Rechargeable Battery Packs Benefit From Integrated Battery Pack Monitor

Increasingly, electronic devices are depending on more than one battery unit for deriving power—driving motors require a higher voltage than does the control system. This includes energy storage systems, toys, scooters, e-bikes, handheld power tools, lawn equipment, and vacuum cleaners. So far, battery monitors could only monitor the entire battery pack and not the individual batteries making up the pack. Now, Intersil has developed a battery pack monitor with a difference. Not only can it monitor 3-to-8 cells simultaneously and individually within a pack, it can cater to different battery chemistries as well.

The battery pack monitor from Intersil, the highly integrated ISL94202, enables designers to restrict their design to only two terminals, while accurately monitoring, protecting, and balancing each cell of a rechargeable battery pack, thus ensuring their safe operation and charging.

Acting as a stand-alone protection system for batteries, the ISL94202 has an internal state machine sporting five pre-programmed modes. Apart from accurately balancing and controlling each cell in the battery pack, these modes also protect the entire pack from catastrophic events such as cell voltage over-discharge/ overcharge, short circuit conditions, and hardware faults. Additionally, the ISL94202 conforms to the pack safety requirements of IEC62133, UL2271/72, and UL2054 standards.

Using the ISL94202 does not require an external microcontroller. Designers can directly program the battery pack monitor, which Intersil claims can control the smallest and least expensive battery packs available in the industry. However, the ISL94202 has an I2C serial communication bus, through which it can transfer data such as the state of health, state of charge, and fuel gauge measurements related to the cells to an external microcontroller. The device has a high-side current measurement feature that enables precise fuel gauge status monitoring.

It is easy to interface the ISL94202 to tools or electric motor equipment, as the battery pack monitor integrates high-side FET drive circuitry for charging and discharging—keeping all electronics at ground level reference. The device also has external passive cell-balancing switch controls, which ensure proper cell energy matching, while protecting the cells individually from chronic undercharging. Manufacturing is greatly simplified as the ISL94202 has the capability to withstand hot plug events such as those happening during factory assembly of battery packs.

According to Philip Chesley, a senior vice president with Precision Products at Intersil, customers can expect all the necessary front-end battery features from the ISL94202, against catastrophic pack failures. The innovative high-side FET control can monitor current and cell measurement while delivering a small footprint solution for efficient battery pack designs.

ISL94202 has a temperature sensor interface, power FET control, current sense monitor, and automatic cell balance using a 14-bit ADC, all without needing recourse to an external microcontroller. It can handle cell voltage level shifts of up to 4.8 V per cell, while monitoring for different battery chemistries such as Li-ion FePO4, Li-ion Mn2O4, and Li-ion CoO2.

For cell balancing, the ISL94202 can use external FETs being driven by the internal state machine of the device, or an external microcontroller. Additionally, the ISL94202 covers the operational industrial temperature range of -40°C to +85°C, measures 6X6 mm, and comes in a 48-lead QFN package.