How puffy is too puffy?

[skybolt]

I’ve had really good luck with the lipos I’ve used over the years, always balanced, never run too low, ect. and I have very little experience with puffy packs.
I have two Gens Ace 3s 8400 packs that have seen a few runs in the ole X Max, I’ve noticed they each have a slight bulge, now on to my question: how much puffy is acceptable? They both have even voltages across all cells and still seem to charge and perform well. At what point does one not trust them??


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[nightcrawler48]

The puffiness we see in lipo batteries is caused by oxygen gas generated by heat in the battery. This heat is a normal product of using the battery and the more demand made of the battery, the more heat and so more oxygen, and so more puffiness. Soft packs are easy to see the puffiness, hard packs not so easy.

The battery may balance properly when charging and voltage between cells may be within 0.15 volts across the cells. The way to measure the "health" of your battery is to test the Internal Resistance. Some high end chargers will measure and display the IR and there are small battery testers that also can measure IR. Internal resistance is measured in milliohms (1,000 milliohms = 1 ohm). A new battery should measure 6 milliohms or less across each cell. As you use the battery the IR will increase and for the first while should be in the range of 7 to 12 milliohms per cell. When the IR goes higher it is time to plan for a battery replacement. 20 milliohms per cell is considered the end of the life of a lipo. With proper use and care a lipo should be good for 300-400 charges. Abuse the battery and the life will be less than that.

So, I have two (2) Nano-tech 2200mAh lipo batteries that have puffed "slightly". I check them every time I use them and at the moment they both average 8 milliohms across all cells. I'm careful using them but consider them to be safe. When the IR gets too high you end up in a vicious circle, more heat because of the resistance so more oxygen is generated causing more resistance and then even more heat. That is the dangerous situation.

You can also end up with a battery that has one cell only with a high IR. As an example I had a 4 year old 5000 mAh lipo with 2 cells with 12 and 16 milliohm IR and the 3rd cell was over 80 milliohm. I disposed of that battery as soon as I was aware of that high resistance.

Probably more noticeable on the lower mAh batteries, if the power seems to drop off quicker than you remember and/or your run time is getting shorter than you remember, it probably means the IR has gone up significantly.

The bottom line is, the puffiness you see may not be a problem or could be an indicator of a developing problem. If you don't have a way to measure the IR, your local hobby shop may be able to help you out by testing the batteries for you. IMHO, if they know what they are doing, they will be able to help you.

[skybolt]

Originally Posted by nightcrawler48

The puffiness we see in lipo batteries is caused by oxygen gas generated by heat in the battery. This heat is a normal product of using the battery and the more demand made of the battery, the more heat and so more oxygen, and so more puffiness. Soft packs are easy to see the puffiness, hard packs not so easy.

The battery may balance properly when charging and voltage between cells may be within 0.15 volts across the cells. The way to measure the "health" of your battery is to test the Internal Resistance. Some high end chargers will measure and display the IR and there are small battery testers that also can measure IR. Internal resistance is measured in milliohms (1,000 milliohms = 1 ohm). A new battery should measure 6 milliohms or less across each cell. As you use the battery the IR will increase and for the first while should be in the range of 7 to 12 milliohms per cell. When the IR goes higher it is time to plan for a battery replacement. 20 milliohms per cell is considered the end of the life of a lipo. With proper use and care a lipo should be good for 300-400 charges. Abuse the battery and the life will be less than that.

So, I have two (2) Nano-tech 2200mAh lipo batteries that have puffed "slightly". I check them every time I use them and at the moment they both average 8 milliohms across all cells. I'm careful using them but consider them to be safe. When the IR gets too high you end up in a vicious circle, more heat because of the resistance so more oxygen is generated causing more resistance and then even more heat. That is the dangerous situation.

You can also end up with a battery that has one cell only with a high IR. As an example I had a 4 year old 5000 mAh lipo with 2 cells with 12 and 16 milliohm IR and the 3rd cell was over 80 milliohm. I disposed of that battery as soon as I was aware of that high resistance.

Probably more noticeable on the lower mAh batteries, if the power seems to drop off quicker than you remember and/or your run time is getting shorter than you remember, it probably means the IR has gone up significantly.

The bottom line is, the puffiness you see may not be a problem or could be an indicator of a developing problem. If you don't have a way to measure the IR, your local hobby shop may be able to help you out by testing the batteries for you. IMHO, if they know what they are doing, they will be able to help you.

Excellent break down, thanks!

