For the sake of beginners, here are some rules/tips to ensure safety and longevity of lithium polymer (LIPO) batteries.
1) Respect them. If not properly taken care of, they are extremely dangerous. I know of a car that burnt down from lipo fire.
2) Always use a balance charger, that can ensure each cell is individually balanced to 4.2 volts. A fully balance charged 3 cell lipo should show a voltage of 3 x 4.2 = 12.6volts.
3) Always charge at a rate of 1C, where C is the capacity of pack. If you have a 2200mah pack, you can charge at 2.2A or less. The correct detection of the number of cells in the pack and setting the appropriate charging rate are the most important aspects of charging lipos (of course, using a balance charger is assumed).
4) Do not over discharge your lipos, by using them for too long between charges. It is best to limit the usage to 80% of the capacity of the pack. If you have a 2000mah lipo, use it in such a way that when you charge it after use, you are putting in around 1600mah. Most modern chargers show you how much are you putting back in. Use of the timers in your tx radios help prevent discharging the packs too much. If you discharge them too much, they tend to puff up, reducing their effectiveness.
5) If you are storing lipos without using for long periods of time (months), better to put them at half charge, which is around 3.9v per cell. So for a 3 cell lipo, keep it charged upto 11.7 volts or so.
6) While disposing lipos, soak them in salt water first.
Anwar, CAN I ADD;
If you ever drop a lipo, keep it on the floor or on a non inflammable surface and observe it for 15 minutes. 40% of them explode and catch fire. This article is very important for all the guys.... I cannot get the images on here so if you can advise your email, I will email it to you to display this complete article.
Thanks
Baggu
Lithium Polymer (LiPo) cells are the newest and most revolutionary cells to come to market. LiPo cells typically maintain a more consistent average voltage over the discharge curve when compared to NiCd or NiMH cells. Add to that the higher nominal voltage of a single LiPo cell (3.7V versus 1.2V for a typically NiCd or NiMH cell), making it possible to have an equivelant or even higher total nominal voltage in a much smaller package. LiPo cells also typically offer very high capacity for their weight, delivering upwards of twice the capacity for sometime ½ the weight of comparable performance NiMH cells and packs. That's right, with LiPos you can often achieve higher voltage and power output, with more capacity, in a lighter weight package.
With all of these benefits, why aren't LiPo packs more widely used? With so much energy packed into such a small space, there are some important safety measures to take when dealing with LiPo cells. A LiPo cell needs to be carefully monitored during charging as overcharging a LiPo cell (to beyond 4.2v), or the charging of a physically damaged or overdischarged cell (discharged to below 3.0v under load) can be a potential fire hazard.
Many LiPo batteries come with safe charging circuitry integrated into it. This circuitry prevents over charging, over discharging, and in some instances helps to balance the pack out. If your pack has a "Charge" lead on it, always charge through that connector.
While some battery chargers can charge either NiCd/NiMH or LiPo cells, chargers that do all three major chemical types are starting to surface. The Dynamite Vision Peak Ultra can charge your LiPo packs along with NiMH and NiCd batteries as well.
If you are going to go the LiPo route, use a charger that can correctly charge them (using a constant current, constant voltage method of charging as LiPo cells can not be "Peak Charged"), such as the Vision Peak Ultra (DYN4053) or the E-flite Celectra 1-3 Cell charger (EFLC3005). Not only must care be taken when charging LiPo cells, but when discharging them as well. You should never over-discharge a LiPo pack to below 3.0v per cell under load, and you must use an ESC programmed to provide the proper low voltage cutoff for your pack (for example, a 9v cut off for a 3 series LiPo pack). Also, you should never dead short a LiPo pack, even if only for an instant, as the large amount of energy stored in the small package can catch fire quite quickly as a result. While these seem like major deterrents to using a LiPo battery, these usage guidelines are quickly becoming well known as they are typically well outlined in the instruction manuals included with most LiPo packs, ESCs and LiPo chargers. However with all of their performance benefits, there is little doubt that lithium polymer battery packs are currently the future of battery technology for electric powered models.
To Build or Not To Build:
Some people prefer to assemble their own battery packs rather than buy preassembled packs. Before you solder on the cells, scuff up the terminals to provide a better connection and more secure solder joint.
Many people damage their battery packs before they use them for the first time with poor soldering techniques. Remember to use an iron with a large enough tip to transfer heat, apply solder to the items being joined and not the iron itself, and don't hold the iron onto the battery for too long.
There are two different ways to purchase your batteries, either as loose cells or as pre-assembled packs. With individual batteries (cells), you'll need to solder the cells together yourself to create your own battery pack. The second option is to purchase a pre-assembled battery pack that comes with the pack pre-assembled and shrink-wrapped, often times with the connectors pre-wired. If you do not have much soldering experience and/or do not have a high-quality soldering iron, it will generally be best to purchase a pre-assembled pack.
