I decided to disassemble a battery powered tea light to see if there was a way to connect it to a decoder for installation into a firebox, and to my surprise, it was pretty easy to do. I tested it with a NCE decoder that hasn’t been installed in a loco yet, and it worked great. I had to use a 12v to 1.5v resistor on the positive side, and wired it to the headlight wires. Once you get it out of the case, it is small enough to fit into just about any firebox even with the motor there. I’m going to mount it into my Precision scale B&O Q4b for starters. I’ll drill out the firedoor holes with a pin vise. I’ll have to see how it looks under the ash pan to see if I need to mask it a little. I’ll take some pics for anyone who might want to try it, and post them here.
Sometimes things defy logic. As in, the tea light is probably just an LED with a flicker circuit, yet you can also probably get them for lower cost than just a plain LED (unless you buy 1000 LEDs at once). Like whent he LED Christmas lights go on sale - the per LED price is less than you cna buy just plain bare LEDs for in small quantities - so what about the cost of the plug, wire, and fuse?
So hey, if it works, and is cost effective - why not? Most decoders do have a ‘firebox flicker’ effect that can be used with plain bulbs or LEDs (still usually require a resistor), but if the tea light works as well - go for it. One notable example of where the decoder is MUCH better is in those Proto 2000 locos with Mars lights, the decoder Mars effect is MUCH better quality than the silly 2 filament light bulb blinker built in to the locos.