Sealed Maintenance-Free Batteries
Updated: Dec 30, 2019
The battery is a major component of the inverter power system. It is from the batteries that the DC is drawn from by the inverter and converted into AC for use in appliances and it is in the batteries that the DC is stored for future use. Batteries are often sold separately from the inverters and have to be bought and installed separately. As batteries contain liquid acid, there are always concerns about safety and constant maintenance. With maintenance-free batteries, these concerns are addressed and eliminated.
Components of Inverter Batteries
Batteries convert chemical energy directly to electrical energy. Its components are constructed in an arrangement that is described as ‘cell’. These components include
Electrolyte. The electrolyte in most wet-cell batteries is sulphuric acid diluted with distilled water. Inverter batteries are mostly wet-cell batteries. The two types of lead-acid batteries that use an acidic electrolyte are wet cell and sealed. Wet cell use liquid electrolyte; sealed batteries use either a gel or liquid electrolyte absorbed into fibreglass matt.
Terminals. The terminals are the pure lead at the negative side and the PbO2 on the positive side both constructed as ‘plates’. With acid electrolyte and lead plates, wet-cell batteries are therefore known as ‘lead-acid’ batteries.
Separators. Separators between the positive and negative plates prevent short-circuit through physical contact, mostly through dendrites but also through shedding of the active material. Most separators are made of rubber. They are more stable in battery acid and provide valuable electrochemical advantages that other materials cannot.
According to their plate technology, a battery can either be Flat Plate or Tubular. Read all about inverter batteries and the differences between flat plate and tubular batteries here.
Tubular batteries have 20% more electrical capacity than flat plate batteries of comparable size and weight. Tubular batteries also provide up to a 30% longer service life than flat plate batteries.
Based on the nature of their electrolytes, batteries can either be
Flooded Lead Acid (FLA)
Valve Regulated Lead Acid (VRLA)
Flooded Lead Acid
Flooded lead acid (FLA), is the traditional battery technology. They have a relatively long service life. They are the most resistant to damage when accidentally over-charged. They support relatively higher rates of charge and discharge.
The major downside of FLA batteries is that the require constant checks and maintenance to achieve optimum performance. Also, they release hydrogen gas when charging which is can lead to explosions. They must be installed in a well-ventilated area, and cannot be placed in living space.
Valve-Regulated Lead Acid
The VRLA batteries are batteries constructed to eliminate the need for constant checks and to eliminate the emission of fumes or gases on a continuous basis and the attending dangers. Thus they are also know as Sealed Maintenance Free (SMF).
They are completely sealed and therefore eliminate the risk of acid spillage during transportation. Due to their construction they can be mounted in any orientation.
This is done in three ways
FLA batteries have openings at top from where distilled water is to be added for maintenance and safe running. This can be sealed off and replaced with a self-regulating valve.
By making the acid electrolyte into gel-like liquid. This is done by adding silica dust to the electrolyte, forming a thick putty-like gel. A battery constructed in this way is called a Gel Cell battery.
By holding the acid electrolyte in glass mats, as opposed to freely flooding the plates. A battery constructed in this way is called Absorbent Glass Material (AGM) battery.
The AGM and Gel Cell are the two main types of Maintenance-Free batteries. While they have a lower lifespan and operate at a lower efficiency than the properly maintained FLA, they will however last much longer than a poorly maintained FLA battery. They are cheaper, easier to transport and store. They can be stored in living areas. They can operate in higher temperatures without the risk of causing explosions. They are the safest battery designs. They emit gases only when severely overcharged. They eliminate worries about explosions and constant maintenance.
At SolarKobo, we help our clients make the best choice of batteries according to their peculiar needs and budget.