To specify a custom battery pack, the design engineer needs to fully understand the service application and load conditions both in normal and exceptional service conditions. Understanding the application for the battery influences load voltage/current, heat rise and recharge time requirements. Other things to consider include the device’s operating environment, the physical envelope available for the batteries, weight constraints and regulatory and transportation requirements.
In this scenario, the weight of the battery pack was an essential constraint. The design engineers needed to develop a pack to replace the legacy sealed lead-acid battery, which was underpowered, heavy and too large for an application where portability was essential.
Once the requirements were fully understood, it was time to work with a supplier to move development forward. At Epec Engineered Technologies in New Bedford, Mass., the development process began with a battery pack application review, followed be a series of steps that can include UL certification when needed. Using their in-house product development and engineering services, Epec worked with the customer in weekly meetings to develop the specifications of the new product.
The design team considered multiple battery chemistries, including lithium and nickel-based technologies, but for this application the final result was an advanced lithium ion phosphate battery with fast-charging capability. The internal battery intelligence, including protection circuits, charge state gauging, serial communications buses, LED indicators, battery authentication, cell balancing and an embedded charger were all designed to meet the engineering requirements. An external plastic case was specially designed to withstand rough field conditions.
With the help of their supplier, the design team developed fully functional prototypes in only six weeks. The prototypes were quickly put through environmental and regulatory testing. The finished product was a super-portable battery weighing only 1.25 lbs – much lighter than the previous 6.25 lbs batteries.
Why customized battery solutions?
Custom battery packs, although more expensive to produce; offer multiple benefits where power solutions have tough size, weight and performance constraints. All batteries are limited by their chemistry; they’re fabricated by series and parallel connection of cells, which are typically cylindrical or rectangular in shape. Off-the-shelf battery packs are similarly designed as simple shapes, which lower production costs, but give away much in weight and power density terms. Custom solutions allow the pack designer to maximize power density in the smallest volume with the best possible integration into the parent device.
There’s another advantage to custom solutions, which is often more important: intelligence. With a custom solution, it’s possible to include advanced battery charging and monitoring circuitry in the battery pack itself, saving weight, space and complexity in the parent device. The strategy also moves the battery management problem to the battery vendor, who carries both the expertise and production knowledge needed for superior battery management. The result can be a cost saving cascade that runs throughout the product design process: simpler, smaller, lighter designs with high performance and guaranteed reliability.
The biggest constraint in battery pack development is usually time. In the example above, the product designers got in touch with their battery supplier as early in the design process as possible. All of the steps, including design, prototype, fabrication, approval and production take time. The more clearly the requirements of the new design are understood and communicated with the battery vendor, the more likely that portable power will be a manageable part of the new product development.
About Epec Engineered Technologies
Epec Engineered Technologies has sponsored this post. It has no editorial input to this post. All opinions are mine – Jim Anderton