I appreciate any help as I try to figure this lightbox project. I need to wire up to 144 3V (built-in resistor) LEDs from flickering tea lights (normally battery powered).
Not sure how many to wire in parallel for a 120V outlet, and what power adapter to get. Suggestions welcome.
3V LEDs can't be wired in parallel and plugged into 120V AC socket.
They will all be destroyed.
They can only be wired in parallel and powered from (approximately) 3V DC
This article "Hacking a Candleflicker LED" suggest that it might not be practical to wire a few in series either as they appear to modulate their power supply.
Edit:
You could drive them in parallel with a 3-5V power supply.
Assuming each LED is no more than 30mA (0.03A), 33 LEDs would be 1A. A 'wall-wart' would be cheap. (The LEDs might be even less power.)
Edit2:
While we haven't got a datasheet for your tea light LEDs, you might want to compare them to this range of Candle Flicker LEDs to get their current rating.
For example, these Yellow 5 mm Clear Candle Flicker LED are rated at forward current of 30mA. They need a current limiting resistor on each LED. Some have quite significant forward current (abut 3x nominal), so decoupling capacitors would help. Also the power supply should be increased significantly to ensure it has some headroom.
I would build the chain in sections and test them using a multi-meter to measure current, to ensure it stays within the capabilities of a power source. Be careful when measuring current because the LEDs are not on all the time, so the reading might be wrong. Give yourself some headroom.
Also, you should account for voltage drop if this is going to be a long run of any sort. 40 ft of 22 guage wire would cost you 2 Volts for instance so you should consider running a 5V power supply to compensate if you are running any lenght. Here is a voltage drop calculator. http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=52.96&voltage=5&phase=dc&noofconductor=1&distance=40&distanceunit=feet&eres=1&x=64&y=21
You have shorted all LEDs. This is not a parallel connection of the LEDs yet. 
Again 3V LED can't tolerate 120V. If you want to connect those LEDs in parallel then you have to use voltages near 3V and some resistances in series to fix the current. One more thing is that you have to keep in mind the current rating of the supply. If you want to connect too many LEDs in parallel then it requires more current.
Try to use the combination of Series and Parallel for LEDs. In this way you might be not worried about the need of high current or voltage. But make sure All the LEDs must have same voltage and current rating otherwise they will get burn.
You could just use thicker wire - your still gonna get a voltage drop but how much is 14 awg wire. Just saves some work of having to solder all those resistors in.
You could also apply a step up transformer if your working with pulsed DC this just factor in .7 for a diode drop and place it were the voltage drops below your target goal starting off a bit high say 3.3 would also help but not any higher
Also if your power supply is unregulated using a higher voltage and adding resistors will allow for a larger change in input power. A regulated power supply will give 3 volts at almost no load and close to 3 volts at max load minis wire loss. So the first LED might 2.95 assuming you start out at 3 volts knowing the exact voltage drop is gonna be tricky .
You could calculate it in say blocks of 5 feet just average it out and expect the voltage at the end of one block will be close to the voltage of the next block. LEDs in the middle will be close to the total average of the entire block minus the expected wire loss to the end of the block. As one block leads into the next it will have all the current for LEDS in current block and all past blocks. You could try to calculate this one LED at a time but that all depends on the exact placement of the LEDs on the wire any any defects in the wire quality of the splicing. For something like this I would take the typical math and add 5 percent to that total.
Your can expect increased loss so that 5 v Power supply should be more like 5.05 or even 5.1 is not gonna hurt heck 5.2 would remain within spec .
Most wall warts do not allow you to adjust them like this. A Meanwell LED power supply will allow for this type of adjustment and they are fairly non expensive in the current range your looking at. Likely not any more than a wallwart once you do all your math put the parts together apply power at 5 volts measure the voltage across each LED ..
If your math was off the ones at the end will be a bit lower than expected. Raise voltage slightly. You could also run 2 or more sets of wire to reduce current say first wire has 15 feet of 40 second set has slightly less 10 feet of 40 3rd set has 7 feet of 40 then 4th set has 5 feet and the last set has 3 feet yes that string will have 40 feet of LEDs. But more than 40 feet of wire as each set of LEDs will have blank wire until the set before it ends this setup will allow for 3.3 volts to be used.
Note the first few LEDs will run a bit high all others will be within spec. If your running 18 small wire still need to know the current draw of the LEDs.
These things run off a button cell battery so they should be pretty small but large numbers it will add up to a bit