[JatoTheRipper]

At what IR do batteries become less than safe to use? Is there a rule of thumb?

[nightcrawler48]

Originally Posted by JatoTheRipper

At what IR do batteries become less than safe to use? Is there a rule of thumb?

Generally speaking, once one of the cells reaches or exceeds 20 milliohms, the battery should be considered to be in the danger zone.

So maybe more information than you ever wanted to know but I can't figure out how to explain this any other way. Lithium-Polymer batteries contain, quite obviously, lithium. Lithium is an alkali metal, meaning it reacts with water and combusts. Lithium also combusts when reacting with oxygen, but only when heated. The process of using the battery, in the sometimes extreme ways that we do in the R/C world, causes there to be excess atoms of Oxygen and excess atoms of Lithium on either end (be it the cathode or anode) of the battery. This can and does cause Lithium Oxide (Li2O) to build up on the anode or cathode. Lithium Oxide is basically corrosion, albeit of the lithium kind; not iron oxide, which is otherwise known as "rust". The Li2O causes the internal resistance of the battery to increase. Internal resistance is best described as the measure of opposition that a circuit presents to the passage of current. The practical result of higher internal resistance is that the battery will heat up more during use.

Heat causes the excess oxygen to build up more and more. Eventually the LiPo pack begins to swell (due to the oxygen gas build up). This is a good time to stop using the battery – it’s trying to tell you that it has come (prematurely or not) to the end of its life. Further use can, and probably will, be dangerous. After the pack has swollen, continued use can cause even more heat to be generated. At this point, a process called Thermal Runaway occurs.

Thermal Runaway is a self-sustaining reaction that is accelerated by increased temperature, in turn releasing energy that further increases temperature. Basically, when this reaction starts, it creates heat. This heat leads to a product that increases resistance (more Li2O), which causes more heat, and the process continues until the battery bursts open from the pressure. At this point, the combination of heat, oxygen, and the humidity in the air all react with the lithium, resulting in a very hot and dangerous fire.

Having said all this and scared everyone to death, I have tested other RC'ers lipo batteries and found more than a few where the IR was in the 50, 60, 70, and even 100 milliohm range and the batteries had not burst in to flames. I kept my distance when they were using these batteries.

It surprises me how many RC'ers have no knowledge of the dangers when using a lipo battery. To me, its just a case of understanding what I am dealing with and taking a few precautions to be safe.

I have to thank the owner of the RC shop I bought my first hobby grade RC at for passing on his knowledge for the care of my first lipo battery. I'm sure the battery came with the information he verbally supplied but how many of us read through all that stuff, especially when the print is so small I need a magnifying glass to read it.

[JatoTheRipper]

Originally Posted by nightcrawler48

Generally speaking, once one of the cells reaches or exceeds 20 milliohms, the battery should be considered to be in the danger zone.



So maybe more information than you ever wanted to know but I can't figure out how to explain this any other way. Lithium-Polymer batteries contain, quite obviously, lithium. Lithium is an alkali metal, meaning it reacts with water and combusts. Lithium also combusts when reacting with oxygen, but only when heated. The process of using the battery, in the sometimes extreme ways that we do in the R/C world, causes there to be excess atoms of Oxygen and excess atoms of Lithium on either end (be it the cathode or anode) of the battery. This can and does cause Lithium Oxide (Li2O) to build up on the anode or cathode. Lithium Oxide is basically corrosion, albeit of the lithium kind; not iron oxide, which is otherwise known as "rust". The Li2O causes the internal resistance of the battery to increase. Internal resistance is best described as the measure of opposition that a circuit presents to the passage of current. The practical result of higher internal resistance is that the battery will heat up more during use.



Heat causes the excess oxygen to build up more and more. Eventually the LiPo pack begins to swell (due to the oxygen gas build up). This is a good time to stop using the battery – it’s trying to tell you that it has come (prematurely or not) to the end of its life. Further use can, and probably will, be dangerous. After the pack has swollen, continued use can cause even more heat to be generated. At this point, a process called Thermal Runaway occurs.



Thermal Runaway is a self-sustaining reaction that is accelerated by increased temperature, in turn releasing energy that further increases temperature. Basically, when this reaction starts, it creates heat. This heat leads to a product that increases resistance (more Li2O), which causes more heat, and the process continues until the battery bursts open from the pressure. At this point, the combination of heat, oxygen, and the humidity in the air all react with the lithium, resulting in a very hot and dangerous fire.



