Using Third-Party Batteries with Sunsynk Inverters in South Africa

Key Takeaways

• Sunsynk advises using batteries from its approved compatibility list and refers to third-party manufacturers for their battery guidance.
• The most common issue with unlisted third-party batteries is inaccurate load readings due to electrical noise.
• Wrapping battery power and BMS communication cables with ferrite rings may reduce electrical noise, but this fix is not guaranteed.
• Always refer to the third-party battery manufacturer's specifications for correct settings like capacity and charge/discharge rates.

Why Sunsynk advises caution with third-party batteries

When integrating a battery energy storage system with a Sunsynk inverter, the manufacturer provides specific guidance for its own range of batteries. For any batteries not made by Sunsynk or not featured on their official compatibility list, these are considered "third-party batteries." Sunsynk's general advice for such cases is to refer to the battery manufacturer's own documentation and support for specific operational parameters and troubleshooting.

An example of a third-party battery type mentioned in Sunsynk's documentation is "Lead Acid Forklift / Traction type Batteries." While these can be used, their integration requires careful attention to settings and potential issues.

The primary challenge: inaccurate load readings

One of the most significant issues observed when using third-party batteries with Sunsynk inverters is the occurrence of inaccurate load readings. Sunsynk has noted instances where the inverter displays load readings that are "significantly higher, sometimes over 3 times, or negative" when these batteries are charging or discharging.

This problem stems from "electrical noise originating from the batteries" which "causes interference which affects CT readings or third-party metering equipment." The inverter's current transformers (CTs) or external metering devices struggle to accurately measure the power flow due to this interference. This can lead to incorrect system performance data, unexpected charging or discharging behaviour, and difficulty in managing your energy usage effectively.

Addressing inaccurate readings with ferrite rings

While Sunsynk's primary recommendation is to "avoid choosing batteries which are not listed on Sunsynk's battery compatibility list," they do offer a potential, though not guaranteed, solution for existing installations experiencing inaccurate load readings.

The suggested fix involves using ferrite rings. You would need to wrap "both battery power cables as well as the BMS communications cable around ferrite rings 3 times." Ferrite rings are passive electronic components that suppress high-frequency noise in electronic circuits. By wrapping the cables, the ferrite material helps to absorb and dissipate the electrical noise, potentially reducing the interference that causes inaccurate readings.

It is important to understand that this is a troubleshooting step and not a guaranteed resolution. The effectiveness can vary depending on the specific battery, the severity of the electrical noise, and the installation environment.

Essential settings for any battery on a Sunsynk inverter

Regardless of whether you are using a Sunsynk-branded battery or a third-party option, certain inverter settings must be correctly configured to ensure proper operation. These settings tell the inverter how to interact with the connected battery bank.

For "Lithium" battery types, the inverter relies on communication with the battery's Battery Management System (BMS) to manage charging and discharging safely and efficiently. This communication is critical. If you are experiencing issues with your battery not charging or discharging, a communication problem is a common cause. For detailed information on setting up BMS communication, including Modbus protocols, CAN/RS485, and DIP switch configurations, refer to our guide on Sunsynk BMS Communication Faults.

When selecting charge and discharge current limits, remember that "you will always be limited to the lowest current value whether that is the inverter or the batteries." This means your system's performance will be capped by the lower of the two ratings.

What you can change yourself, and what you cannot

As a system owner, you can typically adjust settings related to your battery's operation, such as the "Battery Type," "Battery Capacity," and "Max A Charge / Max A Discharge" values, provided you have the correct specifications from your third-party battery manufacturer. These adjustments are usually made through the inverter's display menu or a connected monitoring application.

However, any work involving the physical installation, wiring, or initial configuration of batteries and inverters requires a registered and competent person. This includes connecting battery power cables, BMS communication cables, and ensuring proper earthing. In South Africa, such work must comply with NRS 097-2-1 and be accompanied by a Certificate of Compliance (CoC). Attempting to modify these aspects yourself can be dangerous, void warranties, and invalidate your CoC.

Safety is paramount. For instance, if a "difference of 1.5V or larger between V-Batt and BMS Voltage" is detected, the inverter will stop current flow to protect against a "possible system short or loose connection." This is an automatic safety mechanism. If you suspect a problem with wiring or connections, always consult a qualified professional.

What the published sources do not tell you

Sunsynk's knowledge base, while comprehensive for its own products, does not provide specific settings or detailed integration guides for individual third-party battery brands commonly used in South Africa. This means that while the general principles of battery integration apply, you will need to rely heavily on the documentation provided by your third-party battery manufacturer for precise technical data and recommended configurations.

Furthermore, the suggested fix involving ferrite rings for inaccurate load readings is presented as a "potential, but not guaranteed" solution. The manufacturer does not offer specific performance metrics or guarantees for this workaround, highlighting the inherent uncertainties when integrating unlisted components. The documentation also does not specify which third-party battery brands are more prone to generating electrical noise.