As a safety note, you should NEVER attempt to solder LiPo cells together into a pack configuration yourself. LiPo cells are very susceptible to heat damage, and excessive heat can cause them to possibly leak or even explode. For this and other reasons, most LiPo manufacturers willl offer pre-assembled packs only.
Discharging and Storage:
Discharging and storage really go hand in hand. For NiCd packs, you should completely discharge them, to 0.9v per cell, before you store them NiMH packs should be stored with roughly a 50% charge in them for best performance. And before you charge a NiMH pack for the first time in the day, simply drain the pack completely on a discharger or in the model and you are then ready to charge the pack for use throughout the day.
LiPo batteries are completely different when it comes to discharging and storage. Depending on the output voltage of your pack, you should only discharge your pack so far. For example, during use, a 7.4V LiPo battery (also known as a "2 series" or "2S" pack) should never be discharged below 6.0 volts under load (3.0v per cell). For storage of 2 weeks or more, LiPo packs should be stored at approximately 3.8v per cell to prevent overdischarge or imbalance from developing among series cells in the packs due to differing levels of each cell's self-discharge rate. In the case of a 2S 7.4v pack, the pack should always be stored at 7.6v. You should also store your LiPo batteries in a fireproof container or cabinet and never store your LiPo, or any other battery for that matter, in the model itself.
Pehaps no other item has quite as much effect and influence on our hobby as rechargeable batteries do. There are almost as many different theories and misconceptions out there about rechargeable batteries as there are individual battery sizes and types. Just remember that knowledge is key when it comes to batteries, as is consistent charging, discharging, and storage. Whether you are in the hobby shop or at the flying field, feel free to ask questions of those around you who may be more experienced. That is one of the best ways to learn and grow in the hobby.
Questions from a newbie....
1) do not over discharge lipos
How does one know? What guidelines to use when setting times for first time flight?
2) do not drop lipos
OK, what happens if I crash? Just let the plane lie where it is?
3) If the lipos are so inflamable, do I store them out of my house?
Pankaj
To safely use lipos it is a good idea to own a lipo voltage checcker that tells you the voltage of each cell. DO NOT DISCHARGE EACH INDIVIDUAL CELL BELOW 3.3 Volts. That is what over discharging is about.
If it is a bad crash, wait 15-20 minutes before picking up the battery. It may be a very good &(safe) idea not to reuse the battery. I saw a lipo explode after a crash as a person was throwing it away, before it even hit the ground..
Lipos are probably dangerous when they are charged and discharged at a very rapid rate.
Glow fuel is highly inflamable, nitromethane is borderline explosive. LPG cylinders can explode and so can petrol.
Avijit
What are the reasons of getting Li-Po pack puffed?????????
Sandeep
Main reason is poor maintainance...
also for motors... when they discharge the battery if the discharge it too fast it gets puffed..
the also get puffed if you over charge or over discharge them
Guys,
I still don't get it.
I am aware that the prop dia and pitch determine the amp being drawn from the battery, but I still don;t get the relation or equation to calculate the amp drawn
In such a situation, how am I to estimate the flying time of a lipo? Mind you this is for staters. Probably more experienced flyers have developed some sort of thumb rule for themselves, but for the first (first few) time that the a newbie takes off, how is he/she to determine when he/she should land the plane so that the battery does not over discharge?
Speaking for myself, chances are that I shall try and land every 5 mins, but then as far as I have understood lipo, the volt drop is only drastic at near total discharge, till then it maintains the voltage. Then in this case how do I determine the amount of charge left in the battery?
Pankaj
Dear Pankaj,
In a Glow( i presume you have mainly used glows till now) the engine output is sort of fixed. So if you put a smaller prop then you get high RPM and the RPM drops as you go for larger props.
In electrics, the RPM is sort of fixed- depending on the voltage (2 or 3 or 4 cell pac). So if you run the motor with no prop, it spins at the same rpm, but does very little work and draws very little current.
As you increase the prop size, the rpm remains same, but the workload on the motor increases and it draws more current ( higher amps). There are watt meters available that tell you what the load on the system is for that particular prop at that RPM.
Also after your 5 min flight check the voltage on your lipo. if it is above 3.7v per cell fly again. also the esc will cut out the motor when the cell voltage drops below 3v while the reciever is still powered. like a dead stick landing.
Avijit
Many ESCs allow you to select the cut off voltage. Keeping it on the high side (say 3.3v instead of 3.0v) helps prolong your lipo battery life, at the expense of slightly shorter flight times. It does give you a safety margin in terms of being able to land properly with enough power to drive the receiver and servos.
Yet another method of determining how long you can fly on a battery is to fly for some time, and then try to charge the battery, noting how many "mah" you are putting back into the battery. It is recommended that you deplete lipos only up to about 80% of their rated capacity. So if your battery is, say, 2000mah, use it for 1600mah worth of flying time.
Say if you test flew for 6 minutes, waited the lipo to cool down a bit, and then charged it noting how many mah you put in (most good charges show you that, even though the numbers may not be perfect), and assume that you put in 1200mah. This means that you have about 20% more flying time left, which equates to 2 more minutes (20% of total 10 minutes, not 20% of 6 minutes). Again, these are guidelines, not perfect numbers/calculations.