Having said all this and scared everyone to death, I have tested other RC'ers lipo batteries and found more than a few where the IR was in the 50, 60, 70, and even 100 milliohm range and the batteries had not burst in to flames. I kept my distance when they were using these batteries.



It surprises me how many RC'ers have no knowledge of the dangers when using a lipo battery. To me, its just a case of understanding what I am dealing with and taking a few precautions to be safe.



I have to thank the owner of the RC shop I bought my first hobby grade RC at for passing on his knowledge for the care of my first lipo battery. I'm sure the battery came with the information he verbally supplied but how many of us read through all that stuff, especially when the print is so small I need a magnifying glass to read it.

Great post! Thank you.

[DukeMinnix]

Assuming this is all correct information, I can neither confirm nor deny any of it, I just charge them and hope they don't burn the house down haha, but assuming the information contained is accurate and true, this should be stickied somewhere, maybe combined with an explanation of mah and C ratings. Battery Bible perhaps? Does one exist?

[Itali83]

Awesome reply and information. So to measure the internal resistance of each cell, you take the balance plug and go from the black wire to each of the positive wires for each cell and measure the resistance there? I have a multimeter and know how to use and read it. Just want to make sure I’m checking the correct pins. Again, great info!

Ben

[skybolt]

This reminds me of old school carpet racing when we would balance and match sub “C” cells and create our own packs!

Excellent info guys, appreciate it!


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[nightcrawler48]

Originally Posted by Itali83

Awesome reply and information. So to measure the internal resistance of each cell, you take the balance plug and go from the black wire to each of the positive wires for each cell and measure the resistance there? I have a multimeter and know how to use and read it. Just want to make sure I’m checking the correct pins. Again, great info!

Ben

The balance plug provides voltage so I don't know how you would measure the resistance from that plug with a multimeter. If you set a multimeter to DC volts and test from the black (negative) to the pin right next to it (positive) you'll get 4.2 volts if you have a full charge. Then from ground to the second pin over (positive) you would see 8.4 volts and so on. This assumes the cells are all exactly balanced. That is how the little electronic low voltage plug in alarms work. They read the voltage from each cell and when the voltage reaches the per cell cutoff voltage you've set them at, the alarm sounds. I still use these things on a couple of old ESCs that don't have built-in low voltage cutoff.

If you can figure out how to read IR with your multimeter, please post it up as I'm sure a number of people would be interested in that, myself included.

[nightcrawler48]

Originally Posted by DukeMinnix

Assuming this is all correct information, I can neither confirm nor deny any of it, I just charge them and hope they don't burn the house down haha, but assuming the information contained is accurate and true, this should be stickied somewhere, maybe combined with an explanation of mah and C ratings. Battery Bible perhaps? Does one exist?

Somewhere on the forum I've posted information about mAh and C ratings and "burst rating" (no, not the battery bursting into flames, but max amp output for a limited time frame) and how it all ties together but I can't remember when or where.

I can put something about this together again if people are interested. Just let me know.

[Itali83]

Originally Posted by nightcrawler48

The balance plug provides voltage so I don't know how you would measure the resistance from that plug with a multimeter. If you set a multimeter to DC volts and test from the black (negative) to the pin right next to it (positive) you'll get 4.2 volts if you have a full charge. Then from ground to the second pin over (positive) you would see 8.4 volts and so on. This assumes the cells are all exactly balanced. That is how the little electronic low voltage plug in alarms work. They read the voltage from each cell and when the voltage reaches the per cell cutoff voltage you've set them at, the alarm sounds. I still use these things on a couple of old ESCs that don't have built-in low voltage cutoff.

If you can figure out how to read IR with your multimeter, please post it up as I'm sure a number of people would be interested in that, myself included.

So, how are you measuring the IR if not wth a multimeter?,

[Voodoobrew]

Some chargers have resistance checkers.

[JatoTheRipper]

Originally Posted by nightcrawler48

Somewhere on the forum I've posted information about mAh and C ratings and "burst rating" (no, not the battery bursting into flames, but max amp output for a limited time frame) and how it all ties together but I can't remember when or where.

I can put something about this together again if people are interested. Just let me know.

Was it a thread or a post from you? You should be able to find them in your activity history on this site.

