RC India

Is there any possibility of a 3s lipo giving only 7.4 V. I nearly charged the 3S 2200 mah battery for 2 hours and i used a multimeter to check the voltage. Even then  it only gives 7.4 V at the D -connector end. Can one cell on the lipo might be out. There are no bulges or overheating during the charging period. I checked the imaxB3 lipo charger ports and its perfect at the 4 pins providing parallel charging. To what conclusion should i come? 

Check the voltage of the individual cells through the 4pin charging plug.

One cell of your lipo may be damaged. What is the voltage of individual cells and how many times you have used your lipo?Is your lipo puffed or normal?

It may be undercharged due to overusage.  What i can recommend is charging the battery for a long time until it gets full once more.  The nearly charged phase is not enough,  it will charge fully but takes more time than normal and due to the long time,  your charger may heat up but its normal.  Since you have tha imax b3ac,  it will heat up a lot as the inlets in the sides are small.  I recommend modding the charger so it will let more air in.  All you need to do is take a small scissor and unscrew
The charger cover and take the scissors one arm and poke the inlets thus breaking adjacent inlets either side.  It will make the charger last long.

http://www.rcindia.org/batteries-and-chargers/overdischarged-lipo/
First charge the damaged cell with higher voltage (6-12) with curent limiter (preferably lamp that glow and indicate high charging current started). In deep discharge condition, initial charging current goes very low due to higher internal resistance sometime. Till 3.6 volt increased, u have to charge it, provided by it is not dead short. Give it a thermal shock, or high current charge momentarily, if it shows short... [means charging current and time i. e. AH is two time than capacity, and no improvement in voltage (truely speaking emf) in charging condition.
Look, if even any voltage is seen across the cell, insted of ZERO, there is hope and no internal short circuit occurs. Just charge it, keeping cool, to eliminate further puffing.
A Risky Process and NOT RECOMENDED.. for expert only...
If the voltage is zero, give momentary high current (not uncontrolled, like from 12 volt car battery to direct to cell) corresponding 5-10C, so that shorted part may blow out internally and isolate. (cover battery in blast proof covering, preferably inside brick protection with long lead with sand covering, and of course at outside... It may blast. Sometime puffed cells are punctured to control blast level.)95% NiMH battery survives, but for lipo, success rate is 2 out of three, as per some mad scientist.. but not heard about blast level, because as per him, he cannot get the burst... I don't made the test on lipo, as i do not want to take the risk...

The individual cells measure gives
black wire-
red wire   -3.7 V
red wire    -3.7 V
red wire     -7.4 V
with respect to ground pin

Thanks i ll definitely try that one. :thumbsup:

Hook it up to a lipo voltage checker and see how many cells it detects.

I don't suggest charging your battery pack, as pointed by other members (no offense :) ) , if 3S is not detected.
It is not recommended to charge a lipo which goes under 3V/cell. You might be risking a lot while charging it, and trying it bring to life.

It will be a lot less messier if you could dispose the lipo and get a new one.

Thanks, i ll look into it. Definitely will consider your advice. :thumbsup:

That means your inner cell got discharged. Being 2200mAh,you should charge it near 500mA limit.
Just charge inner cell with a 6-9 volt power supply with a resistance of 12-20 ohm, 10 watt, or a bike/car tail lamp (3-6 watt).
Or you can charge with an cell phone charger (basic, not smartphone) which inherently cannot give more than 1A, keeping constant watch on terminal voltage, and body temerature.
If it improves more than 3 volt, you surely survive the cell.

Even if, you dont want to take risk, just open the pack, isolate 3 cell, make it 2S LiPO after isolating it.