Anwar,
So as I understand, one needs to first imagine that the motor is drawing max rated current and plan for battery drain accordingly and then slowly adjust the time based on the actual drain (calculated by the charge being fed in).
Is this correct?
Pankaj
One good thing about the method I was mentioning is that it takes your flying style and conditions into account. So if you got 6 minutes of flight at the expense of 1200mah drain from your lipo, that is *for your flying style and conditions*. If I did torque rolls the whole time, or flew at full throttle, I may only get 4 minutes for 1200mah.
If you have a new lipo, you would be doing a break-in for them anyways, flying conservatively. Use that as an opportunity to do the above calculation also.
More lipo safety information from AMA posted here :
http://www.rcindia.org/rc-general-topics/satefy-tips-for-rc-flying-and-racing/msg11451/#msg11451
For calculating the amp draw by a motor/prop combo...a very good starting point will be as follows :
The power required to rotate a particular prop at a particular rpm is :
Power = Kp * D^4 * P * Rpm^3
where
Kp is the propeller const. and almost every prop manufacture mentions this. If you dont know the Kp for your prop ageneral assumption will be 1.25.
D is prop dia
P is pitch
and dia and pitch are in feet not inches and rpm is specified in thousands. eg. if your rpm is 8000 then put 8 in the formula.
then amps can be calculated as :
Amps = Power/Volts(of your lipo)
But of course this is theoretical and does not include real world factors.For a detailed understanding of electric power systems please read
http://www.rcindia.org/electric-power/understanding-electric-power-systems/
Hope this helps Pankaj
I was charging my brand new lipos for the first time thought of running a " SEARCH " on our forum & came up with this informative thread...
Great stuff anwar..
Am charging a 2200mah battery at 1.8amps and not 2.2, someone told me its better to charge it at lesser amps... Is it mandatory to balance all the cells for the first charge ? Am not balancing them right now..As they came perfectly balanced from HC..
any comments ?
If you use a balance charger every time you charge, then the above issue becomes irrelevant, right ?
And regarding the 1C charging, that is the max (unless you are using the Hyperion G3 etc). I only know about charging at 0.5C for the first few cycles for lipo "break-in" but even that is disputed. But them my knowledge about cell chemistry issues is rather limited.
As per some guys on the field..Balance charging your lipos after every 10 or 12 cycles is recommended..
Hmmm..as you rightly mentioned Hyperion batteries are awesome..some guys charge them at 5c on the field and these batteries have a huge life..
Love Lipo's...
Quote from: atul_pg on February 25, 2010, 10:53:54 PM
As per some guys on the field..Balance charging your lipos after every 10 or 12 cycles is recommended..
Actually it is always safer and highly recommended that every charge is a balance charge. The chances of an imbalance growing and becoming a problem is pretty significant if you wait for 10 cycles.
That's true..
Thats why I ordered the lipo monitor but I will be doing some experiments personally regarding the charging and balancing..
What's the oldest lipo you have or anyone has ? I know a guy who has a lipo since 5 years and still using it..
Hi Guys,
RE; Never discharge a Lipo to nill... AN EXPENSIVE LESSON..
Two weeks ago I felt like flying my Multiplex Pico Jet, an eight year old brushed motor Delta model that I used to fly on 8cell nimh pack.
It had been tucked away in the attic and I thought I will change the motor to a brushless one if it flies reasonably.
The nimh were lost in the clutter somewhere so I took my 3 cell pack from Park Zone T-28 Trojan and set it up on that. Later, I switched the switch to off and left the 3 cell 1800mah lipo battery pack connected.
On Saturday night, a week later, I tried to charge the Lipo and realised somehow the electric switch even though on off position had somehow let all the current pass and the Lipo was dead.
Tried with 3 different chargers but in vain.
Some batteries have known to come back to life after being totally discharged when connected with olden non balancing type of charges
Today Sai has suggested I should try discharging it... lets see what happens, I would hate to throw away an expensive Park Zone battery that has only had about 6 flights out of it.....
Hope you tried this : http://www.rcindia.org/batteries-and-chargers/how-to-restore-a-low-cell-voltage-on-a-3s-11-1-v-1350-mah-lipo/
pls get a lipo safe bag... one of the lipos almost bursted on me and beleive me its not fun to see this... a guy on helifreak lost his house and managed to save only his family due to a 3 cell lipos... DO NOT charge or discharge without supervision... i had also posted a link on lipo's sometime back, hope it might help...
http://www.rcindia.org/helis/some-good-links-and-info-for-heli-flyers/ (http://www.rcindia.org/helis/some-good-links-and-info-for-heli-flyers/)
i usually chage in storage mode for my lipos ( around 3.85 v per cell)... if the lipos are puffed pls throw them away, they are many guys meddling and puncturing the lipos (HIGHLY NOT RECOMMENDED) and sealing the punctures hole again and using the lipos, pls DO NOT do this...
