I’m pretty green to this whole thing, but i’ve been researching it for a while and have come up with a pretty good idea (I hope at least) for a project.
I want to power an Arduino Uno as well as a few water pumps controlled via a relay with a 12V lead acid car battery (which is not attached to a car) I know the voltage at full charge starts off quite high and this could be an issue with respect to heating up the voltage regulator on the board. I’ve had a pretty good look around and seen this question answered many different times, many different ways, but from what I’ve found it’s mainly been with the battery installed in a car and without concern for the efficiency.
Basically, I want the battery to last as long as possible and as I understand it the voltage regulator is fairly inefficient, particularly at higher voltages, so I wanted to try to avoid going from the battery straight to the Arduino. So I’ve had a few ideas:
Buying a cheap 12V to USB off ebay
Voltage divider (probably more inefficient than the regulator?)
LM7805 and caps
Which way should I go to give the longest time possible between charges?
And, whilst I am here, I would like a way to monitor the battery to determine when I have to charge it again, being lead acid simply measuring the voltage should suffice, so it needs to be <5V, would it be best to use a voltage divider or is there a better way to do it with Zener diodes?