Lead Acid Batteries @ Detailed...

In solar technology or building solar off-grid systems this lead acid batteries  are most known batteries because of its low price but effective performance.This is much practical way of storing sun energy.This is the same type of battery you used in car batteries.

This is ideal for home system where shed is available because heat drastically reduce the lifespan of these batteries.

Construction : Please Follow this link: Lead Acid Batteries

Electrochemistry : 

In the discharged state of a lead acid battery both the positive and the negative terminals become lead(II) sulfate (PbSO
4), and the electrolyte become more water by loosing the dissolved acids.The discharge process is driven by the conduction of the electrons from negative terminals to positive terminals.In the fully charged state, the negative plate consists of lead, and the positive plate lead dioxide, with the electrolyte of concentrated sulfuric acid.Overcharging with high charging voltages generates oxygen and hydrogen gas by electrolysis of water, which is lost to the cell. The design of some types of lead-acid battery allow the electrolyte level to be inspected and topped up with any water that has been lost.

Negative Plate Reaction : 

Pb(s) + HSO−
4(aq) → PbSO
4(s) + H+(aq) + 2e⁻

^{Positive Plate Reaction :}  

^{PbO
2(s) + HSO−
4(aq) + 3H+(aq) + 2e− → PbSO
4(s) + 2H
2O(l)}

^{Total  reaction :} 

^{Pb(s) + PbO
2(s) + 2H
2SO
4(aq) → 2PbSO
4(s) + 2H
2O(l)}

Types of Lead-acid Battery :

• Deep-Cycle Lead Acid Batteries.
• Flooded Lead Acid Batteries 
• VRLA Lead Acid Batteries 
• AGM Lead Acid Batteries 
• Gel Lead Acid Batteries 

Deep-Cycle Battery : Almost every battery used in Solar System are Deep-Cycle Batteries, this is one kind of lead-acid batteries designed to discharge high in capacity almost 45%~75%. In simple language deep-cycle battery is highly dis-chargeable batteries than other batteries i.e you can drain out much energy without harming their lifespan.The best lifespan vs cost method is to keep the average cycle at about 45% discharge. There is an indirect correlation between the depth of discharge (DOD) of the battery, and the number of charge and discharge cycles it can perform.

This deep-cycle batteries basically two types :  i)  Flooded Type ii) VRLA Type

Flooded Lead-acid batteries : The term "flooded" is used because this type of battery contains a quantity of electrolyte fluid so that the plates are completely submerged. The electrolyte level should be above the tops of plates which serves as a reservoir to make sure that water loss during charging does not lower the level below the plate tops and cause damage. Flooded batteries will decompose some water from the electrolyte during charging, so regular maintenance of flooded batteries requires inspection of electrolyte level and addition of water. Major modes of failure of deep-cycle batteries are loss of the active material due to shedding of the plates, and corrosion of the internal grid that supports active material. The capacity of a deep cycle battery is usually limited by electrolyte capacity and not by the plate mass, to improve life expectancy.


A valve-regulated lead-acid battery (VRLA battery) : This is also called sealed lead-acid (SLA). Due to their construction, the Gel and Absorbent Glass Mat (AGM) types of VRLA can be mounted in any orientation, and do not require constant maintenance. The term "maintenance free" is a misnomer as VRLA batteries still require cleaning and regular functional testing. They are widely used in large portable electrical devices, off-grid power systems and similar roles, where large amounts of storage are needed at a lower cost than other low-maintenance technologies like lithium-ion.

AGM (Absorbent glass mat) : This is one type of VRLA battery. AGM batteries differ from flooded lead acid batteries in that the electrolyte is held in the glass mats, as opposed to freely flooding the plates.The plates in an AGM battery may be any shape. Some are flat, others are bent or rolled. AGM batteries, AGM batteries presents better self discharging characteristics than conventional batteries in different range of temperatures.Very thin glass fibers are woven into a mat to increase surface area enough to hold sufficient electrolyte on the cells for their lifetime. The fibers that compose the fine glass mat do not absorb nor are they affected by the acidic electrolyte. These mats are wrung out 2–5% after being soaked in acids, prior to manufacture completion and sealing.As with lead-acid batteries to maximize the life of AGM battery is important to follow charging specifications and a voltage regulated charger is recommended. and also there is a correlation between the depth of discharge (DOD) and the Cycle life of the battery with differences between 500 and 1300 cycles depending on deep of discharge.

Gel battery : A modern gel battery (also known as a "gel cell") is a VRLA battery with a gelified electrolyte; the sulfuric acid is mixed with fumed silica, which makes the resulting mass gel-like and immobile. Unlike a flooded wet-cell lead-acid battery, these batteries do not need to be kept upright. Gel batteries reduce the electrolyte evaporation, spillage (and subsequent corrosion problems) common to the wet-cell battery, and boast greater resistance to shock and vibration. Chemically they are almost the same as wet (non-sealed) batteries except that the antimony in the lead plates is replaced by calcium, and gas recombination can take place.This sealed, non-spill feature made it possible to make very small VRLA batteries (1 –12 Amp hr. range) that fit into the growing portable electronics market. A large market for inexpensive smaller sealed lead acid batteries was generated quickly. Portable TV, light for news cameras, children's toy riding cars, emergency lighting, and UPS systems for computer back-up, to name a few, were powered with small sealed VRLA batteries.

Advantages of Lead Acid Batteries :

• Low cost compared to other batteries like Lithium-Ion.
• Robust,Reliable and Tolerant to abuse.
• Tolerant to overcharging.
• Low internal impedance.
• Can deliver very high currents.
• Can be left on trickle or float charge for prolonged periods.
• Wide range of sizes and capacities available.
• Many suppliers world wide.
• The world's most recycled product. 

Disadvantages of Lead Acid Batteries :

• They take up a lot of space, and many of them emit hydrogen gas. Hence the need for a battery-shed.
• They have a low cycle life (1000-3000 cycles), which means that, depending on how many time a day you charge and discharge them, they will only last  2-8 years tops.
• They generally have a depth of discharge of around 60%. This means that you can only use 60% of their capacity - otherwise you cripple their lifespan.
• Their performance figures are quoted at around 20 ºC ambient - meaning that if your battery shed gets hotter than this  their performance and lifespan will degrade.
• Sulphation may occur if a battery is stored for prolonged periods in a completely discharged state or very low state of charge, or if it is never fully charged.
• Contain hazardous materials  like lead, so not very environment friendly.
• Danger of overheating during charging, not suitable for fast charging.

Note : The Lead Acid batteries are worldly renown batteries, they are high is use due to their lower in cost & availability but still  better performance but this technology is getting outdated because of new coming like Lithium Ion or flow batteries or Ni-Cd Batteries which are higher in cost, so it depends on ones budget to determine how they will go. 

Hope You Like this post (JajakAllahu khair)



Other Posts : 

• Flow Batteries 
• Lithium-ion Batteries