Gel Batteries Technical Manual
Gel Batteries Technical Manual
Version 1.1
Contents
1.
2.
3.
4.
Construction of Gel batteries
Reactions of Gel batteries
Gel batteries characteristics
3.1 Battery capacity
3.2 Battery voltage
3.3 Battery self discharge
3.4 Battery internal resistance
3.5 Battery life
Operation of Gel batteries
4.1 Preparation prior to operation
4.2 Charging methods for standby use batteries
4.3 Charging methods for cyclic use batteries
4.4 Discharge protection of batteries
4.5 Equalization charging
4.6 Thermal runaway phenomena
5.
Maintenance of Gel batteries
5.1 The storage and maintenance of batteries
5.2 The detection and remedy of “defective” batteries
5.3 The recycle of batteries
1
廣隆光電科技股份有限公司 Kung Long Batteries Industrial Co., Ltd.
南投市自立三路 6 號 NO. 6 TZU-LI 3 RD NANTOU CITY TAIWAN R.O.C. TEL:+886-49-2254777~8 FAX:+886-49-2255139
Gel Batteries Technical Manual
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1. Construction of Gel batteries
Positive plate: Pasting the lead paste onto the grid, and transforming the paste
with curing and formation processes to lead dioxide active material. The grid is
made of Pb-Ca alloy, and the lead paste is a mixture of lead oxide and sulfuric
acid.
Negative plate: Pasting the lead paste onto the grid, and transforming the paste
with curing and formation processes to sponge lead active material. The grid is
made of Pb-Ca alloy, and the lead paste is a mixture of lead oxide and sulfuric
acid.
Electrolyte: A high purity gel acid solution, which is a reactant in the battery’s
main reaction and the conducting ions for electricity.
Separator: The absorbent glass mat, which is placed between the positive and
negative plates to prevent shorting and to store the electrolyte.
Safety Valve: A one-way valve made of chloroprene rubber, which is to prevent
the oxygen ingress into the battery and to release gas when internal pressure
exceeds 0.5kgf/cm2.
Case: A container made of ABS plastics, which is filled with plates group and
electrolyte.
2
廣隆光電科技股份有限公司 Kung Long Batteries Industrial Co., Ltd.
南投市自立三路 6 號 NO. 6 TZU-LI 3 RD NANTOU CITY TAIWAN R.O.C. TEL:+886-49-2254777~8 FAX:+886-49-2255139
Gel Batteries Technical Manual
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2. Reactions of Gel Batteries
When the lead acid battery is discharging, the active materials of both the
positive and negative plates are reacted with sulfuric acid to form lead sulfate. After
discharge, the concentration of sulfuric acid in the electrolyte is decreased, and results
in the increase of the internal resistance of the battery.
On charging, the battery reactions are reversed, i.e., the lead sulfate of the
positive plate is converted to lead dioxide, and the lead sulfate of the negative plate is
converted to sponge lead, with the production of sulfuric acid and results in the
increase of electrolyte concentration.
Battery Charged
Battery Discharged
(+ plate) (- plate) (solution)
(+ plate) (- plate) (solution)
Pb
+
2H2SO4 ―→ PbSO4 + PbSO4 +
2H2O
PbO2 +
(lead dioxide) (lead) (sulfuric acid) (lead sulfate)(lead sulfate) (water)
As the charge nears completion little lead sulfate remains to convert to lead
dioxide or lead. The charging current begins to decompose water into oxygen and
hydrogen, i.e., the oxidation of water into oxygen at the surface of positive plate and
the reduction of proton into hydrogen at the surface of negative plate. For the
conventional flooded lead-acid battery, the evolved oxygen and hydrogen bubble to
the top of the electrolyte and escape to outside, and water loss is resulted. For the
valve regulated lead-acid battery, the evolved oxygen from the positive plate is easily
transport to the negative plate to be absorbed through the gas tunnel in the glass mat
separator with starved electrolyte. The absorbed oxygen depolarizes the negative plate
with the formation of lead sulfate, and no hydrogen is generated in this condition.
With very little gas evolution, the water loss of VRLA battery is minimized. Gel
electrolyte is a coherent, rigid three-dimensional network of colloidal particle that filled in
gel batteries. It is also an immobilization of liquid acid, and the electrolyte will not stratify.
3
廣隆光電科技股份有限公司 Kung Long Batteries Industrial Co., Ltd.
