Quick answer
Yes. Set a minimum battery reserve so normal optimisation and trading cannot use it. If several minimum limits apply, use the highest one, such as the maker’s minimum charge, the client’s backup reserve or energy promised to another service. The local inverter or controller should still protect that reserve if the internet goes down.
Yes. A commercial energy management system, or EMS, can keep an agreed minimum amount of charge in the battery so that normal optimisation and trading cannot use it.
If more than one minimum charge setting applies, use the highest one. This may come from:
- The manufacturer’s minimum state of charge
- The reserve chosen by the client
- Energy that the client has committed to backup, a later demand peak, or a grid service
State of charge, or SoC, means how much energy the battery currently holds.
Check which device or controller stops the battery from discharging below the reserve. If the EMS loses its connection to the inverter or the internet connection fails, the inverter or local controller must still stop the battery from discharging below the agreed minimum charge level.
What should the reserve protect?
A client may keep energy in reserve for:
- Backup power, if the client’s battery system already supports backup operation
- A known period of high electricity demand later in the day
- The manufacturer’s minimum SoC, depth-of-discharge, or other warranty limits
- A grid or flexibility service to which the client has already committed part of the battery
For example, a battery with 500 kWh of usable capacity and a 20% reserve would keep 100 kWh unavailable for normal discharge. The EMS could use the rest of the usable capacity for tariff savings, peak shaving, or trading, as long as:
- The inverter can supply the required number of kilowatts
- The client has not committed the same energy to another use
Start by asking why the client wants to keep the energy in reserve. The client may want enough energy to cover critical loads for a set period. Another client may need to keep energy back for a known demand peak later in the day.
Do not count the same energy twice. If the client has already committed part of the battery to a grid service, exclude that part from normal optimisation and trading. That leaves less battery capacity available for normal savings or trading.
How do we keep the reserve available?
First, confirm what creates the reserve requirement and which device or controller enforces it.
The requirement or setting may come from the:
- Battery or battery management system, or BMS
- Inverter controller
- Third-party EMS
- Trading contract
The BMS monitors the battery and applies its safety limits. However, the inverter controller or EMS may apply a higher minimum charge setting for backup, a demand peak, or a grid-service commitment.
If more than one minimum charge setting applies, use the highest one.
You should also check:
- Whether the inverter or local controller keeps the reserve if the EMS connection or internet fails
- Who can change the reserve setting
- Whether a grid service requires the client to hold more charge during part of the day
- Whether the EMS receives the correct SoC reading from the battery
- Whether the battery has enough time to recharge before the next demand peak, backup period, or grid-service instruction
Check that the EMS receives an accurate SoC reading from the battery. If the reading is wrong, the EMS may calculate that more energy remains available than the battery actually holds. This could reduce the reserve below the agreed level.
Every kilowatt-hour that the client holds back reduces the capacity available for savings or trading. Set the reserve according to the client’s backup needs, expected demand peak, or contract commitment. Then test that the inverter or local controller still protects it if the EMS connection or internet goes down.
Related questions
Can a third-party EMS stay within the battery manufacturer's warranty limits?
Can battery trading override peak shaving, backup reserve and other site needs?
What happens to battery control if the site loses its internet connection?