simple ? voltage question

[Delij]

OK, I am new to all this. Bought my first light recently (Cree C3) and it was only a matter of days before I bought my second light (Inova X0),

Just playing around and probably taking foolish chances...knowing I might fry an LED or worse, curiosity and me are pretty much synonymous.

Anyway, my Cree C3 holds a single AA 1.5 volt battery.

Today I tried it with two 28L cells. So knowing nothing else but the increase in voltage (going from 1.5 volts to 12 volts) I fully expected that if I was going to fry a light, this would be the time.

Well, admittedly I did not leave the light on for very long, and so maybe it would have gone "nuclear' in my hand if I left it on for more than a few moments. But I didn't, and I went back to a single 1.5 volt cell.

However, with 12 volts, that little light was BRIGHT!!!!!

Now.....my questions should be obvious - Why didn't 12 volts fry anything right away? Would it if left on any longer? Is this a valid way of getting more light output? And if so, how short do I need to keep the periods of operation (I have gotten both the Cree and the Inova "too hot' just with regular use (normal batteries, just long use).

Thoughts? Advice? Any input appreciated
(you can see this is my first post)..Don't they say 'there are no stupid questions'? (have I proved that old cliche wrong??? lol)

Peace,
D.

 

[Blindasabat]

I am not familiar with the 28L cells, but I suspect that cell can not support much current, so the voltage drop at the current the C3 asked for was considerable. Meaning it probably dropped from 12V way down under 6V for both of them while still not supplying the current the C3 wanted. It was brighter because the power overall was still higher than it is designed to handle due to the high voltage. I suspect if you leave it on for just a few seconds, it will fry. And it will dim over time if you even intermittently use that power source. Nice to try once, but I wouldn't recommend doing it any more.

 

[Delij]

I am not familiar with the 28L cells, but I suspect that cell can not support much current, so the voltage drop at the current the C3 asked for was considerable. Meaning it probably dropped from 12V way down under 6V for both of them while still not supplying the current the C3 wanted.

Thanks for the reply, but I am confused. The 28L cells say they are each 6 volts. Two of them I assumed would be putting out 12 volts. But you talk about "voltage drop" and I'm not sure what that means.....I'll guess that you are saying that the C3 "asked for" less current? That would make sense assuming there is a regulator, but then ou say that it "dropped from 12v way down under 6v for both of them while still not supplying the current the C3 wanted".....do you mean it "wanted" less? More?

It was brighter because the power overall was still higher than it is designed to handle due to the high voltage. I suspect if you leave it on for just a few seconds, it will fry. And it will dim over time if you even intermittently use that power source. Nice to try once, but I wouldn't recommend doing it any more.

OK, this I understand. But how can we know exactly how much voltage an LED is capable of handling? I see that there is an extention module available for this same little light that lets you put in a second AA battery. So that would seemingly mean that the light that runs fine of 1.5 volts will run even better on 3 volts (and I imagine they would not sell a module that would encourage TOO much extra voltage). So how do we find out what the limit is on any particular LED? (Or LED with regulator, etc.).

Thanks again.

Peace,
D.

 

[Blindasabat]

I had a long explanation written up, but my browser crashed opening a huge pdf (wretched Adobe) and I can't retype it now, but here is a short version:
Example: If a 6V battery with current capacity of around 100milliAmps is put in a light that runs off 500mA, then the 6V will drop (sag) as the battery tries to supply higher current than it is capable of at rated voltage. It MAY be able to supply the current at a lower voltage. this is what happens in most coin cell lights. The little CR2016 cells are 3V each for a total of 6V, and that doesn't blow the little LED because they sag down to about 3.5V under even the 5mm LED's load. The LED asks for more current than the tiny coin cells can support, so they try, and lose voltage as a result.
Your little 6V batteries are suffering the same thing.

Thanks for the reply, but I am confused. The 28L cells say they are each 6 volts. Two of them I assumed would be putting out 12 volts. But you talk about "voltage drop" and I'm not sure what that means.....I'll guess that you are saying that the C3 "asked for" less current? That would make sense assuming there is a regulator, but then ou say that it "dropped from 12v way down under 6v for both of them while still not supplying the current the C3 wanted".....do you mean it "wanted" less? More?

 

[Delij]

Tried another experiment. This one made me a bit more nervous because it would be a more costly error if I fried this light.

I tried switching batteries in my Inova X03.....a pretty bright little light to start with. I took out the 2 c123 cells and was able to fit 2 of the 6 volt little 28L cells plus one of the 123 cells .....I probably could get 3 of the 6 volt cells to fit even more easily....giving me 18 volts. As it was, with the two 6 volt cells and one 3 volt for a total of 15 volts, nothing fried, the apparent light output was greater, but not as significantly as the difference with the previous experiment (taking the cree C3 from 1.5 volts to 12 volts, but of course that was a far greater jump).

Anyway, how far do these things go before they blow up? How much regulating do regulators do?

EDIT: I typed and entered the above before seeing your (BlindBat) last respsonse (it is hard working at my office desk, getting calls, etc., and goofing around with this stuff at the same time🙂) So thanks, I think I better understand the relationship between voltage and power used (amperage?). I'd still like to know if there's a way to find out how far we can push without damage. I realize it's most likely a case by case issue, but that too becomes a part of the question....finding out what it is in any particular case.

TIA

Peace,
D.

 

[Blindasabat]

It appears you got even more voltage sag. But different regulators behave different ways...