南投市自立三路 6 號 NO. 6 TZU-LI 3 RD NANTOU CITY TAIWAN R.O.C. TEL:+886-49-2254777~8 FAX:+886-49-2255139
Gel Batteries Technical Manual
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3. Gel batteries characteristics
3.1 Battery Capacity
Battery capacity is expressed as ampere-hour (Ah), which is the product of
discharged current and the discharged time in hours.
Discharge rate is indicated by C/t, C is the nominal capacity of the battery, t
is the discharge time.
The nominal capacity of sealed lead acid battery is according to JIS C8702-1
Standard, a capacity using 20-hour discharge rate. For example, the capacity
of LG45-12 battery is 45Ah, which means that when the battery is
discharged with C/20 rate, i.e., 2.25 amperes, the discharge time will have 20
hours.
The battery capacity is varied with the discharge rate. The larger the
discharge current, the smaller is the battery capacity. The relation between
the battery capacity and the discharge rate is as follows:
Discharge rate
Regular type
Capacity High rate type
Gel type
20HR
100%
100%
100%
10HR
100%
100%
100%
5HR
85%
85%
85%
3HR
77%
80%
77%
1HR
60%
75%
60%
1CA
45%
70%
45%
3CA
35%
50%
35%
The information about the discharge current or power within specific
discharge time of our regular, high rate type and gel type battery products
are available through our product specification catalogues.
The temperature influences the gel battery capacity. The relation between the
capacity and temperature is as follows:
Temperature
Capa 1HR~3CA
city 20HR~1HR
0℃
82%
87%
10℃
91%
93%
20℃
100%
100%
30℃
100%
100%
40℃
100%
100%
The battery capacity may be also expressed by discharge power (watt),
which is the available discharge power within 15 minutes.
4
廣隆光電科技股份有限公司 Kung Long Batteries Industrial Co., Ltd.
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Gel Batteries Technical Manual
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3.2 Battery Voltage
The open circuit voltage of lead acid battery is indicated the equilibrium
voltage of the battery’s main reaction. The concentration of the sulfuric acid
participated in the main reaction is the major factor influencing the open
circuit voltage.
Right after charge or discharge, the concentration of sulfuric acid inside the
plates is still changing due to the diffusion process. It takes several hours to
several days to stabilize the open circuit voltage.
The concentration of sulfuric acid in battery is an indicator of battery
capacity. Therefore, the state of charge of battery is available through
measuring the open circuit voltage. The relation between the battery capacity
and open circuit voltage is as follows:
Capacity
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
6V OCV
V > 6.5V
6.40 < V < 6.50
6.33 < V < 6.40
6.25 < V < 6.33
6.18 < V < 6.25
6.10 < V < 6.18
6.03 < V < 6.10
5.95 < V < 6.03
5.88 < V < 5.95
5.80 < V < 5.88
12V OCV
V > 13.0V
12.80 < V < 13.00
12.65 < V < 12.80
12.50 < V < 12.65
12.35 < V < 12.50
12.20 < V < 12.35
12.05 < V < 12.20
11.90 < V < 12.05
11.75 < V < 11.90
11.60 < V < 11.75
3.3 Battery Self-discharge
The lead acid battery will have self-discharge reaction under open circuit
condition, in which the lead is reacted with sulfuric acid to form lead sulfate
and evolve hydrogen. The reaction is accelerated at higher temperature. The
result of self-discharge is the lowering of voltage and capacity loss.
Batteries will lose capacity due to self-discharge through packing,
transportation and storage process at various temperatures. The relation
between battery capacity and storage temperature and time is as follows:
5
廣隆光電科技股份有限公司 Kung Long Batteries Industrial Co., Ltd.
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Gel Batteries Technical Manual
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Time
1 month
3 month
6 month
12 month
96%
92%
90%
83%
93%
90%
80%
70%
90%
80%
65%
50%
80%
65%
50%
Not allowed
Temperature
0℃ ~ 5℃
5℃ ~ 20℃
20℃ ~ 30℃
30℃ ~ 40℃
The above data is shown in the following graph:
The remaining capacity of battery after storage can be obtained by
measuring its open circuit voltage and referring to the capacity verse OCV
table. Obviously, the OCV should be measured before recharge.
Batteries stored longer than three months should be recharged before
shipping.
3.4 Battery Internal Resistance
As the capacity of lead acid battery decreased or the battery is aged, its
internal resistance will be increased. Therefore, the internal resistance data
6
廣隆光電科技股份有限公司 Kung Long Batteries Industrial Co., Ltd.
