I have a SparkFun USB LiPoly charger that by (default) is set at 500mA. If I try and measure the charge current with my DIY multimeters, the charging LED goes out and the meter reports zero current?

I guess this is because of the multimeter's internal series Vsense resistor confusing the onboard MCP73831 controller chip?

If this assumption is correct, can anyone suggest a DIY method method of measuring small Lithium battery charge currents?

  • \$\begingroup\$ What current range are you using on the multimeter? I'd assume the sense resistor value should be tiny on the 10A range. \$\endgroup\$ – tangrs Nov 30 '18 at 9:01
  • \$\begingroup\$ please add a schematic showing how you connect the multimeter. I suspect that you are doing it incorrectly. \$\endgroup\$ – Jasen Nov 30 '18 at 9:39
  • \$\begingroup\$ Thank you. Yes the 10A range does have the lowest sense resistor (0.1ohm) but on that range the resolution is only +or- 0.01A. The 200mA range (on many meters that I have checked) averages 2ohm but even at that value it seems to be sufficient to cause the charger to miscalculate the battery voltage and turn off? \$\endgroup\$ – mprowe Nov 30 '18 at 11:43

Add a low value resistor and measure the voltage drop across that.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.