LIPOS Gone Bad. Tips/Stories

[Kurt0326]

I have thought about doing this thread for a couple of days now. As I am still relatively new to this hobby, I am still learning.

I want to talk about one of the more dangerous pieces of your RC tools, the lithium polymer battery. There are many treads talking about how to pick the right battery or how to charge them, but no thing really about what to look for in a battery that is starting to go bad. So I want to cover that and I don't know all the answers myself. So a few topics I'd like to cover buy not limited to are...

- what are the clues that your lipo is starting to get tired. Please add proper reference if any.
- what you should look for in deciding if it's time to retire a lipo. Please add proper reference if any.
- show how to retire a lipo properly. Please add proper reference if any.
- what can you to safely cannibalize from a retired lipo. Please add proper reference if any.
- and most importantly STORIES! I know there's a few out there. I like story time!:applause:

Please add Title to your tips

If you have a story to tell involving Lipos, please add the Title "Story Time" to your post.

A few links to help out the beginners.
Beginner Series - Batteries and Safety by FliteTest
Choosing a LiPo Battery by FliteTest
Lipo Battery Bunker by FliteTest
TIP - Lipos - FliteTest Argentina Season 5 by flitetest_argentina

Battery Reviews
Turnigy Lipo Pack by FliteTest
Battery Testing Disappointment by FliteTest

 

[joshuabardwell]

One sign that your LiPo is starting to get tired is reduced capacity. If you assume that you always run your battery down to a constant voltage level, you can see either reduced flight time, or if you have a current sensor, reduced mAh provided.

If you only fly based on a stopwatch, it's important to check your battery voltage after each flight to detect when batteries are starting to go flat. However, you must be aware that a battery's voltage will sag under load, sometimes significantly. With one of my planes, I see as much as 0.7 volts of sag at full throttle, and 0.3 to 0.5 volts of sag at cruise. I land the plane somewhere around 10.9-11.0 volts, but by the time the battery has rested, it's back up to around 11.4 volts. That final number might give me the impression that I had a lot of capacity left, but in actuality, I don't.

Another sign that your LiPo is starting to get old is imbalance between the cells. If you always balance charge (as you should), the batteries should have almost no imbalance after charging. Check the max-min difference immediately after landing for a good perspective. When I am done charging, my packs typically have less than 0.005 volts difference between the cells. I just checked three batteries that have been sitting at "storage" voltage (11.4 volts, I think) for a week or two and they had 0.020 volts max-min. One battery that was at 11.4 volts and then I used it to do some testing on my video transmitter was at 0.028 volts. These are relatively new packs, with maybe less than 15 flights on them, so I would probably consider those to be "good" numbers. I don't know what a threshold would be for "bad" numbers. Certainly, if the pack got so imbalanced that any of the cells was getting close to 3.0-3.2 volts during normal discharge (e.g. total pack voltage around 10.6-11.0 volts) I would be concerned.

The "standard" way of retiring a LiPo is to put it in a bucket of salt water. I use a little more methodical approach.

1. Put it on the charger and run the Discharge cycle. This runs it down to 3.0 volts per cell.
2. Use Ohm's Law to calculate resistance at 3.0 volts per cell (9 volts for a 3S) to create a low current. Maybe 0.1C is a good starting place, so for a 2200 mAh battery, that would be 220 mA. R = V/I = 9.0 / 0.220 = 40.9 Ohms.
3. Choose the next largest standard resistor size. In this case, 47 Ohm is the next largest value.
4. Use the resistor to bridge the outer-most pins of the balance connector. Just stick the legs of the resistor in to the sockets of the balance connector. This will drain current in a slow, controlled manner. Place the battery in a fire-safe location for a day or so.
5. After a day or so, the battery will be well and truly flat. Cut a small length of solid-core wire, bend it into a U shape and replace the resistor with it. Alternatively, cut the main power leads and twist/solder them together. Anything to ensure that the pack stays shorted.
6. If you didn't cut the discharge connector(s) off in step 5, do it now, to ensure that nobody ever charges this battery again.

Turn the battery in for recycling or dispose of it in the trash. LiPos are inert and can be disposed of in the trash, but I believe that recycling allows the lithium metal to be reclaimed.

 

[Craftydan]

The "standard" way of retiring a LiPo is to put it in a bucket of salt water. I use a little more methodical approach.

yeah, I don't like that method either -- too much evidence the salt either does nothing or corrodes the contacts, depending on the conentration . . . but . . .

2.Use Ohm's Law to calculate resistance at 3.0 volts per cell (9 volts for a 3S) to create a low current. Maybe 0.1C is a good starting place, so for a 2200 mAh battery, that would be 220 mA. R = V/I = 9.0 / 0.220 = 40.9 Ohms.
3. Choose the next largest standard resistor size. In this case, 47 Ohm is the next largest value.

Incandescent Automotive lightbulb. Done.

Even near full charge most of bulbs will keep the current down enough the bateries don't mnd, and they generaly go dark after a few minutes on a weak 3S pack.