I did tinker with it all Sunday evening but did not leave it long enough. Will try it again without connecting balance connecter...
As I do not leave them unattended, did not really have any time...
No Sujju, I never try to tinker with PUFFED or PUNTURED ones. Best to throw them away... as Sai says leave them in salty water and they will disintegrate themselves..
Thanks Anwar
Deepak
am not too sure about the salt water thing.. there are some mixed reaction with the guys around... if you google around there are some more info on some pros and cons for salt water, etc...
http://www.rcgroups.com/forums/showthread.php?t=209187 (http://www.rcgroups.com/forums/showthread.php?t=209187)
opps... forgot to send this link in my earlier reply regarding salt water disposal..
http://www.wattflyer.com/forums/showthread.php?t=12173 (http://www.wattflyer.com/forums/showthread.php?t=12173)
Quote from: b4ggu on April 12, 2010, 11:43:27 PM
Some batteries have known to come back to life after being totally discharged when connected with olden non balancing type of charges
B4ggu... i had a similar problem and was lucky to get this sorted out.. used my intellegent charger to charge the lipos using nimh or nicd mode... got the voltage to around 3.1 and charged them as lipos again (but again with supervision around and on a concrete floor).. i now have had around 15 cycles with this lipo and doing good... on the other hand 2 of my 6 cell turnigy lipos went bust when on cell got to 0V ( dont know how)... so rahter than throwing them away i removed the bad cell from one lipos and replaced a good cell from another lipos (again you need to know what you are doing here)... and now again i have had 5 cycles on this 6 cell lipos and its fine and strong...
Wow, guys my 3 cell Parkzone Lipo is revived... Thanks to Anwar and Sujju.
My clubmates were insisting on binning it...
A lesson for them and can you imagine the feelings of them and other electric heli pilots at our field who are burning pound notes on 5 and 6 cells and have to throw them away.... OOOOOH that hurts.. and they could have revived them all.
Well once again, thanks lads.
I am proud to be a part of this forum.
I spent whole evening last Saturday tinkering with the charger to get it to work somehow, but it just would not switch on.
Tried without balance leads, with them, on 0.5 Amps, 1 amp, lipo setting, Nimh selection... NO GOOD.
At last by chance I tried connecting WITHOUT CONNECTING balance leads and tried various combinations again.
The charger initially did not like the name nimh but some how nicd tiptoed the trip mechanism (I know it is electronic... captain pls do not quote me on this;) I need to add some masala for the recipe....:)
Will fly with it at the weekend and see how it performs...
Deepak
deepak..that's great to hear...i would prefer that you go easy on the lipo for about 3 cycles and then treat them as normal... and pls keep posted on how they are behaving... would love to hear it... my "tinkered" lipos are like new and have now around 9 cycles.. going tomorrow to the field with my protos and will give the lipos a punch and will see the outcome.. ;D
Another tip, Store your lipos at lipo store voltage if you know you are not using them within 10 days. I already see a slight puff in my lipos for storing them fully charged like 25 days.
Quote from: vinay on April 16, 2010, 07:25:27 AM
Another tip, Store your lipos at lipo store voltage if you know you are not using them within 10 days.
How do you discharge them to the "store" voltage?
If you have a modern charger, they will have a store charge option in it. Mine stores it at 3.80 volts. You can also moniter the voltage as it charges and stop it there if your charger does not support it.
Another tip, when you come back from the flying field. Charge your lipo to store voltage until the next time you goto the field. this way you can prevent the puffing from your side atleast.
Like if you go fly on sundays, charge the lipos to 3.8 on sundays after you come back, and charge them completely the next saturday.
careful when you are charging lipo batteries, by the grace of god i just escaped from putting my house into fire.i put the charger on with alipo 22.2 volt without a balancer and went for a movie, only my dog was inside,coming back i saw black smoke only, and my puppy was barking.lucklly i didnt connect with electricity so the charger was little away from the wooden furniture, i connect with car battery any charger and the 12v car burne4d and ashes left, two days to clear the smoke and smel
Oh my god! Everything is fine right?
Scary!!
really scary.That looks bad.Now,I am getting doubts about buying a LiPO. :(
Quote from: prakkat on July 06, 2010, 05:16:06 PM
and went for a movie,
Thats where the issue is. I dont leave any batteries unattended on charge even if its NiMH. Atleast we can take some corrective action.
When one has many batteries to charge, it is not practical to stay around the battery the whole time. If a battery acts up, it can still be problematic if you are away in another room, and the fire has spread. Simple precautions like below can greatly reduce the risk.
1. Charge away from carpets, cloths, curtains etc.
2. Use a lipo charging pouch/bag that is fire resistent. They were expensive before, but have become affordable now. They are good for carrying lipos around also.
If a lipo was dropped or was impacted in a crash, it is pretty much a must that you wait around for 10s of minutes when you put it back on charge the first time, periodically testing the temperature.
