Indanao: Morning Star 60 amp MPPT based system questions

System

This discussion was created from comments split from: Need help with batteries.

Make your own threads to keep the discussion focused on your needs.

-Bill

Indanao

Good day. For a 48V System/3080Watts of Panels how many amps would the Charge Controler need to be, I wonder? Also, if I onlly have 6 batteries on a 48V System, and I put 4 in series and the other 2 Parallel to 2 of them,or will it cause uneven charge discharge even if they are all the same? Or, can I use 2 Charge Controllers, with a 48V hooked to 48Vbank and a 12V hooked to 2/12Vs? Maybe I should just buy 2 more batteries but they are expensive.

mike95490

Indanao said:

Good day. For a 48V System/3080Watts of Panels how many amps would the Charge Controler need to be,

3080w / 50v = 61A     so, i would expect any quality 60A controller to work OK.   A 60A controller is what I use on my 3Kw array

BB.

I would even suggest (on average) the "maximum" cost effective array would be:

• 60 Amps * 59 volts charging * 1/0.77 panel+controller = 4,597 Watt array "cost effective maximum'" for 60 amp MPPT controller in a moderate to warm climate

It will not be often that a 3,080 Watt array in non-freezing weather will exceed the 60 amp charging current (hit controller output regulation limit) (few cool/clear/spring/fall hours per day a few days of the year).

-Bill

Dave Angelini

The second OP here needs to be careful with having different banks here, It is a path to failure if not done right.
Definitely max out the controller as Bill suggests, the good ones will current limit to protect themselves.
This should be a separate thread as the original OP is not who we are responding with now.

MStar1

There is no easy way to connect two 12V batteries to a 48V battery bank. 
The non-parallel section of the battery will go through twice the DoD as the other section which has two batteries in parallel. For an LVD = 48V it will disconnect the 24V sections at maybe 23.4V and 24.6V. It is hard to say if it will complete the charging together also and whether there would be an imbalance during voltage regulation.
Two 24V controllers in series might avoid the imbalanced charging issue but it requires separate PV arrays.
A Relay Driver can trigger an LVD from the non-parallel 24V battery section since it will reach LVD first.
If you don't need the full Ah from the extra batteries it would be possible to reconfigure the parallel batteries into a 48V bank when the smaller battery bank is depleted. Is it worth it compared to the cost of 2 more batteries?
Some people ask us about using this kind of configuration when they have loads that have different nominal voltages. However, by the time they configure two controllers and two arrays in series it usually will make more sense to have two completely separate PV systems with separate battery banks.