Charge and discharge rates of a battery are governed by crates. Battery a battery is a number of cells connected together. Interpreting battery parameters and specification sheets ae. Smaller batteries are rated at a 1c discharge rate. C rate and service times when charging and discharging. C rate is used to scale the charge and discharge current of a battery. Calculation of battery bank capacity, crate, runtime.
A reasonable testing scheme for 1 c rate, i suppose, is to obtain the current value for a discharge of the battery in one hour at the operating volatge of 4. To get a ballpark idea of the c20 rating of a battery, divide the cca by 20. While rarely stated explicitly, the unit of the crate is h. Calculating charge and discharge rate for each battery made the charge and discharge rate is determined for each battery depending on the mass of active material in each battery. For absorbent glass mat agm batteries, the number is usually between 1. V0v1i in the case of large current discharge, it needs to consider the ir drop, which is caused during the early discharge stage derived from capacitors ir direct current resistance and the discharge current. Typical value of battery rating at different discharge rate battery capacity c20 c10 c5 c3 c1 5 ah 5 120 100 86 60 150 ah 150 125 104 90 62. An agm300 battery is rated to deliver 104amps for 5 hours 300 minutes to 1. Battery congress april 1516, 20 ann arbor, michigan. Total vah 18 x 12 x 28 6048 vah the following assumptions have been made in the above calculations. It is defined as the current through the battery divided by the theoretical current draw under which the battery would deliver its nominal rated capacity in one hour. Calculating charge and discharge rate for each battery made. Peukerts law is t h c ih k in which h is the rated discharge time in hours, c is the rated capacity of the discharge rate in amphours also called the ah amphour rating, i is the discharge current in amps, k is the peukert constant without dimensions and t is the actual discharge time. The system was 65f, was discharged at 104amps and the systems end cell voltage was reached at 4 hours and 25 minutes 265 minutes.
The batt ery crate refers to the rate at which a battery is charged or discharged. Typical discharge curves of lead acid as a function of crate. After a 5 minute rest without recharge, the battery is discharged at the 20x rate and the voltage is measured after 5 seconds. When the discharging rate is halved and the time it takes to discharge the battery is doubled to 20 hours, the battery capacity rises to y. Ah the ah or amperehour capacity is the current a battery can provide over a. A cca battery is roughly equivalent to at 50ah battery. Figure 1 illustrates the discharge times of a lead acid battery at various loads as expressed in c rate. Battery performance characteristics how to specify and test. C rate is used to describe how fast a battery charges and discharges.
Some highperformance batteries can be charged and discharged above 1c with moderate stress. Interpreting battery parameters and specification sheets. Sizing loads will be explained later in terms of the c rating. The actual percentage rated capacity of the battery would then be calculated as 77.
A 1c or c 1 charge loads a battery that is rated at, say, ah at a during one hour, so at the end of the hour. A 1c rate means that the discharge current will discharge the entire battery in 1 hour. Capacity and energy of a battery or storage system. The c rate or rate of discharge refers to the amount of current that a. Current rate crate is a measure of the discharge current relative to its capacity. Measurement of power loss during electric vehicle charging. A 1c or c1 charge loads a battery that is rated at, say, ah at a during one hour, so at the end of the hour. The crate is defined as the charge or discharge current divided by the batterys capacity to store an electrical charge. For example, a crate of 1c for 100 ah capacity battery would correspond to a discharge current of 100 a over 1 hour. The c rating of a battery is the power capacity of a battery. All high voltage battery packs are made up from battery cells arranged in strings and modules. When peak is reached and voltage begins to drop the battery is fully charged. A c rating is simply a batterys capacity or ahamp hour rating when discharged over a specific period of time. This paper describes the main components and functions of a battery system, and discusses the reasons why vendor pre.
Design and specification for safe and reliable battery. The crate is a measure of the rate at which a battery is being charged or discharged. Doing the math for a charging rate of a 0ma battery, we calculate. For example, a 1c battery needs one hour at 100 a to load 100 ah.
Most batteries cases say something like 25c to 40c discharge rate. A 5c rate for this battery would be 500 amps, and a c 2 rate would. For example, a c rate of 1c for 100 ah capacity battery would correspond to a discharge current of 100 a over 1 hour. Assume the battery were discharged at the 391 w c rate with the expectation of 15 minutes of operating time to 1. Assume the battery were discharged at the 391 wc rate with the expectation of 15 minutes of operating time to 1. A c rate is a measure of the rate at which a battery is discharged relative to its maximum capacity. This means that 25c is the nominal discharge rate and 40c is the maximum burst discharge rate. Shortcircuit currents in dc auxiliary installations in power. Essentially, charging a battery at a 1c rate means charging at the batterys capacity. For a given capacity, crate is a measure that indicate at what current a battery is charged and discharged to reach its defined capacity. Alternatively, a discharge rate may be specified by its charge rate or crate, which is expressed as a multiple of the rated capacity of the cell or battery. The c rate or rate of discharge refers to the amount of current that a battery can sustain for. Description calculations steps results number of strings divide the bah by the batterys 100hour rate if 5 days autonomy selected or a rate that approximates the actual autonomy hours for the system a number of batteries cells.
