Battery Holder - Design Considerations

Design Considerations

Design of the battery holder requires knowledge of how and where the larger product will be used. Human factors to be considered include ease of battery exchange, age range and physical condition of the intended user. These elements must be taken into account for a design to be successful and are part of the design process. A designer must select between a battery holder molded into the product case or made as a separate part. For many products regulations and product safety standards affect the battery holder selection.

Most current battery holders are made with polypropylene or nylon bodies rated for 80-100°C. Lithium coin cell holders are made with high temperature PBT, nylon or LCP bodies because they normally are circuit board mounted and require wave soldering at 180-240°C or reflow soldering at 260-300°C.

Battery contacts are the most important part of the design and require serious consideration. Since batteries are nickel plated, it is recommended the contacts be nickel plated to prevent galvanic corrosion between dissimilar metals. Battery contacts may be fixed contacts, flexible contacts, or some combination of the two.

Fixed contacts are inexpensive but prone to loss of electrical connection. Combination of fixed and flexible contacts are a better solution, but this is subject to an open circuit upon movement in the direction away from the fixed position; the spring contact compresses and allows the battery to move away from the fixed contact. A flexible contact allows for slight expansion of the cell on discharge, as internal chemicals increase in volume. Flexible contacts with multiple fingers touching the anode and cathode allow for movement in multiple directions without losing electrical connection.

Features like polarity, or reverse battery, protection can be part of the design. The contact for the anode side can be recessed behind plastic and receive a battery nub common on Alkaline batteries. Another method is a plastic channel to receive a battery post or terminal. In July 2010, Microsoft announced its plans to partner with several other companies, including Duracell and MPD, to utilize its patent no. 2007/0275299 A1, which is a new kind of polarity protection in which a battery can be inserted into a battery holder in either orientation and still operate properly. Although other technologies have existed which could do this, they were expensive or caused a passive energy drain on the battery, whereas this solution is purely mechanical and affordable to produce.

Battery types such as the 9-volt have snap-on contacts.

Battery holders for zinc-air batteries must not be completely air-tight since approximately 1 litre of air is required per ampere-hour of discharge per cell. The battery holder may include a valve integrated with the device power switch to allow air to be admitted when the device is switched on.