Solar Batteries

                                                                                                    Solar Batteries brands

Terms used when dealing with solar batteries:
DoD –  Depth of discharge (it is the percentage of energy discharged from a battery relative to the overall capacity of the battery.
KWH –  it shows the number of kilowatts used per hour (it’s a measure of Energy usage)
AH –  is the amount of energy charge in a battery that will allow one ampere of Current to flow for one hour.
SOC –  State of charge
BMS –  Battery monitoring system
ALM –  Represents alarms, it’s normally a red LED light.
C-RATE –  It is a measure of the rate at which a battery is discharged, relative to its maximum capacity.

There are many types of solar batteries that are on the market and these are:
1.Lithium batteries
2.Gel batteries
3.Lead acid batteries
4.Saltwater batteries

1. LITHIUM BATTERIES

Lithium batteries are the best so far on the market because of their light weight, longer life span and a high depth of discharge. The lifespan of lithium batteries ranges from 10 years and above depending on manufacturer, as for the depth of discharge they range from 80% to 90% depending on the manufacturer. For instance, the depth of discharge of Pylontech lithium batteries is at 90% even though they recommend the batteries to operate below 90%. The operating temperature of lithium batteries ranges from 0 degrees to 40 degrees. Charging or storing in a high temperature environment may permanently damage the battery capacity and further accelerate battery life degradation, resulting in a rapid reduction in standby time. When using the device at low temperatures, you may find that the battery life is shortened. This is the characteristic of all lithium-ion batteries at low temperatures, but this phenomenon is temporary, when the battery temperature returns to the normal range, performance will also return to normal. Lithium batteries normally come with a battery monitoring system(BMS) which provides the battery with protection against short circuit, overcurrent, over temperature, over discharge and overcharging. Most of the lithium batteries like the pylontech battery enters a sleep mode to avoid overdischarging. Also in some lithium batteries there is a centralized unit in BMS, that enables functions such as remote measurement, remote communication and remote controlling to be available. Lithium batteries are more than 95% efficient.

The graph below is showing how lithium batteries discharge.

The graph below is showing the charging of lithium batteries relative to lead acid batteries.

Advantages
• Maintenance free.
• They have a high energy density (Lithium is a highly reactive element, meaning that a lot of energy can be stored in its atomic bonds.
• They have a relatively low self-discharge
• They’re generally much lighter than other types of rechargeable batteries of the same size. The electrodes of a lithium-ion battery are made of lightweight lithium and carbon.

Disadvantages
• They are expensive (this is directly related to their manufacturing process)
• Requires protection circuit to maintain voltage and current within safe limits.
• They are extremely sensitive to high temperature.

2. GEL BATTERIES

A gel battery, also known as a “Gel Cell”, is a VRLA (valve-regulated lead–acid) battery, a type of Sealed Acid Battery. The technology used in making gel cells is similar to AGM batteries. However, instead of utilizing the Absorbent Glass Material that AGM batteries use, gel batteries make use of gelled electrolytes. The solidified electrolytes reduce the risk of spillage and evaporation that results in corrosion problems. This technology uses a small amount of solidified electrolyte to keep the acid immobile. Gel batteries have longer lifespan than traditional batteries, this is due to the fact that the gelled solution can hold their charge for a longer time. This battery type is also durable and can withstand extreme ranges in temperature. The Gel batteries like the lead acid batteries they have a depth of discharge of 50% which is lower than that of lithium.

Advantages
• Less chance of spilling the acid
• Lighter than ordinary batteries
• Can be used in cold weather
• Maintenance free
• Air transportable
• No corrosion
• Installs upright or on its side
• Superior deep cycle life
• Very low to no gassing (unless overcharged)
• Compatible with sensitive electronic equipment
• Superior shelf life
• Rugged and vibration resistant
• Very safe at sea with no chlorine gas in bulge (due to sulfuric acid and salt water mixing)

Disadvantages
• Slower charging rate and voltage than ordinary batteries
• Higher initial cost
• Heavier weight than Lithium battery
• Water cannot be replaced if continually overcharged
• Automatic temperature sensing, voltage- regulated chargers must be used
• Charge voltage must be limited to extend life

3. LEAD ACID BATTERIES

Lead acid batteries uses sponge lead and lead peroxide for the conversion of the chemical energy into electrical power.
The graph below is showing how a lead acid battery discharges.

The graph below is showing how a lead acid battery charges.

Advantages
• Inexpensive and simple to manufacture.
• Mature, reliable and well-understood technology – when used correctly, lead-acid is durable and provides dependable service.
• The self-discharge is among the lowest of rechargeable battery systems.
• Capable of high discharge rates.

4. SALTWATER BATTERIES
These batteries have a different chemistry than other batteries like lead acid, lithium and Gel batteries. The primary ingredient for conducting electricity in these batteries is Sodium, the same element used in making table salt. In saltwater batteries, a liquid solution of salt water is used to capture, store, and eventually discharge energy

Advantages
• They are safe, the saltwater in the system means that there is essentially no fire risk with saltwater battery technology. Additionally, saltwater batteries don’t use the same toxic metals and other materials that most lead-acid or lithium-ion batteries use.

• They have a long lifespan; saltwater batteries have long lifecycles, which means they can be used for longer periods of time than many other battery options on the market. This has many implications – for example, you likely wouldn’t have to replace a saltwater battery as often as you would with most lithium-ion batteries, which can save you money in the long run.

• They are easily recyclable, because they lack availability of heavy metals and toxic materials.

Disadvantages
• They are expensive compared to the market leading technology like lithium batteries.
• They have a lower energy density than other batteries like lithium meaning they store less energy in the same amount of space.
• They are useful in installations where space is not an issue.

 

Compiled by:

Naison Charapuse