Tried another experiment. This one made me a bit more nervous because it would be a more costly error if I fried this light.

I tried switching batteries in my Inova X03.....a pretty bright little light to start with. I took out the 2 c123 cells and was able to fit 2 of the 6 volt little 28L cells plus one of the 123 cells .....I probably could get 3 of the 6 volt cells to fit even more easily....giving me 18 volts. As it was, with the two 6 volt cells and one 3 volt for a total of 15 volts, nothing fried, the apparent light output was greater, but not as significantly as the difference with the previous experiment (taking the cree C3 from 1.5 volts to 12 volts, but of course that was a far greater jump).

Anyway, how far do these things go before they blow up? How much regulating do regulators do?

TIA

Peace,
D.

 

[Delij]

It appears you got even more voltage sag. But different regulators behave different ways...

LOL....seems we are typing at the same time.


Peace,
D.

 

[Fenris]

I tried switching batteries in my Inova X03.....a pretty bright little light to start with. I took out the 2 c123 cells and was able to fit 2 of the 6 volt little 28L cells plus one of the 123 cells

You need to do a search about the dangers of lithium batteries.

 

[Delij]

You need to do a search about the dangers of lithium batteries.

Will do, thanks. But in the case of substituting lithium for lithium, it would seem to only be an issue of voltage. No?

D.

 

[lctorana]

in the case of substituting lithium for lithium, it would seem to only be an issue of voltage. No?

D.

No.

Whenever you put batteries in ANY appliance (and the higher the drain, the more this matters, which is why this is especially important for torches), it is essential that all the batteries are of the same type, grade and state of charge.

Why? Their current capacity should match.

When you first put the cells in, all contribute to the output. But say 1 cell is of lesser capacity than the others - it will go flat first.

Then - draw the circuit if it helps - current will be going THROUGH the flat cell in the opposite direction to its natural polarity, flattening it more and more until it's voltage is flattened to zero - and beyond.

The dreaded cell reversal now happens. And when this happens, that flat cell is completely ruined.

And could leak, or burst.

Those warnings on batteries "do not mix type and grade" and "always replace all cells at the same time" are not just there to sell more batteries, they are also there to protect people who put batteries in and never check them until the thing stops working completely.


So, back to your experiments - when you are testing for a few minutes, your assumption is correct - it's only voltage that matters, but you can't leave them in the torch for use after that - not unless you are sure all cells in the chain have the same capacity at the time you put them in. And with batteries of different voltages, you couldn't be sure of that.

Apologies for the length of this post.

 

[Delij]

So, back to your experiments - when you are testing for a few minutes, your assumption is correct - it's only voltage that matters, but you can't leave them in the torch for use after that - not unless you are sure all cells in the chain have the same capacity at the time you put them in. And with batteries of different voltages, you couldn't be sure of that.

Apologies for the length of this post.

Great explanation....thanks, I appreciate it.

When I switched batteries in the Cree, it was one AA for two of the little 6 volt camera batteries, so there was no mixing of types of cells....it was just in the second "experiment" with the Inova where I had two of the 6 volt and one 3 volt...I easily could have fit three of the six volt batteries and therefore would have had three of the same capacity, etc.

Would that have been a more "safe' way to go? Or am I endangering the lights with too much voltage (in both cases)?

Thanks,
D.

 

[Fenris]

I was referring to different capacity, different voltage, and at different states of discharge.

 

[TorchBoy]

Anyway, how far do these things go before they blow up?

Normally just a little bit less than you hoped. 😉 Same with LEDs, except for the blowing up.

I hadn't heard of a 28L before, so looked it up. Lithium, 6.0 V, 170 mAh. Very similar to the 6 volt 4LR44 battery (which is just four LR44 cells in series), except for chemistry.

I've used a single 4LR44 directly with a 1W Edison Opto LED (ie, no resistor or driver) and as I expected, the voltage of the battery under load sagged until it balanced with the operating voltage of the LED, evening out about 230mA... 220mA... 210mA. (Yeah, it drops pretty quick.)

For interest's sake just now I tried it with a Cree XR-E. Thanks to a different operating voltage it started at about 330mA. It would make a really impressive keyring torch for short burst use. :twothumbs

I'm not sure I'd like to use a 6V lithium the same way, and certainly not two without something to limit the current... Too risky for me. I like to experiment, but I also like to live. And intact, at that. You had the advantage that you had some sort of driver in each of the torches you were playing with, so the LEDs didn't see as much current as they would have if you had been direct driving, but lithiums aren't the safest things to play with.

Could I respectfully suggest you restrict your experiments to non-lithium batteries? And do you have a multimeter so you can find out how the LEDs are being treated?

And never mix battery types, even if they're both lithium. Cheers.

 

[Delij]

Could I respectfully suggest you restrict your experiments to non-lithium batteries? And do you have a multimeter so you can find out how the LEDs are being treated?

And never mix battery types, even if they're both lithium. Cheers.

Good suggestions! LOL

Too bad I can't just be satisfied without the experiments. And no, i don't own meter, but I guess I should. (Just what I needed...another expensive hobby).

My son is a Navy Nuke....I thought he'd know everything I could ever want to know about currents and electricity. But it turns out he was trained originally as a mechinists mate, not an electritian's mate.....I had a 50/50 shot and lost (he went that way to get to be an ELT if anyone here knows what that is).

Well, I guess I better go shop for a few tools and keep reading here.

Thanks all.

Peace,
D.