Per-Cell BMS? Maxim Energy Meter MAX17048-17049

[amberwolf]

Only for 1 or 2 cells, but perhaps this could be used one per cell or parallel cell group, to truly monitor capacity of a pack at the cell level. I think it would need optical isolation for the serial data lines and the ALRT line to the outside world but I'm not sure. If so, each cell would power it's own MAX1704x chip and optos.

You'd have to write code for an MCU to control these chips and track their data, but it could then easily keep track of an entire pack's *true* SOC, as it would know what each cell or cell group's actual SOC is, and how it degrades over time with pack age. Then the MCU could warn you, or even (using other hardware) physically disconnect the pack from the outside world if it reached a critical state that coudl cause a fire if it continued to be discharged or charged beyond that point.

View attachment MAX17048-MAX17049.pdf

Industry’s Simplest Micropower Fuel Gauge from Maxim Integrated Reduces Quiescent Current by 4x and Size by 3x

http://www.maximintegrated.com/company/newsroom/pr_products/show.mvp/npk/1691
http://www.maximintegrated.com/datasheet/index.mvp/id/7636
http://www.maximintegrated.com/app-notes/index.mvp/id/5539

http://www.maximintegrated.com/design/tools/applications/evkit-software/index.cfm?EVKit=1025
http://www.maximintegrated.com/design/tools/applications/evkit-software/index.cfm?EVKit=1024
http://www.maximintegrated.com/datasheet/index.mvp/id/7782
http://www.maximintegrated.com/datasheet/index.mvp/id/7783
http://www.maximintegrated.com/app-notes/index.mvp/id/5037

http://datasheets.maximintegrated.com/en/ds/MAX17048-MAX17049.pdf

Description
The MAX17048/MAX17049 ICs are tiny, micropower current fuel gauges for lithium-ion (Li+) batteries in handheld and portable equipment. The MAX17048 operates with a single lithium cell and the MAX17049 with two lithium cells in series.
The ICs use the sophisticated Li+ battery-modeling algorithm ModelGauge™ to track the battery relative state-of-charge (SOC) continuously over widely varying charge and discharge conditions. The ModelGauge algorithm eliminates current-sense resistor and battery-learn cycles required in traditional fuel gauges. Temperature compensation is implemented using the system microcontroller.
The ICs automatically detect when the battery enters a low-current state and switches into a low-power 4µA hibernate mode, while still providing accurate fuel gauging. The ICs automatically exit hibernate mode when the system returns to active state.
On battery insertion, the ICs debounce initial voltage measurements to improve the initial SOC estimate, thus allowing them to be located on system side. SOC, voltage, and rate information is accessed using the I²C interface. The ICs are available in a tiny 0.9mm × 1.7mm, 8-bump wafer-level package (WLP), or a 2mm × 2mm, 8-pin TDFN package.
	
Data Sheet
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An evaluation kit is available: MAX17048EVKIT, MAX17049EVKIT MAX17048XEVKIT, MAX17049XEVKIT

NOTE: This product uses the following:
MAX17049 EVKit Software
MAX17048 EVKit Software

Key Features

    * MAX17048: 1 Cell, MAX17049: 2 Cells
    * Precision ±7.5m­V/Cell Voltage Measurement
    * ModelGauge Algorithm
          o Provides Accurate State-of-Charge
          o Compensates for Temperature/Load Variation
          o Does Not Accumulate Errors, Unlike Coulomb Counters
          o Eliminates Learning
          o Eliminates Current-Sense Resistor 
    * Ultra-Low Quiescent Current
          o 4µA Hibernate, 23µA Active
          o Fuel Gauges in Hibernate Mode
          o Automatically Enters and Exits Hibernate Mode 
    * Reports Charge and Discharge Rate
    * Battery-Insertion Debounce
          o Best of 16 Samples to Estimate Initial SOC
    * Programmable Reset for Battery Swap
          o 2.28V to 3.48V Range
    * Configurable Alert Indicator
          o Low SOC
          o 1% Change in SOC
          o Battery Undervoltage/Overvoltage
          o VRESET Alert
    * I²C Interface
    * 8-Bit OTP ID Register (Contact Factory)

