Understanding Lithium Polymer batteries

[Dezy]

that sounds like your reading off each cell, in which case 0-3 is great, 4 and up is leaving ya,,, over 8 on a 6s is sucking wind..... the cells as a whole was how i read his numbers and that includes the plug the power goest through.... i don't even look at the balance plug cause i'm monitoring it at the power plug, when that goes up i'll take a look at the balance plug to see what it has to say about the situation.... i charger will read either or.....

Thanks, Kloner
Maybe my batteries are already leaving me…….
On one battery, cell IR reading is 4, 4, 7, 7
And the other battery is 5, 5, 7, 7
These are Turnigys, bought from Hobby King – maybe they set on the shelf for a year or two….

 

[kloner]

the c rating is based around this number so a low c like 20c is usually low...... cell matching is a technique to make these better, they typically come very close IR when they are matched, turnigy are usually pretty fresh cause of there turnover rate, but matched cells wouldnt be what there known for..... it's hard to say in your case, it should be acting like they won't fly all 80% of there capacity,,,, should take forever to balance charge, shows damage.... you can do it in one flight over discharging the pack,,, starts it all

 

[Dezy]

Thanks, Kloner
These are Nano-tech 4S 4000Mah 25-50C batteries.
I balance charge them to about 4.18 v per cell, before the charger’s timer goes off, and usually takes about 50 min. / 4 amp charge to put back in 2700 Mah. This is after keeping a light F550 quad aloft for 10 min. with 8” props on Tiger MT2216-12 motors.
I guess I’ll just monitor the IR and discharge/recharge times closely……

 

[Will]

Thanks for the help guys & sorry for the late reply.

...I always keep them in a "bunker" I built using a metal box and sand. This way, worst case the sand extinguishes the flames. Then I make sure that I fly through all the batteries by the end of the day - that way the storage discharge doesn't take quite as long.

do you have a storage function on your charger?...

Yes, I've got storage mode on my charger but that can take 2 hours per battery pack (x 5 packs = 10 hours to put my batteries to storage voltage) - not ideal if I get home late, especially as each one takes about an hour to charge (x 5 batteries = 5 hours). If I can't leave batteries charged safely overnight, I could spend up to 15 hours a day with them plugged in to the charger - so no time left for flying anyway!

I love the bunker - I may have to build something similar. :02.47-tranquillity:

Reading through the posts (inc the datasheet that seems to suggest an undamaged battery can be stored fully charged for a whole year and the only risk is a loss of capacity), it seems that I don't really need to worry at all. Please correct me if I'm wrong but the 'catching-fire' risks aren't a risk when they're sitting on a shelf, even fully charged - the danger areas are charging, discharging, flying, and after sustaining physical damage. Is that right? Has anyone here actually had an undamaged lipo catch fire while sitting alone on a shelf? Anyone?

you want to contain the flare, but you don't want the box on anything flammable, keep it away from walls, trash, etc and do not seal it..... if you do, it can make more problems than venting the smoke....

The main damage from these is smoke damage unless it ignites something. It's a plasticy most likely unhealthy smoke..... they don't need air to burn, seen em going underwater, etc.

Thanks Kloner! The problem is that I live in an apartment with no garage, no workshop, no active ventilation and LOTS of hard-wired smoke alarms that will evacuate the whole building. I supervise battery charging/discharging so I can get them out on the balcony pretty quickly if it happens then, but if they burn while I'm out or asleep (even in a flame-proof 'bunker') - I have a problem.

 

[Motopreserve]

I think the fires typically happen when there is damage to the Lipo. It hasn't happen to me (fingers crossed) yet, but I think if you inspect the batteries well before/after flights for puffing, or strange readings, that's when you are safe to store them. Can't hurt to have a Lipo "burn bag" and a sand bunker in the corner of the apartment - just to protect those things around it in event of a burn...

Hopefully someone who has experienced a fire can weigh in.

 

[kloner]

the loss of capacity from storing full is what we call damage to IR..... it IS what kills lipos, IR gets to moving, so does the pack to the trash or in a crash, take your pick....

