Magnum Energy Integration Guide

REV070219
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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 the model.
Charge Example A
This example uses the following calculation:
B
#PV
≥ I
PVChrgMax
/ I
BatChrgMax
This example assumes the following:
• Max. continuous charge current for PHI 3.8 48V = 37.5A
• PV charge controller max = 100A
The calculation and assumptions correspond to:
B
#PV
≥ 100A/37.5A = 2.67
In this example, a properly sized PHI battery bank based on the available PV charge has a
minimum of 3 batteries. This maximizes the use of available PV while ensuring the batteries are never
stressed by overcharging. If the PHI battery bank includes fewer batteries than calculated, configure the
charge controller settings to limit the controller’s current output. These settings are described in more
detail in the following sections of this Integration Guide.
Charge Example B
This example uses the following calculation:
B
#PV
≥ I
PVChrgMax
/ I
BatChrgMax
This example assumes the following:
• Max. continuous charge current for PHI 3.8 24V = 45A
• PV charge controller max = 100A
The calculation and assumptions correspond to:
B
#PV
≥ 100A/45A = 2.22
In this example, a properly sized PHI battery bank based on the available PV charge also has a
minimum of 3 batteries.
In summary: When designing a system using the Discharge Calculation and the Charge
Calculation, the minimum number of batteries should be the greater of the two sizing calculation
results.