I tried to imagine a situation when light is needed without power and failed.
This logic is good in real life, but in game I want area illuminated. With this logic I would need another lamp.
If only this lamp would be another color it can be power failure indicator.
If you add Mode value I can suggest:
Mode=
0 - light if On=1 (as in base game)
1 - light if On=Power_good
2 - light if On=1 or Power_bad and Tick_is_odd (to flash)
3 - light if On=1 or Power_bad and Tick_is_even (antiphase)

Probably you can use On>1.

It is only an idea of course.

Best wishes.

thanks for checking that out.
i put a little more thought into "how do i want to use battery lights?" and turns out there's only 2 different ways i'd be using them in about 95% of placements:
1) your backup lights
2) my wireless lights.

I've never been "efficient" with wireless lights; i'd often run them around the clock. toggling like 20 lights by hand daily was no good. i consider it to be "cheaper" to spend 1 game afternoon adding panels/turbines/gens. then some rooms (like gas storage) that i could go months without going in. they were where manual control was useful.

thing is (and i'm kinda embarrassed i hadn't realized earlier...) but i can just turn off the power transmitter omni that charges wireless batts if i want to turn the lights off. super easy to set in logic.

unless i misunderstood, the mod should already allow both. setting var for manual control seems good. i actually keep a logic writer on me to toggle device variables for these kind of case.

@froggx
Presently, it will auto turn on if you tried to turn it off.
Another user on the discord (Sukasa) asked about adding a way to have manual control of the lights.
I'm looking into it, since it should be pretty doable, but have not yet have a chance to. This would likely be done by having a logic value where if you write 1 to it, it won't auto turn off even if power is restored.
Might not help your case though where you never run a cable, and thus could never write a logic value.

Due to the way the power grids work in the game, there isn't a good way to make it only happen "once" when power first goes out, so instead it has to do the check every tick hence it turns back on.

I could make it so no cable = normal light functionality though. I originally associated that state as the same as no power.

if there's no cable connected then can the wall light batteries still be turned off (and back on) manually? it seems like it'd be super cool to have emergency backup lighting but my primary use case for these lights is to pop in wireless batteries and light up my base without doing hard stuff like, ya know, running cables (cause my difficulty threshold is just that low).