Yes, the Innova is great for finding parasitic leaks in boats and cars. Turn everything off..... EVERYTHING and then disconnect the negative battery cable. Insert the meter in series with the neg bat terminal and the end of the cable. If there is a current leak it will show on the meter when it is set on the AMPS function. Becareful that you don't turn anything on when the meter is connected because the AMP mode is not fused. If a current reading shows on the meter start pulling fuses and disconnecting devices until the reading drops to zero therefore isolating the problem
Often rechargeable batteries (depending on the chemistry) are less than 1.5 v at full charge, as low as 1.2 v, and the rechargeable might be low enough to trigger the low battery indicator, or worse make inaccurate readings, though that should not be the case.
This tester will show any voltage across its probes, AC or DC. So, the answer is yes, it will register 3.6 if your battery is good. It is a good tester, the only downside being the letters around the dial are in dark ink on a dark background. You may need a flashlight to set the dial.
I see the same thing with another green LED. I tried checking an old rectifier I had, a 200 v 15 amp diode, and the screen shows .471 when checking in forward, .0L when checking in reverse. I confess, I don't know what this means.
BTW, I connected the LED to a 3v supply to verify that it was OK.
I use the Meter mostly to check on computer Power Supplies, However I also have wireless Security system that uses batteries in the sensors. You ill see 3 holes( ports) at the bottom of the meter. Place the black lead into the black port and the red lead into the red one on the right. If you are testing AA batteries (1.5V)move the dial from the off position to the left to 1.5V, touch the black lead to the negative side of the battery and the red lead to the positive side of the battery, the meter should read about 1.560 or there about for a fully charged battery. Note: a Green LED = good battery, a yellow =a failing battery, a red = a dead battery.
Repeat the same procedure to test the 6V,9V 12V. One very good feature of the meter is that it will power off if you should forget to do it.