# What voltage do we use for battery cut off voltage?

I have a battery that states a 2.75v battery discharge cut-off voltage. Is that voltage measured at the poles of the battery while it is connected to the load or they are talking about the electromotive voltage?

For example. A Sony battery I have, when I measure it with a multi-meter it displays 3.61v EMV but when connected on the load it only gives 1.81V at the poles of it. Which voltage I should consider to stop discharging it?

Why such a large difference in voltage?

EDIT: Since you asked, the battery is a Sony US18650GR - O7. It is connected on a custom made circuit with 2 parallel 4.7ohm (5 watt) resistors (2.35 in total) plus some mOhms (maybe 0.5-1 Ohm) due to cables, shunt resistor (current sensing) and connectors resistance. At start it draws something like 1.2 Amps and when the voltage dips at something like 1.81v it draws 600-700 mA. No cut-off (over-discharge) circuit.

• Different cell chemistries have differing charge and discharge requirements. Look up the specific recommendations for that battery. Aug 28, 2019 at 21:28
• Yes, but they don't state if that voltage is the electromotive force or the voltage when connected to a load. Aug 28, 2019 at 21:43
• @ekalyvio Are you referring to the unloaded (open-circuit voltage) vs the loaded voltage (voltage while supplying current?) If so, it still varies from battery to battery. If it is under load you just have to know what the "dead" voltage is for a given current draw. Aug 28, 2019 at 22:10
• Your battery sounds somewhat "troubled". See test results here for a typical Sony 18650 cell - NOT your one. You c an see the sort of voltage drop you'd expect at various loads - yours is dropping to what sounds like a dangerously low voltage under reasonably modest load. | Measurement conditions are specified by manufacturer (or should be) but "under specified load" is the usual expectation. secondlifestorage.com/image/lqdvib. Aug 29, 2019 at 12:13
• I am not saying the my cell is in good condition. It was removed from an old laptop battery that I replaced the cells. I also tried an other 'good' semi-charged Samsung ICR18650-26H cell and this again drops the voltage to 3.0-3.1v under load. I guess that it is because the circuit I am using. But... my question is not about the battery but on if the voltage cut-off is measured with the battery under load or it is the electromotive force of it. Aug 29, 2019 at 12:47