Download EV Traction Dry Cell Performance

Suite 880 - 999 West Broadway
Vancouver BC V5Z 1K5 Canada
T: 604.730.2877 | F: 604.730.2898
E: [email protected] | www.discover-energy.com
EV Traction Dry Cell Performance
OCV:
Open-Circuit Voltage: Open-circuit voltage varies according to ambient temperature and the remaining capacity of a battery. Normally, OCV is
determined by the gravity of the electrolyte. Discharging a battery lowers the gravity.
Battery Voltage (V)
Relationship of OCV and State of Charge (20˚C)
Relative State of Charge (%)
SHELF LIFE & STORAGE:
Self-Discharge Characteristics: Low internal resistance and chemistry in the electrodes ensure a low self discharge rate and longer shelf life. If
maintained at 20°C, approximately 60% of the nominal capacity remains after one year of storage. Due to the self-discharge characteristics of this
type of battery, and in order to prevent sulfation and permanent loss of capacity, it is important to charge the battery within 6 months of storage.
Self - Discharge Characteristics
100
Charging is not
necessary unless
100% of capacity is
required.
Capacity (%)
80
5˚C / 41˚F
60
40˚C / 104˚F
30˚C / 86˚F
Charge may fail to
restore full capacity.
Do not let battery
reach this state.
20˚C / 68˚F
40
1
2
4
6
8
10
12
14
16
Charging before
use is necessary to
recover full capacity.
18
20
Storage Time (months)
PAGE 1
Discover® and Clean & Green® are registered trade marks and are used under license. All Rights Reserved.
Updated: November 7, 2013
INNOVATIVE POWER SOLUTIONS
Suite 880 - 999 West Broadway
Vancouver BC V5Z 1K5 Canada
T: 604.730.2877 | F: 604.730.2898
E: [email protected] | www.discover-energy.com
TEMPERATURE:
Relationship Between Charging Voltage and Temperature: Activity in a battery increases when temperature rises and decreases when temperature
falls. When temperature rises, the charging voltage should be reduced in order to prevent overcharging. Conversely, when temperature falls,
charging voltage should be increased in order to prevent undercharging. Normally, a temperature-compensated charger is recommended to
achieve ideal service life.
V/ Cell
V/ 4V
V/ 6V
V/ 8V
V/ 12V
The standard centre point for temperature compensation is 20°C. The figure below shows the relationship between charging voltages and temperature in both cyclic and standby (float) applications.
Relationship Between Charging
Voltage and Temperature
Cyc
le U
se
Stand
by Us
e
Ambient Temperature (˚C)
Temperature Effects on Capacity: Actual capacity is a function of ambient temperature and rate of discharge. The capacity increases slowly and
decreases as the temperature falls. At any ambient temperature, the higher the rate of discharge the lower the available capacity.
Temperature Effects on Capacity
Capacity (%)
C
0.1 ˚
C
0.2 ˚
C
1.0 ˚
C
2.0 ˚
Temperature (˚C)
PAGE 2
Discover® and Clean & Green® are registered trade marks and are used under license. All Rights Reserved.
Updated: November 7, 2013
INNOVATIVE POWER SOLUTIONS
Suite 880 - 999 West Broadway
Vancouver BC V5Z 1K5 Canada
T: 604.730.2877 | F: 604.730.2898
E: [email protected] | www.discover-energy.com
CHARGING:
Constant Current IUI with Pulse Termination: This algorithm uses a pulse termination criterion. As a safety precaution during the Finish phase, if the
average cell voltage, or volts per cell (vpc), exceeds V2 and the charger output has been on for more than 30 seconds, the output is shut off until the
vpc falls to V3. The finish phase then resumes and this “pulsing” continues until the target overcharge (108% - 112%) is reached.