 

[Motopreserve]

the loss of capacity from storing full is what we call damage to IR..... it IS what kills lipos, IR gets to moving, so does the pack to the trash or in a crash, take your pick....

Kloner, would you say that of batteries are well cared for (not run too low, always balanced, discharged and charged to proper storing capacity) that you would physically notice (puffing?) a battery heading toward dangerous? Or is this something so random that bites people even when they've been diligent?

thanks!

 

[kloner]

It is totaly random, your dealing with chemistry and it seems the higher the c rating the easier it is to damage em..... i had these killer 60c packs on a single rotor, stored it right, month later 2 of 6 were puffed...... i've also seen them blow a cell before there puffed.....all we can do is be diligent in storing them at the right volts at the right temp or fly em often.....

one thing you will see is Ir on chargers made to measure it, and you'll see it change then you see if rise.....

i've had battery checkers before, the kind you look over the packs cells with that showed how close the cells were matched in voltage,,, that also kinda
gave a battery health indication at a glance....

View attachment 17127

http://hobbyking.com/hobbyking/store/__10952__Cell_Log_8M_Cell_Voltage_Monitor_2_8S_Lipo.html

 

[Motopreserve]

I always check my cells in the field after flights with a simple monitor like that (not as fancy). Just to keep track of what's happening.

I think we are dodging all the right things, or as much as we can. Then it just comes down to keeping the fingers crossed...

 

[Will]

I think you're right. I personally take the following precautions (because I Googled it and apparently crossed-fingers are no defense against a lipo fire - damit)...

1. Set each lipo back to storage voltage within 48 hours of a flight or an unused full-charge
2. Balance charge my lipos every time at between 1C & 1.5C [lipos are 25C-out/2C-in] (taking extra time to double-check my charge settings before hitting 'start' and flipping over to view the individual cell readings once or twice per charge)
3. Never parallel charge multiple packs (most fire videos I've seen seem to involve parallel charging)
4. Charge and store in individual lipo-safe bags (sitting inside small teflon-coated loaf baking trays, mounted on a hard wood surface)
5. Use a cell-checker in the field both before and after a flight and isolate any lipos with weird readings
6. Feel for any undue heat, damage or bloating of the packs whenever I handle them
7. I number all my packs and make a note of anything unusual about charging, flight times, damage or heat so that corrective action can be taken and uncorrectable lipos can be identified and disposed of
8. Never let them run below 3.3v per cell under load (in a hover), and if it ever short-circuits on anything I'll quarantine it somewhere very fire-proof and observe it on & off for about an hour


I'm not sure there's a lot more I could do but I'm sure this will help me to avoid the worst for as long as possible. I guess I won't really know what the real likelihood of having a lipo fire until I actually have one, but I'd still like to hear from any other highly diligent users who've still had problems.

 

[morrisnathan]

Like most batteries, the temperature of a Li-Po has an impact on its performance. Consider that batteries rely on a chemical reaction in order to provide a current – a low temperature reduces the speed of this reaction and a reduction in overall pack performance may be observed on a cold day. Allowing a Li-Po pack to freeze is certainly not recommended, as this would almost certainly damage the pack.

 

[Peter Hudson]

Wow. Great job. Seems you know battery very well. How about tell us which battery to choose? As there are so many brands, not easy.

 

[Hood49]

Thanks for the great thread on Lipo's. Very interesting and as I am a novice I really need to understand this. Especially with the wife telling me off that I am bringing bombs in the house! So I need to do this good.

After this thread I think saying that you have not understood means that you need to go back to first grade. However I have one question to all of you readying this.
I know that it is not good to store fully charged Lipo's. However, how long is long? I charged mine two hours ago to go flying right now, but my wife reminded me that we have an appointment in the family (**###@@M¨%%%). I will fly tomorrow. Is it better to discharge my 2200 Mah 3S to 3.75 a cell and charge again tomorrow?

Thanks in advance.

 

[Motopreserve]

Thanks for the great thread on Lipo's. Very interesting and as I am a novice I really need to understand this. Especially with the wife telling me off that I am bringing bombs in the house! So I need to do this good.

