I'm powering my raspberry pi with 2 no-break batteries. I want to know if is there any way for me to know how many percent of the battery is left. If is there anyway to measure it would be great so I could know when to charge, and when to turn off without damaging the SD card.
Already found out how to make it. If someone else needs it too, you will measure the voltage of the battery, and with that you can convert in percentage with a table like here: http://www.mmbalmainauto.com.au/PDF/State_of_charge_12_volt_batteries.pdf
eg. with battery of 12v: 100% - 12.7V 90% - 12.64V etc..