Fault Ⅰ: Fault Features of Plate Vulcanization
Fault feature
A layer of white coarse grain of PbSO4 is generated on negative plate and good plate is black, which can not be converted into PbO2 and Pb in normal charging.
（1）When vulcanized battery discharges, voltage is reduced sharply down to terminate voltage prematurely, and battery capacity would be reduced. When there is slow or no reaction during charging, voltage rises fast but capacity rises slowly, its specific gravity is below normal value and will be low for a long time.
（2）When the voltage of unit cell is rising too fast during charging, electrolyte temperature of the battery will rise rapidly but density will increase slowly. And bubbles will be produced prematurely even as soon as charging begins.
Reason of Fault
（1）Long-term insufficient charging or failure of timely charging of battery will lead to some PbSO4 of the plate dissolved in the electrolyte. And when the temperature is higher, its solubility is greater. When temperature decreases, its solubility decreases either and PbSO4 dissolved will precipitate out and crystallize again on the plate to form sulfide.
（2）When liquid level of electrolyte is too low, upper plate is exposed to air and oxidized. Electrolyte, fluctuating and contacting with oxidized part in driving, will generate large-grained PbSO4 hardening layer to vulcanize the upper part.
（3）Long-term excessive discharge or deep discharge of low current will generate PbSO4 within pores of active substances in deep part of the plate.
（4）When charging is not complete for new batteries, the active sustenance is not fully reduced.
（5）When density of electrolyte is high and its composition is not pure, external temperature will change dramatically.

Fault Ⅱ: Falling Off of Active Substance
Fault Feature
It mainly refers to falling off of PbO2 from positive plate. Positive plate is taupe and good plate is bronzing. When charging, the reaction is obvious with many bubbles. But at the same time the capacity rises slowly and the accumulator capacity decreases. Brown substance can be seen from liquid adding hole and electrolyte is turbid (kind of red) when charging.
Reason of Fault
（1）When battery charging current is too large and the electrolyte temperature is too high, the active substance will expand and become soft and easy to fall off.
（2）When overcharging too often, plenty of gas will escape from plate pore and produce pressure in plate pore, thus leading to the falling off of active substance
（3）Frequent heavy load discharge and low temperature will make plate bending and deformation, which often leads to active substance falling off.
（4）When electrolyte is not pure and it contains nitric acid ingredients, the falling off of active substance will be accelerated.
（5）Vehicle turbulence and vibration when driving.

Fault Ⅲ: Corrosion of Plate Grid
Fault Feature
Mainly features positive plate grid corrosion, presenting decay state; blocky accumulation of active substances will occur between the septum and the battery output capacity will be decreased.
Reason of Fault
（1） Battery overcharges too often and oxygen produced at the positive plate oxidizes the grid.
（2）High density and temperature of electrolyte as well as long time charging will accelerate plate corrosion.
（3）Impure electrolyte
（4）Low temperature and heavy load discharge.

Fault Ⅳ: Short-Circuit of Plate
Fault Feature
Direct contact between positive and negative plate or other conductive substance connection is called short-circuit of plate.
(1)Low open circuit voltage and closed circuit voltage (discharge) will soon reach final voltage.
(2)When discharging in high current, terminal voltage decreases dramatically to zero.
(3)When the circuit is open and electrolyte density is low, electrolyte freezing phenomenon will appear in low temperature environment.
(4)When charging, voltage increases slowly and always stays at low value (sometimes drops to zero). The temperature of electrolyte rises quickly and its density rises slowly or almost undergoes no change. When electrolyte density dropped to below 1.15, few bubbles appear or appear very late when charging.
Reason of Fault
(1)If septum quality is bad or has defect, the active substance of plate can go through, which leads to connection or direct connection of positive and negative plate.
(2)Septum movement leads to the connection of positive and negative plate.
(3)Active substance on the plate expends and falls off and due to its excessive loss, positive and negative plate bottom edge or side edge is connected with sediments, which causes positive and negative plates connection.
(4)Conductive object falls into the battery and causes the connection of positive and negative plate.
(5)“Lead flow” formed by failure to removal welding group, or "lead pellet " exists between the positive and negative plate in assembly, septum is damaged in the process of charging and discharging and positive and negative plates is thus connected.
(6）Plate dendrites generate short-circuit.

Fault Ⅴ: Self- discharge
Fault Features
When battery is under no load condition, the phenomenon of automatic power disappearance is called self-discharge.
Reason of Fault
（1）Electrolyte is impure, and battery plate substance is impure, so potential difference will be formed between impurities and the plate and impurities attached to the plate, and partially discharge through the electrolyte will occur.
（2）Long-term storage of the battery and subsidence of sulfuric acid causes potential difference between its top and bottom, which leads to self- discharge.
（3）The overflow of battery electrolyte accumulates on the surface of the battery cover, forming access between positive and negative column.
（4） Falling off of active substance on the plate and excessive bottom sediment will cause short-circuit of plate.

