Few things to take into account when replacing the batteries, are the cells conneted in parallel (higher current) or in series (higher voltage)? Does your device have a regulator and reverse voltage protection? Shorting an LiSOCl will just make it warmer, shorting a LiPo cell might cause an explosion.
You said it is a wireless device, 2 1/2AA LiSOCl cells in parallel can provide a 200mA pulse, check if your intended replacement cell can provide it.
Self discharge: LiSOCl cells have low self discharge and very long shelf life. Rechargeable cells have much higher self discharge and if the cell drops below a certain threshold, it cannot be used anymore.
Measuring the battery voltage "as received" prior to charging "is always wise"
However, this is a scam.
Battery
The battery contains 3 x 3.7V cells (nominal) rated at 1380 mAh each.
Placing 3 in series would at best give you a 11.1V x 1380 mAh battery.
IF they had been in paralle it would nominally be a 3.7V x 4140 mAh battery
So the 12V x 3000 mAh claim is spurious.
A LiPo cell has a
maximum voltage of 4.2 V (So 3 x 4.2 = 12.6 = Vmax_charged)
an average voltage over the whole discharge of ABOUT 3.6V or 3.7V / cell
and a minimum voltage of about 3V/cell.
Discharge tyo much below 3V/cell is liable to damage the cells and discharge to 2V/cell will fatally damage the cells.
So not only did they sell you fake junk, they sold you dead fake junk :-(.
There are many of these for sale on the internet at various prices.
IF you bought one from Seeed studios or Deal Extreme you could very likely get your $ back.
From elsewhere YMMV.
Dead Jim You Tube.
Ali Express $13.80
DX.com - capacity claim 1500 mAh V still suspect <- Somewhat reputable seller.
Amazon $31.80 junk
Amazon $28 whatever
Bang good $18.10 low price junk
Fasttech $16.45 even cheaper junk
:-(
ADDED 1/2016 in response to reader query.
How is it fake? I have a couple of this exact same battery, and they work fine and they each report 12.6V when fully charged, from the 3 x 4.2V cells. That's how you measure voltage in series.
Read the above explanation carefully and you should see where the claims are wrong. The 3 x 4.2 = 12.6V is indeed what he should see when fully charged - that's what you get, which is good. He gets ~= 2V which is fatally bad.
Even if the 3 cells in a 3S pack were 500 mAh, or even 50 mAh capacity, they would still measure 12.65V when fully charged, so battery voltage within range tells you very little. Battery voltage outside range tells you much.
Vbattery
over about 12.8V is very bad and
under about 9V is also bad.
under about 8.5V is possibly fatally bad
(2 x 3V marginal and 1 x 2.5V death's door).
under about 7.5V is junk.
When you place cells in series (3S here) the voltages add (as you say), but the mAh of the combination is that of the lowest capacity in the string - in this case 1,380 mAh for THE WHOLE string as they are all have the same capacity = 1380 mAh.
LiIon and LiPo cells have a mean operating voltage of around 3.6V to 3.7V and this is whyat is usually used for quoting battery voltage. Vmax is 4.2V/cell and SOME manufacturers use this voltage when specifying battery voltage, but this is a marginal practice - anyone who does it without comment is quite likely to be "cutting corners" elsewhere.
If you add batteries in parallel (3P if you did that here) (they must all be the same voltage) the mAh ratings DO add but Vout is V for one battery. So his battery could legitimately be described as
[10.8V, 1380 mAh] (at 3.6V/cell), or
[12V, 1380 mAh] (at the marketing hype 4.2V/cell) OR
[3.6v TO 4.2v, 4140 mAh]
but NOT [12V, 3000 mAh].
That is what makes it fake.
IF the cells used are in fact 1380 mAh (and they may be lower)(ask me how I know*) then capacity = 1380/3000 = 46% of claimed. That's fake, alas :-(.
IF your version has 1380 mAh cells the same applies.
The battery cam be 12V, 3000 mAh with 3 cells ONLY if it contains at least 3 x 3000 mAh cells.
If readers disagree with this or do not understand it please do comment or ask - the aim here is to learn.
- I've spent 6+ months in China on over a dozen electronics manufacturing related visits in the last decade - which has taught me a lot about what you may expect worst case. China can and does make excellent products. But, also, extreme rubbish if uncaring profit focused and/or ill informed resellers let them get away with it. Unfortunately, many do. Almost no specification or claim is trustable if the reseller does not stand behind it and has not done enough "due diligence" to be certain that their supplier is reputable and reliable.
A very large proportion of product from "no name" manufacturers or suppliers does not meet claims and/or specifications to some extent.
Best Answer
Let's see- unknown brand name, claims of storage capacity beyond that of any remotely trustworthy manufacturer, found in a drawer so likely not engineering samples liberated from a top-secret skunkworks, and inability to spell the word "battery" on the label (BRTTERY?).
The whole thing screams arbitrarily labeled Asian-made product of the most dubious of origins. If you're lucky they'll function and have 2000mAh capacity for a few hundred charges.
If your computer thinks there is an alkaline AA cell in there it will report about half capacity since the NiMH cells have a lower voltage (1.2V vs 1.55V) when fully charged and a flatter discharge curve.
You could test the battery roughly by fully charging it and discharging it with a resistor but you'd have to monitor it to ensure the cell voltage did not drop below about 1V or the battery could be damaged. Make a measurement every 30 min or whatever and plot the result.