Can lead acid batteries compete in the modern era?
The answer to this question is yes. Lead acid is the oldest rechargeable battery, invented for commercial use by the French physician Gaston Plante in 1859. 150 years later, we have yet to find a cost-effective alternative to cars, wheelchairs, scooters, golf carts and UPS systems. The lead-acid battery has retained market share in cases where newer chemical batteries are too expensive.
Lead acid battery charging
Lead acid does not charge very quickly. Normal charging time is 8 to 16 hours. Periodic fully saturated charging is essential to prevent sulfation, and the battery must always be stored in a charged state. Leaving the battery discharged will cause sulfation and may not be able to be recharged.
Finding the ideal voltage for charging is very important. High voltage (above 2.40V per cell) results in better charging performance.
Car batteries have 6 cells, the ideal charge of which is 14.4 volts. That is, if we need 2.4 volts per cell for charging, the ideal charge for a battery is 14.4 volts.
Deep discharge and charge and discharge cycle
Lead acid battery does not like deep cycle. A full discharge causes extra strain and destroys the battery life every cycle. This wear characteristic also applies to other battery chemistries to varying degrees. A larger battery is recommended to prevent the battery from being stressed by repeated deep discharges. Lead-acid is inexpensive, but operating costs can be higher than a nickel-based system if repeated complete cycles are required.
Sealed lead acid provides 200-300 discharge/charge cycles, depending on depth of discharge and operating temperature. The main reason for its relatively short cycle life is the corrosion of the positive electrode network, the discharge of active materials and the expansion of the positive plates. These changes are more visible at higher operating temperatures.
Density and self-discharge
The lead-acid battery has one of the lowest energy densities, making it unsuitable for portable devices. Furthermore, performance at low temperatures is marginal. The self-discharge rate is about 40% per year, which is one of the best in rechargeable batteries. In comparison, nickel-cadmium depletes this amount in three months. The high content of lead makes lead acid incompatible for the environment.
Plate thickness
The life of a lead acid battery can be measured to some extent by the thickness of the positive plates. The thicker the plates, the longer they will last. During charging and discharging, the lead on the plates is gradually corroded and the deposits fall to the bottom. Battery weight is a good indicator of lead content and lifespan.
Car starter battery plates are about 0.040 inches (1 mm) thick, while typical golf cart batteries have plates between 0.07 and 0.11 inches (1.8 and 2.8 mm). Forklift batteries may have plates greater than 0.250 in. (6 mm). Most industrial deep cycle batteries use lead-antimony plates. This improves the life of the screen, but increases gassing and water loss.
Lead acid shielded battery
In the mid-1970s, researchers developed the lead-acid battery, a maintenance-free battery that could work in any situation. The liquid electrolyte is gelled into the wet separators and the chamber is sealed. Safety valves allow venting during charging, discharging and changes in atmospheric pressure.
According to the different needs of the market, two lead acid systems emerged:
- Typical sealed lead acid batteries
- A valve regulated lead-acid (VRLA) that is divided into two groups of jelly batteries and EGM.
Both batteries are similar. Engineers may argue that the term “sealed lead-acid” is a misnomer because no rechargeable battery can be completely sealed.
Unlike the flooded lead-acid battery, both SLA and VRLA are designed with a low overvoltage potential to prevent the battery from reaching its gassing potential during charging because overcharging causes gassing and water discharge. As a result, these batteries can never be charged to their full potential. To reduce dryness, sealed lead-acid batteries use lead-calcium instead of lead-antimony.
The effect of temperature on the battery
The optimal operating temperature for a lead-acid battery is 77 degrees Fahrenheit, equivalent to 25 degrees Celsius. High temperature will reduce the lifespan. As a guideline, every 8°C (15°F) rise in temperature will cut battery life in half. A VRLA that lasts for 10 years at 25°C (77°F) is only good for 5 years at 33°C (92°F) to operate. The same battery would fail after 2 1/2 years if kept at a constant desert temperature of 41°C (106°F).
Sealed lead acid battery
SEALED LEAD ACID BATTERY Batteries that are known as atomic batteries in Iran
The lead-acid shielded battery has a discharge of 5 hours (0.2) and 20 hours (0.05 °C). Longer discharge times produce higher capacitance readings due to lower losses. Lead acid performs well at high load currents.
AGM batteries
AGM is a newer type of lead-acid battery that uses woven layers of fiberglass between the plates. It is sealed, maintenance free, meaning no need to change battery water. Its plates have a good resistance to shock and high vibration. Almost all AGM batteries are recombinant, meaning they can recombine 99% of the oxygen and hydrogen. Almost no water is lost in the chemical process.
The charging voltage is the same as other lead-acid batteries. Even under extreme supercharging conditions, hydrogen emissions are below the 4% set for aircraft and confined spaces. Low self-discharge of 1-3% per month allows for long storage before recharging. AGM costs twice as much as the sealed version of the same capacity. Due to durability, high performance German cars use AGM batteries.
benefits
- Cheap and simple to make.
- Mature, reliable and well-understood technology – if used correctly, the lead-acid battery is durable and long-lasting, providing reliable power.
- Self-discharge in this type of batteries is very low and has one of the lowest self-discharge among rechargeable battery systems.
- High discharge speed
Disadvantages
- They produce less energy than their weight.
- It cannot be stored in a discharged condition – the cell voltage should never fall below 2.10V.
- Allows only a limited number of full discharge cycles – suitable for standby applications and machines that only require occasional deep discharges.
- The lead content and electrolyte make the battery incompatible with the environment.
- Transportation restrictions on submerged lead acid – There are environmental concerns about spills.
- Thermal runaway may occur if improperly charged.
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