NI-MH batteries

With the exception of a few voltage sensitive devices, most devices have a critical low voltage cut off at around 1V per cell. As long as you stay above that it doesn't matter if the initial voltage is 1.2 or 1.5. So a point and shoot camera that uses 4AA cells will shut off at 4V.

Like mentioned earlier, alkaline chemistry does not allow for high current, the internal resistance is too high. When placed in a high drain device like a point and shoot, or my kids leap pad, the alkaline battery can't meet the current demand which causes the terminal voltage to sag. The alkaline batteries very quickly come off 1.5V and then quickly sag below that 1V threshold and the device shuts off. The voltage then rebounds and when you test the battery it looks ok, and in fact can still be used in something like a remote.

The NiMH batteries, while having a lower initial voltage, can supply the current, have almost no voltage sag, and will not drop below that 1V threshold until almost completely exhausted.

Example: My kids leap pads use 4AA batteries and is a high current device. A set of alkaline lasted 2 hrs. I pulled them out and they tested ok but would not power up the device. They lived the rest of their life in remotes and clocks. The eneloop NiMH batteries lasted over a WEEK of on and off usage.

If you are looking for NiMH rechargeable, the standard eneloops are some of the best. While they have a lower overall capacity than some others, they are hybrids so they do not self discharge very fast, and they have one of if not the best voltage support under load in the industry. Costco usually has a good buy on them. I have enough now that I do not buy alkaline anymore. Some of my eneloops are 4 years old

MEXICOWANDERER wrote:
They do indeed make 1.5 volt LITHIUM rechargeable batteries in AAA and AA sizes. But you would faint at their cost. You can't make a canary sing baritone and nickel metal hydride is imprisoned at 1.2 volts per cell by the call of nature.

Tenergy for one, makes low self-discharging NiMH batteries at an expense of around a 10% loss in mah capacity.

There is a ton of garbage grade metal hydride batteries out there. I stick with eneloop and Tenergy.

And I also go with the Eneloop made in Japan, not china. Good deals from Costco.

They do indeed make 1.5 volt LITHIUM rechargeable batteries in AAA and AA sizes. But you would faint at their cost. You can't make a canary sing baritone and nickel metal hydride is imprisoned at 1.2 volts per cell by the call of nature.

Tenergy for one, makes low self-discharging NiMH batteries at an expense of around a 10% loss in mah capacity.

There is a ton of garbage grade metal hydride batteries out there. I stick with eneloop and Tenergy.

Yeah, they seem to last a long time in my camera. I just check voltage on batteries on them before I toss e'm. I did the tounge test on a 9v battery and it passed. Wouldn't work in my smoke alarm but did in my sprinkler time clock for the memory. Thought alarm was shot but when I checked the battery it only had 7v. Not good enough but a new battery cured it.
Edit:Great guide, thanks

ChopperBill,

As someone else pointed out, the nominal voltage depends upon the materials used to create the battery, that is, it's chemistry. NiMH/NiCd = 1.2V, alkaline cell = 1.5V

The NiMH (and older NiCd) work best in applications in which high current has to be supplied, but terminal voltage isn't that critical (motors, cameras, camera flashes). The traditional AA batteries put out a higher terminal voltage but generally can't match the sustained current draw of the NiMH. Plus the advantage of the NiMH is that they can be recharged hundreds of times.

RJsfishin,

There are numerous materials which can be used to make different terminal voltages, but due to capacity/cost/etc. only certain chemistries become viable and common. For instance, there are 9V NiMH batteries. An alkaline 9V battery consists of 6 separate 1.5V cells to create the 9V. (The cells are placed in series to boost the voltage.) However, the NiMH 9V batteries may consist of 6, 7, or 8 separate 1.2V cells for a total terminal voltage of 7.2V, 8.4V or 9.6V respectively, depending upon the manufacturer. 9V Rechargeable Battery Comparison

Here's an interesting Battery Guide which helps tabulate and summarize the differences.

Hope this helps.

~Rick

I asked that same question here a year a couple years ago, and instead of "I don't know" answers, I got answers that didn't make sense at all.
I then asked it in a different way, like.....Why don't they make a AA rechargable battery that has 1.5 volts like other batteries, and got the same ridiculous answers, so I just gave it up.
Anyway, the 1,25 don't last near as long in voltage sensive devices. Like you said, 1,2 is considered dead in many cases. So I quit using them, as they are not worth the hassle. If you buy large quantities of AA alkalines, at like HD, you are way ahead,

ChopperBill wrote:
I inherited a charger and 4 MI-MH AA batteries that I use in my camera. When I got done charging them they only showed 1.42V. Thought They were shot then I looked at the battery and they said they were 1.2V. Why is a regular AA battery 1.5V and these NI-MH AA batteries only 1.2V and why do they work in the other batteries place? Heck I toss my regular batteries when they get that low except where I use them in my garage clocks.

Because they are a different chemistry! Nicad batteries are the same 1.2 nominal voltage.
For comparison, think lead/acid at 2.0 volts per cell or LiPo/LiFe at 3.7.
You really need FIVE NiMh batteries if you need 6 volts, but most devices will work with 4.8.
The difference is that a carbon-zinc or alkaline battery IS nearly exhausted at 1.4, but these NiMh/NiCad ones have LOTS of charge left at that level.