Article supplied by FranklinWH
Battery cells degrade over time, which is why devices such as mobile phones tend to lose performance after a few years of use. The same principle applies to home battery systems.
This is why having an intelligent Battery Management System (BMS) is critical. The cells within a home battery can be compared to athletes on a sports team, with the BMS acting as the team doctor monitoring their health to maximise performance and longevity.
However, not all BMS are equal. Lower-cost systems may reduce inputs, for example by monitoring temperature across only one or two cells and averaging the results. In contrast, premium solutions such as dedicated temperature sensors on each of FranklinWH’s aPower’s 16 battery cells ensures optimal performance across the entire system.
The followng article assesses three key BMS capabilities that help counteract ageing and support the long-term performance of the FranklinWH aPower.
Why battery capacity declines over time
Over time, homeowners may notice a drop in battery capacity. This is often not due to uniform degradation across the entire battery pack, but rather because one or more cells degrade faster than others. These weaker cells then limit the performance of the entire system.
Two primary approaches exist to manage cell imbalance:
- Passive balancing – A reactive method that dissipates excess energy once imbalance has occurred, typically with limited efficiency
- Active balancing – A proactive approach that redistributes energy between cells to prevent imbalance from developing.
While active balancing is more complex and costly, systems that rely solely on passive balancing often struggle to maintain performance in later stages of battery life.
FranklinWH uses a dual balancing strategy, combining both active and passive methods. During operation, energy is actively redistributed between cells to minimise differences, with passive balancing used to fine-tune the system.
Compared with traditional solutions, the balancing capability is improved by more than tenfold, bringing very direct benefits:
- Avoiding ‘not fully charging’ and ‘not fully discharging’
- More stable capacity in the mid-to-late stages of life
- Preventing a single cell from becoming a weak link.
In essence, advanced cell imbalance management improves battery longevity and reliability by keeping all cells performing evenly rather than letting one weak cell drag down the entire pack.
The role of thermal management
Temperature significantly impacts battery performance. At low temperatures, chemical reactions slow and internal resistance increases, reducing capacity and power output. Many conventional systems rely on limited temperature sensing, which can miss localised hot or cold spots.
FranklinWH addresses this by using a flame-retardant Flexible Printed Circuit with 16 temperature sensors, enabling precise, cell-level monitoring.
This allows the system to:
- Detect detailed thermal behaviour
- Apply targeted heating or cooling
- Maintain more consistent performance across all cells.
Combined with structural design features that reduce mechanical and thermal stress, the system helps slow long-term degradation. Testing shows the FranklinWH aPower can operate effectively across a temperature range of -20 to 50 degrees Celsius.
Batteries need health checks
State of Health (SOH) measures how much capacity a battery retains compared to when it was new. While SOH naturally declines over time, advanced systems can slow this process.
The FranklinWH aPower incorporates a comprehensive monitoring framework that continuously analyses temperature behaviour, charge and discharge patterns, and ageing trends. Based on this data, the system regularly calibrates and optimises performance, ensuring the battery operates within healthy parameters throughout its lifecycle.
A rare 12 year warranty
A common industry warranty standard for residential batteries is a 10 year warranty with a minimum of 60 per cent SOH remaining capacity. That level is often defined as the end of life threshold, meaning the battery’s capacity has declined to a level considered the end of its useful life under the warranty.
The FranklinWH aPower X offers a 12 year warranty with a 70 per cent SOH guarantee. What’s behind this is an integrated management system that significantly improves battery longevity:
- Cell-level thermal control to manage temperature dynamically and keep cells in their optimal range
- Dual balancing (active plus passive) to maintain long-term consistency across cells
- SOH monitoring and management to slow overall degradation and accurately track health over time.
