Battery Charge Derating for Regenerative Braking on Descents
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Solution Overview
Problem
Regenerative braking in electric vehicles can lead to battery overcharging during altitude descent, causing the vehicle to lose power or become improperly controlled.
Innovation Solution
A method to derate battery charging power by predicting the increase in charging current based on altitude and descent speed data, using a battery management system to calculate cumulative energy and adjust charging power proportionally to prevent overcharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If regenerative braking is used to charge the battery during altitude descent, then the battery charging efficiency is improved, but the battery may become overcharged causing vehicle power loss
Solution Approach 1:
The battery management system performs preliminary assessment of regenerative braking energy based on altitude data and descent speed data before actual charging occurs. By calculating the prediction value of charging current increase in advance and comparing it with the state of charge, the system determines whether to allow regenerative braking charging, thereby preventing overcharging before it happens
Solution Approach 2:
The system continuously monitors altitude data, descent speed data, and battery state of charge, and adjusts the charging acceptance accordingly. When the prediction value indicates potential overcharging risk, the system provides feedback to limit or reject regenerative braking energy, creating a closed-loop control that maintains battery safety while maximizing charging efficiency
2Reliability
If the battery connection is severed to prevent overcharging, then the battery overcharging risk is eliminated, but the vehicle loses power from the battery
Solution Approach 1:
Instead of completely severing the battery connection to prevent overcharging, the system applies partial action by selectively accepting or rejecting regenerative braking energy based on the predicted charging current increase. This allows the battery to remain connected and functional while only limiting the excessive charging input that would cause overcharging
Solution Approach 2:
The system changes the charging power parameter dynamically based on altitude and descent speed conditions. By calculating the prediction value of charging current increase and comparing it with state of charge thresholds, the system adjusts the charging acceptance parameter to prevent overcharging while maintaining normal power supply functionality
Data Source
AI summary
A method for derating a charge power of a battery, includes: obtaining altitude data of a vehicle; obtaining descent speed data of the vehicle; calculating, based on the altitude data and the descent speed data, a prediction value of an increase in a charging current of the battery equipped in the vehicle due to regenerative braking; and derating the charging power of the battery based on the calculated prediction value.