Solar Batteries

iSustain Australia offers a range of deep cycle batteries that are ideal for photovoltaic and alternative energy applications.
Practically all solar batteries used in PV systems and most backup systems are lead-acid type batteries, this includes the standard flooded wet cell battery, dry gel/dry cell, sealed and agm (absorbed glass mat). A deep-cycle battery is designed to deliver a consistent voltage as the battery discharges and can be charged with a lower current than regular batteries making them ideal for solar system set ups.

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Wet Cell Batteries

Wet Cell, or Flooded batteries are the most common lead-acid battery in use today. Wet cell deep cycle batteries are one of the best storage solutions for the average Off grid system. They can be forgiving to a point and are not as delicate as the Gel and AGM's when it comes to an overcharge situation. The cost and life cycle is certainly lower than the alternatives. Wet cell deep cycle batteries have thick lead plates that are alloyed with antimony, and are flooded with an electrolyte and water mix.

The electrolyte levels must be checked monthly and topped off with distilled water. Wet cell batteries can be ruined by not maintaining proper electrolyte levels. Wet cell batteries should never be installed in living areas, and should be stored in a compartment with ventilation. This is due to the gas that is given off as a natural result of charging. High quality deep-cycle wet cell batteries will offer good performance and are available in many dimensional sizes and Ah capacities.

 

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Gel Cell Batteries

A gel cell is a VRLA lead-acid battery with a gelified electrolyte.
VRLA stands for valve-regulated lead-acid and is the designation for low-maintenance lead-acid rechargeable batteries. Because of their construction, VRLA batteries do not require regular addition of water to the cells.
VRLA batteries are commonly further classified as:
• Absorbent glass mat battery
• Gel battery

Gel cell batteries are often referred to as sealed lead-acid (SLA) batteries due to their non-leaking containers, but they are not completely sealed, the valve regulation system allows gas to be expelled. Unlike a traditional wet cell lead-acid battery, these batteries do not need to be kept upright and are non-spillable, therefore can be operated in virtually any position. However installation upside down is not recommended.
As Gel cells are sealed and cannot be re-filled with electrolyte, controlling the rate of charge is very important, they are prone to damage if gassing is allowed to occur.
They must be charged at a slower rate (C/20) to prevent excess gas from damaging the cells. Gel cells use slightly lower charging voltages than flooded cells and thus the set-points for charging equipment have to be adjusted. Most good quality inverters commonly used in solar electric systems can be set to limit charging current to the batteries. Gel cells can be used in virtually any flooded wet cell application (in conjunction with well-regulated charging) as well as applications where wet cells cannot be used.
Because of their unique features and benefits, gel cells are particularly well suited for:

• Deep Cycle Deep Discharge Applications (Portable Power, Electronics, Solar Applications)
• Standby and Emergency Backup Applications (UPS, Emergency Lighting)
• Unusual and Demanding Applications (Air-transported equipment, Marine Starting)

 

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AGM Batteries

Absorbed Glass Mat (AGM) batteries are the latest step in the evolution of lead-acid batteries. AGM 's are typically VRLA, valve-regulated lead-acid and are a type of low-maintenance lead-acid rechargeable battery. Because of their construction, VRLA batteries do not require regular addition of water to the cells.
VRLA batteries are commonly further classified as:
• Absorbent glass mat battery
• Gel battery

Instead of using a gel, an AGM uses a fiberglass like separator to hold the electrolyte in place. These types of batteries have all the advantages of gel cell batteries, but can take much more abuse. They are also called "starved electrolyte", as the mat is about 95% saturated rather than fully soaked. That means that they will not leak acid even if broken.

Some advantages over gel cells and flooded deep cycle batteries:
• they cannot spill, even if broken, as all electrolyte (acid) is contained in the glass mats. In addition, since there is no liquid to freeze and expand, they are practically immune from freezing damage.
• charging voltages are the same as for any standard battery - no need for any special adjustments or problems with incompatible chargers or charge controls.
• low self-discharge - from 1% to 3% per month is usual. This means that they can sit in storage for much longer periods without charging than standard batteries.

Basically, an AGM can do anything a gel cell can, only better. However, since they are also sealed, charging has to be controlled carefully or they can be ruined. AGM batteries are superior for marine and RV applications.

 

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