Output using AA NimH vs. Alkaline

nickdolin

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Hello... quick Q... seeing as there is a slight voltage difference between rechargables (1.2) vs. 1.5 of alkalines , would it make any significant difference in brightness in AA light output? Or would it be so small that I wouldn't likely miss the difference?
 

RCM

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NIMH usually is 1.3-1.4 volts and supplies an average 1.25 volts during discharge down to 1.1 or 1 volt per cell...and it depends on the light incandescent will be more noticable.
 
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nickdolin

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I had a sneaking suspicion that the output wouldn't be too badly effected... thanks for the input... anyone else care to chime in? :)
 

nickdolin

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As a newb to batteries (I've always used primaries) can you charge a 14500 in a normal AA/AAA charger? I'm thinking no but I guess it's worth asking.
 

RCM

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No, the charger will hopefully reject the ones that are tried though and your risking a vent with flame if its tried! I use lithiums in some lights, eneloops in the others
 

Lynx_Arc

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Hello... quick Q... seeing as there is a slight voltage difference between rechargables (1.2) vs. 1.5 of alkalines , would it make any significant difference in brightness in AA light output? Or would it be so small that I wouldn't likely miss the difference?
It depends a lot on the device they are used in. Some devices that are lower current draw may run better off of alkaline while heavier current draw may favor nimh.
 

AnAppleSnail

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As a newb to batteries (I've always used primaries) can you charge a 14500 in a normal AA/AAA charger? I'm thinking no but I guess it's worth asking.

No. Only use a charger for the battery chemistry it's built for.

Good NiMH batteries tend to be brighter in high-power lights since alky chemistry sags its voltage under high load.
 

Lynx_Arc

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As a newb to batteries (I've always used primaries) can you charge a 14500 in a normal AA/AAA charger? I'm thinking no but I guess it's worth asking.
"normal" AA/AAA chargers are for nimh (possibly nicd too) while a 14500 is lithium ion. Lithium ion can be dangerous if not properly treated, so use only chargers you are sure won't hurt them (designed for them).
 

nickdolin

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Thanks for the quick answers. The light I'm primarily referring to is my Romisen that has a Q3 and runs in 1xAA. I'd assume it's a lower draw but when I swapped in an Alky and didn't notice a difference in lumens (I realise that there has to be a significant difference before humans notice it ) but I'll stick with my NiMh for the higher capacity then.
 

Mr Happy

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Hello... quick Q... seeing as there is a slight voltage difference between rechargables (1.2) vs. 1.5 of alkalines , would it make any significant difference in brightness in AA light output? Or would it be so small that I wouldn't likely miss the difference?
If you look at an alkaline battery data sheet (e.g. http://data.energizer.com/PDFs/E91.pdf) you can see how the "1.5" volts of alkalines is only a temporary condition. In practical terms the voltage of an NiMH cell is more or less equivalent to an alkaline cell.
 

nickdolin

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Very helpful and detailed info (some of which is over my newbish head) but I figured out enough to see that indeed the 1.5V is on a fresh cell and depletes after some usage.

Thanks

PS- In fact, it seems that he alky spends the most of it's service life in the 1.0-1.2V range. It drops from the 1.5 range rather quickly.
 
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RCM

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Yep! It's really noticable with incandescent flashlights, I use alkalines a lot in my 1xAAA EDC light which is incandescent, and as the voltage sags the color shifts to yellowish, and then very slowly after about 3 hours gets to the point where it is barely putting out any useful light, which is when I change it. rechargables last a little bit longer but I have a crap load of AAA alkaline cells that I can use...my light draws about 21mA from a fresh cell (tested with GP alkaline before posting this)
 

rcozer

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I use both NiMH and Alkaline. NiMH for long run times and constant brightness. Alkaline for the "brightness wow factor".

If you like the "wow factor" of brightness that lasts for a short period of time with fresh alkalines then try NiZn (Nickel-Zinc) rechargeable AA cells. It delivers 1.6 Volts. Use caution, there are reports that fresh off the charger the voltage is much higher and could damage electronics; so let the NiZn cells rest before using. Also some users complain about the capacity being low compared to NiMH.

While the "brightness wow factor" is really cool, it is more practical to have a consistent useable level of brightness for a longer duration (until the battery runs down) as with the use of NiMH AA cells. Good for long night hikes, emergency lighting, and you can see when cycling. :)

For Eneloop, the NiMH cell runs twice as long as generic Alkaline AA and the voltage stays above 1.2V until the NiMH AA is almost depleted. See the 500mA graph for on the Sanyo Eneloop NiMH page http://www.eneloop.info/home/performance-details/capacity.html. Staying above 1.2V for the duration of the NiMH charge (at constant current) is the key to the consistent brightness factor. Notice how the Alkaline cell drops almost linearly in Voltage over time which results in the light dimming over time until it dies. (If you have a voltage regulated LED light for constant brightness then the NiMH cell has more capacity than an Alkaline AA).

For my Planet Bike Blaze 2W LED lamp, the manufacturer rating is 5 hours on high setting (about 100 lumens) for two Excell Alkaline AA's. With brand new Lenmar R2U (ready to go) 2150 mAh NiMH AA's the run time was 3.5 hours one night plus another 10 continuous hours next day before the two NiMH AA's were below 1.1V.

Years ago, I received 1st generation rechargeable AAA Alkalines by Pure Energy for a gift. I use those to power my Petzl headlamp (40 lumens) which has a low current draw so capacity is not a big issue. I top off the batteries often to get that "brightness wow factor". Otherwise for long trips, I use brand name AAA Alkalines. I prefer Low Self Discharge NiMH AAA's, but I use what I have on-hand.
 
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VegasF6

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Thanks for the quick answers. The light I'm primarily referring to is my Romisen that has a Q3 and runs in 1xAA. I'd assume it's a lower draw but when I swapped in an Alky and didn't notice a difference in lumens (I realise that there has to be a significant difference before humans notice it ) but I'll stick with my NiMh for the higher capacity then.

You are talking about a regulated boost circuit light driving an led. The job of the regulator is to boost the output voltage to a point that it can drive the led at whatever current that particular regulator is set for. This range will probably be around 3 - 3.5V. In theory, that will be a constant for the entire life of the cell (though no regulator is perfect, it will probably drop off some) There should be no difference in brightness regardless of cell chemistry. What you should be asking is which one will last longer.

Only in an unregulated light, IE 100 year old technology light emitting resistor connected directly to a cell or battery of cells would this be a factor.
 
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