Recently, I bought a DC 12300, a 12V battery with high capacity 3000mAh and I got a charger 12.6V and 500mA output. First thing I did when I got the battery, I measured its voltage and it was 2V. After 6 hours of charging, (I presumed that it was 3000mAh-6 hours of charging). I got the same result. But as batteries are all connected in series their capacity is still 1380mAh.
My first question is: Did I overcharge the battery considering the fact that I charged 1380mAh instead of 3000mAh? It says also "Over-charge/discharge protection".
I proceeded by measuring the voltage individually for each small battery and I got 3.7V and 0V for 2 others.
My second question is: Can I try to recharge the battery separately using a 4V charger or my battery is definitely damaged?
Best Answer
Measuring the battery voltage "as received" prior to charging "is always wise"
However, this is a scam.
Battery
Voltages add if cells are in series
mAh capacity stays the same if cells are in series
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.
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.