I have had my own share of an accident in the initial days, when I got a new charger. Even though I remember setting the amps to 0.8 for an 800mAH lipo, it had gone back to the default of 3A when I started charging. The battery and foamie next to it got fire, but was caught in time to douse the flames. The biggest mistake with lipos is NOT to limit the charging current to 1C, and NOT choosing the right number of cells (target voltage). One cannot do much about equipment malfunction, but the other cases can be prevented with care.
Used with some respect, they are very very safe, and have made Rc accessible to so many people who would not be able to enjoy this hobby otherwise. No need to worry about them unnecessarily, just take good care of them (which also includes disposing them off if the situation warrants!).
I have heard different opinions on what type and amount of "puffing" is acceptable. Soft seems to be considered alright, but
to what extent?
Any one knows the reason/s for puffing when stored in a charged state? Doesn't seem to affect other batteries, particularly in laptops.
Not sure if there is an exact answer to this. We can only go by personal experiences. I have not had issues of safety with puffed lipos (I would say "fairly" puffed), but the flight times do not last as long as before. Not a huge loss, I would put around 20% in most cases initially, and then they gradually lose more (but then all lipos die down gradually).
If you are referring to why half-charge is recommended for long term storage, it would be cell chemistry differences. I have not seen any of my lipos puff from storage alone (I have had them fully charged for many many months by mistake, like 7 months or so in some cases). But there must be a reason for the recommendation for long term storage at half charge, and slight puffing may be one of the consequences otherwise.
ALL my batteries have puffed up with hardly any use. Maybe it's just the quality (or lack of).
I have a DVR from a company called archos.My first battery got puffed like crazy.(It was a Li ion).It gave a life of 3minutes against 2hours when watching a movie. Even my brother said that it was dur to overcharging.Now,my new battery is also acting like taht but gives upto 1 and a half hours of life.It won't explode in flames right?I keep it on to record TV shows I miss.
Mine puffed slightly coz I stored them fully charged for 3 to 4 months. Batts were turnigy Flightmax and rhino. Not only puffed now they store 10 to 15% less charge then before. So if you plan to use ur battery after few weeks then better put them in store mode.
Quote from: iamahuman on July 07, 2010, 02:02:01 PM
I have a DVR from a company called archos.
Slightly off-topic.... the owner of the company which makes Archos is Sam from Bangalore, who is an avid RC enthusiast :)
What!!!I got mine from Germany.Actually,two.One for my bro and one for me.
Now we have all seen videos of LiPo's blowing up.. Now how about one that refuses to blow up.. ;D
http://www.youtube.com/watch?v=XM9E_PnhFgI
Quote from: vinay on July 07, 2010, 02:15:06 PM
Mine puffed slightly coz I stored them fully charged for 3 to 4 months. Batts were turnigy Flightmax and rhino. Not only puffed now they store 10 to 15% less charge then before. So if you plan to use ur battery after few weeks then better put them in store mode.
PLEASE DO NOT STORE YOUR BATTERIES FULLY CHARGED. The storing voltage should be around 3.2V per cell.
Nowadays all chargers have an option of "Lipo Storage" in them. so when you select that option, input your battery specs, the charger will automatically balance your battery and set the voltage to the storage voltage, SAFE VOLTAGE, and then you can store it at room temperature...
I suggest all the newbies to ue a Lipo Sack. It prevents the fire... You will have to then use wire extenders for the balance plugs and the discharge plug so that you can use the Lipo Sack.
Have a look at this:
http://www.youtube.com/watch?v=iX1MdkSU56M
Quote from: anam_funny on July 07, 2010, 10:39:29 PM
[PLEASE DO NOT STORE YOUR BATTERIES FULLY CHARGED. The storing voltage should be around 3.2V per cell.
The storage voltage is around 3.8 to 3.85 volts per cell. Making the cells to go below 3.3 to 3.4V is a bad thing that can happen to a lipo. ;)
Yes... Sorry... That is the low voltage....
do lipo safe bags really work?
:)
http://www.youtube.com/watch?v=hcwOwf55Rtc
Some Useful information on Lipos...
https://sites.google.com/site/tjinguytech/charging-how-tos
Quote from: saurabhhsrivastavaa on July 19, 2010, 02:20:57 PM
Some Useful information on Lipos...
https://sites.google.com/site/tjinguytech/charging-how-tos
Sorry for the duplicate post... i guess people have already posted this link... :)
Not creating a separate thread for this. I am a new user of lipos. See the images for a fully discharged and full charged 4S 5800mah lipo.
Please let me know if the cell voltages are fine for both. How much high and low can they ideally go when fully charged and full discharged?
Fully charged should be ideally 4.20v in each cell. Note that slight discrepancies can arise out of less than perfect balancing, accuracy errors in the measuring device itself etc.
Discharged volts is a bit more flexible, keeping it around 3.3v per cell would work OK.
I follow the 80% discharge rule and end up with about 3.7V after discharge. Your pack is low comparatively.
Following the 80% discharge rule is best practice, but 3.7v after 80% discharge sounds high. Should be more like 3.4v to 3.5v per cell, in my experience.
