Custom Nickel Metal Hydride (NiMH) Battery Packs
Custom Nickel Metal Hydride (NiMH) battery packs are an increasingly popular choice for many applications due to their low cost, durability, and low operating risks for the end user. This chemistry type can offer a wider operating temperature range than some lithium batteries, which, combined with the much lower development and product costs, makes NiMH the product of choice for many commercial and industrial applications.
Commonly used in applications that require low discharge rates, and where cost is a key factor, the nominal voltage rating of a Nickel Metal Hydride (NiMH) cell is 1.2V, with energy usable in the range of 1.0V – 1.45V per cell. A variety of cylindrical cell sizes are available, providing a capacity range from a few hundred mAh to above 10Ah, which gives designers of custom NiMH battery packs many different options when solving customer problems. NiMH battery packs can accept charge and discharge rates as high as 1C, and as a result, these custom battery packs are able to perform challenging tasks and require minimal time to recharge.
NiMH battery packs prefer a constant current charge where a standard charge can be C/10 for 14 hours. NiMH batteries can take a charge in as little as one hour with dT/dt (delta temperature/delta time) or peak voltage detect termination, along with several other metrics that can be monitors. It is always a good practice to incorporate a timer as backup in case the other methods fail to activate.
Specific Characteristics of NiMH Cells
- Cell Voltage: 1.2V (nominal)
- Energy by Weight: 60-120-Watt Hour/Kilogram
- Energy Density: 140-300 Wh/L
- Cycle Life: 500-2000 Cycles
- Temperature Range: -20° C to +60° C
- Preferred Charge Methods: DT/dt - Peak Voltage Detect and Timer
Download the Panasonic NiMH Cell Catalog for more information.
Battery Protection and Management Circuits
Typically, the protection and BMS circuits are more commonly used with lithium chemistries in order to mitigate the risk of fire in custom battery packs. To help increase the safety of NiMH batteries and extend service life stand-alone and integrated PTC (positive temperature coefficient) protection devices as well as PCM (protection circuit modules) are available in custom Nickel Metal Hydride (NiMH) battery packs.
Our engineering team is experienced in developing NiMH PCM and BMS systems to fit virtually any application in a very cost-effective manner. PTC provides temporary over-current protection with auto recovery where a BMS typically handles the same protections found with PCMs using a microprocessor. This allows for additional monitoring, control, and reporting of a wide variety of parameters and allows users to gain real-time access to an abundance of data through traditional communication protocols (I2C/CAN bus).
Some of the features available for NiMH PCM and BMS systems:
- Over-discharge protection
- Over-current protection
- Over-temperature protection
- Fuel gauge
- Current sensing and limiting
- Temperature monitoring
- State of charge and state of health monitoring
- Voltage monitoring
- Internal resistance monitoring
Choosing the Best Solution for Your Application
As portable electronic devices have become smaller, lighter, and more sophisticated, the batteries that power these devices have had to provide ever-increasing levels of energy. Our battery design team uses the latest design tools to optimize the reliability, safety, and manufacturability of your custom NiMH battery packs. While NiMH is not as closely regulated as lithium products, there are certain transportation regulations that need to be followed when shipping Nickel Metal Hydride (NiMH) battery packs.
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