FAQ – SECTIONS
Question: What is VRLA battery, Gel battery and AGM battery?
Answer: A VRLA battery (valve-regulated lead-acid battery), more commonly known as a Sealed Lead Acid battery (SLA battery) or Maintenance Free battery (MF battery), is a type of lead-acid rechargeable battery. Due to their construction, they can be mounted in any orientation, and do not require constant maintenance. During the normal operation, there are very less gas released from the battery due to the high efficiency of inner gas recommendation, so there is very less water loss during normal operation. So the VRLA battery are not required for filling water or acid during normal operation. The term “maintenance free” is a misnomer as VRLA batteries still require cleaning and regular functional testing. They are widely used in electric vehicles, 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.
There are two primary types of VRLA batteries, Gel type and AGM Type. Gel battery add silica dust to the electrolyte, forming a thick putty-like gel. These are sometimes referred to as “silicone batteries”. AGM, short for “absorbed glass mat”, batteries feature fiberglass mesh between the battery plates which serves to contain the electrolyte. Both designs offer advantages and disadvantages compared to conventional batteries, as well as each other.
Question: What is Polymer Gel battery or so called “AGM + Gel battery”?
Answer: Polymer Gel battery or AGM+Gel battery, sometimes it has also been called as “semi-gel battery”, is developed based on AGM technology but the difference is the electrolyte. Polymer Gel battery has utilized polymer Gel in the electrolyte and it offers the battery better high/low temperature performance and cycle performance compare to AGM battery.
Question.What is the 2hr, 3hr, 5hr, 10hr… rate mentioned while the VRLA battery capacity is given?
Answer: Normally, the VRLA battery’s capacity is given at Ampere-hours, a unit of measurement for battery capacity, it is obtained by multiplying a discharge current in amperes and a time in hours. For example, electric bike battery 6-DZM-20, 12V 20Ah/2hr, it is defined at 2hr rate and the capacity is 20Ah, which means that the battery can be discharge at a constant current 10 Amperes for 2 hours to the end voltage (10.5V/Block). For the same battery, if the battery is discharged at 7 Amperes to end voltage, the discharge time may reach 3 hours, so the battery’s 3hr rate capacity is 7 Amperes X 3 hours = 21Ah, etc.
Question: What is the service life of a VRLA battery?
Answer: A VRLA battery’s service life mostly depend on the design, working temperature, sufficient charging after each discharge and regular re-charging. For example, electric bike battery 6-DZM-20, it may reach 600 cycles @ 80% if the battery is proper charged and the working temperature is at 25 Degree C, but in actual working condition, the cycle life may not reach 600 cycles due to the variable conditions, i.e. high temperature, insufficient charging, etc.
Question: What if the battery is overcharged?
Answer: Overcharge is a problem which originates from insufficient battery capacity causing the batteries to be overworked. Discharges deeper than 50%significantly shorten the Cycle Life of a battery without increasing the usable depth of cycle. Infrequent or inadequate complete recharging can also cause overdischarge symptoms called SULFATION. Despite that charging equipment is regulating back properly, overdischarging symptoms are displayed as loss of battery capacity and lower than normal specific gravity. Sulfation occurs when sulfur from the electrolyte combines with the lead on the plates and forms lead-sulfate. Once this condition becomes chronic, marine battery chargers will not remove the hardened sulfate. Sulfation can usually be removed by a proper desulfation or equalization charge with external manual battery chargers. Sealed AGM batteries should be brought to 2.35 volts per cell and then discharged to 1.75 volts per cell and their this process must be repeated until the capacity returns to the battery. Gel batteries may not recover. In most cases, the battery may be returned to complete its service life.
Question: How can I evaluate the health and charge state of a battery?
Answer: Routine battery examinations divulge irregularities in the charging system as well as in the batteries. The principle method is to examine the electrochemistry of the battery through hydrometric electrolyte inspection. As previously discussed, this important examination cannot be accomplished with sealed absorption or gel batteries. Voltage readings alone require experience to interpret. Hydrometric readings will uncover early warnings of overcharging or overdischarging before batteries are damaged. The state-of-charge and reliability of a lead acid battery can best be determined by the specific gravity of the electrolyte measured directly with a common bulb-type hydrometer with a glass float. We do not recommend the ball float type hydrometer. Specific gravity is a unit of measurement for determining the sulfuric acid content of the electrolyte. The recommended fully charged specific gravity of marine batteries is 1.255 to 1.265 taken at 80ĄăC More than .025 spread in readings between fully charged cells indicates that the battery may need an equalization charge. If this condition persists, the cell is failing and the battery should be replaced. Since water has a value of 1.000, electrolyte with a specific gravity of 1.260 means it is 1.260 times heavier than pure water while pure concentrated sulfuric acid has a specific gravity of 1.835.
Question:What information required for sizing or selecting a proper battery for my system?
Answer: When you are sizing or selecting a proper battery for your system, i.e. energy storage system, electric vehicles, etc., you have to consider the factors mentioned below:
-The system voltage of the battery bank
-The power or current of the load (or the power of electric motor for electric vehicle)
-The working condition, i.e. working temperature, charging condition, etc.
-The required back-up time of the battery bank (or the maximum voyage and speed of the electric vehicle if the battery is used for electric vehicle)
-The maximum discharge power or current, as well as the time of at such maximum discharge power or current
-The required service life
-Other information required from the manufacturer