Internal Battery Temperature Estimation for Power Tools
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Solution Overview
Problem
Conventional battery temperature sensors detect ambient temperatures, not internal battery temperatures, leading to inaccurate temperature readings during charge/discharge, which can result in either premature suspension of battery activity or failure to protect the battery from overheating in electric power tools.
Innovation Solution
An internal temperature estimation unit calculates the internal battery temperature by reading initial and subsequent temperature values from a temperature detection device, accounting for temperature differences between the surface and internal temperatures, and adjusts settings to prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a temperature sensor is disposed around the battery to detect battery temperature, then the battery can be protected from overheating, but the detected temperature is only the ambient temperature and not the internal temperature, leading to inaccurate temperature readings
Solution Approach 1:
The patent introduces an intermediary calculation method that uses the relationship between ambient temperature (detected by sensor) and internal temperature. A temperature difference value is calculated based on charge/discharge current and time, which serves as a mediator to bridge the gap between what the sensor detects and what the internal temperature actually is. This allows accurate internal temperature estimation without direct contact with the battery interior.
Solution Approach 2:
The patent replaces the direct mechanical/physical measurement approach (placing sensor inside battery) with a computational/mathematical approach. Instead of directly measuring internal temperature through physical contact, the system uses calculations based on electrical parameters (current, time) and thermal relationships to derive the internal temperature indirectly.
2Reliability
If charge/discharge is limited based on detected ambient temperature, then battery protection is activated, but the internal temperature may have already exceeded safe limits, resulting in insufficient protection
Solution Approach 1:
The patent performs preliminary calculation of the temperature difference value before making protection decisions. By calculating how much the internal temperature has risen above ambient temperature based on charge/discharge history, the system can predict when the internal temperature will reach dangerous levels and take preventive action before actual overheating occurs.
Solution Approach 2:
The system continuously monitors charge/discharge current and time, updates the temperature difference calculation in real-time, and uses this feedback to dynamically adjust the temperature threshold for protection activation. This closed-loop feedback ensures the protection mechanism responds accurately to actual internal temperature conditions rather than static ambient readings.
3Reliability
If the sensor detects ambient temperature close to upper limit, then charge/discharge is suspended, but the internal temperature may not have reached the limit, causing premature suspension of battery activity
Solution Approach 1:
The patent calculates the temperature difference in advance based on charge/discharge parameters, allowing the system to determine the actual internal temperature status before suspending battery operations. This preliminary calculation prevents premature suspension by providing accurate internal temperature information ahead of time.
Solution Approach 2:
The protection threshold is made dynamic rather than static. Instead of using a fixed ambient temperature threshold, the system adjusts the effective threshold by adding the calculated temperature difference, allowing the suspension decision to adapt to actual internal temperature conditions and avoid unnecessary interruptions to battery usage.
Data Source
AI summary
An internal temperature estimation unit, which reads a detected temperature of a cell of a battery for an electric power tool to estimate an internal temperature of the battery based on the detected temperature, includes: an initial-value setting device which reads, when a discharge/charge of the battery is started, the detected temperature and sets the detected temperature as an initial value; and a temperature increase amount calculation device which calculates a temperature increase amount of the cell of the battery based on a latest value of the detected temperature and the initial value set by the initial-value setting device; the internal temperature estimation unit outputs the temperature increase amount as an estimated value representing the internal temperature of the battery.