Frequently Asked Question

CLASSIC - NIFE - Using the Classic to Charge NiFe Battery
Last Updated 4 years ago

The following information has been compiled using Classic 150 & Classic 200 Charge Controllers.
The Nickel-Iron Battery was manufactured by ENCELL in the USA. It was a 300Ah Battery pack.
Nominal 48 volt pack using 39 300Ah cells. Classics in Follow-Me.
Classic #1 is BTS Master & Wbjr equipped. (called the BTS MASTER)
4 Classics total, battery current seen up to 140 amps at times.
About 11Kw of installed PV.  Grid-Tied battery Backup with SELL Setup.

CLASSIC SETTINGS:
Battery voltage selection = 60 volt. (During the setup Wizard or changed using the Local App)
ABSORB = 63v (1.615v / cell x 39 cells)
ABSORB TIME = 30 minutes for Master Classic and 40 minutes for all Followers.
FLOAT = 56.4v (1.45v / cell x 39 cells)
EQ = 65v (1.66v. cell x 39 cells)
 
BTS HIGH LIMIT set to 50 deg C. (ENCELL has a 60 deg C limit, other NiFe unless noted have a 45 deg C limit)

T-COMP is 30 cell count (60/2) as Classic uses 2V / cell for Lead / Acid battery.
Set to -2.0Mv / deg C / Cell
REF = 20 deg C (Set in the WBjr setup pages)

Absorb set @ 63.0v is T-Comp to 61.9v @ 38 deg C (1.59v / cell)
Float    set @ 56.4v is T-Comp to 55.3v @ 38 deg C (1.42v / cell)
REBULK set to 55.6V

CHARGING OBSERVATIONS:
Absorb timer is running for voltages 62v to 62.5v, stops @ less than 62v.
It takes 50 amps to get to & hold 61.0 volts
It takes 40 amps to get to & hold 60.5 volts.

Without enough sustained current to maintain the Absorb Voltage the battery just gasses and the electrolyte temperature just rises because the Classic stops the Absorb Timer.  If the battery terminal voltage continues to drop due to low current the Classic may go back into BULK Mode.

Sustained battery current greater than 10 amps in any mode causes electrolyte temperature to rise. This situation is worse when electrolyte temperature is greater than 40 deg C.  The terminal voltage depresses which causes the Classic to increase charging current in an attempt to reach the absorb or float voltage.  The only recourse is to find a T-Comp value that accounts for this.  Presently trying -1 to -3 Mv.

INVERTER SETTINGS:
Using NiFe batteries in a grid-tie selling mode can be problematic.  This test uses older TRACE SW5548 Inverters stacked for 11KW at 120/240Vac.  Internal battery chargers can not be turned off so are set to low values as to disable charging. Grid use is also disabled. 1 amp AC is as low as the settings go but tests show this is really 2 amps per inverter.  boB must have started the code from zero, step-0 + step-1 = 2 amps.

SELL set to = 55.6V (same as REBULK above)
The thinking is is we are in Float @ 56.4v to 55.6v and the Grid is down, the Classic will maintain Float @ greater than 55.6v.
If the Grid comes back, we start selling to 55.6v and Rebulk puts the Classics back into Bulk mode for better sell mode operation.



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