Sequential Battery Pack Relay Switching to Limit Inrush Current
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Solution Overview
Problem
Electric working machines with multiple battery packs connected in parallel are prone to internal relay failure due to inrush current when activated, particularly when battery packs with varying performance are connected concurrently.
Innovation Solution
The electric working machine is configured to connect battery packs sequentially, using external relays to manage the connection process, ensuring that internal relays of subsequent battery packs are brought into a closed state only after the first pack is connected, thereby reducing the impact of inrush current on the relays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If internal relays of multiple battery packs are concurrently brought into the closed state to electrically connect the battery packs to the electric device, then the battery packs are connected in parallel to provide sufficient power, but the internal relays are subjected to high inrush current resulting in a higher possibility of battery pack failure
Solution Approach 1:
The patent applies preliminary action by bringing the internal relay of the first battery pack into the closed state before connecting it to the electric device. This preliminary connection allows the first battery pack to be already connected when subsequent battery packs are connected in parallel, thereby avoiding simultaneous closing of all internal relays and reducing inrush current damage while maintaining sufficient power output.
2Ease of operation
If internal relays of battery packs connected in parallel are concurrently brought into the closed state, then the battery packs are electrically connected to the electric device, but electric current flows from high-voltage battery pack to low-voltage battery pack causing higher inrush current
Solution Approach 1:
The patent applies preliminary action by pre-connecting the first battery pack to the electric device before connecting subsequent battery packs in parallel. This sequential approach prevents simultaneous relay closing that would cause current flow from high-voltage to low-voltage packs, thereby reducing inrush current damage while maintaining operational simplicity.
Solution Approach 2:
The patent applies segmentation by dividing the battery pack connection process into sequential stages: first connecting the first battery pack, then subsequently connecting second and later battery packs in parallel. This segmentation of the connection process prevents simultaneous relay closing and the associated harmful current flow between battery packs of different voltages.
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
This approach significantly reduces the likelihood of battery pack failure by minimizing the exposure of internal relays to high inrush currents, thus extending the lifespan and reliability of the machine.
Implementation Method 1
the battery packs each including at least one internal relay to open and close an internal circuit
Implementation Method 2
the electric circuitry includes external relays corresponding to the respective battery packs to open and close respective circuits connecting the respective corresponding battery packs to the electric device
Data Source
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AI summary
One or more example embodiments of the present invention include an electric device (20), electric circuitry (21), battery packs (22) to be connected sequentially to an electric device (20) via the electric circuitry (21) such that they are parallelly connected, the battery packs (22) including internal relay(s) (220) to open/close an internal circuit (222), and a controller. The electric circuitry (21) includes external relays (211) corresponding to the respective battery packs (22). The controller is configured or programmed to perform a first latter process wherein, while a first battery pack (22) to be connected first to the electric device (20) is in electrical connection with the electric device (20), the controller brings the internal relay(s) (220) of a second battery pack (22) to be connected second or later to the electric device (20) into a closed state, and a second latter process wherein the controller brings, into the closed state, the external relay (211) corresponding to the second battery pack (22) where the internal relay(s) (22) is in the closed state.