Alkaline flashlight batteries.

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Chris142

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I have lots of gizmo's that take 3 batteries. 3cell Maglights, little hf flashlights,my ac dye light etc. Why does one battery always fail but the other 2 are still ok? I get this too often for it to be a coincidence.

Example. Just tonight I grabbed my 3 "D" cell maglight to take the trash out to the dumpster. It's beam was very poor so I pulled the batteries. 2 are 1.36v and the 3rd is 0.00v.

Why dont they all run down at the same or nearly the same time?

Does having 3 batteries have a negative effect on the batteries? It does not matter if they are HF cheapies or a major brand. I'm always finding 1 dead battery in my stuff that takes 3 batteries.
 
What brand are the batteries? Also, where are the flashlights stored and how clean are the battery socket terminals? Even a little corrosion can drain a battery. I've seen it happen many times. How old are the batteries when this happens?
 
Originally Posted By: Chris142
I have lots of gizmo's that take 3 batteries. 3cell Maglights, little hf flashlights,my ac dye light etc. Why does one battery always fail but the other 2 are still ok? I get this too often for it to be a coincidence.

Example. Just tonight I grabbed my 3 "D" cell maglight to take the trash out to the dumpster. It's beam was very poor so I pulled the batteries. 2 are 1.36v and the 3rd is 0.00v.

Why dont they all run down at the same or nearly the same time?

Does having 3 batteries have a negative effect on the batteries? It does not matter if they are HF cheapies or a major brand. I'm always finding 1 dead battery in my stuff that takes 3 batteries.


You can admit it, you buy HF batteries!!

I assume when you find one dead and 2 somewhat good you replace all 3, or only the dead one?
 
The batteries have been everything from cheap Chinese ones from HF or Osh to Duracell's and Rayovacs. The contacts are clean. Most are less than 2 yrs old and have an expiration date far away..Like 2018 or longer.

I dont have any trouble with my stuff that uses 2 or 4 batteries. I'm thinking an odd # of batteries kills one somehow.
 
Tonight I replaced all 3. But if 2 have 1.50v or more im inclined to just replace the dead one. The one dead one I had tonight was a rayovac. and I put 3 new ones in
 
Its all about the statistics of production. Some cells will have higher impedance (related to resistance in the build of the cell as well as other chemical and thermal elements related to diffusion, surface concentration of active species, buildup of insulating layers, etc).

Thus they will not be able to source current without either a higher voltage drop than the other cells, and/or will not source the current causing other cells to have to pick up the slack (how current is shared is dependent upon the configuration of the cells).

In extreme cases, the weakest cell will go into reversal, which can be damaging or even hazardous, depending upon chemistry.

But it all stems back to manufacturing variations. Even the big Chinese and Japanese lines that make tens of millions of cells have decent variability. It manifests itself as self discharge under low/no load operations, and other worse conditions under higher load operations.

Though its a different chemistry, and its rechargable, a recent paper in the Journal of Power Sources did a study that indicated that a 20% impedance mismatch yields a 40% reduction in life.
 
With small batteries like the button type, and maybe even AAA, if you get oil from your fingers across the + to - insulation, that oil can act as a constant drain on the battery, and after a few months it can reduce the life expectancy of the battery. When I worked for a computer company, we had to be sure that when we put the battery for the clock on the computer, that we never touched that cell with our fingers, as the oil from your fingers conducts enough to reduce the battery life expectancy to half of normal.

I also have noticed that the streamlihgt 3 C cell flashlight tends to always have the first cell (the cell directly behind the LEDs) go bad while the other 2 are still OK. The only thing I can think of is that the cell directly behind the LEDs gets heat from the LEDs.
 
Originally Posted By: JimPghPA
With small batteries like the button type, and maybe even AAA, if you get oil from your fingers across the + to - insulation, that oil can act as a constant drain on the battery, and after a few months it can reduce the life expectancy of the battery.

Thats interesting. Ill try not to touch them
 
You are wise to test them individually. The fault is a minor manufacturing defect and probably only shows up after some extended time.

You should keep the two at 1.36 and just replace the dead one. Even though they are weakened they will work for quite a while.
If you buy four you can install one and keep three for the next set.
Usually batteries sell in multiples of 2. 2, 4, 8 cells in a pack.
This is kind of inconvenient.

I have found some LED flashlights that only need two cells.

I have a DURACELL branded D cell LED flashlight that uses 2.

I have a Black and Decker LED flashlight that uses two AA cells.

I have two LED lanterns that use 2 and 4 cells.

I think I bought all of them from Walmart, but read the specs carefully to find the ones that use two or four cells.
 