3.3v is more of a lower limit. Note that most ESCs offer lipo cut off voltages around 3.0v.
Most of the mah the battery consumes during charging is above 3.70 volts. i will post a voltage/mah graph once Iam free.
So in my opinion 3.7 volts has < 20 % charge or approx 20% charge. From what I read from other sites. If discharged by only 80% all the time, then the cycle life can be doubled. But AFAIK, The battery gets destroyed in crashes by then atleast for me :giggle:.
My Turnigy and Flightmax 3000mAh packs end up at 3.7x or 3.6x worst case after 80% discharge. I got out of electrics long ago, so no recent experience with a variety of other packs.
I have kept auto lipo detect setting on my ESC which cuts off power at 3.0v per cell. Should I increase that?
Yes, it is best for the health of the lipo that you do not go that low.
Ideally, the 80% rule is the way to decide how much you can routinely extract out of a lipo. But I am not sure if this can be easily done in the case of electric cars, as you are constantly playing with throttle which makes it difficult to time the usage. If you can follow the 80% rule (described as item [4] in the beginner post of this thread http://www.rcindia.org/batteries-and-chargers/taking-care-of-lipos/msg194/#msg194) for cars, that is what you should follow.
Quote from: anwar on September 22, 2010, 12:35:20 PM
Following the 80% discharge rule is best practice, but 3.7v after 80% discharge sounds high. Should be more like 3.4v to 3.5v per cell, in my experience.
3.3v is more of a lower limit. Note that most ESCs offer lipo cut off voltages around 3.0v.
depends on how much amp u pull from the battery but 3.7 sounds about right to me with new chemistry lipos do they hold volt much better. old lipos 3,4-5
i have 3.3V as default cut-off for car
i guess thats fine, pls correct if wrong..
I see that below 3.65 Volts the cells already start going off balance on my flight max batteries.
Quote from: mail4ajo on September 22, 2010, 06:31:00 PM
I have kept auto lipo detect setting on my ESC which cuts off power at 3.0v per cell. Should I increase that?
a cell should never go under 3v under load, if u have the lvc to 3 volt it is 99.9% chance that your cells are out of balance and the lvc take a average volt mean that min 1 cell will be to low.
there is lipo warner that monitor each cell in the pack instead of taking a average volt
Quote from: traxxrc1 on October 05, 2010, 09:38:20 PM
i have 3.3V as default cut-off for car
i guess thats fine, pls correct if wrong..
3,3 should b ok, but using it as a limiter and run until lvc kicks in your batteries will probably not last long,best is to get some thing that monitors the cells individual if u want to get max out of your batteries.
especially if u have high burst like on a heli
lipodimatic is a very god device to get max runtime out of your batteries
See image. Are the cells badly unbalanced? Is is ok to charge?
You can charge them back using a balance charger.
Avoid draining this low next time around (stop flying/bashing/racing earlier, with more charge left in the cells).
Quote from: mail4ajo on October 18, 2010, 01:13:20 PM
See image. Are the cells badly unbalanced? Is is ok to charge?
u are killing your batteries.
new formula lipos hold volt very good and when u start to drop to 3,4-3,3 under load they are empty, allmost 0 left. when u have 3-1 3,4 with no load all your cells have been under 3 v under load, this is probably 1 of the best ways to make sure the battery would not survive for long and give u crap performance
Quote from: anwar on October 18, 2010, 03:20:52 PM
You can charge them back using a balance charger.
Avoid draining this low next time around (stop flying/bashing/racing earlier, with more charge left in the cells).
So its safe to charge, right? I will set my ESC cutoff at 3.4V/cell. Its 3V/cell now, default by ESC. Will that work or better to set at 3.7V?
How low per cell is seriously bad?
I dont think 3V is good... I preffer 3.2V. even 0.01V matters.
Lipos tend to last longer if the 80% rule is followed. The newer lipos end up with 20% of charge left when the voltage comes down to 3.7v per cell (per Vinay/Rotorzone/others... I did not test this again recently with newer packs). So it would be a good idea to stop using them at 3.7V per cell.
Below 3 volts is pretty bad, and further down it gets significantly worse.
the lvc is not a safe way to manage the lipos. if u want to use the batteries to the max u need a lipodimatic to monitor watch cell in the pack. they are cheap and work very well
Quote from: clayboy on October 18, 2010, 08:46:42 PM
u need a lipodimatic to monitor watch cell in the pack. they are cheap and work very well
Where or how can I get one? Where can I read more on this device?
I send u a pm when I get back home
http://www.youtube.com/watch?v=NczQwVTI2bY
This should help !
http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=15237
Thats for the old-school dean boys ;). (God knows how many will offend me after reading this >:D)
The latest and the neatest is here:
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=14856
Hi everybody. I am facing a problem. Three hours ago i discharged my 3 cell lipo to 8.76V . The battery puffed up a little. What should i do now. When should i recharge? How close i was to get it smoked or fired up?
