enphase IQ System Controller 1 Technical Brief page 2

Overview
This document provides a complete list of equipment and the procedure to recover an
Enphase Energy System when it stops forming a microgrid due to excessive discharge of batteries.
This situation may arise if there is an extended utility grid outage and solar power is limited or
unavailable during the outage. The steps outlined here can be used in the event of battery charge
depletion during a natural disaster, such as a hurricane. The information provided in this document
supplements the information in the data sheets, quick installation guides, and product manuals. This
technical brief may include only some requirements from additional state and local codes, standards,
and other requirements from Authorities Having Jurisdiction (AHJs) applicable to a site.
The Enphase storage system has built-in intelligence that enables automatic battery charge recovery.
This technical brief provides steps to recover the battery in emergencies when it is completely discharged
(for example, due to the absence of solar power production during an extended grid outage).
This procedure should not be used in systems that already have a permanent generator connected.
Refer to the Generator integration with Enphase Energy System Tech Brief
permanent generator.
Automatic charge recovery
IQ8-Series microinverters on the roof in backup systems support Sunlight JumpStart. Sunlight
JumpStart enables batteries to charge from solar if load is less than solar power produced. Sunlight
Jumpstart does not require batteries to form the microgrid.
In addition, the IQ Batteries support an intelligent automatic charge recovery algorithm that does
battery-based microgrid restarts in the search for sufficient solar power to charge from. The IQ Battery's
automatic charge recovery algorithm works in any system with PV.
When forming a microgrid (that is, a system operating in backup mode), the IQ Batteries stop
discharging when their state of charge (SoC) reaches a very low SoC limit (VLS) (default- 10%, which is
configurable by the homeowner). The automatic charge recovery algorithm starts functioning in this
scenario:
•
The algorithm works when the battery SoC is between 2% and 10%.
• The algorithm restarts the system, forms a microgrid, and charges from available solar power.
• Each attempt to restart and charge lasts for a maximum of six minutes or until the battery loses
0.5% SoC, whichever occurs earlier. If the battery cannot charge from solar within this time, the
battery will stop forming the microgrid and try again after the timeout described above.
• The algorithm follows an exponential timeout between restart attempts, that is, 10 minutes,
20 minutes, 40 minutes, and 120 minutes. The maximum timeout is 120 minutes. The system will
continue to try to form a microgrid and attempt to charge the batteries from solar power every
120 minutes.
• When the battery SoC reaches 2% or lower, the automatic charge recovery algorithm is turned
off, and all electronics within the battery are shut down to prevent irrecoverable damage to the
batteries.
• The algorithm for charge recovery only operates during good solar production time, that is,
9.30 a.m. and 5.30 p.m. local time, to avoid wasting battery charge at night.
NOTE : For successful automatic charge recovery, homeowners must turn off all loads in the
home to ensure that a microgrid can be successfully formed without overloading and that
batteries can start charging.
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State of charge recovery for an Enphase Energy System
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for systems with a
June 2024
TEB-00084-2.0