RC Model Airplanes/Cars/Boats/Is my LiPo swollen?


QUESTION: I have a special blue edition Syma X5SW Quadcopter with 2 batteries. The batteries have received equal use. They are (what I can tell from the labeling) 3.7 volt, 500 mAh, 1.85 Wh, 12c, manufactured June 5, 2015. I think one is swollen. It is not visibly swollen, still fits into the Quadcopter, and provides normal flight time. When I hold it, it feels like there is gas inside.
The potentially swolen battery has the following labeling:
-HW 752540P
3.7V X5S
500 mAh
+ 20150605
The normal battery has the following labeling:
- PB752540HP
12C Li-po
500mAh 3.7v
+ 5F 06 1.9Wh
I really want to know if this battery is safe to use in my Quadcopter.

ANSWER: Hi Bruce,

What you call swelling is commonly called puffing.  Puffing is an indication of damage to the cell and the gas is most likely carbon dioxide.  There is no way to ‘bring this cell back’, despite what you may read online.

You should be keeping your Lithium Polymer (LiPo) batteries in a fireproof container and storing them away from any flammable items.

Some people will say to continue to use a puffed battery as long as it is still providing the performance you want.

I don’t recommend that.  The cell is damaged and the damage will just get worse in a short time.  If it becomes too damaged, it could go into thermal runaway during a charge or discharge.

For more information on Lithium Polymer batteries:

You can find suggestions on how to discharge and dispose of a LiPo battery online.

Hope this helps,

---------- FOLLOW-UP ----------

QUESTION: Ok, I will take the required measures. How can I prevent this from happening to my other battery? And, I am not planning on using that battery again, but how damaged is too damaged?

ANSWER: Hi Bruce,

The causes of puffing are many.  It can just be defective manufacturing.  It can be from pulling too high of a current for too long.  It can be from demanding too much current from a battery in a cold ambient temperature, under 60 degrees F.  Trying to diagnose what caused it is almost impossible.  It can be from too deep of a discharge.

All of those things are pointed out in the document I linked to.

Sorry, I'm not trying to sound vague.  LiPo batteries are just very difficult to keep happy.

We, in the RC sport, are using them 'on the ragged edge' with no protection circuits for over-charging, over current and over-discharging, like phones, tablets and laptops have.

I honestly wish that I could tell you that you did something wrong and what not to do next time, but I really can't, as there is a very good chance you did absolutely nothing wrong.

Damage is damage.  Kind of a dumb statement, but once the cell is damaged, it is more easily damaged on the next high current run for too long, over charging or over discharging.  I can't quantify how much damage is too much.  Very sorry.

I hope you find this somewhat helpful,

---------- FOLLOW-UP ----------

My LiPo
My LiPo  
QUESTION: Somehow, it "unpuffed". There is not physical damage. It is not leaking. The article says it can still be used, but I want to confirm that this LiPo is safe.

Hi Bruce,

It appears to be a case of 'reversible' puffing, mentioned in the article.
I cannot confirm that it is safe, but personally, I'd probably still use it.  I'd be extremely cautious when and where charging and especially in storing it.
I am not saying use it.  Only you can make that decision.  Be smart and be safe.


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Ken Myers


I can answer beginning, advanced and expert questions about electrically powered R/C model aircraft, and many questions about R/C model aircraft of all types, except helicopters. I`ve been building, flying and designing R/C model aircraft for 40 years.


I have been building and flying radio controlled model aircraft since 1960. I'm the president of the Electric Flyers Only, Inc., located in southeasten Michigan. I'm a past president of the National Electric Aircraft Council. I'm vice-president of the Midwest R/C Society. I was president and main founder of the UFO (Union Lake Flying Organization). I've built and flown most types of model aircraft except helicopters.

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