# Fuel gauge accuracy

**URL:** <https://community.particle.io/t/fuel-gauge-accuracy/33588>\
**Category:** Firmware\
**Created:** [June 7, 2017, 2:10pm UTC](https://community.particle.io/t/fuel-gauge-accuracy/33588 "2017-06-07T14:10:20Z")\
**Posts on this page:** 1\
**Showing post:** 5

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**Author:** ![bko](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/bko/32/20704_2.png) [@bko](https://community.particle.io/u/bko)\
**Post date:** [June 7, 2017, 8:54pm UTC](https://community.particle.io/t/fuel-gauge-accuracy/33588/5 "2017-06-07T20:54:16Z")

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I will admit to trying to simplify things a bit. The charging IC has trickle, pre-charge, constant current (fast charge), and constant voltage charging modes. See Figure 11 in the datasheet.

When the constant current phase ends and the device enters the constant voltage phase, it is hard to know what the actual state of charge is. The reliable indicator is the charging current at that point since the voltage will be constant.

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