# Why wont my 3volt LED light up with two 1.5volt Batteries?

I have two 1.5 Volt batteries, a Red 3V LED, and some cables.

The batteries I have connected in series like

+- +-


From my studying I believe I should now have 3 Volts ready when I need.

I connected two copper cables, 1 at the negative end and 1 at the positive end.

I believe the volts should push the current from the negative end of the battery towards the LED and then back out towards the positive end of the battery.

I noticed the length of the leg cable on one pin on the LED is longer than the other, I have tried two different LEDS both ways and the LED still does not light.

I have attached a picture below.

I have also tried inserting a 270 ohm resistor at the end of the negative cable of the battery but before the LED - This still doesnt allow the LED to light.

What am I doing wrong here? Is my understanding correct?

I have also tried lighting the LED with just one battery, it does not work either.

• I suspect that you have poor (or no) contact between cells or between the wires and the cell terminals - bits of sticky tape do not make a good battery holder! Aug 12, 2015 at 0:57
• if I remove the LED and touch the wires, the terminals get very hot, shouldnt this indicate that we have a full circuit? Aug 12, 2015 at 0:58
• Assuming it is a normal red LED, it should definitely glow. I don't think there is anything wrong with your conceptual understanding. The problem must be related to the setup. The polarity does matter. You have to connect the LED cathode to battery - terminal, and LED anode to battery + terminal. If you are not sure just try it both ways. Aug 12, 2015 at 1:02
• Also remember that the LED may be manufactured with a longer lead indication the anode (+), BUT one could easily snip the leads to make them shorter. If you look at the LED closely you will see that the LED isn't perfectly round, there is a flat edge. This flat edge indicates the cathode (-). Make sure polarity is correct. And it is always good practice to place a resistor in series with the LED. Cheers! Aug 12, 2015 at 1:52
• @PeterBennett Your first comment was right, it was the poor contact, Thanks Aug 12, 2015 at 2:43

Everything seems fine to me, these are few things that might be wrong:
1) Batteries are bad, maybe not completely empty, but empty enough to not give needed voltage. Try different ones
2) LEDs are dead, they may burn if you connect them without resistor, so its better to connect at least any resistance(if you don't have specific values like 330 Ohms, just put anything around it). But if they are dead - they are dead, you need different one then.
3) Check if you have any conductive stuff around batteries that may connect them directly to each other(between two poles), this will make a short circuit and current will not flow through LED.