ive got a string of LED christmas lights here, and have discovered i can substitute the tiny 2 AA power supply with one 18650 and it'll run fine?
@pearshapes I have to advise against doing that, though, unless it's a protected 18650. A bare lithium cell hooked up like that runs the risk of over-discharging.
@Rosemary a protected 18650? the ones i have have protection circuitry i believe
@pearshapes Make sure of that, if you can. While overdischarging isn't as risky as overcharging, especially in terms of fire potential, it can still cause problems.
@Rosemary yeah, it's the little lip on the positive terminal right? there's an IC in there?
@pearshapes I'm not sure exactly how they arrange them. I would look up the part number if there's one printed on it.
@Rosemary you think i should just lump a thermistor on it or st if i ever consider running it for a long time? lol
@pearshapes Unfortunately, you need more advanced control than that. If a lithium cell ever discharges below about 2.5 volts, it will never be able to charge back to its full capacity again. It doesn't matter how slowly it discharges to that point.
@pearshapes If you're not concerned about being able to recharge the battery though, you should be okay to use it. Just know that you'll be irreversably damaging the battery.
@Rosemary maybe... a zener diode rated for 3v?
@pearshapes If you put that in, you won't have enough voltage left to power the lights.
@Rosemary so, what, does the zener just absorb the power? i dont understand
@pearshapes Could you explain what circuit topology you're thinking of? Draw a schematic or something?
@Rosemary i'm no electronics engineer! i'm just tinkering
i'm a software developer and i pulled a multimeter out of a bag i found while cleaning then clipped some components off of a busted power supply's board and went "huh, zap zoop do funny thing with needle"
@pearshapes Right, but I'm trying to understand exactly where you intend to put the zener diode, so I can explain what happens with it.
@Rosemary just like. slurp that thing straight into the circuit and cause a small explosion
@Rosemary like, in series with the battery
@pearshapes Ah, yes, the thing about zener diodes is that the voltage across a reverse-biased zener diode is fixed to its zener voltage. The first-order approximation is to think of it like a voltage source.
@pearshapes This one wouldn't cause a small explosion, or at least I don't think it would. It just wouldn't do anything useful.
