Highest Voltage NiMH AA under low load

stamat

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I have this great Mp3 player that takes one alkaline/ NiMH AA battery.
Quite convenient as I can always bring an extra battery (I dislike built-in batteries).
By the way this MP3 player hobby goes pretty nicely with evening walks and a flashlight hobby :grin2:

Anyways I noticed that sound quality at loud volumes goes down a little as the batteries discharge. The base becomes a little 'muddy' with old alkalines. It must be the lower voltage or something about the higher internal resistance which makes the voltage load dependent.

So the question is this:
Which brand NiMH AA would have highes discharge voltage under 120mA to 180mA discharge?
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LuxLuthor

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SilverFox is the expert on the aspect of that discharge rate, but my couple of recommendations based on high current hog incandescent MagLite mods would be either the Powerex AA 2500 mAh, Titanium 2400's or Sanyo. Check his pinned thread here.

It takes a bit to sift through the graphs, but for each battery, he ran a bunch of various amp discharge rate curves. To make it a little easier for you, look at the time these last three last on the bottom axis for the 1 am current discharge rates. Not that many of the AA tests go over the 2 hour run time with a useful voltage remaining.

If one of these goes 2+ hours at 1A discharge, then you can extrapolate your MP3 player rate of 160-180mA should last 13-14+ hours (the 1,000 mA curve is about 6 times your MP3's rate)

PowerexAA2500atVariousRates.gif



TitaniumAA2700atVariousRates.gif



SanyoAA2700atVariousRates.gif
 
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stamat

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Thanks, LuxLuthor.
From that Thread it seems the Eneloops are the way to go. The discharge curve is quite flat and they show nearly 1.5 volt off the charger.

Now I see why they come with a sticker "ideal for MP3 players".
I thought it was only a marketing gimmick.
 

LuxLuthor

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stamat said:
Thanks, LuxLuthor.
From that Thread it seems the Eneloops are the way to go. The discharge curve is quite flat and they show nearly 1.5 volt off the charger.

Now I see why they come with a sticker "ideal for MP3 players".
I thought it was only a marketing gimmick.

Be careful how you interpret the usefulness of the Eneloops. Look at the very first chart to see how far down they are on the ranking of 1 Amp run times. They will not last as long on total run time as most of those I mentioned which are in the top 5.

However, the main feature of the Eneloops is they keep their charge when left sitting unused for long periods...whereas other NiMH cells otherwise steadily release their charge over time even if not used.

So if you use your MP3 once every few weeks, and longer run time is less important, then they are your battery. However, if you are like me, you use your MP3 player frequently (daily or several times a week), and it's not a big deal to charge it in between your frequent uses, then my earlier recommendations are the way to go.
 
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