MorningStar Integration Guide

REV070219
SimpliPhi Power, Inc. | 3100 Camino Del Sol | Oxnard, CA 93030, USA | [phone] | [e-mail] | SimpliPhiPower.com
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3.0 – Battery Bank Sizing
A properly sized PHI battery bank should be at least double (2x) the kW rating of the inverter(s) and have
a C/2 rating greater than the maximum charge controller rating. Depending on the specifications of the
equipment used in the system, sizing the PHI battery bank based on these two criteria may yield different
results. Therefore, the best practice is to calculate the PHI battery bank based on both criteria and use
the greater of the two results as the minimum quantity. We can compare these two calculation methods
assuming the nomenclature below:
• Battery rated continuous power = Bat
kWh
(typically @ C/2)
• Inverter power full load = Inv
kW
• Maximum battery charge current = I
BatChrgMax
• PV charge controller maximum = I
PVChrgMax
• Recommended minimum number of batteries = B
#
Discharge equation: B
#Inv
≥ Inv
kW
/ Bat
kWh
Charge equation: B
#PV
≥ I
PVChrgMax
/ I
BatChrgMax
3.1 – Discharge Calculation: Inverter Power Bank Sizing
To optimize the PHI battery bank and protect against over-discharge (voiding the battery Warranty), the
PHI battery bank should be sized at least double (2x) the kW rating of the inverter.
Morningstar does not manufacture an inverter with a 48V or 24V DC Input; the SureSine-300 has a 12V
DC Input, so only the PHI 1.4-12V or PHI 750-12V model batteries are compatible. When pairing with the
SureSine-300, a minimum quantity of only one of either the PHI 1.4-12V and PHI 750-12V model
batteries is needed to ensure either battery does not over-discharge.
Discharge Example: B
#Inv
≥ Inv
kW
/ Bat
kWh
• Inverter is rated at 300W, with a 12VDC battery input
• PHI 730-12V battery is rated at 730W, therefore the C/2 rating is 365W
B
#Inv
≥ 300 W / 365 kW = 0.82
A properly sized PHI battery bank based on maximum discharge of the inverter would have a
minimum of 1 battery. This ensures no greater than C/2 battery load.
3.2 - Charge Calculation: Charge Controller Power Bank
Sizing
To optimize solar harvesting, a properly sized PHI battery bank should be able to accept the maximum
PV charge current. To determine the minimum number of PHI batteries required to optimize PV, divide
the output of the charge controller(s) by the “max continuous charge current” per PHI battery. Be sure to
verify the “max continuous charge current” for the PHI battery model that you’re using, because it may
differ from C/2 depending on model.
Charge Example A: B
#PV
≥ I
PVChrgMax
/ I
BatChrgMax
• Max. continuous charge current for PHI 730 12V = 28.5A
• PV charge controller max = 60A
B
#PV
≥ 60A / 28.5A = 2.1
A properly sized PHI battery bank based on available PV charge would have a minimum of 3
batteries.