Battery packs are designed to have fixed capacities and voltages to power specific applications for a required length of time before recharging. To transfer this power to the device, connectors, and interfaces are required to form the connection between the battery cells and the devices, as well as with the chargers.
When designing a custom battery pack, care must be taken to select the appropriate connector to ensure there is no disruption to the provided power and that the connector is transferring the appropriate voltage and current based on the device's requirements.
Overview of Connector Types
When evaluating battery connectors, take into consideration the battery chemistry. A connector for a lithium-ion battery will significantly differ from a lead acid battery, alkaline, or nickel-based battery. Some connectors consist of battery terminal connectors, wire-to-board connectors, and wire-to-wire connectors.
Custom battery pack with connector.
Terminal Connectors
For lead acid batteries or battery types used for heavy-duty applications such as automotive, industrial machinery, or marine systems, battery terminal connectors are commonly used for these applications. These connectors are made from brass, aluminum, or copper and may use a bolting system to attach them into place. Types of terminal connectors include:
- Post Terminal: Threaded stud to form connection
- Clamp Terminal: Spring-loaded clips as they may also be called alligator clips
- Splice Terminal: May consist of twist-on, heat-shrink, or crimp-on connectors to join several wires
- Lug Terminal: A U-shaped connector
- Ring Terminal: Circular ring to attach to a battery post/stud
- Flag Terminal: Rectangular and flat terminals with holes for wire attachments
Alkaline batteries may also use clip terminal connectors for devices. The connectors may have snap-on metal clips that are under tension, surface-mounted contacts on a plate, or contact springs.
Wire-to-Board Connectors
Wire-to-board connectors consist of pins and sockets placed on boards that are located on lead wires. They rely on crimp designs as the number of pins will need to match the number of receptacles on the connector for the device. This feature allows for proper mating between the pins and sockets for a secure connection that will not easily pull apart due to vibrations, shocks, or other environmental factors. Wire to board is common for lithium-based batteries.
There are several different ways that connectors mate for battery packs. These configurations will be based on the available space within the device while not compromising the amperage, current, or charging capabilities. Three main configurations consist of the following:
- Coplanar: When the connectors are mated, the boards run along the same plane.
- Perpendicular: When the connectors are mated, the boards meet each other at a right angle.
- Parallel: When the connectors are mated, the boards will not intersect.
The connectors typically have conductor pins that are longer than the others that act as the ground for the current that returns from the device. The other pins will either provide a pathway for the current to flow from the battery pack into the device or provide a pathway for the flow of power from the device into the batteries. Consumer products, electronics, and some medical devices may use wire-to-terminal connectors.
Wire-to-Wire Connectors
Lithium-based and nickel-based chemistries may use wire-to-wire connectors. As the name implies, wire-to-wire connectors attach two sets of wires together. At the end of the lead wires are a male and female connector.
The connectors may snap lock in place or use crimping technology to form a secure attachment. Some connectors may have a small tab to unlock the connectors to disconnect the batteries. These connectors are often found for automotive, medical, marine, and electronic applications.
Selecting Connector Types
The connectors themselves will have differing sizes and shapes when attached to the device or the battery pack. The connectors may provide easy and quick attachment, provide a temporary connection, or be designed for long-term usage.
When selecting the connector type, take into consideration the power requirements of the application as well as the wire size to select a connector that is compatible with both. You also want to select materials that offer good conductivity and are strong in their connections. For certain applications, you may require a connector that can easily be installed or disengaged when needed.
Common Connector Failures
Corrosion that is caused by environmental factors, moisture, humidity, or battery aging can cause batteries to fail. It can appear as a powdery substance that is greenish and bluish in color along the terminals. Other common connector failures include wires that don't properly mate together, which can cause loose connections, high temperatures, overcharging, or faulty cables.
Loose connections or faulty connections may be caused by manufacturing issues, damage to the connectors during assembly or transport, environmental factors, or mishandling of the device while in use. Performing testing of the connectors can determine potential issues and rectify these problems.
Summary
Connectors for custom battery packs can come in several different sizes, shapes, and mating configurations. Knowing what the options are based on the specific application can allow customers to select the appropriate connector for their battery pack.
Speaking with battery engineers can allow a customer to determine the types of materials and connector locking devices to use, especially for applications that may be prone to moisture or vibrations that could cause loose connections or wires to become faulty.
Key Takeaways
- Connector Types Vary by Battery Chemistry: Connectors differ based on the battery type, such as lithium-ion, lead-acid, or nickel-based batteries, and include terminal, wire-to-board, and wire-to-wire connectors.
- Terminal Connectors for Heavy-Duty Applications: Common for automotive, industrial, and marine systems, terminal connectors come in various forms like post, clamp, ring, lug, splice, and flag terminals, offering versatile connection options.
- Wire-to-Board Connectors for Secure Connections: These connectors are ideal for lithium-based batteries, using configurations like coplanar, perpendicular, and parallel for secure connections that withstand vibrations and shocks.
- Wire-to-Wire Connectors for Flexible Applications: Used in automotive, medical, and electronic devices, these connectors securely attach wires with snap locks or crimping, often offering easy disconnection via a tab.
- Key Factors in Connector Selection: Consider power requirements, wire size, conductivity, and durability. Applications prone to moisture or vibration may require specialized connectors for long-term reliability.
- Common Connector Failures: Corrosion, loose connections, and faulty mating are frequent issues caused by environmental factors, manufacturing defects, or mishandling. Proper testing and material selection can prevent failures.
- Consult Battery Engineers: Working with engineers during design ensures the correct materials, locking mechanisms, and configurations are chosen to meet the application’s performance and environmental needs.
