When charging E-bike batteries it is recommended to only charge to 80% for general use and store at 60% for maximum life of the cells so accurate checking of the voltage is useful.
Sure you can use a multi-meter and manually check them every now and again but I wanted a way to charge and monitor multiple batteries quickly from a distance so i Created a plug in battery meter for my Hailong style batteries
To build the meter you will also need the following parts...
'Male' battery connector for example https://www.aliexpress.com/item/32973417333.html
panel style Voltage Meter https://www.aliexpress.com/item/33023255446.html
4 x M3x20mm hex bolts