After this thread I think saying that you have not understood means that you need to go back to first grade. However I have one question to all of you readying this.
I know that it is not good to store fully charged Lipo's. However, how long is long? I charged mine two hours ago to go flying right now, but my wife reminded me that we have an appointment in the family (**###@@M¨%%%). I will fly tomorrow. Is it better to discharge my 2200 Mah 3S to 3.75 a cell and charge again tomorrow?

Thanks in advance.

Overnight should be fine. Go to THIS thread and scroll to post #6. It has an interesting paper on this subject.

 

[Hood49]

Very interesting. Thanks for your swift response.
Looks like storing them charged overnight is not such a big deal. However, will I be able to sleep?:livid:

 

[Motopreserve]

Very interesting. Thanks for your swift response.
Looks like storing them charged overnight is not such a big deal. However, will I be able to sleep?:livid:

The adverse effect of storing them overnight, and whether they burn your house down, are two totally different things

i built a storage/charging box with sand as protection. Seemed prudent given the possibilities. Better yet, if you have a garage, put a storage box out there.

 

[cootertwo]

I don't care, call me "stupid". I know it's a good thing to be as safe as one can be, But I've NEVER discharged any of my 30 odd lipos. And I usually charge em right back up, after they've cooled off. But I do usually go through 3 or 4 packs about every day (retired old fart). I store most in a metal ammo box. At the moment, there are about a dozen charged packs laying on my kitchen counter, 2,3,and 4 cell, all topped off and ready to fly. They been laying there all night. I know these things can ignite, fizzle and fart, but I've only had 1 pack go out, and lucky for me it was only a 450mh 3C pack. I was using it for testing on my bench, and let the two wires get together in all the mess. No flames, just a strange smell, and smoke. If you think about it, these lipos are laying all around your home. Cell phones, laptops, GPS units, MP3 player, your watch that's strapped to your wrist, on and on.

 

[Motopreserve]

Cooter. I keep my batteries charged and ready to go too. But if I feel there will be an extended period (leaving town), I'll discharge them to storage capacity and put them in a burn-bag in the fridge. I also use ammo boxes for transporting them to the field and room-temp storage at home.

If you check out that paper I linked - it shows the tested effects of different storage scenarios. None of them lead one to believe that storing them fully charged for a bit will have drastic ill effects. But then again, these things are pricey and it never hurts to follow some tried and true guidelines for protecting the investment, if they will go long periods of time unused.

As far as them burning up - I feel it's better not to take the risk. Just because we use them in other appliances doesn't mean these won't be the ones that burn the house down

 

[cootertwo]

The 450mh pack I had go up in smoke, was the first time I've experienced a lipo going off. Really a strange thing. My bench was covered with stuff, jumper cables, parts, etc. etc. When the thing first started, I heard a "hissing" sound, and smelled a chemical odor. And not a stink, but kinda a sweet chemical type smell. My first thought, was that an aerosol can of something was going off, (WD-40, butane lighter fuel can ???). Started looking around, and saw the plastic wrapping on the little 450 pack had split open, and the pack was about twice it's normal size. Never did spit out flames, but was probably close. Picked it up by the wires, and dropped it in a glass of water. Jelly like stuff oozing out of the packs. Very strange things, these lipo's.

 

[WacoJohn]

First quad. Battery question, please.

sCell count (Number of cells in the pack, represented by the letter S)
Capacity (The amount of energy the pack is capable of providing once fully charged, designated by the letters mah)
Current (The maximum amount of current or amps the battery can provide at its rated Voltage)

​
Reading your sticky carefully, (thank you for that) I can ID my LiPo thus:

Capacity 1,000 mAh
Current???? hmm says 'CHARGE AT 1A MAX' but also says '11.1v'
Cell count??? Don't see that anywhere.

I believe electricity is the work of Satan .. and I stay as far away from it as I can. Man will NEVER control it :tennis:

Still, I provide the following ... as I am forced to deal with it ... it seems. Below is a scan of all technical data printed on this hard shell battery. I expect the view is expandable. If not, I will have to present it differently. Thank you in advance for any help/advice in advance.