(1) What is a valve-regulated maintenance free lead-acid battery (VRLA)?
As opposed to traditional flooded batteries, valve-regulated maintenance free lead-acid batteries do not require maintenance. VRLA’s are sealed to prevent any acid leakage or dissipation. In addition, one-way safety valves automatically release excess gases if pressure exceeds safety limits. This allows the battery to maintain healthy pressure levels without outside support.
(2) What types of valves regulate a maintenance free lead-acid battery?
Currently, there are two types of lead-acid batteries: general type batteries (AGM) and Gel batteries. AGM batteries utilize a fiberglass mat to immobolize liquid lead electrolytes; the electrolytes are absorbed on the plate and cannot flow into the battery. Gel batteries utilize silica and other gelling agents to solidify and absorb the electrolytes, forming a thick putty-like gel. These can be used as starting batteries, stationary batteries, traction type batteries, etc.
(3) What is the rated capacity of the battery?
Due to the design of the battery, the battery releases at the lowest capacity. Expressed by the symbol C, capacity is strongly influenced by the discharge rate, which is the number expressed directly after C (such as C2=50Ah). This equation expresses that with a 20 hour discharge rate, the capacity of the battery is 50 amps/hour. Informally, with the capacity of 50 amps/hour, a battery in full charge can be discharged for 50 hours with 1 amp of current.
(4) What is open-circuit voltage?
Open-circuit voltage (OCV) refers to a battery which is disconnected from any circuits and has no external currents flowing between terminals. An electric meter measures the voltage between the two terminals; and though the OCV cannot be utilized as a standard to measure battery voltage, the differences of electrical potential can be compared to one another to determine the state of the charged battery.
(5) What is cut-off voltage of the battery?
The cut-off voltage is the allowable minimum voltage of battery discharge. At this point, additional discharge can lead to chemical instability and cause harm to the battery plates, resulting in a reduced battery lifetime. The cut-off voltage directly corresponds with the discharge rate of the batter- the greater the discharge current is, the less a battery can hold capacity.
(6) What is end-of-charge voltage of the battery?
When the battery is fully charged, the active materials of the lead plates have reached saturation; the battery voltage will not increase, even with additional charging.
(7) What is the depth of discharge?
During battery use, the battery capacity will discharge a percentage of it rated capacity. This is called depth of discharge (DOD); DOD at 60% means the discharged capacity of the battery has reached 60%, and 40% of its capacity remains.
(8) What is the “float use” and recycling usage of batteries?
Recycling: The battery is used as a direct power supply for equipment, which mainly applies to circulation charge and discharge of electrical hand tools, portable electronics, etc.
Float Use: The battery is used as an emergency power supply for equipment to provide emergency power or energy storage in the event of a power outage (ex: power plant, UPS power supply, emergency lighting, etc.).
(9) What are the methods of battery charging?
The main methods of battery charging are constant-current charging, constant-voltage charging, constant-current with limited voltage charging, equalizing charging, float charging, and pulse charging.
(10) What are float charging and equalizing charging?
Float charging: A battery powered by a circuit in the event that the normal power supply is interrupted. The terminal is always connected to a constant-voltage power supply to maintain the battery’s charge.
Equalizing charging: It is a deliberate overcharge to ensure that each monomer of battery is equally charged.
(11) What are the purposes of utilizing sulfur on lead plating?
The purposes are listed below:
① The battery charge is insufficient or the initial charge was interrupted;
② The battery was consistently undercharged;
③ Failure to charge timely after discharge;
④ Frequent over-discharging or over-charging;
⑤ The density of electrolytes or high temperatures-lead sulfate is formed and not easy to eliminate;
⑥ The battery was stored away for long periods of time without being regularly charged;
⑦ Impure electrolytes, which caused rapid self-discharge.
(12) What are the requirements for proper battery storage?
Proper storage requires an environment with stable flooring, good ventilation, dry conditions, and lower temperatures (around 25 degrees Celsius). Even when in storage, the battery should be charged every 3 months.

2.The maintenance of lead-acid battery

(1) Routine maintenance
Battery owners often mistakenly believe that VRLA’s are maintenance-free, when in fact, battery upkeep and maintenance are necessary to ensure optimal function. It is recommended to regularly keep operating records and to check batteries monthly for the following:
①The floating voltage of batteries and battery groups,
②The temperatures of the shell and pole of the battery,
③The battery shell shows no signs of deformation or leakage,
④Any seepage or acid fog collecting near poles or valves,
⑤If the connection strip is tightened there will be a loose connection with the battery, which increases the resistance of the joint during large current charging and discharging. This can lead to overheating of the connector or even melting of the battery core. If not resolved, this may start a fire.
(2) Internal resistance of the battery
If the battery has been running for more than 4 years, the internal resistance has increased, which may cause the different internal resistance levels for each battery; in this case, the client should ask the manufacturer to reactivate the battery in order to reduce the internal resistance and regain capacity.
(3) Battery voltage
Some manufacturer thicker plates to improve battery service life, but it's difficult to control the uniformity of battery voltage. It usually needs to run for more than 2 years before the voltage can achieve uniformity. In addition, low battery voltage can also be to lightly discharge the whole battery group. Find out whether the battery discharge voltage has significantly decreased- if so, contact the manufacturer to dispose of it.
(4) Battery capacity testing
If the battery has been running for more than 3 years, annual discharge tests should be conducted if releasing 30-40 % of rated capacity (as according to actual discharge rate calculation). Conduct a capacity discharge test every three years if the battery is releasing 80% of the rated capacity.
(5) Timely charging
The reaction of salinization begins during battery discharge, transforming the properties of lead sulfate into gel-like lead and lead dioxide over time. If the battery is discharged for more than 12 hours, the lead sulfate crystals become larger crystal particles again, irreversibly transforming into sulfate.
(6) Full discharge on regular basis
Under floating charge conditions, the battery should be fully discharged on a regular basis to refresh the battery’s plating and test the actual capacity of the battery.
(7) Do not storage with less electricity
If the battery has not been utilized, it should be fully charging before being put into storage, and at least once a month while in storage.
(8) Do not mix old and new batteries together
Avoid mixing old and new batteries as doing so could cause different loading currents.
(9) Working environment
VRLA batteries should be installed in a clean environment away from heat or flammable materials. We recommend a room temperature between 15-35 degrees Celsius, preferably in an air-conditioned environment at 25 degrees Celsius. Moisture, poor ventilation, solar radiation, unstable flooring can shorten the valve-regulated battery life. A clean environment, good ventilation, ambient temperatures, and protection from direct sunlight are necessary. In addition, battery maintenance requires a large or ample sized space.