LiPo 2S charging problem

[OttawaNoob]

My son and I are working on our first RC plane. I bought this little 7.4V LiPo Tattu battery from the FT store and am trying to charge it.
Battery -> https://store.flitetest.com/tattu-800mah-7-4v-45c-2s1p-lipo-battery-pack-with-xt30-plug/
Charger -> https://store.flitetest.com/b6-charger/

The charger seems to only be recognizing one cell "R: 1SER" and gives a "CELL CONNECT" error.


Measuring the voltage of each cell through the balance port they are about 3.4 V (need a new screen on the volt meter ha!)

and the XT30 output is also 3.4 V which seems weird to me (expected it would be 2x3.4 =6.8?)

Any suggestions on what to try?

 

[Foamforce]

Either one of the cells is completely dead or both are extremely low. Measure from the center pin of the balance connector to each side to get the individual cell voltages and report back. Regardless, it sounds like a bad battery.

Edit: Ope, I see that you measured from middle to one side on one of the cells, just do that on the other side as well. It should measure about the same. Apparently it is close to zero, indicating a completely dead cell.

 

[OttawaNoob]

Either one of the cells is completely dead or both are extremely low. Measure from the center pin of the balance connector to each side to get the individual cell voltages and report back. Regardless, it sounds like a bad battery.

Edit: Ope, I see that you measured from middle to one side on one of the cells, just do that on the other side as well. It should measure about the same. Apparently it is close to zero, indicating a completely dead cell.

Just measured the voltage between the two black wires is about 0.5 V

 

[Foamforce]

Just measured the voltage between the two black wires is about 0.5 V

Sorry, that’s a completely dead battery that can’t be revived. Discharge it all the way and dispose of it safely. There are a lot of threads on how to do that.

 

[OttawaNoob]

Sorry, that’s a completely dead battery that can’t be revived. Discharge it all the way and dispose of it safely. There are a lot of threads on how to do that.

Darn! That's unfortunate.
Thanks for your help figuring out what was going on.

 

[Shurik-1960]

Carefully remove the packaging from the battery. Check the integrity of the soldered wires. It is possible that the battery is damaged, but it will still work.Measure the voltage on the clean soldered contacts of the battery compartments.If the voltage on the jar is less than 3 volts, it can be removed: using a syringe, pour the expander between the jars and slowly disconnect it with a wooden spatula. 1 working jar can work as 1S battery (for charging the phone).

 

[Shurik-1960]

I had a separation of the hard wires from the cans to the plug and the smart charger refused to charge the battery.

 

[randyrls]

If the battery is new, Flite Test may replace the battery.

 

[Bricks]

If you have another 2 cell lipo around hook + to + and - to - and let it sit for 5-10 minutes check voltage in battery that was low many times it will bring the voltage up enough to let the charger see it. I have done this many times being stupid and draining down a lipo to far. Keep an eye on it the first few times you charge it, if this does not help then what Shurik-1960 said

 

[OttawaNoob]

If you have another 2 cell lipo around hook + to + and - to - and let it sit for 5-10 minutes check voltage in battery that was low many times it will bring the voltage up enough to let the charger see it. I have done this many times being stupid and draining down a lipo to far. Keep an eye on it the first few times you charge it, if this does not help then what Shurik-1960 said

Thanks for this suggestion! I was able to get the charger to recognize the battery again and it has been charged on balance mode and it works again!

 

[OttawaNoob]

Thanks everyone for your ideas and support on this. Much appreciated

 

[Foamforce]

Oof, bringing it back from .5v for a cell is still not great. At best, it‘s a seriously degraded battery. Keep a close eye on that battery when you charge it in the future. I regularly use batteries that have gone down to 3v, or even a little below, but .5v is an extreme example. I personally wouldn’t use that battery. As Randyrls said, I would try to exchange that.

 

[Merv]

...Any suggestions on what to try?

Try gently tugging on the balance leads, try pulling them out of the pack.
On occasion a solder joint will fail, the balance wire is not making contact with the cell. If so the wire will literally fall off into your hand.

 

[Foamforce]

For others listening along, he tested between the first and second lead of the balance connector (cell 1) and got 3.4v. He the tested between the second and third lead (cell 2) and got .5v. That could be due to a faulty balance lead except that he also measured across the main terminals and also got 3.4v. Well ok, he’s not exactly sure what the second digit is, because that’s out on his tester, so it’s probably 3.9v across the main leads. The point is that if it were just a bad balance lead causing the .5v reading on the second cell, then reading across the main terminals should read 6.8v or similar because the reading across the main terminals wouldn’t be affected by a bad balance wire. The voltage between the two cells is transferred by the positive tab of one cell that is welded to the negative tab of the other. The middle balance lead is soldered to those tabs as well, but if it comes off, it doesn’t affect the voltage flowing through the tabs and therefore to the voltage measured off the main leads.

Did I misinterpret anything? If I didn’t, then it was a fire hazard to resuscitate this battery, right? I’m open to being wrong about this.

 

[Shurik-1960]

During the 20 years of my passion for aircraft modeling (the break was from 1977 to 2006), the battery has NEVER been restored if the voltage in the bank was less than 2 volts. I ALWAYS throw these cans on the bonfire - it's a lot of fun... As a rule, such a jar swells sharply when charging and can burst, which is not fun at all..