Fault Ⅵ: Cell Polarity Reversed
Fault Feature
The original positive plate of cell becomes negative plate, and the negative plate becomes positive plate. At this moment, the voltage of battery falls rapidly and the capacity thereof falls too, which is unavailable for use.
The color of plate gets abnormal. Severe phenomenon of electrode poles being assembled oppositely will lead to active material falling off and plate bending.
Reason of Fault
Don’t find faulted cell timely (such as short-circuit of plates and active material falling off). When battery discharges, this cell will firstly discharge off because of its lower capacity; with continuous discharging, discharging current of other cells will charge this cell, thus causing polarity reversal.
When charging, polarity reversal happens.


Fault Ⅶ: Active Material of Negative Plate Shrinks
Fault Features
Negative plate shrinks. Capacity of battery drops
Reason of Fault
Frequent over-discharge of battery leads to hardening of sponge lead of negative plates of battery.

Fault Ⅷ: Septum Being Damaged
Fault Feature
Battery gets short-circuit
Reason of Fault
Electrolyte temperature is too high
Natural damage due to long time use of battery

Fault Ⅸ: Amount of Electrolyte Being Reduced
Fault Feature
Internal resistance of battery rises; Terminal voltage and capacity drop.
Plates of battery exposes to the surface of electrolytic solution, thus negative plate is oxidized and hardened. After adding electrolyte, hardened plates will remain with white layer.
Reason of Fault
（1）The housing of battery has cracks.
（2）The temperature inside the battery is too high, thus most of the water evaporates, with no feeding water for a long time.
（3）Too high charging current or prolonged overcharging will lead to strong outgoing gas.

Fault Ⅹ: Internal Resistance of Battery Rises
Fault Feature
（1）Discharging voltage is low, and the voltage drops quickly.
（2）Charging voltage is high, and the temperature of electrolytic solution rises quickly when charging.
Reason of Fault
（1）Soldering quality of plate group is bad, with pseudo soldering or bad soldering of polarity terminal and connector of the battery.
（2）The sulfidation of plates gets more serious, which makes internal resistance of battery rise.
 

Fault Ⅺ: Battery Being Frozen
Fault Feature
（1）There is ice trace that lies in upper layer of electrolyte.
（2）Service life of battery is greatly shortened.
Reason of Fault
（1）Under the environment with too low temperature, battery hadn’t been charged timely after discharging.
（2）Negative plate does not dry completely during manufacturing process.

Fault Ⅻ: Cell Connector Being Damaged
Fault Feature
（1）Current disappears suddenly.
（2）Sparking
Reason of Fault
（1）Bad soldering between cell connector and cell polarity terminal; there exists pseudo soldering, and unsoldering will be caused after using for a period of time, which will lead to block circuit
（2）When dismounting battery, carelessly make black line connect the negative of battery (ground) or make positive pole and negative pole connect instantly, which lead to short circuit of battery and cause burning out of cell connectors .

Fault ⅩⅢ: Battery can’t recover performances after being charged
Fault Feature
After charging battery, its terminal voltage and capacity can’t be restored to the original value and drop obviously.
Reason of Fault
（1）Due to discharging, plates in the depth become lead sulfate, so charging is hard to be restored
（2）Due to charging or uneven coating diachylum, the counter electrode get out of shape and active material falls off.
（3）Being used under half charging state for a long time, plates of battery have been vulcanized .
（4）Impure electrolyte containing impurities leads to self discharging.

Fault ⅩⅣ: Unbalanced Battery Group
Fault Feature
The balance of serial battery group is a world problem, and there are always batteries “lagging behind” in the process of using.
Reason of Fault
There are all kinds of reasons such as production, raw materials and use.
 

Fault ⅩⅤ: Battery can’t be Charged
Fault Feature
The battery is unavailable for charging
Reason of Fault
There are all kinds of reasons such as unreliable connection of charging circuit, drying phenomenon inside the batteries or serious lack of water and the existence of irreversible sulphation.

Fault ⅩⅥ: Thermal Runaway of Batteries
Fault Feature
Batteries generates a lot of heat during charging, which leads to the deforming of its housing.
Reason of Fault
（1）“Passageway” of oxygen gets unimpeded, which makes the oxygen being generated by positive pole reach negative pole easily.
（2）Heat capacity gets reduced. In battery, water has the largest heat capacity. After the water is lost, heat capacity of battery will be reduced greatly. Generated heat makes the temperature of battery rise quickly.
（3）Since ultra fine glass fiber separator in battery will shrink after the water is lost, adhesive force between glass fiber and positive or negative pole will get worse, internal resistance will be increased and more heat will be generated during charging. Through the above process, the heat being generated from the inside of battery can only be dissipated by battery jar. If the amount of dissipated heat is less than that of generated heat, the temperature will rise, and then electric potential will be lowered in the outgoing gas process of battery. With the increased amount of outgoing gas, large amount of oxygen of positive pole will pass “passageway” to react on the surface of negative pole, a lot of heat will be generated, the temperature will be risen quickly, and forming a vicious circle. That is the so-called “thermal runaway”. When the temperature reaches over 80℃, deformation will happen.

Fault ⅩVII: Battery Leakage
Fault Feature
The electrolyte is leaked
Reason of Fault
Firstly, the seal is bad between upper cover and bottom groove or the electrolyte is leaked because of collision or the cracking of sealing compound;
Secondly, bonnet valve leaks acid or electrolyte;
Thirdly, wiring terminal leaks acid or electrolyte;
Fourthly, other parts leak acid or electrolyte.