Lead Acid Batteries – AGM / VRLA
Lead acid batteries are a group of batteries that includes VRLA (Valve Regulated Lead Acid) and AGM (Absorbent Glass Matt).
The technology behind lead acid batteries was invented in the mid-1800’s and was the first rechargeable battery created that was suitable for commercial use. Today, it is still a popular choice for batteries due to its low cost and reliability, and is most commonly used in photovoltaic systems.
There are two key types of lead acid batteries, both identical in their internal chemistry. The most significant differences between the two types are the system level design considerations. The first type, flooded lead acid batteries, requires upright orientation to prevent electrolyte leakage, a ventilated environment to diffuse gases created during cycling, and routine maintenance of the electrolyte. The second type, known as a valve regulated lead acid (VRLA) battery, does not have the same requirements.
Both VRLA and flooded lead acid batteries have deep cycle and shallow cycle variations. Shallow cycle VRLA batteries are commonly used for automobiles, to deliver short, high energy pulses of power. Deep cycle batteries are best suited to stationary uses, as the batteries often discharge at a low rate over the course of multiple hours.
Lead Acid Batteries – Advantages
Lead acid batteries are a group of batteries that includes VRLA (Valve Regulated Lead Acid) and AGM (Absorbant Glass Matt) these battery types are often used in cars, boats and trucks.
When used correctly, lead acid batteries are long-lasting and reliable. They offer low self-discharge, among the lowest out of available rechargeable battery systems, but are capable of high discharge rates. The maintenance requirements for these batteries are low, with no memory or electrolyte to fill.
VRLA batteries specifically are affordable and simple to manufacture, offering the least expensive cost per watt hours. In addition to this, VRLA batteries are a mature, reliable and well understood technology.
Lead Acid Batteries – Disadvantages
Lead acid batteries cannot be stored in a discharged condition, and have a limited number of full discharge cycles. They are better suited for standby applications that only require occasional deep discharges. The poor weight-to-energy density limits lead acid battery use to stationary and wheeled applications.
There is a risk of thermal runaway occurring with improper charging, which causes the battery to rapidly generate heat internally and can eventually destroy the battery.
Lead acid batteries have a resource-intensive manufacturing process; requiring large amounts of raw material, which has a lasting effect on the environment during the mining process. The lead processing industry also generates large amounts of pollution.
Li-ion Batteries – Advantages
Lithium ion batteries are generally more reliable than other battery types such as nickel-cadmium and don’t suffer from the “memory effect” problem where batteries become harder to charge unless they are completely discharged first. Since lithium-ion batteries don’t contain cadmium (which is a a toxic, heavy metal), they are theoretically better for the environment and we are all for that! — It is worth mentioning that improper disposal of any batteries lithium or otherwise is destructive to the environment.
Batteries contain metals, plastics, and a variety of other chemicals that should never find their way into landfills. Compared to lead-acid batteries and VRLA batteries used in some of our solar street lighting products, lithium-ion batteries are relatively lightweight for the amount of energy they can store making them a serious advantage for portable devices and other applications that need to remain mobile such as electric cars.
Li-ion Batteries – Disadvantages
Lithium-ion batteries biggest issue is safety: Li-ion batteries will catch fire if they’re overcharged or if they short circuit or malfunction in any way the batteries heat up in what’s called thermal runaway, which can lead to fire or explosion. This problem is mitigated through the use of a current interrupt device or CID, which kills the charging current when the voltage reaches a maximum, if the batteries get too hot, or their internal pressure rises too high. This technology is managed through Green Frog Systems’ MPPT solar charge controllers that regulate the flow of current into the battery throughout the charging cycle including active over-discharge and short circuit protection.
Lithium Iron Phosphate (LiFePO4) – Advantages
The key benefit of Lithium Iron Phosphate (LiFePO4) battery technology is that it has a high current rating and long cycle life, increasing thermal stability and enhanced tolerance if anything goes wrong. The overall safety of this battery type allows for batteries to handle full charge conditions when kept at high voltage for a prolonged time.
Ultra Safe LFP’s high thermal runaway temperature and optimum energy density make them the safest and most popular lithium-Ion battery system. Green Frog Systems integrated BMS removes the possibility of incorrect connection or installation that can be associated with independent BMS systems. Finally, lithium iron phosphate produces no explosive gasses during charge or discharge, unlike lead-acid systems.
Fast Charging Compared to AGM and lead-acid batteries, lithium-ion batteries not only charge faster with a full recharge typically taking just 2.5 hours in a 100Ah battery at the optimum rate of charge.
Highly Efficient When it comes to the efficiency of lead batteries versus lithium iron, the choice is clear. Lead acid batteries typically store around 70-80% of the energy provided in a whole charge cycle. However, when operating in the top 20% state of charge and in hotter climates, this can drop to below 60% of the charge energy provided being stored during the absorption phase. This leads to slow charge cycles and wasted solar energy. On the other hand, lithium iron phosphate batteries store more than 95-97% of charge energy supplied and have no absorption phase leading to ultra-efficient use of the available energy and faster recharge times.
Longer Lifespan Lithium Iron Phosphate batteries last up to 15 times longer than budget flooded lead-acid batteries. With a 50% depth of discharge, more than 6000 cycles can be achieved. For most people, the investment in lithium will save time and money in the long run, delaying the need for a battery replacement in their solar lighting assets.
Lightweight They are up to 60% lighter than equivalent lead-acid batteries, making them a lightweight option. Their ultra-compact size allows you to increase capacity and maximise space. Bulky batteries can, therefore, be a thing of the past! This is vital in modern, sleeker designed solar lighting systems with in-pole battery storage such as the GFS-ASPIRE solar light range.
DID YOU KNOW ? : A 300Ah Lithium battery weighs about 27kg, but provides the SAME USABLE ENERGY as a 480Ah flooded lead-acid system that would weigh around 120kg!
Environmental Impact and Sustainability
We can all do our bit to reduce our carbon footprint and dispose of waste in the safest way possible. Another positive characteristic of LiFePO4 batteries is that they contains non-toxic and biodegradable materials. Additionally Iron and phosphate do not produce toxic gases when operating and do not contain any heavy metal materials that can contaminate if they come into contact with nature upon disposal.
Lithium Iron Phosphate (LiFePO4) – Disadvantages
Similar to most batteries, cold temperature reduces the performance of Lithium Iron Phosphate (LiFePO4) batteries and high temperature shortens the service life. LiFePO4 has a higher self-discharge than other Li-ion batteries, which can cause cell balancing issues as they age.
This is only avoided by using high quality cells and sophisticated battery management control systems. All our LiFePO4 batteries come with a battery management system (BMS) to protect the battery. These battery management circuits ensure the longest possible lifespan from this battery type with more recent product releases such as the DEFENDER-55 solar light making use of passive cell balancing technology to further extend battery life and reliability.
