Universal Li-ion Battery Charge Indicator 1S - 8S 18650
http://alii.pub/5ofxc3 - universal LED indicator
Review and test of the universal battery level indicator, suitable for measurements with a choice of 1 to 8 series-connected elements with an upper threshold of 4.2V and a lower threshold of 2.5V per cell.
More indicators
http://alii.pub/5oimh6 - LED indicator and voltmeter
http://alii.pub/5oimod - LCD indicator and percentage/voltmeter
http://alii.pub/5oin4w - LCD indicator, voltmeter and percentage
http://alii.pub/5oimwx - LED indicator, percentage, voltmeter and temperature
http://ali.pub/34fek8 - accurate capacity indicator, wattmeter
http://alii.pub/5og3j4 - vacuum cleaner motor
http://alii.pub/5ofxpw - Li-ion 26650