LiFePO4 Starter Battery Charging Without BMS for Small Engines
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Solution Overview
Problem
Existing electric starting systems for internal combustion engines, particularly in outdoor power equipment, face challenges with lead-acid batteries that are temperature-sensitive and prone to premature failure due to infrequent use, and lithium-ion batteries require complex battery management systems to prevent overcharging and deep discharge.
Innovation Solution
A starter battery system using lithium iron phosphate cells with a charging circuit powered by the engine, eliminating the need for battery management circuitry by maintaining a voltage below the overcharge threshold and utilizing a low self-discharge rate to extend battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium-ion batteries are used instead of lead-acid batteries, then battery life and reliability are improved, but device complexity increases due to the need for battery management systems
Solution Approach 1:
The patent extracts and removes the battery management system from the lithium-ion battery configuration, using only the basic battery cells without complex control electronics. This eliminates the complexity issue while retaining the reliability benefits of lithium-ion chemistry.
Solution Approach 2:
The patent employs a simple, minimalistic battery design that foregoes expensive and complex battery management systems, accepting a more basic configuration that is easier to manufacture and less complex, while still achieving the desired performance through proper battery chemistry selection.
2Object-affected harmful factors
If lithium-ion batteries are used instead of lead-acid batteries, then temperature sensitivity is reduced, but device complexity increases due to charging control requirements
Solution Approach 1:
The patent removes the complex charging control circuitry from the system, using a simplified charging approach that eliminates the need for sophisticated temperature compensation and charge management electronics, while still benefiting from the reduced temperature sensitivity of lithium-ion batteries.
3Device complexity
If lead-acid batteries are used in electric starting systems, then device complexity is minimized, but reliability deteriorates due to premature failure from infrequent use
Solution Approach 1:
The patent changes the fundamental chemical parameter of the battery system by switching from lead-acid chemistry to lithium-ion chemistry. This parameter change fundamentally alters the battery's self-discharge characteristics and durability profile, enabling reliable performance in infrequent-use applications while maintaining operational simplicity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The lithium iron phosphate battery system provides reliable starting power with a long lifespan and low self-discharge rate, reducing the need for complex management systems and minimizing capacity loss, while ensuring safe charging and discharge operations.
Implementation Method 1
A starter battery system using lithium iron phosphate cells with a charging circuit powered by the engine
Implementation Method 2
a charging circuit configured to be powered by rotation of an air cooled engine
Data Source
AI summary
A starter battery system for an air cooled engine rated at less than 50 horsepower. The system includes four lithium iron phosphate cells and a charging circuit configured to be powered by rotation of an air cooled engine. A voltage developed by the charging circuit is applied to the four lithium iron phosphate cells without battery management circuitry provided between the charging circuitry and the four lithium iron phosphate cells.An engine which includes at least one piston, a rotatable crankshaft coupled to the at least one piston, a starter motor configured to selectively initiate rotation of the crankshaft, a lithium-ion battery in electrical communication with the starter motor, the lithium-ion battery having at least one cell, and a charging system configured to be powered by motion of at least one component of the engine. The charging system is configured to continuously apply a voltage potential to the at least one cell while the engine is in a running condition.An engine including at least one piston, a rotatable crankshaft coupled to the at least one piston, a starter motor configured to selectively initiate rotation of the crankshaft, a lithium-ion battery in electrical communication with the starter motor, the lithium-ion battery having four lithium iron phosphate cells, and a charging system configured to be powered by the engine. The charging system is electrically coupled to the lithium-ion battery and configured to charge the lithium-ion battery and no battery management circuitry is provided between the charging system and the lithium-ion battery.