Battery testers

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Red Squirrel

No Lifer
May 24, 2003
70,722
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www.anyf.ca
What the...
This is like the 5hr energy drink of batteries. What's the science behind this?

Basically their "science" is that devices stop working when the voltage of the battery is too low, so it uses a DC-DC converter to boost it up so the device keeps working. I use the word science very loosely here. :D
 

mindless1

Diamond Member
Aug 11, 2001
8,766
1,765
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Well surely, there is an amount a AA NiMH for example can be charged to when new and a point below which it can no longer hold any charge.

The peak charge is around 1.45V, then anything more is just shed as heat, or vents the cell if the internal pressure rises too high from getting too hot.

There is no point below which it can no longer hold any charge, from a recovery (recharge) standpoint. Well that point is 0V. If you have something like a cordless power tool that puts several cells in series, continuing to use the tool after the weakest cell has reached 0V will begin to reverse charge that cell and damage it.

Otherwise you'd look at the discharge graph for the cell in question. The remaining usable capacity is much lower once a cell approaches and drops below about 1.1V. Usable means it depends on the discharge rate as a higher rate will cause a greater voltage depression so the cell(s) drop below the minimum voltage threshold a device can use, sooner.

The typical mAH capacity rating is determined by a manufacturer specified test, using a specific discharge rate, for example C/3 (one third the rated capacity) down to 0.8 to 0.9V, but by the time the voltage hits 1.1V, there's usually only a single digit % of capacity remaining.
 
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Muse

Lifer
Jul 11, 2001
40,989
10,263
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I'd love a straightforward chart that tells what dead to full is on every kind of battery (NiMH, NiCd, Alkaline, etc) for every size and capacity.
I don't have a chart but I have a ton of experience.

A NiCd or NiMH much under 1.20 volts is ready for a recharge. It will peter out very very soon if you are not already experiencing your device having problems.

Alkaline 1.5 volt batteries that are showing voltage of around 1.45 volts or lower with a multimeter I will just toss in my battery recycle bag which is disposed of at a recycling facility eventually. Similarly, a 9 volt alkaline showing less than 9 volts goes in that bag.
 

mindless1

Diamond Member
Aug 11, 2001
8,766
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I don't have a chart but I have a ton of experience.

A NiCd or NiMH much under 1.20 volts is ready for a recharge. It will peter out very very soon if you are not already experiencing your device having problems.

Alkaline 1.5 volt batteries that are showing voltage of around 1.45 volts or lower with a multimeter I will just toss in my battery recycle bag which is disposed of at a recycling facility eventually. Similarly, a 9 volt alkaline showing less than 9 volts goes in that bag.

Umm, Whut? Alkaline at 1.45V or 9V just below 9V, still have over half their capacity remaining.
 

tinpanalley

Golden Member
Jul 13, 2011
1,511
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Umm, Whut? Alkaline at 1.45V or 9V just below 9V, still have over half their capacity remaining.
Yeah, I was gonna say, I don' t know ANYthing and that sounds wrong to me just on general high school electronics knowledge.
 

mindless1

Diamond Member
Aug 11, 2001
8,766
1,765
136
That's 1.45V hot off a charger. Give it a few minutes or longer to settle down and they can be closer to 1.40V.