Dead Cell and Balanced Charger

[DavidKersting]

So, ran down a 14.8V 4S battery and after the last flight is was a wee bit hot. Tried to recover it with all the advice online.....no luck. The question I have is, on a 4S battery connected to a balanced charger, how do I know which battery cell is toast from the screen? Dont have a multimeter with me.

 

[HighTechPauper]

They go left to right, top to bottom, so 1, 2, and 3 are at the top and 4, 5, and 6 are at the bottom, so cell #3 is dead.
Batteries will get warm to extremely warm from flying, the harder you fly the hotter it will be, the goal is to be around 15V when rested (fully cooled, usually after about an hour)
Do not charge until the battery is rested and cool to the touch. If you charge at 1C (1.5 amps for a 1500mah) and the battery is good and undamaged, it will actually get a bit cold as it charges and should never get very warm (or hot) fi charged at 1C. If I have a battery that gets warm instead of cold, I know to keep a close eye on it.
You need telemetry or OSD to have voltage reading, or you just need to land early and see where the battery rests and if it is much over 15.2 after resting you can add 15 or 30 seconds to your timer. I want all my batts to be 14.8v or above once rested and hopefully closer to 15v. You NEED a cheap battery checker if you are going to be in this hobby, it wont be exact but is close enough.

 

[jswander]

FWIW, with your charger (I have same), a press of either status button will give the voltage of each cell as it charges.

 

[Wayno52]

True js but they are not at all reliable.
Get a good cell checker like Randy said.
It can tell you what your packs are like and balance discharge.

 

[Wayno52]

This is great.

 

[DavidKersting]

Im in. Can you loan me $15.50.....money is gone on other drone stuff.....Ill dig through the couch. Im sure its in there,,,,,,if not Ill sell the couch. Im sure the wife wont mind.
Thanks to flying to music and earbuds (in secluded area) cant hear all the warning beeps....Hmmm, yet to be resolved.

 

[DavidKersting]

forgot to ask, I get the 1-6 cell readings on the charger, but....on the battery is 1 the + terminal and 4 the - terminal or the other way around? Battery label is on the + side. Real question, which is cell 3 physically on the battery.

 

[HighTechPauper]

The ground wire (first wire) on the balance plug goes to the main ground and the ground side of cell #1, from there is goes in order c1+ to c2- the c2+ to c3-, and so on until c4+ comes out the last wire in the balance connector and the main positive lead giving you the added voltages of those 4 cells while still allowing the balancer to access each of the cells individual voltages independently in an isolated fashion. In this way the main leads can have a charge applied and the balance leads can "bleed off" any cell that goes over the set voltage (4.21v)

 

[DavidKersting]

Just dawned on me I forgot to say thanks HighTechPauper...thanks.
Now then...
I have two 4 cell batteries that each have one bad cell. Want to turn both into one good 4 cell battery? They are both identical batteries (ordered 2) and have less than 10 flights on each. Any safety tips other than never let +/- contact each other via tools, solder iron or other.
Dave

 

[HighTechPauper]

Not really a lot of experience with that, I only have a few bad ones and I haven't torn into them to salvage the cells that work yet. I would just be extremely cautious, and have a work area that can be transported out to a safe spot in the concrete quickly, work with plastic tools as much as possible and have a fire extinguisher handy to be safer. Soldering iron will likely need to be at full blast to get a quick joint on the large battery tabs, good bit of metal there to sink your heat. Good luck and let us know how it goes and what you find. BTW, your welcome!

 

[DavidKersting]

Its alive.
So then, your comment on the heat sink is mighty true. Felt like I was soldering with a popsicle. Considered buying a blow torch good experience though. Plastic tools....agree. I also recommend keeping a multi-meter handy to make sure the + / - are in line and to check voltage before and after soldering.
All in all, batteries are cheap enough that I will buy new next time....now my drone is relying on my battery building/soldering skills.....might not be my so smart on my part.....we will see. Thanks for the help again...and again...and again.

Though it was fun getting this done (hotel boredom), I don't recommend battery mods. Most of us buy batteries, not build them. These are not something that I feel mistakes are easily forgiven. Just ask my wife about the inferno in the lawn

Thanks again.

 

[HighTechPauper]

Lawn infernos are rarely a good thing, LOL