– How many voltage is equal to how many percentage charged.
The state of charge of a battery can be determined by measuring the gravity of the fluid in the cells. As this is very unhandy for the daily life, can the state of charge also to some exten be measured by the voltage of the battery – and to be accurate has the battery to have rested for some hours, without charge or discharge. The later can also be somehow unhandy as it hinders the charge or use for some hours. So the voltage can in daily life actually just be used as lose indication of the state of charge. This is actually also fine, as you will strive to have them at between 50 and 100 percentage anyway for them to last as long as possible.
As you are working with low voltage, the amperes can get dangerous. This is based in the fact, that the amperes are influencing how much energy is left in your cables – and if this gets to high in any way, you can melt the cables and start a fire. – SO, BE AWARE of the risks and choose the right dimensions.