Midnite Classic 250s in Parallel with Outback Charge Controller

[mammone70]

Vic, that makes sense but I'm not sure what numbers to use for max current. I was using the max output amperage of the controllers: 55A for classics and 60A for the Outback @48V.

I assume you're asking for ISC at STC of each array? 18.82A on each classic and 25.11A on the Outback. Are these the numbers I should be using? I may be misunderstanding how MPPT charge controllers work.

[Vic]

Hi mammone70,

Sorry about the imprecision of my question ...
I should have asked,   what is the total power rating of each PV array on each of the CCs  (this is the listed power rating,  called the STC power rating).

From this,   the nominal array output current can be estimated,  at a certain battery Absorption voltage.

And,   one more question,   what is the brand and model number of the battery that the system will use,   or,   at least,  what is the expected Absorption voltage that will be used.

This info can be used to approximate the maximum battery charge current produced by each of the three arrays.

Thanks,   Vic

[mammone70]

Hey Vic,

2800W on each Classic and 1620W on the Outback.

The batteries are U.S. Battery US 305HC XC2s. 16 total (2 strings of . According to the manufacturer, I read it as 58.8 Volts for the absorption voltage.

Thanks,
Matt

[Vic]

Hi Matt,

Thanks for the info.

Using standard rules-of-thumb,  seems that  the total nominal max current available from the three CCs is about 92 Amps, or so (assuming that about 75% of the rated PV power could be produced by all CCs).

Loads will reduce the amount of current that will go to the battery as charge current.

The Follow Me function of the Classics is very useful,   but why not try the two Classics and one MX-60 to start with.

You can try adjusting the exact Absorb voltages to try to make the three CCs behave fairly well on average.  In some ways,   it is good that the MX,   without Follow Me,   has a smaller PV array.

More later,  Vic