. . . not to mention, they're handy for testing ESCs after you flash them, which is the real reason I have a few on my bench.

 

[joshuabardwell]

Incandescent Automotive lightbulb. Done.

Well, sure, but then you don't get to use Ohm's Law.

 

[Craftydan]

Oh, as for scavenging . . . connectors -- always after the drain, cut one lead at a time as close to the pack as I can.

The battery connector can be used to replace battery connectors on new batteries that don't match (or XT-60's and EC3's can be broken apart for the female 3mm bullet connector inside). The balance plugs can be used to repair other batteries, either one lead at a time or all at once. they seem to be the first thing to bend/deform/break/burn out for me. Replacing a pin or even swapping out the plastic connector can return a troubled battery to a full and productive life.

I *have* on RARE ocasion turned a 3S pack into a 2S pack, but only if one of the two outer cells had physical damage, the remaining two cells look *PERFECT* and the damaged cell comes cleanly off when the shrink cover and tape is removed. If something's not right with any of those, then on to the lightbulb it goes for that deep down discharge.

 

[Kurt0326]

Thanks for the tips!

Now, I know you old guys have stories. Aren't you going to share?

Okay, I know a good video where a lipo spontaneously combusted on a desk

The lesson is to store lipos in a lipo bag.


Which after watching this I very quickly bought some.

 

[joshuabardwell]

BTW, if you really want to know about a LiPo's health, the ultimate measure is the internal resistance of the cells. For more on that topic, read this: http://www.helifreak.com/showthread.php?t=233111

You can get a reasonably priced meter that will test internal resistance, such as this one:
http://hobbyking.com/hobbyking/stor..._Battery_Checker_Watt_Meter_Servo_Tester.html

 

[RichB]

I've neutralized a few packs by leaving a voltage alarm plugged in . . . for a couple weeks . . .

 

[Kurt0326]

I've neutralized a few packs by leaving a voltage alarm plugged in . . . for a couple weeks . . . View attachment 38416

Wait, you didn't hear the alarm?

 

[joshuabardwell]

I've neutralized a few packs by leaving a voltage alarm plugged in . . . for a couple weeks . . . View attachment 38416

I killed the little 2S LiPo that came with my FatShark goggles and a spare LiFe that I had by leaving them plugged into the goggles overnight. Now I only use a NiMh, so if I accidentally leave it plugged in, at least it's not completely ruined.

 

[Nerobro]

Story Time - Getting back a 4000ma 2s from the grave..

Allow me to preface this... Don't do what I did indoors, or on anything flammable.

Three years ago I bought a Tamiya M05. I wanted to go racing with some people at a local track. I ended up never racing with them... and the M05 uses a special (round case) battery pack.

With all the best intentions, I charged the battery, stuffed it in the car, plugged it in, tested it, and waited to go racing. A day that never came.

A week ago, I dug out the car, and decided to see how healthy the battery was. It was dead flat. I had left the ESC plugged in, and it had a slow drain on the battery. My charger refused to even believe I had a LiPo plugged in.

So I set my charger to NiMh mode, and set it to 4amps. (A 1c charge) My charger will refuse to respond to any lipo under 3v. And I started the charger. I didn't look away. I didn't blink. I had my non-contact thermometer on hand. The charger was confused, it kept expecting to see the normal NiMh voltage blocks, and it wasn't finding them. The charge current would ramp up to 4amps.. and then drop off. Then it would ramp up again.

Quickly the counted mAh clocked up. As did the temperature of the charger. The battery.. kept it's cool. I kept watching the voltage, and when I saw the volts sit at 6.58 during an "off" pulse of the charger I shut down the charge. It had taken 550mAh to get the battery up to that level.

I swapped the charger back to LiPo-Balance. I set the charge current to 5amps, and hit start. And it took it! Well the battery took it. Like a champ. It sucked down another 2800mAh before the charger shut down. Evidently my cheap and cheerful chinese charger can't do 5amps for a 2s pack for that long. Being silly, I just restarted the charger, and got another 500mAh into the pack before it shut down again.

After letting things cool, and doing a final charge, the pack took something like 5500 mAh to reach a full charge. But.. it did reach a full charge.

 

[Raptortech]

I've found lipos to be startlingly resilient, and have had my own share of successful revivals from voltages as low a 1v per cell. However, just because it usually works out, doesn't mean that is always the case. Lipos are unpredictable, and should be treated with care, handled with caution, and stored safely. One time, I shorted a tiny 2s 300 accidentally for just a fraction of a second and it instantly puffed up, popped, and started spewing smoke. Luckily no flames.

 

[f91ddr]

I had a battery failure on my mobius cam, but it was only when I ordered a replacement and took the old battery out, did I see that there was a hole in the corner, and the lipo was actually quite puffy on that side. I think someone at the factory stuck a screwdriver into one of the two holes in back that are for securing the tripod mount, but the screwdriver punctured the casing of the lipo. Just remembered; when I charged the cam with the old battery in place, my whole USB hub went flat (mouse died, external HDD crashed- which stopped my nice xPlane 10 flight..). Maybe the old battery was drawing dangerous amounts of amperage? The new one doesn't do this at all, though.

