Types of batteries commonly used in (PV) systems

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Solar batteries are batteries it is function store the electrical energy generated by photovoltaic solar panels in the brightness of the sun during daylight hours in order to use this stored electrical energy stored in the batteries during the period of absence of the evening sun

1- Lead – acid batteries

Using an electrolyte consisting of sulphuric acid .the cells can store amounts of electrical energy in a relatively small space (this energy is stored in chemical form with in lead grids mounted inside the battery) 

Flooded or wet operates by means of a liquid electrolyte (battery acid) covering all internal parts

Wet batteries produce gas when overcharging this gas must be able to escape which is why some refer to this type of battery as vented cell battery

Lead – acid battery

Flooded electrolyte advantages

•  Lowest initial cost
•  Higher cranking amps
•  Water can be added (if accessible
•  Excellent for starting applications
•  Replacements readily available
•  Good under extreme cold conditions when fully charged

 Flooded electrolyte disadvantages

•  Operates upright only
•  Shorter shelf life
•  Fewer shipping options
•  Cannot be installed near sensitive electronic equipment
•  Watering may be required (if accessible

 Flooded applications

•  Used in power vehicles
•  Used in cars
•  Used in industry for standby power
•  Used in power station for standby power

2- Gelled batteries (gel)

Initially designed for electronic instruments and consumer devices, gelled lead-acid batteries typically use lead-calcium grids. The electrolyte is 'gelled' by the addition of silicon dioxide to the electrolyte, which is then added to the battery in a warm liquid form and gels as it cools

Gel Batteries

,A gel battery is a storage battery that

• It is sealed using special pressure valves and should never be opened
•  It is completely maintenance – free
•  Uses gelled electrolyte
•  Uses a recombination reaction to prevent the escape of hydrogen and oxygen gases normally lost in a flooded lead – acid battery

Gelled batteries advantages

•  Totally maintenance – free
•  Leak proof
•  No corrosion
•  Superior deep cycle life
•  Installs upright or onside (side installation may lose about 10% capacity
•  Very low to no gassing
•  Compatible with sensitive electronic equipment
•  Superior recharge ability (from 0% to 90% in 3.5 hours
•  No recharge current limitation 13.8 volts
•  Rugged and vibration – resistant
•  Very safe at sea
•  Operates in wet environments – even under 30 feet of water
•  Lowest cost – per – month (cost ÷ life cycles

 Gelled batteries disadvantages

•  Higher initial cost
•  Heavier weight
•  Water cannot be replaced if continually over charged
•  Automatic temperature - sensing voltage – regulated chargers must be used
•  Charge voltage must be limited to extend life (13.8 to 14.1 volts maximum)

3- Absorbed glass mat (AGM

Another sealed, or valve regulated lead-acid battery, the electrolyte in an AGM battery is absorbed in glass mats that are sandwiched in layers between the plates. However, the electrolyte is not gelled. Similar in other respects to gelled batteries, AGM batteries are also intolerant to overcharge and high operating temperatures

AGM Technology

,An AGM battery is a battery that

•  It is sealed using special (pressure valves and should never be opened
•  It is completely maintenance – free
•  Has all of it is electrolyte absorbed in separators consisting of a sponge – like mass of matted glass fibers
•  Uses a recombination reaction to prevent the escape of hydrogen and oxygen gases normally lost in flooded lead – acid battery (particularly in deep cycle applications 

Deep discharge	Starting batteries	Deep cycle batteries
100%	12-15 cycle	150-200 cycle
50%	100-120 cycle	400-500 cycle
30%	130-150 cycle	1000 cycle

Performance cycle for starting batteries and deep cycle batteries

 Absorbed electrolyte advantages

1) Totally maintenance – free

2) Leak proof

3) No corrosion

4) Installs upright or onside (side installation may lose about 10% capacity)

5) Lower cost than gel cell batteries

6) Compatible with sensitive electronic equipment

7) Very low to no gassing 

8) Excellent for starting and stationary applications

9) Superior for shorter duration higher rate discharges

10) Superior shelf life

11) Superior recharge ability (from 0% to 90% in 3.5 hours)

12) Rugged and vibration – resistant

13) Very safe at sea

14) Operates in wet environments even under 30 feet of water

Absorbed electrolyte disadvantages

1) Shorter cycle life than gel in very deep cycle applications

2) Water cannot be replaced if continually overcharged

3) Automatic temperature - sensing voltage – regulated chargers must be used

4) Charge voltage must be limited to extend life (14.4 to 14.6 volts maximum)

Different between GEL and AGM.

• In a gel battery the electrolyte does not flow like a normal liquid
• Gel faster than an AGM batteries as the temperature drops below 32 degree
• GEL and AGM batteries protects the plates during heavy deep – discharges
• The GEL battery is more starved giving more protection to the plate
• Gel battery suited for super – deep discharge applications (because the physical properties of the gelled electrolyte
• AGM are all of the liquid electrolyte is trapped in the sponge – like matted glass fiber separator material
• AGM excel for high current – high power applications and in extremely cold environments