I am trying to power a cabooses lights with a 9 Volt battery. I have 3 LED's which if I am not mistaken equals 9 volts. I connect them as they should be but two of them keep burning out. What am I doing wrong?
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your drawing to much current led's are only designed for 20ma or so you need to use a resistor to drop enough voltage so the current is much lower! I would suggest you try n run from track power with a diode in series with a dropping resistor and led plus add 220 ohm resister! I think you'll find out just before they burn out they get very hot and then short or open !
My guess is you wired them in parallel to the battery, that's not a proper configuration.
Wire the three white LED's in series and then connect the 9V battery, you'll have much better luck. I'd recommend adding a 150 ohm series resistor as well.
I suspect you don't have power pickups on the caboose, right? If you have power from the track, Alan is obviously right about using track power.
I have added lights to a couple of cabooses with a 9 volt battery and an on/ off switch using LED's from Evan Designs. They cost a little more, but use built in resistors and are a breeze to hook up. I've never had one burn out.
Hard to understand why I wouldn't use track power for an already lighted caboose. The parts to power the flashing LED and the flashing LED are around 75 cents, a diode, a cap, and a CL2 constant current source. Add flashing LED and you're set.
Truthfully, it isn't hard for me to understand why it's hard to sell the battery idea to the customers. 
In my case, one caboose was a cheap model with no lights. The other was another cheap lighted one in which the pickup roller system was beyond repair. A simple fix and no more flickering light.
The already lit caboose would have been great but for some reason this caboose would ground out a cause a short. I examined everything thoroughly and I could not find the reason why it did this. I have all of the LED's I need but I do not know what CL2 is. I have a simple circuit for constant voltage but I found a YT video that show a 330 resistor being used. I will try that so I do not have to worry about blowing those two lights out. I made my own sockets with polystyrene tubing so pulling LEDs in and out are easy to replace. I will post pictures when I am done.
I got the caboose to light after I rewired the roller pickups and grounds. However, when I connected 3 lED's to a nine volt battery with a 330 ohm resistor only one light would light. Thanks for the help all.
LED's in parallel will only work if all the LEDs are exactly the same type. If you're connecting different color LED's in parallel, only the LED with the lowest operating voltage will light, probably a red one.
I'd either wire them in series with the appropriate resistor (best as it's the most efficient use of the battery power), or parallel with individual resistors.
