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Old Jan 12, 2006, 10:37 AM   #1
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I noticed that all my NiMH batteries are rated at 1.2V. This is less than the 1.5V for alkaline batteries. Are all NiMH batteries at 1.2V?
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Old Jan 12, 2006, 12:12 PM   #2
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That's pretty much it for the no-load situation.

However, under heavy instantaneous loads, the NiMH's may "droop" less, so in use, the alkalines mayactually get pulled to lower voltage than the NiMH's. A practical example of this would be a camera that pulled a lotof current can run fine on NiMH's, but won't get thru the startup withfresh alkalines (voltage gets pulled too low) - I've seen that happen.

The battery designers apparently do have a few tricks up their sleeves that can make alkalines "stiffer" - that'sthe "digital alkalines" you see in the stores. In that example of the camera not being able to start with regular alkalines, it was able to start and run fine on the "digital" alkalines.

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Old Jan 12, 2006, 1:11 PM   #3
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Peva wrote:
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However, under heavy instantaneous loads, the NiMH's may "droop" less, so in use, the alkalines may¬*actually get pulled to lower voltage than the NiMH's.
Voltage of any alkalines/standard disposable cells comes crashing down if put under heavier current, no matter if they're claimed to be some "hyper super ultra" batteries.
As example discharge current used by some battery testers in testing of battery voltage is 150mA. Now power hungry digicam can take ten times as much which leads to total collapse of output voltage.
NiMHs again can procide such current without problems... that's why NiMHs (or any other rechargeable) batteries should be stored in pocket without any case, if there's shortcut those can cause burns or even start fire because of big power output capability.

Also just charged NiMHs have voltage of 1.4V and it settles to about 1.35V. 1.2V is voltage of about empty cell.
Alkalines again loose voltage constantly for whole discharge time and especially with bigger current drop is considerable even with full battery.


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The battery designers apparently do have a few tricks up their sleeves that can make alkalines "stiffer" - that's¬*the "digital alkalines" you see in the stores.¬* In that example of the camera not being able to start with regular alkalines, it was able to start and run fine on the "digital" alkalines.
I bet that Camera wasn't any of Minolta's 7-serie models.

I just checked datasheet of Energizer e2's which should be meant for power hungry devices and they clearly admit that with 1A current capasity drops "under the graph". (actually they have same graphs in datasheet of standard alkalines)
Same applies to Duracells, capacity drops badly already much before 1A discharge current.

And now digicams don't take that current evenly, they take that in "fast big gulps" which means even worse real world results.


In some very light current digicams disposables could work half decently but in most digicams life would be lousy compared to rechargeables and they would be suitable only for emergency.
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Old Jan 12, 2006, 10:07 PM   #4
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So, with NiMH, we have lower voltage than alkaline, but this voltage stays constant for a very long time. This is contrasted against alkalines which tend to drop voltages after long use. So, it sounds like digital cameras are very sensitive to voltages.

Thanks for the lesson in NiMH batteries.
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Old Jan 13, 2006, 6:22 AM   #5
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Webapprentice wrote:
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So, with NiMH, we have lower voltage than alkaline, but this voltage stays constant for a very long time. This is contrasted against alkalines which tend to drop voltages after long use...
You missed one other point that we mentioned:Alkalines have more internal resistance; i.e., on an *instantaneous* basis, their voltage will be pulled down a lotmore (than NiMH)with a given heavier load. As E.T pointed out, one of the implications of that is that when the load fluctuates from light to heavy (say, during camera startup, or during zoom motor operation), the camera may decide to shut offwhen thevoltage momentarily drops below the camera's cutoff threshold.

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Old Jan 13, 2006, 1:24 PM   #6
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Hi Peva,
I missed that. I think I actually had that happen to me. I have slightly used alkaline batteries, and when I try to power the camera up, it would light up the LEDs indicating "no power." That must be the voltage drop phenonmenon you describe.
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Old Jan 13, 2006, 2:07 PM   #7
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Webapprentice wrote:
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Hi Peva,
I missed that. I think I actually had that happen to me. I have slightly used alkaline batteries, and when I try to power the camera up, it would light up the LEDs indicating "no power." That must be the voltage drop phenonmenon you describe.
Probably - yes.
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