I'm sort of surprised that these little batteries don't die more frequently. It seems like nothing under 1000 mAh will every randomly combust.

 

[joshuabardwell]

After letting things cool, and doing a final charge, the pack took something like 5500 mAh to reach a full charge. But.. it did reach a full charge.

The real test is what happens when you load it. My experience with this sort of thing has been that you can nurse the battery back to full charge if you try hard enough, but as soon as you load it, the voltage craters, and the actual effective capacity of the battery is very low.

 

[Nerobro]

I won't claim it's undamaged. But I did fully cycle it afterwords, and I got most of the rated capacity from the battery. Given that it's a 3-4 year old pack now.. I'd call that a success. That said, it's never going to see actual high discharge rate. Running a beer can tamiya 550 motor isn't going to even phase a 4000ma pack.

 

[aslansknight]

What is your opinion on my oopsie

I charged up a LiPo pack for a day of flying that ended up not happening. Then I forgot to discharge it to "storage" mode (yes, I'm bad...). About a month later, I realized my mistake when I got the battery out and it was pretty swollen. I haven't used it since I discharged it.

Do you guys think it is safe to use? Right now it's stuck in a LiPo bag and I'm not sure how safe that is either...

 

[ExperimentalRC]

Ive actually had a couple puffed lipos unpuff themselves. A venom 5000 3s and an admiral 2600 3s. They work perfectly fine, and i use them daily. As for the storage charge, Ive never used that feature on my charger, and I probably never will. I think that most lipo fires are caused by unbalanced cells. You should ALWAYS balance charge lipos.

 

[aslansknight]

Thanks! That makes me feel a lot better! Glad to know I'm not sitting on a time... fire. I always balance charge my LiPo batteries - but it's good to know that I'm doing THAT right, at least!

 

[Balu]

I'd still be very cautious with any puffed LiPo. If it goes flat again, fine. But I'd never take my chance with a puffed LiPo.

 

[rockyboy]

Story Time: Beware cheap eBay batteries

Many weeks ago I ordered a multi-connector battery charging cable from an eBay vendor that covered JST, Walkera, and some other weird 2 cell type connectors on a single squid cable.

But the eBayer didn't send me that - instead I got a pack of (3) 2s 200mah batteries with a "FlyThunder" name on a really cheaply designed logo. So I figured what the heck - I'm not sending these back to HongKong, and trying to argue with the vendor for less than $5 wasn't going to be worth my time.

So I clipped off the strange battery power connector, soldered on a good old fashioned JST, checked the voltage (3.8 per cell) and plugged the first one in to charge.

Immediately I heard a nasty hissing noise and the battery started to puff up like an angry cat! So I grabbed the battery to unplug it. Not smart #1 - it got VERY hot in just a second or two. So I pulled the other end of the charging cable out of the battery charger and went sprinting for the back door of the house.

Did I mention that I was charging in an upstairs bedroom? Not smart #2.

When I made it outside I tossed the battery into an empty clay flower that was sitting nearby, and it just sat there, hissing softly and growing for a few more seconds before settling into an evil menacing silence.

I thought "that sucked - must have been a bad battery. Never heard of one that before."

So I took my charger cable back upstairs and plugged in the second battery. Not smart #3. Immediately repeat previous scene, but without grabbing the hot battery directly this time. (See - I am trainable... sort of...)

After the second battery joined it's evil twin in the flower pot (and catching my breath after running through the house twice in rapid succession), I finally had a smart idea. I took the charger outside for battery #3. When this one hissed and puffed up, it was already in the flower pot with it's nasty little friends.

So with the flower pot way out in the middle of the back yard on the metal table, I went inside for some internet research. Can't find anything about those specific batteries. The brand doesn't seem to exist, but I'm not too surprised at this point. I do find some good information on disposing of bad LiPo's. Over the rest of the afternoon, each of these little evil packages gets hooked up to a 12v motor and run down to 0 volts, connectors snipped off, and leads hooked together before heading to the local Batteries Plus store for recycling.

After all this excitement, I still have no idea why all three of these 2 cell batteries died when connected to my charger. I have charged other 2 cell batteries successfully before and after these evil ones, so I trust my charger. I have soldered many many connectors in my time, so I don't imagine anything went wrong for all three batteries in a row in that soldering process. Afterwards I started to wonder if the leads were actually reversed - black to positive, but I had already dropped them off at the recycle center before I thought to check that.

So what did I learn? If working indoors, keep your charging station near an exit. Charge in a LiPo bag (which I did have handy, but the hissing started before I even got them into it). Build a LiPo bunker - I'll be doing that this weekend.

And don't trust mysterious no-brand batteries that show up in your mailbox from eBay vendors. Keep them outside in flower pots or metal boxes or something else fire proof until you're sure they charge and discharge normally.