Discover EV Traction Dry Cell - Constant Current IUI with Pulse Termination
Bulk
Absorption
V2 = 2.60vpc
U = 2.435 +/- .015vpc
Dv/Dt = 2.5mV/Cell/Hr
or 108% - 112% recharge
V3 = 2.35vpc
I2 = .01 x C20 Capacity
Volts Per Cell (VPC)
Initial Charging Current
I = X C20 Rating
I1 = .25 x C20 Capacity +/- .05 x C20 (minimum I1 =0.10 x C20)
Balance/Termination
Temperature Coef. +/- .005vpc/C, 0.003vpc /F from 25˚C (77˚F)
Max 18 Hrs
Max 5 Hrs
Max 4 Hrs
Maximum Charge Time Must be Limited to 24 Hours
Constant Current IUI: A constant current charger can also be used, however it is important to adhere to the termination criteria to minimize the
chance of excessive over-charge.
Bulk: Set the charger to the initial current I1 (I1 =0.10 x C20) until the voltage limit U (U=2.465 +/- .015vpc) is reached.
Absorption: Set the charger to the voltage U (U=2.465 +/- .015vpc) until the current tapers to I1 (I1 =0.10 x C20).
Balance/Termination: Set the charger to the finish current I1 (Max = 16% I1). If the charger can be programmed, the charge should terminate
when the voltage stops increasing over time. This is called a dV/dT termination. The charge should terminate when the dV/dT is equal to
2.5mV/cell/hour.
The charge time in the final phase should not exceed 8 hours and the total charge time should not exceed 24 hours. The percentage recharge
should be between 108%-112%.
Discover EV Traction Dry Cell - Constant Current IUI
An indefinite float phase may be added at 2.27vpc
Bulk
Absorption
Balance/Termination
I1 = .25 x C20 Capacity +/- .05 x C20 (minimum I1 =0.10 x C20)
U = 2.465 +/- .015vpc
Temperature Coef. +/- .005vpc/C, .003vpc /F from 25˚C (77˚F)
Max 14 Hrs
Max 5 Hrs
108% - 112% recharge
Volts Per Cell (VPC)
Initial Charging Current
I = X C20 Rating
V2 = 2.60vpc
Max 16% I1
Max 4 Hrs
Maximum Charge Time Must be Limited to 24 Hours
PAGE 3
Discover® and Clean & Green® are registered trade marks and are used under license. All Rights Reserved.
Updated: November 7, 2013
INNOVATIVE POWER SOLUTIONS
Suite 880 - 999 West Broadway
Vancouver BC V5Z 1K5 Canada
T: 604.730.2877 | F: 604.730.2898
E: [email protected] | www.discover-energy.com
CHARGING:
Voltage Regulated IUU: Over and under-charging a battery will result in shortened service life. The best protection from improper charging is the
use of a quality charger and routinely checking that the charger current and voltage settings are maintained.
Bulk: The charger should deliver the initial current I1 (I1 =0.10 x C20) until the voltage limit U (U = 2.45 +/- .015vpc) is reached.
Absorption: The charger should maintain the voltage U (U = 2.45 +/- .015vpc) until the current tapers to I1 (I1 =0.10 x C20).
Float: The charger can maintain the current I1 (Max = 16% I1 indefinitely or until the charger is shut off or unplugged.
This stage is ideal to maintain battery state of charge. As the temperature decreases, the voltage should be increased and as the temperature
increases the voltage should be decreased.
Discover EV Traction Dry Cell - Voltage Regulated IUU
Bulk
Absorption
Float
Volts Per Cell (VPC)
Initial Charging Current
I = X C20 Rating
I1 = .25 x C20 Capacity +/- .05 x C20 (minimum I1 =0.10 x C20)
U = 2.45 +/- .015vpc
U2 = 2.27vpc
Temperature Coef. +/- .005vpc/C, .003vpc /F from 25˚C (77˚F)
Max 14 Hrs
Max 8 Hrs
No Time Limit
BATTERY LIFE:
Cycle Service Life in Relation to Depth of Discharge (D.O.D): The number of charge/discharge cycles depends on the capacity taken from the
battery, operating temperature and the charging methods.
Capacity (%)
Cycle Service Life in Relation to Depth of Discharge
80% D.O.D
50% D.O.D
20% D.O.D
Number of Cycles
PAGE 4
Discover® and Clean & Green™ are registered trade marks of BDI Inc. and are used under license. © BDI Inc. All Rights Reserved.
Discover® and Clean & Green® are registered trade marks and are used under license. All Rights Reserved.
Updated: November 7, 2013
INNOVATIVE POWER SOLUTIONS