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Gel Batteries Technical Manual
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may be used to evaluate the battery’s condition.
There are several internal resistance measurement methods, and their
obtained values are sometimes different each other.
Conductance, i.e., the reciprocal of internal resistance, which is expressed as
mho or Siemens, has some kind of positive proportionate relationship with
the battery capacity.
3.5 Battery Life
Standby use battery life: 7 ~ 10 years under 2.25~2.3Vpc and 25℃ floating
charge condition.
Cycle use battery life: 250 cycles (100%DOD)
300 cycles (80%DOD)
1000 cycles (50%DOD)
7
廣隆光電科技股份有限公司 Kung Long Batteries Industrial Co., Ltd.
南投市自立三路 6 號 NO. 6 TZU-LI 3 RD NANTOU CITY TAIWAN R.O.C. TEL:+886-49-2254777~8 FAX:+886-49-2255139
Gel Batteries Technical Manual
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4. Operation of Gel batteries
4.1 Preparation prior to operation
Batteries should always be fully charged prior to use, especially when use it
for the first time right after purchasing or after long period storage. Batteries
after long period storage will lose some capacity due to self-discharge, and
need recharge to restore its full performance.
Do not put batteries in airtight containers, or install the batteries in a room
without ventilation. Gas generated by over charging reactions in the battery
may explode if ignited by sparks from machinery or switches.
Tightly screw the connector with the terminal of the batteries.
Do not lay metallic object on top of a battery.
Insert insulation that is acid and heat resistant between the batteries and any
metallic housing.
Do not charge the battery with upside down position, it may cause acid
leakage.
upright (○)
side(△)
side(△)
upside down(╳)
Batteries must be stored or used in the temperature range of:
Charging:
-15℃ ~ 40℃
Discharging: -15℃ ~ 50℃
Storage:
-15℃ ~ 40℃
Temperatures above or below these ranges could result in damage or deformity
of the battery.
4.2 Charging methods for standby use batteries
The purpose of charging standby use batteries is to compensate
self-discharge. The constant voltage charging method is commonly applied.
Standby batteries are continuously overcharged at a voltage only slightly
above their open circuit voltage, called float voltage. The low float voltage
8
廣隆光電科技股份有限公司 Kung Long Batteries Industrial Co., Ltd.
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Gel Batteries Technical Manual
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induces low float current and minimum grid corrosion, which are the
requirements for long battery’s float service life. Such charging mode, which
is called floating charge, allows batteries to be continuously overcharged all
the year round in order to provide full and stable capacity.
The float charge voltage is 2.25~2.3V/cell at 25℃. However, when the
ambient temperature is too high or too low, the above voltage setting may
induce either too high side reaction rates or not enough charge. Therefore,
the float voltage is suggested to change with temperature, and the
compensation coefficient is –3.3mV/℃/cell, or as the following table:
Temperature(℃) 0
Float voltage(Vpc) 2.32
5
2.31
10
2.29
15
2.28
20
2.26
25
2.25
30
2.23
35
2.22
40
2.20
4.3 Charging methods for cyclic use batteries
The cycle life of batteries is influenced by the following factors: the
charging mode, the battery’s temperature, the battery’s charging frequency,
and the depth of discharge. Proper charging mode is the most important
factor affecting battery’s cycle life.
The charging voltage for gel battery should not be larger than the gassing
voltage, i.e., 2.3~2.35V/cell. The gassing voltage varies with temperature,
and is decreased as the temperature is increased. Its temperature coefficient
is –5.0mV/℃/cell, or as the following table:
Temperature(℃)
Gassing
voltage(Vpc)
0
5
10
15
20
25
30
35
40
2.48
2.45
2.43
2.40
2.38
2.35
2.33
2.30
2.28
The most effective charging method for gel battery is the constant voltage
(CV) charging mode. For the fully discharged (100%DOD) battery, for
example, it may be charged at 2.3 ~ 2.35V/cell, with the highest possible
current limit, in about 16 hours. For the 50% discharged battery, it may be
charged in 8 to 10 hours using a CV of 2.3 ~ 2.35V/cell.
The popular charging method for gel battery is the constant current/ constant
voltage (CICV) charging mode. In the first stage, the constant current
(0.1C~0.3C) charging is performed before reaching the voltage limit. The
9
廣隆光電科技股份有限公司 Kung Long Batteries Industrial Co., Ltd.
