to -16°C there is no problem with it.


However, I have just seen in the PDF, that the MPPT calculator assume a Float Voltage of 55,2V which mean, there is seriously a software problem.


Have a nice day @Alexandra

2023, 11:20:31 AM.pdf