another cool little voltage monitor but I had some requirements - I wanted it to be self powered and have an onboard load so I could check any 9 volt battery with it.
this is for a active pickup system so the self powered part of the design wasn't hard to factor in as usable voltage is around 5 ish volts in the EMG's I have.
and Last of all I wanted to use the LM3914 (DATASHEET) cause I've got loads of them from another project I never got around to doing.
I used a 82 ohm resistor (switched in by pressing the push to make switch) this will allow you to test the battery under a normal load which will give you a better indication of the batterys chargethe 82ohm resistor draws almost 110mA
I have done a circuit like this before which was a 0 - 10v voltage monitor (HERE) but the difference between that one and this is that this one is powered by the battery you're testing and the other one though more accurate needs a second power supply.