Should be usable. Watch it the first time you charge it though, and do the charge at a lower rate (just being cautious).
If the charger refuses to charge it as a 3 cell, search this forum for "trickle charge" methods, as an attempt to revive it.
Quote from: anwar on October 18, 2010, 08:04:39 PM
So it would be a good idea to stop using them at 3.7V per cell.
So is there any ESC that allows programming LVC to higher values like 3.7 or even higher may be?
what u want is something that monitor each cell in the pack under load. like schultze lipodimatic. it will slow down motor when fist cell is on 3,3v so no cell will go under 3v, it will cut power to motor if 1 cell reach 3v under load
The highest that I have used has an LVC at 3.3V. Not sure if there are ESC that can be programmed to 3.7 or higher. Usually they have fixed number of options. (Low, Mid, High) (2.8V, 3.0V, 3.3V)
Lipodimatic is an awesome system but it also has the same (2.8V, 3.0V, 3.3V) setup option, 3.3V is too low IMO.
why?
I can c for low 3d smack down heli flying but that involve any lvc
I had one esc cut down my 3s 2200 lipo in flight, measured each cell had 3.3V. Later i recharged it no problem but on next flight it hit LVC again within 15 minutes, I used to get more than 30 minutes on that battery without hitting LVC. I still have it but dont use it as the capacity seems to drop every time i use it.
And all this on a glider :( no 3D no helli nothing.
well that is a bit different, that is 3,3 with no load, with lipodimatic it is under load and when volt is dropping batteries get very unbalanced
and a lvc set on a average of 3,3 even under load 1 or more cell can drop way under 3v,
with lipodimatic it monitor each cell and can not go under 3v mean it will never damage battery,
lipodimatic is made for old formula batteries and today when battery hold volt so good until they are totally empty u have to land pretty quick with a heli, i am not using it anymore do i start to fly alot lower and harder and if low inverted and have to do a hard stop i maight not be able to stop fast enough if slow down motor and maybe crash but if u are up a bit it is no problem or for a car if u not respond to the slow down or the other setting it will cut and u just have to walk and get it
makes sense! thanks for explaining.
thanks. I am glad to help
I have this charger
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7637
and have 11.1v zippy 1500mah.....and 1450mah turnigy.
how to store them??.(i will not be using it for atleast 4-5 months)
________________________________________________________________
I had 1600mah turnigy..but it got puffed(but the puffing is not hard,i.e. when i press the puffing area it gets pressed).I left it about 3 months unused .so can i revive it?
Thanks
SS
1)No store function there on that charger. You have to store the cells at approx 3.8X volts per cell. 3.85- 3.89 would be just fine. The charger has a charging current of 800 ma, so if the lipo is completely weak(around < 3.6 volts per cell), then charge the lipos for approx 55 minutes and you should be good to go.
2)If the lipo is slightly puffed during use/store(if stored at very less charge or full charge it will slightly puff), you can still use it. Its hard to judge w/o a pic :)
How can i measure individual cell voltage?by opening the cover and measuring each one?
Can lipo be stored in refrigrator?
You don't have to open the cover. You can measure individual cell voltage on the charging plug.
I stored a LiPo (in a plastic box) in a refridgerator for 6 months. It's safe.
Just don't freeze it below 0 degrees.
No, just use a cell monitor - something like this - http://www.hobbyking.com/hobbyking/store/__19066__HobbyKing_Cell_Key_6s_Lipoly_Cell_checker.html
If you dont have one, you dont open the cell package - use the balance terminals to measure voltage. If its a 2S lipo there will be 3 wires going to the balance terminal. measure the voltage between the first and second wire - this should be the first cell voltage. Then measure the voltage between 2nd and 3rd terminal, this would be the second cell voltage - which should be same as 1st cell.
Charging plug = balance terminals. :)
Do use DMM probes with nice pointy tips!
Do be careful when measuring voltage with a voltmeter, sometimes a simple short circuit means the terminals inside the package melt and the cell becomes useless.
http://www.hobbyking.com/hobbyking/store/__18588__Hobbyking_2_8S_Cell_Checker_with_Low_Voltage_Alarm.html
will this device solve all the problem??
i.e. worrying about low voltage while flying
and checking voltage of each cell for lipo storage.?
Yes
Quote from: vinay on March 26, 2012, 03:15:24 PM
2)If the lipo is slightly puffed during use/store(if stored at very less charge or full charge it will slightly puff), you can still use it. Its hard to judge w/o a pic :)
unfortunately i am unable to upload pics. but yes it seems like their is air in between.(which gets pressed when pressed with fingers.
when i am trying to connect that puffed lipo3s to the esc nothing happens ...i measured the voltage from discharge plug and is not same as my other 3slipo which works fine but IS LESS.(unable to determine exact coz multimeter reading are faded.)
How can i revive it back??
If its much puffed and cell voltage are low, then it may not be a good idea to revive it back. I have never revived a lipo before, so wait for answers.
My charging plug of Turnigy 1600 maH got destroyed !! Is the charging plug replaceable ??
