Storage charge/discharge control

ID: func:storage-control
IRI: https://solarlattice.org/kb/func/storage-control
Status: active
Also known as: battery control, storage basic controls, Time of Use, Charge Control, Smart Charge & Discharge, Storage System Control, ESS Operating Mode
Category: Energy management
Function kind: energy-management

Storage control decides when a battery charges or discharges and at what rate. On Solis hybrids, Time of Use sets charge and discharge periods, each with a current setpoint and a settable cut-off voltage, and it takes priority over the other storage modes. On the SMA Sunny Tripower Storage 60, you can command charging or discharging over Modbus by writing the active power setpoint to SMA SSC register 1237 or SunSpec register 40349. A negative value charges and a positive value discharges, and Peak Load Shaving and Time of Use must both be enabled. Tesla systems can charge or discharge until the remaining battery energy meets a Maintain Energy Target sent from an external interface. With SMA battery inverters, the Sunny Home Manager uses the load profile and the yield forecast to control when lead-acid batteries discharge, so that room is left for forecast PV energy. In off-grid systems, charge controllers limit charging voltage or current through regulation set points. They also prevent over-discharge with low-voltage disconnect and reconnect set points. At commercial sites, the rate structure and the load profile drive the charge and discharge strategy, for example for demand charge management. These strategies often use forecasting.

<!-- review notes

sentence 1: support check: partial - The passage supports the Time of Use description, but it never mentions Solis hybrids by name.
sentence 2: support check: partial - The register details, signs and enablement are all stated, but the article never names the Sunny Tripower Storage 60 model beyond its STS60-10 title. -->

Claims

`requires`

c1 drafted · lead Qualified person

Scope: standard NFPA 70 (NEC) 2017 proposed

All adjustable means for control of the charging process shall be accessible only to qualified persons.
— NFPA 70 (NEC) 2017 §706.23(A). Quoted with attribution; the text remains the publisher's copyright.

NEC2017 706 [code/standard] sec=h18 h=a87ae1939663

review note: support check: partial - NEC 706.23 says adjustable charge-control means must be accessible only to qualified persons, but it says nothing about discharge control.

c2 drafted · lead SunSpec Modbus

Scope: products Sunny Tripower Storage 60 proposed

Option for manual charge/discharge via the active power setpoint register 40349 (unit ID 125); the SMA Storage System Control register 1237 (unit ID 25) is the alternative.

STS60-10 - Battery charge/discharge control via Modbus register sec=h1 h=0c32d6f1c381

review note: review: partial - The passage says Modbus control of P_ref works through either the SunSpec register 40349 (unit ID 125) or the SMA SSC register 1237 (unit ID 25), so SunSpec is one of two options rather than a requirement, although the note…

c3 verified · fact SMA Inverter Manager

Scope: products Sunny Tripower Storage 60 proposed

Modbus charge/discharge commands are addressed to the inverter manager by unit ID.