Battery voltage logger? Random shutdowns on Macbook Air

Is there any direct way (command line) someone could share, to recursively log into a file the voltage level of the battery? I just bought a new battery for my loyal macbook air (2012). After a few months of usage, it abruptly and randomly shuts off the laptop at 70% or less. Then it starts again as if nothing happened, but it can anytime randomly happen again–it did. With power cord everything is fine. I'm in contact with the battery manufacturer, they are quite old and reputed IMO (Kingsener), but I would like to gather some more info. Maybe a logger can detect a voltage drop right before it shuts off. This would also prove that the battery is interrupting the supply, instead of some hardware problem at my power management circuit or anything they could claim. I found this app that seems to draw graphics, but it is paid and I wouldn't like pay in these circumstances. https://www.bresink.com/osx/0BatteryMonitor/Docs-en/pgs/0040-Graphs.html Any other suggestions on the cause of the problem are welcomed! Reset SMC is done. Winter cold maybe? Greets, Domingo