Ni-MH Open Circuit Voltage vs State of Charge

Can we tell the state of charge of NiMH cell by measuring its open circuit voltage?

According to papers I read on internet it is possible. So let’s put it into test.

Methodology

Test object: Panasonic Eneloop for its consistency and low self-discharge
Currents: 1.0A charge current, 0.5A discharge current
Test steps: for different state of charge repeat:

Voc as a function of SoC

** !!! DRAFT - THIS IS STILL A WORK IN PROGRESS !!! **

Voc as a function of SoC

SoC as a function of Voc

By swapping X and Y we get the inverse function - useful for estimating the state of charge from open circuit voltage.

SoC as an inverse function of Voc

Conclusion