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I've been through a few design iterations of an 8 bit MCU, using a voltage divider and ADC to display the battery level of a system. It works okay, but I've found reading battery voltages requires a bit of acrobatics in the software to average and clean and hide any gremlins from the end user as the batteries age and start acting funky.

I'm loosely aware of gas gauge ICs, and what they do -- also how much they cost... not cheap (well compared to a "free" ADC on your MCU + two resistors for the divider network).

Is anyone aware of any alternative ICs or approaches, that cost less than a gas gauge IC but require a bit less development time than an ADC + Voltage Divider? (I'm thinking like ~$0.10). I'm seeing low cost gas gauge ICs reading voltages and calculating current, so looks like the most recent approach?

I haven't been around embedded systems very long, so maybe there are some older ICs prior to gas gauge ICs that can get the job done? Some different approach?

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    \$\begingroup\$ You want to read the voltage or the state of charge? These are pretty different. \$\endgroup\$ – Eugene Sh. Feb 28 '18 at 20:50
  • \$\begingroup\$ Read the voltage, I'll clarify that. (I see Gas Gauge ICs from ST with both functions integrated...). \$\endgroup\$ – Leroy105 Feb 28 '18 at 20:52
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    \$\begingroup\$ Then you really don't need a fuel gauge or a special IC. ADC should work just fine. \$\endgroup\$ – Eugene Sh. Feb 28 '18 at 20:53
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    \$\begingroup\$ @Leroy105 The voltage is very poor indication of the SOC. Batteries have memory and a very non-linear response. There are many variables the fuel gauge is trying to integrate. But even then it is not very accurate. \$\endgroup\$ – Eugene Sh. Feb 28 '18 at 21:01
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    \$\begingroup\$ Older ICs didn't get the job done ... older batteries were less critical about blowing up if mis-handled, and nobody expected accurate gauges. \$\endgroup\$ – Brian Drummond Feb 28 '18 at 21:05
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1 cell LiPo battery guage $0.15/ea for IC only DS2782

Precision Voltage, Temperature, and Current Measurement System
Accurate Stable Internal Time Base
Absolute and Relative Capacity Estimated from Coulomb Count, Discharge Rate, Temperature and Battery Cell Characteristics
Accurate Warning of Low Battery Conditions
Automatic Backup of Coulomb Count and Age Estimation to Nonvolatile (NV) EEPROM
Gain and Tempco Calibration Allows the Use of Low-Cost Sense Resistors
24-Byte User EEPROM or 16-Byte User EEPROM and Unique 64-Bit ID
Industry 2-Wire Interface with Programmable Slave Address
Tiny 8-Pin TSSOP and 10-TDFN Packages Embed Easily in Thin Prismatic Cell Packs 
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