Do light bulbs store energy?

[solvejskovlund]

I wanted to figure out which of my used li-on cells that would match, so I connected them all in parallel to make them equal, then connected them in series for a discharge test. This meant I needed something to use for discharging.... accepting over 800V. What I came up with was borrowing 3x 250V (ac) old style light bulbs from a lamp and connect them in series.

This setup was running for several days, I switched it on/off several times, to make sure it was only running while I was around and able to monitor the process. It all worked out great.

Several weeks later I put those light bulbs back into the lamp I borrowed them from running on 241V ac. At the very moment the light switch was turned on, there was a huge flash, and all the bulbs burned out immediately. Why did that happen?

I could imagine that the light bulbs can store energy, have some voltage. But not for several weeks. This does not make sense to me.

 

[berkeman]

I wanted to figure out which of my used li-on cells that would match, so I connected them all in parallel to make them equal,

That's not a good idea. Batteries should only be placed in parallel if they have equal voltages and the same discharge/charge history. Connecting them in parallel can result in some of the stronger batteries trying to charge the weaker ones, which can cause heating and the potential for fire/explosion.

Several weeks later I put those light bulbs back into the lamp I borrowed them from running on 241V ac. At the very moment the light switch was turned on, there was a huge flash, and all the bulbs burned out immediately.

What kind of light bulbs are these? Are they incandescent or LED or some other technology?

 

[Borek]

I wanted to figure out which of my used li-on cells that would match, so I connected them all in parallel to make them equal, then connected them in series for a discharge test. This meant I needed something to use for discharging.... accepting over 800V.

Perhaps I am missing something, but what kind of li-ion batteries produces over 800V? As far as I am aware it is 4.2 V per fully charged cell, to get to 800+ volts you need almost 200 cells - but connected in series.

 

[DaveE]

The only energy an incandescent bulb can store is the thermal energy of the hot filament. This energy will dissipate quickly and isn't really accessible in practice.

I think your issue relates to damage done to the bulbs, which could have occurred in a few different ways. The lifetime of incandescent filaments can be pretty sensitive to electrical (thermal) stress and mechanical stress. They like AC better than DC, and they don't like the thermal shock of being turned on and off, although those failures take a while. For example, a common assumption is that the life of the bulb versus applied voltage is something like the 13th power of the ratio applied/rated voltage.

The common light bulbs in your house are cost optimized for not being moved, operating from a very stable AC electrical source, and not being turned on/off more than a few of times each day.

https://en.wikipedia.org/wiki/Incandescent_light_bulb#Light_output_and_lifetime

 

[solvejskovlund]

Perhaps I am missing something, but what kind of li-ion batteries produces over 800V? As far as I am aware it is 4.2 V per fully charged cell, to get to 800+ volts you need almost 200 cells - but connected in series.

You're right. 192 cells in series.

 

[solvejskovlund]

I think your issue relates to damage done to the bulbs, which could have occurred in a few different ways. The lifetime of incandescent filaments can be pretty sensitive to electrical (thermal) stress and mechanical stress. They like AC better than DC, and they don't like the thermal shock of being turned on and off, although those failures take a while. For example, a common assumption is that the life of the bulb versus applied voltage is something like the 13th power of the ratio applied/rated voltage.

The shock of being turned on should be way heavier with the 800Vdc/3 (=266Vdc) that they survived several times than the first 241Vac shock that came only once. Any power on shock may kill a bulb. But all 3 of them at the same instant cannot be explained by ware. Most likely they had different use hours before going into my experiment.

 

[DaveE]

The shock of being turned on should be way heavier with the 800Vdc/3 (=266Vdc) that they survived several times than the first 241Vac shock that came only once. Any power on shock may kill a bulb. But all 3 of them at the same instant cannot be explained by ware. Most likely they had different use hours before going into my experiment.

OK. We don't know. Neither do you. That's how it goes with experiments that aren't scrupulously controlled. The fact that they all failed immediately makes me think you did something to them to greatly depleted their lifetime.

As a side note (I'll spare y'all the full diatribe), lightbulbs don't make great resistors. They are a lot more complex than many people realize.

 

[berkeman]

That's not a good idea. Batteries should only be placed in parallel if they have equal voltages and the same discharge/charge history. Connecting them in parallel can result in some of the stronger batteries trying to charge the weaker ones, which can cause heating and the potential for fire/explosion.

@solvejskovlund -- Do you understand my comment/admonishment/warning? From your previous PF posts I know that you do not have much experience with electronics, so it is extremely important that you understand and acknowledge this warning. Please do not start a fire that could harm you or your loved ones or neighbors.

https://www.google.com/url?sa=t&sou...cKEwig3I-K64mSAxUAAAAAHQAAAAAQCA&opi=89978449

 

[solvejskovlund]

That's not a good idea. Batteries should only be placed in parallel if they have equal voltages and the same discharge/charge history. Connecting them in parallel can result in some of the stronger batteries trying to charge the weaker ones, which can cause heating and the potential for fire/explosion.

Sure. That's why they have to be prepared for the mission - make sure voltage is within a 50mV difference before connecting them. The purpose of parallel connection before series is to make sure they are perfectly balanced.

What kind of light bulbs are these? Are they incandescent or LED or some other technology?

The old style, with a thin wire coil inside.

 

[solvejskovlund]

OK. We don't know. Neither do you. That's how it goes with experiments that aren't scrupulously controlled. The fact that they all failed immediately makes me think you did something to them to greatly depleted their lifetime.

As a side note (I'll spare y'all the full diatribe), lightbulbs don't make great resistors. They are a lot more complex than many people realize.

You're right. We don't know. At least I don't know.
I find it strange that the could be switched on/off many times during the test. If that load was weakening them so much, I find it strange that I would happen to stop the experiment at the very last power on/off they could handle. I feel confident that they would light up on DC once more if I had cycled the dc power once more. I think it must be something related to the apply AC after being used with DC, but I can't figure out what it is.

 

[berkeman]

The old style, with a thin wire coil inside.

So incandescent bulbs, and some overstress by your stress is the likely issue in their failure.

 

[solvejskovlund]

@solvejskovlund -- Do you understand my comment/admonishment/warning? From your previous PF posts I know that you do not have much experience with electronics, so it is extremely important that you understand and acknowledge this warning. Please do not start a fire that could harm you or your loved ones or neighbors.

My loved ones were kidnapped two years ago. There's nothing I can do with a battery to harm them.

Regarding my previous posts, I see them as there are 3 or 4 highly active users in here that focuses details that I don't see as relevant for the question asked, and they use that "missing", not relevant, information to bring the thread off topic by assuming that I ask something very different from what I write. These users may be the technical experts. But they are not experts in reading posts from not native english speaker who often don't know the proper english technical term. As an example there have been threads where I write that we have 240V grid supply here, and these "experts" assume I'm in the USA with 120V grid, and being an idiot for not understanding that I'm not living where they are.... Ḯ'm trying to not be offensive to anyone. Not even these "experts".