A Battery can be modelled as an RC network, which has an impedance. If we take 4.2V L-ion battery with internal resistance of 0.1 ohm, and by applying 4.2 V, at OCV of 3.7V, it will not accept 5A.

What actually happens electrically while charging the battery?

  • \$\begingroup\$ from my understanding. Internal resistant is not constant value. It use for correct the experiment result. \$\endgroup\$ – M lab Aug 9 '20 at 5:50
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    \$\begingroup\$ Oh you forget that battery have voltage in it. let say it 3.7V when you apply 4.2 the voltage across resistant is 4.2-3.7 = 0.5V and you got 5A \$\endgroup\$ – M lab Aug 9 '20 at 5:52
  • \$\begingroup\$ @Mlab you are right. But over the period of time, it may rise to 3.8V, 4 V and finally 4.2V. So charging current reduces to 4A, 3A and finally it accepts only trickle charge. I have a doubt that to make the Charging current constant, do we increase the charging voltage? \$\endgroup\$ – raghul Aug 9 '20 at 6:08
  • \$\begingroup\$ @Chu I mean DC model. \$\endgroup\$ – raghul Aug 9 '20 at 6:24
  • \$\begingroup\$ Actually it just CC, CV regulator.the circuit has current sensor when it detect overcurrent it just decrese voltage until charging current equal setting current. but the voltage must not exceed CV setting. \$\endgroup\$ – M lab Aug 9 '20 at 7:36

A battery will need a charging regime to match its chemistry.

So, this regime will change over time as the battery state changes.

The charging circuit is designed to supply some fraction of the current capacity as some batteries are capable of supplying hundreds, or thousands, of amps for short periods of time - usually seconds.

Charging the battery at its max rate causes overheating, damage and a much reduced lifetime.

So while a battery at a particular point in its charging cycle may be assumed to appear to match Ohm’s law, the chemical reaction may not.


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