What causes hybrid batteries to degrade and fail?
Eventually all batteries will fail. Hybrid Electric Vehicle (HEV) NiMh batteries have a life cycle. When the hybrid battery does not last as long as the rest of the vehicle, replacing it costs several thousand dollars and creates hazardous environmental waste. Delaying battery failure beyond the service life of the vehicle will reduce the negative environmental impact of hybrid vehicle ownership and save the vehicle owner thousands of dollars.
This graph depicts the typical life cycle of a Hybrid Electric Vehicle (HEV) hybrid battery:
There are three major phases of hybrid battery lifespan. Usable capacity and performance decreasing as the battery ages:
||Healthy hybrid battery
||Weakened/weakening hybrid battery
||“Failed” hybrid battery (DTC code present)
Each hybrid battery ‘pack’ is comprised of many individual battery cells. Consumer hybrid electric vehicles have anywhere from 120 to 240 individual battery cells. Each cell is about the size of a typical D cell battery. At the beginning of the hybrid battery’s life, each cell easily provides all of the energy needed to propel the vehicle and to stay in sync with other cells in the battery pack. As time progresses, the battery will start to degrade and the cells will fall out of sync with each other. Results of this degradation include:
(1) usable cell capacity is reduced
(2) cells drift out of balance with each other (voltage delta).
The speed of this deterioration is determined by a variety of factors, including vehicle make/model, climate, driving habits, variation in battery cell construction, and more.
This battery deterioration means that the individual cells within the battery pack can have a different charge level and capacity – they are no longer ‘in sync’ with each other. Some cells can be ‘full’ while other cells in the same battery pack are ’empty’. The overall battery pack performance is limited by the vehicle’s battery management system to the weakest cell when discharging and the strongest cell while charging. As a result, the wider the cell imbalance, the narrower the usable range of the hybrid battery becomes. The car’s battery management system uses only a limited range of the battery cells actual physical capacity (80%-40% for Toyota and 80%-20% for Honda). As the usable capacity decreases and the cells become further and further out of balance with each other, the vehicle us able to use less and less of the batteries actual capacity. The vehicle cannot correct this imbalance problem on its own. The car cannot force the cells back into balance with each other.
If no attention is given to the hybrid battery, it will ‘fail’ and the check engine light/hybrid battery light will be illuminated. If this happens you are not helpless! It may not be too late. Your car needs help – battery care from Prolong Battery Systems.