Originally Posted By: JimPghPA
I also have noticed that the streamlihgt 3 C cell flashlight tends to always have the first cell (the cell directly behind the LEDs) go bad while the other 2 are still OK. The only thing I can think of is that the cell directly behind the LEDs gets heat from the LEDs.


Excellent observation!

Heat accelerates chemical reaction rates, including the self-discharge rates. Plus it destabilizes the chemistry. It will also lower the impedance so that cell can source more current, depending upon design.
 
I have had other applications where just one of the batteries went bad. In fact I just changed a set in my weather radio and one of them was so bad it leaked gunk inside. The others were ok.I don't think heat was involved.

Interesting theory, but I don't really think LEDs make that much heat, and I don't think the batteries are close enough to the LED to be bothered even if they did.
 
High power LED's make lots of heat it seems. I've seen a few app notes about metal clad boards for the purpose of heatsinking.

Might only be a "real" issue for huge panels of LED's, but I wouldn't be surprised if a good LED light could be felt to warm up.

I also suspect the market is flooded with cheapo ones too, which could very well attempt to use the battery pack as heatsinking. Although, I suspect the pos lead from the pack is what conducts heat to the first battery--it's a good straight shot (thermally) from the PCB (which makes the heat) to the battery pack. Neg terminal probably uses the flashlight housing, which is a good heatsink.
 
I agree high power LEDs make a lot of heat, at least the 110 v conversion circuitry does. But the circuitry is not needed in low power LED flashlight applications because they run right on 4.5 v .

Most of the 3 cell flashlights I have seen use a removable cartridge to load the cells into, distancing the batteries even further from the LED.

I'm not saying this is impossible but just using speculations the argument can go either way.

Most of the batteries I have fail from just sitting in a drawer, they just get old. And often it is just one that goes leaving two usable ones.
 
Originally Posted By: supton
High power LED's make lots of heat it seems. I've seen a few app notes about metal clad boards for the purpose of heatsinking.

Might only be a "real" issue for huge panels of LED's, but I wouldn't be surprised if a good LED light could be felt to warm up.

I also suspect the market is flooded with cheapo ones too, which could very well attempt to use the battery pack as heatsinking. Although, I suspect the pos lead from the pack is what conducts heat to the first battery--it's a good straight shot (thermally) from the PCB (which makes the heat) to the battery pack. Neg terminal probably uses the flashlight housing, which is a good heatsink.



Yes i have a light made by Olight which is an S20 baton using a Cree XML T6 LED and on high for extended periods of time it can get hot enough to burn you.

You are also correct there are lots of cheapo lights on the market, which is why i stick to brands like Olight, which offer good value with high quality. A couple of other good but not too expensive flashlight makers are Jetbeam, Nitecore, Sunwayman, Lumapower, and Klarus. Pretty much anything on batteryjunction website.

I would worry more about using cheap fake batteries than cheap flashlights.
 
Originally Posted By: Donald
Originally Posted By: Chris142
I have lots of gizmo's that take 3 batteries. 3cell Maglights, little hf flashlights,my ac dye light etc. Why does one battery always fail but the other 2 are still ok? I get this too often for it to be a coincidence.

Example. Just tonight I grabbed my 3 "D" cell maglight to take the trash out to the dumpster. It's beam was very poor so I pulled the batteries. 2 are 1.36v and the 3rd is 0.00v.

Why dont they all run down at the same or nearly the same time?

Does having 3 batteries have a negative effect on the batteries? It does not matter if they are HF cheapies or a major brand. I'm always finding 1 dead battery in my stuff that takes 3 batteries.


You can admit it, you buy HF batteries!!

I assume when you find one dead and 2 somewhat good you replace all 3, or only the dead one?


Speaking of which, anyone ever try HF batteries?
 
Originally Posted By: supton
High power LED's make lots of heat it seems. I've seen a few app notes about metal clad boards for the purpose of heatsinking.


Exactly. They typically have heatsinks on them, but in lights, the thermal mass of the battery and flashlight casing acts as the heatsink.

The new LEDs are much more efficient than old incandescent bulbs, but as a result they are much brighter, so the actual thermal load can be higher than an incandescent used previously. Also the location and direction of heat flow may be different, ad waste heat is generated at different points.
 
Originally Posted By: Chris142
Originally Posted By: JimPghPA
With small batteries like the button type, and maybe even AAA, if you get oil from your fingers across the + to - insulation, that oil can act as a constant drain on the battery, and after a few months it can reduce the life expectancy of the battery.


Thats interesting. Ill try not to touch them


Or clean them with 91% alcohol, and then handle/install them with a microfiber cloth.
wink.gif
 
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