Capacity fade during cycling hall boeing, 20052006. Pdf a battery model for constantpower discharge including. How to calculate battery runtime when design equipment. The battery bank capacity can now be used to determine the amount of batteries needed for the installation. When engineering a new quadcopter, we have to consider the amp draw of the motorprop combination, and the max battery size we can fit on the quad to determine the right battery for the job. If this were a 200 amp hour battery, it will last for 40 minutes if discharged at 200 amps and will last for 58 minutes if discharged at a rate of 40 amps. For a given capacity, c rate is a measure that indicate at what current a battery is charged and discharged to reach its defined capacity. Crate is used to describe how fast a battery charges and discharges. The battery pack purchased by ac propulsion is composed of 48 lipf 6 cobalt modules in series, providing a rated voltage of 345 v and a rated capacity of 106 ah. Battery temperature above 125 degrees can lead to cell damage. The lcoe for each technologysegment combination is determined for a speci c u. Use a voltmeter to monitor battery voltage during charging with simple charger. This means that 25c is the nominal discharge rate and 40c is the maximum burst. If you open the advanced mode of this battery capacity calculator, you will be able to compute three other parameters of a battery.
Table 1 illustrates typical times at various c rates. The rate of rise of the fault current time constant in milliseconds is dependent. So a 2000ma battery should be charged at 2000ma, a 1. A 5c rate for this battery would be 500 amps, and a c2 rate would. The crate is the governing measurement of what current a battery is charged or discharged at. For example, a battery may have a rating of 200 ah at a c10 discharge rate. Current rate c rate is a measure of the discharge current relative to its capacity. How to calculate battery runtime when design equipment using. Charge and discharge characterization of lithiumion.
Figure 1 illustrates the discharge times of a lead acid battery at various loads as expressed in crate. Center for transportation technologies and systems. Rate of discharge consider two different 10hour duty cycle diagrams. State of charge soc refers to the present available battery capacity as a percentage of nominal capacity. For a battery with a capacity of 100 amphrs, this equates to a discharge current of 100 amps. At the 4x rate, the battery voltage is measured at 20 seconds. A crate is a measure of the rate at which a battery is discharged relative to its maximum capacity. Why does a battery have a c5, c20 and c100 ah rating. This rating is acquired by adding a specific size load to a battery to make it completely dead in a 3, 5, 8, 10, 20 or 100 hour period. The letter c in those expressions in more easily understood if you think of it as simply the value of the amp hour rating. This number is usually given with the number of hours at which the rate was taken. Battery discharge performance depends on the load the battery has to supply.
Stringbank a battery string or bank comprises a number of cellsbatteries connected in series to produce a battery or battery string with the required usable voltagepotential e. The following formula was used to calculate the standby battery load in table 03. If a battery is labeled 2000mah, then its 1c rating is 2000mah. The initial crate is based on the batterys rated capacity, although during aging cycles the leadacid crate is rescaled to the initial measured capacity, which is lower than rated. Some battery chemistries give much fewer amp hours if you discharge them fast. A battery cell can be regarded as the smallest division of the voltage. The capacity of a battery is commonly rated at 1c, meaning that a fully charged battery rated at 1ah should provide 1a for one hour. The capacity of a battery or accumulator is the amount of energy stored according to specific temperature, charge and discharge current value and time of charge or discharge. On the other hand, a c rate of 2c for the same battery would correspond to a discharge current of 200 a over half an hour. The discharge rate is determined by the equation below. Voltage, amphour capacity, and c rate rate of discharge. A c rate of 1c is also known as a onehour discharge.
On the other hand, a crate of 2c for the same battery would correspond to a discharge current of 200 a over half an hour. Apart from the cells, a discharge rate is defined by the letter c. Battery charging and discharging parameters pveducation. To make this simple, the battery should provide 1c current for one hour. It is normally expressed in terms numbers that look like 1c, 2c, 0.
The discharge rate when discharging the battery in 10 hours is found by dividing the capacity by the time. For example, the posted mah of the battery is the 1c rating. Table 1 indicates the gassing rate to be expected from each of the vrla batteries at the charging voltages of 2. I standby current ah amperehour rating of battery h standby hours 1. Its advisable to stay on or below nominal discharge level to preserve battery future life. Voltsdetermines number of cells that can be adequately. The number in these expressions is simply a multiplier. If the temperature becomes excessive or the cells begin to gas vigorously, reduce the rate of charge. Crate is used to scale the charge and discharge current of a battery. Battery performance characteristics how to specify and. The battery pack will be designed for an average energy consumption of 161.
If the calculation requires a 220 ah battery, and the next cell size up is 250 ah. A battery model for constantpower discharge including rate effects article pdf available in energy conversion and management 88. However, it needs to consider the decrease rate of voltage from the self discharge in the. You can use peukerts law to determine the discharge rate of a battery. Capacity fade during storage smart nasajpl, 2009 t 0c, 10c, 23c, 40c, 55c broussely saft, 2001 v 3. Storage size determination for gridconnected photovoltaic. If the discharge takes place over a long period of several hours as with some high rate applications such as electric vehicles, the effective capacity of the battery can be as much as double the specified capacity at the c rate. Typical discharge curves of lead acid as a function of c rate. Design and specification for safe and reliable battery systems for large ups revision 0 by pearl hu white paper 207 a properly designed ups battery solution is important for safe and reliable operation.