The buffer effect in electric vehicle (EV) batteries helps reduce battery degradation primarily by preventing the battery from charging to full 100% state of charge (SOC) or discharging completely to 0% SOC. This is done through manufacturer-set buffers at the high and low ends of the battery’s charge range, commonly known as the top and bottom buffers.
How the Buffer Effect Reduces Degradation
- Limits Extreme SOC Levels: Charging or discharging a battery near its absolute maximum (100%) or minimum (0%) SOC significantly accelerates degradation. The chemical and physical stresses at these extremes reduce battery lifespan. Buffers create a margin that stops the battery from reaching these damaging states, thus preserving battery health.
- Maintains a Narrow Usable SOC Window: The battery management system (BMS) regulates charging and discharging so the battery operates within this safe limited window, avoiding the harmful effects of overcharging or deep discharging.
- Extends Battery Life: By avoiding the extremes, batteries degrade more slowly. For example, the Chevrolet Volt used relatively large top and bottom buffers with dynamic adjustments as the battery aged, resulting in slower-than-average degradation compared to other EVs.
- Adjustable Buffer Sizes: Some EV manufacturers allow buffer sizes to be changed via software updates or through user settings (e.g., capping maximum charge at 75% instead of 100%), enabling further optimization of battery longevity based on usage patterns.
- Prevents Battery “Bricking”: The bottom buffer is sometimes referred to as a “brick buffer” because it stops SOC from reaching 0%, a state that can permanently damage or “brick” battery cells.
Why Buffers Are Not Used to Hide Degradation
Battery buffers are not intended to mask battery degradation or hide the true capacity loss. Changing buffer sizes to artificially inflate usable battery capacity would involve adjusting cell voltage limits, which could actually accelerate degradation. Manufacturers generally avoid this practice.
Summary
The buffer effect is a protective design approach that limits EV batteries from experiencing damaging high and low SOC levels. This controlled operating window mitigates chemical stresses inside cells, thereby slowing capacity loss and extending battery lifespan. Though it slightly reduces the usable range, the trade-off is a longer-lasting battery with better overall health.
This approach is widely adopted in modern EVs, sometimes combined with user-configurable settings, to optimize battery longevity and performance.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-buffer-effect-in-ev-batteries-help-in-reducing-degradation/