南投市自立三路 6 號 NO. 6 TZU-LI 3 RD NANTOU CITY TAIWAN R.O.C. TEL:+886-49-2254777~8 FAX:+886-49-2255139
Gel Batteries Technical Manual
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voltage limit is 2.3 ~ 2.35V/cell.
2.3~2.35V/cell
2.25~2.3V/cell
0.1C~0.3C
8~16hr
Time
The above charging mode need long enough time to fully charge the battery.
However, for charging the electric vehicle battery system with limited time,
the CICV charging mode may sometimes not be able to fully charge the
battery. If one battery is not fully charged in a long string of batteries, that
battery will have faster degradation and then cause a capacity loss of the
long string after many cycles of deep discharge. Such result comes from the
little differences in charging efficiency among different cells. In the constant
voltage charging stage, the current density is gradually decreased to very
small value; it is difficult to allow all cells to have the same amount of
charge unless charging with long enough time. In discharge, all cells should
deliver the same amount of charge. In consequence, the lower capacity cells
will experience deeper discharge and faster degradation.
A three-stages charging mode is introduced for long string and deep
discharge cyclic applications, which would allow every cell to be fully
charged in short duration. The first two steps are the same as the CICV
method, with the modification that the constant current should be larger than
0.6CA and may be as high as 2CA for some electric vehicle battery
applications. The constant voltage step may be lasted for 1 to 3 hours with
voltage limit of 2.3~2.35V/cell. A third stage is added and it is the constant
current charging with current density smaller than 10-hour rate (10-hour to
40-hour rate), and with duration limited to 1 to 2 hours. In this third stage,
there is no voltage ceiling, although the cell voltage will always be finally
flattened around 2.55 ~ 2.7V/cell. The voltage of the final stage may seem
too high, however, with the small current and short duration restriction, the
10
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negative effect on the battery is minimized.
2.55V~2.7V/cell
2.3~2.35V/cell
0.1~2CA
C/20~C/40
←
→
←
3hr
→ ←
1~2hr →
4.4 Discharge protection of batteries
The discharge cut off voltage of gel batteries should be decreased when the
discharge rate is increased. The recommended values for 12 volts batteries is
as follows:
Discharge rate
Discharge cut
off voltage
20HR
10HR
5HR
4HR
3HR
1HR
1 ~ 3CA
10.8V
10.8V
10.5V
10.2V
10.2V
9.6V
9.6V
To deeply discharge the battery to values below 1.60V/cell, or to leave the
battery in a discharged state for long period, the battery be will seriously
damaged, and this situation should be avoided.
The discharged batteries should be recharged or floating charged
immediately.
4.5 Equalization charging
Cyclic use batteries after charge and discharge for 20 to 40 cycles are
suggested to perform one equalization charge. Before such equalization
charge, it is beneficial to allow the battery to be deep discharged with small
current. The purpose of this treatment is to activate the plates and to restore
the capacity of the battery.
11
廣隆光電科技股份有限公司 Kung Long Batteries Industrial Co., Ltd.
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The discharge / charge treatment starts with further discharging the already
high rate discharged battery with constant current of 40 hour rate (C/40 Amp)
to 1.75V/cell. After rest for one hour, a proper equalization charge to fully
charge the battery is performed. A two-stage constant current charging is
suggested. The first stage is the charging with 0.3CA constant current to
2.4V/cell. The second stage is the charging with 20-hour rate (C/20 Amp)
constant current to maximum voltage until the voltage is leveled up for three
hours.
4.6 Thermal runaway phenomena
Thermal runaway is an abnormal phenomenon happened in charging
process, which is shown as a bloated battery. Thermal runaway means a state of
operation where heat generation increases faster than heat dissipation, which may
be happened on severe overcharging or electrolyte dry-out. The result is an
increase of the battery’s temperature. At elevated temperature, the internal
oxygen cycle is accelerated, and the developed heat causes further increase of the
battery temperature. With this self-accelerating cycle, the thermal runaway is
resulted, and the battery will be severely deformed and bloated. Several
precautions are listed as follows to prevent the thermal runaway:
Avoid the dry-out of batteries: Do not charge at voltage higher than gassing
voltage (2.4V/cell) for too long duration, e.g. >12 hours.
Any defective battery, e.g., the short-circuited or aged battery, in a long
string of batteries should be removed immediately to prevent the
overcharging of other batteries.
The internal oxygen cycle reaction is usually happened in the overcharging
stage, where the originally decreasing current density may increase instead
in the constant-voltage-charging mode. If the cut-off condition for the
charger is relied on the smallness of the current density, this setting may be
too low to be fulfilled when the battery is aged. The charger is continued to
overcharge the battery until the thermal runaway happened.
