The darker winter months lead to reduced PV production, which often prevents the battery from charging fully. What can be done to optimize battery operation during winter?
This whitepaper deals with the SBR battery, the SHxxRT(-20), and the SHxxT hybrid inverter from Sungrow.
Temperature plays a significant role in lithium-ion battery performance, directly influencing charging and discharging capabilities. As temperatures drop, (dis)charge rates decrease accordingly. This should always be taken into account when selecting battery installation sites.
The temperature limits of the Sungrow SBR battery are:
Charging: 0°C – 50°C
Discharging: -20°C – 50°C
Reduced charging power in winter is often mistakenly identified as a fault. However, this is simply the battery's adjusted response to ambient temperature conditions.
Temperature also affects the available battery power. This is because as the temperature decreases, the battery voltage also drops, since the internal resistance increases. This can lead to the battery not being able to provide the nominal power as stated in the datasheet. This does also not indicate a faulty battery. For improved system stability during rapid load changes, we therefore recommend configuring the battery's installed capacity (= lower operating voltage - discharge current) in the advanced iSolarCloud settings under the “Battery Parameters” tab in the “Max. Charging Power” and in the “Max. Discharging Power” field.
SHxxRT – Adjustment of charging and discharging power for improved system stability.
Fig. 1.
SHxxT – Adjustment of charging and discharging power for improved system stability.
During winter, it is generally advisable to set a reserve SOC of 50%, as this keeps the battery in its mid-voltage range, close to the nominal voltage.
Fig. 2.
SHxxRT – Setting the reserve SOC
Fig. 3.
SHxxT – Setting the reserve SOC
Where local regulations permit, the iSolarCloud provides the option to recharge the battery from the grid at specific times to maintain the reserve SOC even during winter.
For example, the forced charging target can be set around 3% below the configured reserve SOC. With a reserve SOC of 50%, this would correspond to a forced charging target of 47%. These settings are located in the general parameter settings and can therefore also be adjusted by end customers.
Fig. 4.
SHxxRT – Setting Forced Charging
Fig. 5.
SHxxT – Setting Forced Charging
In this context, balancing refers to the process of equalizing the module voltages within the SBR battery tower. This process occurs, for example, when the SOC remains at 99% for an extended period and the charging power is low. In summer, balancing is usually less noticeable because sufficient PV energy is available.
As the operator of a PV system, balancing can be initiated in a controlled manner by setting the reserve SOC to 90% for a few days. To successfully equalize cell voltages, an SOC of 100% must be reached around three to four times. The reserve SOC must then be set to 5% for a few days to allow the battery to perform an SOC calibration. A sudden SOC jump is normal during this process. Once the procedure is complete, the desired reserve SOC can be restored.
The 'Balancing & Calibration' process often has a positive impact on the battery's SOH as well.
Acronyms:
SOC [%] | State of Charge | The charge level of a battery |
SOH [%] | State of Health | The remaining capacity of a battery, which decreases with age and usage. |
For more information, please refer to the user manual for the SHxxRT(-20), SHxxT, SBR, and the training courses on hybrid and battery systems.
This manual is intended for qualified personnel responsible for installing and commissioning the inverter, as well as for the owners of the inverters who may interact with them. Always read the manual and all associated documents before handling or operating the inverter. The documents must be stored carefully and kept readily accessible at all times. Their contents may be regularly updated or revised as the result of product development. The information in this manual may be changed at any time without prior notice. The latest manual can be obtained from https://ger.sungrowpower.com/.