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FranklinWH•aPower

Analysis by Marcus & Team

FranklinWH aPower Battery Only Charging to 80% - Diagnosis

Diagnosing a FranklinWH aPower battery that stops charging at 80%. Potential causes, solutions, safety precautions, and expert tips for residential energy storage systems.

Frequently Asked Questions

•What is the ambient operating temperature?

High temperatures can reduce charge capacity.

•Is there an external energy management system connected?

Third party devices can be configured to prevent full charging.

•When was the last firmware update completed?

Older firmware versions may contain software bugs that prevent full charging.

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Marcus leads the technical research department at Storage Faults. Together with a team of systems analysts, he specializes in translating complex solar storage error codes into actionable diagnostic steps for the US market.

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Technical Overview:

The FranklinWH aPower system integrates a lithium iron phosphate (LFP) battery, a bidirectional inverter, and a Battery Management System (BMS). The BMS monitors cell voltages, temperature, and current to optimize performance and prevent damage. Charging is controlled by a multi-stage algorithm, including constant current (CC) and constant voltage (CV) phases. Premature termination at 80% SOC suggests a BMS limitation, cell imbalance, or external control setting.

Observed Symptoms:

The FranklinWH aPower battery system consistently stops charging at approximately 80% State of Charge (SOC), despite available grid power or solar production and no active fault codes displayed on the monitoring app.

Important Warnings:

Battery systems operate at high DC voltages. Improper handling can result in severe electric shock or arc flash. Always de-energize the system using the DC disconnect switch before performing any maintenance or troubleshooting. Refer to NEC Article 690 for solar photovoltaic (PV) systems and related battery storage. A qualified electrician is mandatory for any invasive work.

Recommended Action:

1

Verify external control settings: Check any energy management system or grid services programs to ensure they are not limiting the SOC to 80%.
2

Review FranklinWH monitoring app: Check for any error messages, warnings, or SOC limiting settings within the FranklinWH app or web portal.
3

Check cell voltages: Using a multimeter (after disconnecting DC power following NEC guidelines), measure the individual cell group voltages within the battery. Significant voltage imbalance can cause early charge termination. Qualified personnel only.
4

Check temperature sensors: Use an IR thermometer to verify the temperature of the battery enclosure and compare to the BMS reported temperature. Inaccurate temperature readings may falsely trigger charge limiting.
5

Perform a full system reset: Cycle the AC and DC disconnects to reset the inverter and BMS. Monitor the charging behavior afterward.
6

Update Firmware: Ensure the FranklinWH system has the latest firmware installed. Firmware updates often address bugs and improve BMS accuracy.
7

Contact FranklinWH support: If the issue persists, contact FranklinWH technical support for further diagnosis and potential warranty service. Provide detailed logs and observations.

Common Causes:

BMS software bug limiting maximum SOC.
Inaccurate cell voltage sensing, leading to premature termination of the charging cycle.
One or more cells reaching maximum voltage limits before the others, triggering early cut-off by the BMS.
External control system (e.g., energy management system) programmed to limit SOC to 80%.
Capacity degradation over time, resulting in the BMS miscalculating the SOC.
Temperature derating: the BMS will reduce charging at higher temperatures.

Technical Recommendation:

Access the FranklinWH service menu (consult the system manual for the key combination or contact FranklinWH support) and check the individual cell voltage readings reported by the BMS. This provides a more granular view of cell balance than standard monitoring and can pinpoint specific cell groups causing the problem.

Preventative Care:

Regularly monitor the battery SOC and system performance through the FranklinWH app.
Implement a scheduled capacity test (if supported by the BMS) to track battery health and identify degradation early.
Ensure adequate ventilation around the battery system to prevent overheating.
Keep the system firmware up to date.
Periodically inspect the battery enclosure for any signs of damage or corrosion.