fuel.getSoC() return 22% of car battery fully charged

Hi all,

I am powering Boron with 12V battery and step down to 3.7V to connect it to Boron Lipo battery slot “please see attachment.” however, it sent me signals shows 22% and i know the battery is

fully charged, any idea how to solve that?

when i use a normal LiPo battery it works fine.


A fully charged LiPO would give you 4.2V (~100%)
Consequently with a current reading of 3.7V and a “save” minimum of 3.6V these 22% seem not too far off.

The SoC reading merely applies the typical discharge characteristic of a single cell LiPO to derive the “probable” state of charge judging from the voltage.
If you add a complete unknown (i.e. a different battery and a step-down converter) the fuel gauge has no way of knowing the actual state of your battery.

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the plan to put the unit away , so how to find out the battery "car battery " nearly flat ? shall i use the 22% is my full charge indication?

Thank you

even if i directly connect the 12V battery to Boron Vin?

The Boron’s fuel gauge is not meant to monitor the Vin pin.
If you want a state of charge of a 12V battery you need to find a hardware solution specifically for that - particularly the used chemistry.

If you are using a 12V lead battery, the Boron will happily do its job way past the time that would be any good for the car’s needs.
You’d need to read the raw voltage of the battery and compare that to a useful threshold for the car’s needs not for the Borons.


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