Originally Posted by Itali83

So, how are you measuring the IR if not wth a multimeter?,

As was said, some chargers have this function or you can get a simple meter like this:

https://www.rcjuice.com/smart-batter...pm-tester.html

[GA Dawg]

Originally Posted by JatoTheRipper

As was said, some chargers have this function or you can get a simple meter like this:

https://www.rcjuice.com/smart-batter...pm-tester.html

I have one of those and only use it for checking voltage. I should really put it to more use.

[nightcrawler48]

Originally Posted by JatoTheRipper

As was said, some chargers have this function or you can get a simple meter like this:

https://www.rcjuice.com/smart-batter...pm-tester.html

Yup. That's what I've used for a few years now. To anyone looking for one of these, make sure it says it will do IR. Some when I was looking listed a bunch of tests but nothing about IR so I stayed away from those. There are a number of different brands and price ranges and $10 - $15 is about average.

[CM9000]

Originally Posted by nightcrawler48

The balance plug provides voltage so I don't know how you would measure the resistance from that plug with a multimeter. If you set a multimeter to DC volts and test from the black (negative) to the pin right next to it (positive) you'll get 4.2 volts if you have a full charge. Then from ground to the second pin over (positive) you would see 8.4 volts and so on. This assumes the cells are all exactly balanced. That is how the little electronic low voltage plug in alarms work. They read the voltage from each cell and when the voltage reaches the per cell cutoff voltage you've set them at, the alarm sounds. I still use these things on a couple of old ESCs that don't have built-in low voltage cutoff.

If you can figure out how to read IR with your multimeter, please post it up as I'm sure a number of people would be interested in that, myself included.

correct but wrong.

[nightcrawler48]

Originally Posted by nightcrawler48
The balance plug provides voltage so I don't know how you would measure the resistance from that plug with a multimeter. If you set a multimeter to DC volts and test from the black (negative) to the pin right next to it (positive) you'll get 4.2 volts if you have a full charge. Then from ground to the second pin over (positive) you would see 8.4 volts and so on. This assumes the cells are all exactly balanced. That is how the little electronic low voltage plug in alarms work. They read the voltage from each cell and when the voltage reaches the per cell cutoff voltage you've set them at, the alarm sounds. I still use these things on a couple of old ESCs that don't have built-in low voltage cutoff.

If you can figure out how to read IR with your multimeter, please post it up as I'm sure a number of people would be interested in that, myself included.

Originally Posted by CM9000
correct but wrong.

Okaaaaaaaay? Either I didn't do a very good job of explaining this or my multimeter has gremlins. Lets try this again. Multimeter set to DC volts. Balance plug pins are identified as negative (-) for the pin with the black wire, the pin next to the negative (-) pin is the positive (+) pin of the first cell and is identified as pin 1, even though it is actually the second pin on the balance plug (I'll call this cell 1), next to positive (+) pin 1 is positive (+) pin 2 (cell 2), next to positive (+) pin 2 is positive (+) pin 3 (cell 3) and so on depending on the number of cells the battery has. Positive (+) wires from the battery cells to the balance plug can be any color, there is no standard for color related to the cell number. Black lead (-) from the multimeter to black pin (-) on the battery balance plug, red lead (+) from the multimeter to positive (+) pin 1 (cell 1) on the balance plug that is right next to the black negative (-) pin. Leave the black multimeter lead on the black balance plug negative (-)pin and move the red multimeter lead (+) to balance plug positive (+) pin 2. This will give you a voltage reading for the combined voltages of cell 1 and cell 2. For a 3 cell lipo, move the red multimeter lead (+) to balance plug positive (+) pin 3 and you will see a voltage reading for the combined voltages of cell 1, cell 2, and cell 3. And so on and so on.

I think this is getting more confusing as I go along.

Maybe CM9000 can explain better what he sees that is wrong.

[Voodoobrew]

This just tells you the voltage and not really the health of the batteries as stated previously. It's best to not check this with a multimeter as it's easy to short the probes which is bad. Best to just invest in a charger or checker that measures voltage and internal resistance. We don't want people blowing themselves up.

[nightcrawler48]

Originally Posted by Voodoobrew

This just tells you the voltage and not really the health of the batteries as stated previously. It's best to not check this with a multimeter as it's easy to short the probes which is bad. Best to just invest in a charger or checker that measures voltage and internal resistance. We don't want people blowing themselves up.

ABSOLUTELY.

I only started the multimeter thing because Itali83 asked if IR could be checked with a multimeter. Maybe I got way too carried away with my response on that one. Forgot the KISS principle (Keep It Simple Stupid).

And, thanks for reeling me in Voodoo. And I like you're trying to keep everyone safe.