	  	
Applications/Uses

    * Digital Still and Video Cameras
    * e-Readers
    * Portable Game Players
    * Portable Medical Equipment
    * Smartphones/PDAs
    * Tablets and Handheld Computers
    * Wireless Handsets

	  	 
Key Specifications:
Battery Protectors, Selectors and Monitors
Part Number 	Functions 	Battery Type 	Interface 	Parameters Measured 	VSUPPLY
(V) 	VSUPPLY
(V) 	Package/Pins 	Smallest Available Pckg.
(mm2) 	Oper. Temp.
(°C) 	Budgetary
Price
min 	max 	max w/pins 	See Notes
MAX17048  	Fuel Gauge 	1 Cell Li-Ion 	2-Wire 	
C Rate
State of Charge
Voltage
	2.5 	4.5 	
TDFN/8
	4.4 	-40 to +85 	$1.12 @1k
MAX17049  	2 Cell Li-Ion 	
TDFN/8
See All Battery Protectors, Selectors and Monitors (34)

Maxim's ModelGauge™ algorithm reduces design complexity and maximizes battery runtime.

San Jose, CA—January 2, 2013—Maxim Integrated Products, Inc. (NASDAQ: MXIM) today announced that it is now sampling the MAX17048, the industry's simplest low-power fuel gauge for Lithium-ion (Li+) batteries. Operating at only 23µA, this battery fuel gauge uses 4x less power than competitive devices and even less in micropower hibernate mode, in which the fuel gauge continues to operate. It needs only one external capacitor, not the multiple external devices of competitive devices, so it simplifies designs, shrinks solution size by 3x, and reduces costs. This fuel gauge is ideal for portable battery-powered applications where size, cost, and power are critical, such as smartphones, wireless handsets, and mobile accessories, including Bluetooth® headsets, portable speakers, fitness devices, and Wi-Fi® routers.

Traditional fuel gauge designs require multiple external components including current-sense resistors, which increase both bill of materials (BOM) cost and design complexity. Those fuel gauges also use coulomb counting, which can drift and affect the accuracy of the gauge over time. The MAX17048 features the proven ModelGauge™ algorithm and does not require coulomb counting to report accurate battery state-of-charge, thus extending runtime. The MAX17048 functionality is also integrated into the company's TINI® Power System-on-Chip (SoC) to make it easier to upgrade designs to more complex systems.

Key Advantages

    * Accurate fuel gauging: ModelGauge algorithm provides accurate state of charge and compensates for temperature and load variation.
    * Simplified design: The algorithm also eliminates the need for the current-sense resistor required in competing coulomb-counting fuel gauges.
    * Power conservation: The MAX17048 automatically detects when the battery enters a low-current state and switches into a low-power 4µA hibernate mode, while still providing accurate fuel gauging. The IC automatically exits hibernate mode when the system returns to active state.
    * Upgrade path to full power management: The MAX17048 functionality is available in a Power SoC with identical IP to facilitate a complete power-management solution in a shortened time to market. 

Industry Commentary

    * "Mobile device manufacturers are increasingly paying attention to enhancing user experience to set themselves apart from their competition," said Bakul Damle, Business Director at Maxim Integrated. "Having a simple but trustworthy fuel gauge to correctly inform the user about the battery status as well as improve runtime goes a long way in achieving this goal."
    * "Although fuel gauges have traditionally been found in notebook computer applications, they are increasingly appearing as a critical 'must-have' element in consumer devices. With a highly accurate fuel gauge, customers know how much battery is left in their mobile device and that gives them confidence in the product," said Susie Inouye, Principal Analyst of Databeans. 

Availability and Pricing

    * The MAX17048 is available in an 8-bump WLP package (0.9mm x 1.7mm) and an 8-pin TDFN package (2mm x 2mm).
    * Pricing starts at $1.12 (1000-up, FOB USA). 

About Maxim Integrated
At Maxim Integrated, we put analog together in a way that sets our customers apart. In Fiscal 2012, we reported revenues of $2.4 billion.

Contact: 	Ferda Millan
408-601-5429
Ferda.Millan@maximintegrated.com
Additional Information: 	MAX17048, MAX17049
High-resolution images: 	Download RGB: (TIF.ZIP)
Download CMYK: (PDF)