Mike Dolt Enterprises
Mike Dolt Enterprises
User: alboities, Location: Vancouver, WA
Asked on: Thursday, April 14, 2011 at 4:18 pm EDT
Answered on: Tuesday, May 14, 2024 at 4:12 am EDT
Question: Hi, my name is Albert and I currently working on a project in one of my undergrad classes.For my project, we are looking into finding how long a car needs to be charged in order to reach a certain mile distance. My specific portion is to find how fast the car charges over time under lvl 1 (120V 15A) and lvl 2 (240V 60A) charging. I have searched the web and have only been able to find how much time is needed to recharge the entire battery using these two levels.However I need specific data for the intermediate charging area (between max and min). We assumed that the charge rate is non linear so that the time it takes to charge a car from 40% to 60% state of charge is not the same as charging the battery from 60% to 80%. (Assuming other variables, temperature/heat are constant)I was using the specific car the Nissan Leaf as my specific example which has a Lithium-Ion 24kWh battery and a 80% depth of discharge.The ultimate goal is to write a program in MatLab which recieves two inputs: current state of charge and target state of charge) and then outputs the required time to reach the target state of charge under lvl 1 and lvl 2 charge rates for an electric vehicle.I am currently very lost and have been unable to find relevant data and was hoping if any of you could help or point me in the right direction.I have already looked at discharge/charge cycles for various batteries and am getting confused with all the varying terminolgy (I'm a MechE not a EE, sadly ). I was considering looking at charge/discharge rates vs state of charge for smaller sized batteries and then scaling these to electric vehicle rates, and was wondering if this was the right direction?Any help would be greatly appreciated, but if anyone could find a graph or tabulated data on this that would be amazing.
Understanding Battery Charging Battery Capacity
The amount of energy a battery can store, typically measured in kilowatt-hours (kWh).
State of Charge (SOC)
The percentage of the battery's capacity that is currently charged.
Depth of Discharge (DOD)
The percentage of the battery's capacity that is used before recharging.
Charging Levels
Level 1 (120V, 15A): Slowest charging rate, typically used for overnight charging. Level 2 (240V, 60A): Faster charging rate, commonly used at public charging stations.
Non-Linear Charging Rate
The charging rate of a battery is not constant over its entire discharge range. Factors such as battery chemistry, temperature, and SOC can influence the charging rate. Typically, the charging rate is highest when the battery is nearly depleted and slows down as it approaches a higher SOC.
Finding Intermediate Charging Data
Unfortunately, manufacturers typically only provide information on the total charging time for a given battery from 0% to 100% SOC. However, you may consider the following approaches: Real-World Testing
Conduct actual charging tests on an electric vehicle with the Nissan Leaf battery under controlled conditions (temperature, load). Record the charging rate at different SOC intervals.
Battery Modeling
Use battery modeling techniques to estimate the charging rate as a function of SOC. This requires knowledge of the battery's specific chemistry and parameters.
Voltage Profiling
Monitor the battery's voltage during charging. Since voltage is related to SOC, you can infer the charging rate by plotting the voltage change over time.
Scaling to Electric Vehicle Batteries
Once you have data for smaller batteries, scaling to electric vehicle batteries can be done using the following assumptions: The charging rate is proportional to the battery capacity. The charging curve is similar for batteries of the same chemistry.
MatLab Program
Your program can use the following algorithm:
batteryCapacity dod - currentSOC batteryCapacity dod;% Estimate charging rates for Level 1 and Level 2lvl1Rate = 120 15; % Wattslvl2Rate = 240 60; % Watts% Calculate charging time for Level 1 and Level 2lvl1Time = chargeToAdd / lvl1Rate;lvl2Time = chargeToAdd / lvl2Rate;endAdditional Resources [Battery Charge Rate vs. State of Charge](https://www.nrel.gov/docs/fy18osti/69598.pdf) [Modeling the Charging Rate of Li-Ion Batteries](https://www.mdpi.com/1996-1073/13/3/305) [Nissan Leaf Battery Charging Curve](https://ev-database.org/en/car/1163/Nissan-LEAF-2018) Flag for reviewmatlabfunction [lvl1Time, lvl2Time] = chargingTime(currentSOC, targetSOC)% Get battery capacity and DOD from given Nissan Leaf parametersbatteryCapacity = 24; % kWhdod = 0.8;% Calculate amount of charge to be addedchargeToAdd = targetSOC