Always avoid the local overheating of batteries. Be equipped with heat
dissipating devices or temperature sensors in order to stop charging when
necessary.
12
廣隆光電科技股份有限公司 Kung Long Batteries Industrial Co., Ltd.
南投市自立三路 6 號 NO. 6 TZU-LI 3 RD NANTOU CITY TAIWAN R.O.C. TEL:+886-49-2254777~8 FAX:+886-49-2255139
Gel Batteries Technical Manual
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5. Maintenance of Gel batteries
5.1 The storage and maintenance of batteries
The storage temperature range: -30 ℃ ~ 50 ℃ , the humidity range:
25%-85%.
Fully charge the batteries before storage; if not, battery life will be shorter.
Use the batteries on a first-come basis, as batteries gradually deteriorate
even under proper storage conditions. Batteries stored for over long periods
may not restore to their initial capacity even after recharging.
Batteries under storage at ambient temperature of 25℃ should be recharged
every six months to maintain their quality, performance and reliability. The
interval of this charge should be reduced to 50% by each 10℃ rise in
temperature above 25℃.
Charge the batteries based on storage temperatures, as follows:
<20℃(68℉) storage:
charge every 9 months
20℃~30℃(68℉-86℉) storage:
charge every 6 months
>30℃ (86℉) storage:
charge every 3 months
Recharge method: To charge with constant voltage of 2.3 ~2.35V/cell and
initial current of 0.4CA and total duration of 5 ~ 8 hours.
5.2 The detection and remedy of “defective” batteries
This paragraph will describe how to differentiate the defective batteries from
the restorable batteries when abnormal phenomena happened during the
early usage or warranty period.
Measuring the following parameters may disclose the battery’s condition:
open circuit voltage, internal resistance, battery capacity and the charging
behavior. Using one parameter for criterion is better double-checked by
other parameters. The most commonly method is the measurement of open
circuit voltage.
The OCV of new batteries should be above 6.45V(for 6V battery) or
12.9V(for 12V battery). After transportation, storage and different discharge
factors, batteries’ OCV will have values from 12.9V to even 0.0V. If the
battery’s OCV is below 1.93Vpc, or 5.79V(for 6V battery), or 11.58V(for
13
廣隆光電科技股份有限公司 Kung Long Batteries Industrial Co., Ltd.
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Gel Batteries Technical Manual
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12V battery), this battery is a defective battery due to over-discharging or
some kind of deterioration. This kind of battery has permanent damage even
after recharge. If remedy of such kind of battery is desired, please contact
our Company. To evaluate batteries with voltages higher than the
above-mentioned value, fully recharge the battery is necessary before any
measurements.
If the fully recharging of batteries is not possible, battery with OCV or
internal resistance values far from its average values can be classified as
defective battery.
The OCV should be measured one hour (24 hours is better) after recharge.
The fully charged battery with OCV smaller than 6.2V(for 6V battery) or
12.5V(for 12V battery) is a defective battery.
The fully charged battery should have OCV higher than 6.45V(for 6V
battery) or 12.9V(for 12V battery). If the battery has values between 6.2 ~
6.45V(for 6V battery) or 12.5 ~ 12.9V(for 12V battery), it may not be fully
charged, and may need recharge with proper charger. If this condition is not
improved, the battery’s capacity may have been reduced.
The remedy method for charging the hard-to-recharge battery is available
through contact with our Company.
5.3 The recycle of batteries
The defective and used batteries should be recycled.
When cycling batteries, the battery terminals should have insulation
treatments. The batteries have residual capacity even for the used batteries.
Batteries with terminals not insulated may cause danger of explosion or fire.
The scrap lead-acid battery recycling in Taiwan is currently collected by
Thai Wey Industrial Co., Ltd. with First Class Collection Certificate (Tel:
886-7-7872283 ext. 131), and treated by Thye Ming Industrial Co., Ltd. with
First Class Treatment Certificate.
It is lawful for people to return the scrap batteries to the sale store for
recycling. For larger quantity of scrap batteries, please contact resources
recycling telephone 0800-085717 and the information about recycling
companies will be provided.
14
廣隆光電科技股份有限公司 Kung Long Batteries Industrial Co., Ltd.
南投市自立三路 6 號 NO. 6 TZU-LI 3 RD NANTOU CITY TAIWAN R.O.C. TEL:+886-49-2254777~8 FAX:+886-49-2255139
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