The life of a battery is adversely affected by several factors like cycle life, depth of discharge, recharge rate, and temperature. I will explain the major issues in detail related to battery performance.
Performance Factors for Battery Life
We will discuss the following performance factors for battery life.
- Cycle life
- Depth of Discharge (DOD) effect
- Temperature Effect
- Recharge Voltage and Rate
- Local Galvanic Action
- Loss of Active Material
- Electrolytic Action
- Low Water Level
1 Cyclic life
The number of use cycles a battery undergoes largely determines its life. AGM or flooded batteries typically last between 300 and 700 cycles under normal conditions, while gel batteries can last from 500 to 5000 cycles.
A battery completes a cycle when a battery is charged, and after that, it is fully discharged. The battery cycles may vary from application to application. If we take the example of a solar system, the batteries get charged during the daytime and discharge at night. The battery cycle is 24 hours. The life of the battery greatly depends on the charge and discharge cycle. The battery that is frequently charged and discharged will have a shorter life.
2 Depth of Discharge (DOD) effect
The life of a battery is directly related to the capacity it delivers. The harder the battery works, the faster it will deteriorate and ultimately fail. Thus, a higher capacity withdrawal from the battery causes a reduction in its useful life. The battery will last longer if the amount of energy withdrawn from it exceeds its rated capacity. The amount of energy withdrawn from the battery compared to its total capacity is called the depth of discharge. The deeper the discharge, the shorter the battery life cycle. The table below outlines the effect of depth of discharge on the battery’s performance and lifespan.
| Typical VRLA Battery Cycling Ability vs. Depth of Discharge | ||
| Typical Life Cycles | ||
| Capacity Withdrawn | Gel Battery | AGM or Flooded Battery |
| 100% | 450 | 200 |
| 80% | 600 | 250 |
| 50% | 1000 | 500 |
| 25% | 2100 | 1200 |
| 10% | 5700 | 3200 |
From the above table, it is clear that the life cycle of the battery increases with a decrease in depth of discharge.
3 Temperature effect
The performance of batteries is significantly affected by temperature. The temperature has a significant impact on battery life, charging speed, and voltage control. When the temperature is high, the chemical activity inside the battery increases, leading to a higher capacity. The performance of the battery increases by 12% at an elevated temperature of 50°C.
Conversely, the battery’s capacity decreases when temperatures are too low. For instance, a battery bank kept outdoors during winter will have a lower capacity than usual. Therefore, proper temperature management is critical in ensuring that batteries perform optimally.
However, operating a battery at above 50°C for a longer period negatively affects the useful life of the battery. Therefore, the battery should be operated within the recommended temperature range (65° to 90°F) to get the optimum capacity.
4 Recharge Voltage and Rate
During the charging process, all lead-acid batteries release hydrogen gas from the negative plate and oxygen gas from the positive plate. In contrast, the valve-regulated batteries (VRLA) are equipped with pressure-sensitive valves that help to retain pressure within the cells. In VRLA batteries, it is crucial to prevent the loss of hydrogen and oxygen to the atmosphere, which can lead to the drying out of the electrolyte and separators over time. Excessive overcharging causes a VRLA battery to dry out and reduce the battery life.
A battery has a limited capacity to store electricity, and it must not be overcharged. As the battery approaches its full charge, the rate of charging must be slowed down.
In general, the first 60% of the charging time is used to charge the battery up to 90% capacity, while the remaining 10% can take up to 40% of the total charging time. In order to avoid overcharging, it is crucial to use a suitable charge controller that can regulate both the voltage and the charge rate.
Overcharging and undercharging both negatively affect the life of the battery. The battery undercharging leads to sulphation formation on the plates of the lead acid battery which lowers the life of the battery.
5. Local Galvanic Action
When galvanic action occurs throughout the battery, it demands more charging current to boost the battery voltage. Yet, if the local galvanic action is limited to a single battery cell, overcharging the battery does not lead to a voltage increase. In such cases, the only viable solution is to charge that specific battery cell separately. However, it’s important to note that excessive charging can significantly decrease the life of the battery.
6. Loss of Active Material
When active material in a lead acid battery becomes depleted, it accumulates as sediment at the battery’s base. This leads to a surge in current draw during charging, resulting in a decrease in the battery’s ampere-hour capacity. Additionally, as the battery plates steadily lose active material, the battery’s lifespan is shortened.
7. Electrolytic Action
The electrolytic action in a lead-acid battery occurs when the electrolyte contacts the positive plate grid, which can cause cracks and breakage.
8. Low Water Level
A low water level can cause local galvanic action, which lowers battery voltage. Thus, it is necessary to maintain the water level in your battery accurately to ensure optimal battery performance