Actually its a four pin entering charging plug and a piece of metal pin got inserted accidentally .
Its now coming out nd its tightly present inside the hole.. Please help me out if the plug is replacable or if it can repaired by an electrician ?? :help:
you can remove the particular pin from the connector..... use a pin to press a lock in the connector while pressing the lock pull the wire out. then remove the inserted metal and open the lock notch a little and insert again.
Hi,
You have to solder that pin in its position also.
I have the charging plugs. But postage will be much more than original price.
The cost is Rs. 2/pin in Kolkata for male/female assembly and surely you can get this in any electronics spare shop. I have shown them to VC in Kolkata and he purchased a lot (2,3,4 pin) thin and thick one. I use them (Thick one, you can see inside DVD player power connecter PCB) in low current motor/ESC and Bat/ESC connector(10A ESC). and they works grate.
You can send me your address and I can send it to you (F.O.C.) by EMS.
thanks
There is no lock notch... There are four connecting pin holes and i one pin hole a metal pin got inserted nd not coming out.. I cant break it open as it is complete piece of connecting jack..
Should i take to electrical shop do some soldering or melting process to take that pin out..
the battery is working perfectly just i m not able to charge it which has become a problem.. ???
I have an wolfpack 1300mah 2s lipo one of the cell is 3.83v and the other is 3.79v so my battery is unbalanced how do I balance it. I have an plain simple dummy charger. One more thing while i was checking the voltage of the individual cells using my multimeter and the balance lead by mistake i just let the 2 wires touch each other this led to the two wires melting and joining to each other. I immediately removed it.
Seems like the lipo is in real trouble. can you post pic of the damaged lead. 0.04V difference wont make a big issue as far as you are charging in a balanced charger. if you are referring to the 2-3S basic charger as dummy charger, you are wrong. though it doesnt have much functions, its good for lipo health since you cannot charge it more than 600mah.
Ashok.P
@rcrcnitesh
0.04 diff is not an imbalance issue at all.
The real issue is that you've blown one of the cells.
You are lucky it didn't explode in your face!
Surely you realise this - you've been on this forum over a year now!
The cell is still working properly.
Which one? The one you shorted?
How did you conclude that it is still working properly?
Had a similar experience while trying to solder bullets. Result: bloated battery, voltage zero!
I checked the voltage perfect 3.79v the cell is not bloated.
Congrats, you're lucky!
the voltage is open circuit voltage. there are lot of things that might go wrong with a millisecond short of a Lipo which cannot be determined with just open circuit voltage alone. capacity, IR, Discharge rate, max voltage hold are a few of them.
Ashok.P
Yep very lucky, though lipos arent a safety issue if you take care of them. Had tested a old one by shorting it multiple times, didnt catch fire but eventually died out(Do not try this at home or anywhere else without proper safety measures in place)
The minute difference in voltage can be caused by multimeter too.
Quote from: K K Iyer on September 19, 2014, 11:02:37 PM
Had a similar experience while trying to solder bullets.
Sir you are very courageous
@rcrcnitesh
Hard to believe a lipo cell is ok after shorting.
Suggestion:
Since already below 50%, first charge, and see voltage of each cell.
If more or less equal, within .05v, measure voltage under load.
Ie, monitor each cell while running a motor.
See if one cell drops faster than the other.
Could anything have happened to the internal resistance?
can we check the voltage of a lipo using a multimeter???
Quote from: rohan123 on September 20, 2014, 02:04:49 AM
can we check the voltage of a lipo using a multimeter???
Of course you can ......but u need to be careful....really careful
Iyer sir how do I monitor my lipo while charging using a basic charger as well as how do I monitor my lipo while it is under load.
I am now thinking on using this lipo on my tx and buying an new 1800mah2s for my plane.
Quote from: rcrcnitesh on September 20, 2014, 02:32:39 PM
Iyer sir how do I monitor my lipo while charging using a basic charger as well as how do I monitor my lipo while it is under load.
Connect a lipo checker/monitor to the balance plug. It will keep on displaying the voltage of each cell (and total) as the motor keeps running. Rs 180 from RC Bazaar. I normally do not take lipos below 3.6v per cell under load. On disconnecting they usually show 3.70-3.75.
Normally all cells will be within 0.02-0.04v of each other. I balance them if this is exceeded.
Much more difference is an indicator of a cell starting to go bad.
Or buy a wattmeter - can do some much more
1. Measure your battery's Volts total, %age left till eg 3.7,
2. Individual Cells
3. Use on the field to get your safe flying time (and set that on your Tx)
4. Measure Watts, Volts, Amps in a running motor
I have been using this one since I re-started in the hobby about 1 1/2 years ago; works good. Was called "Draupadi" by the RC Boltz cause everyone used her :rofl:
(http://www.hobbyking.com/hobbyking/store/catalog/HK-010.jpg)
http://www.hobbyking.com/hobbyking/store/__10786__HobbyKing_HK_010_Wattmeter_Voltage_Analyzer.html (http://www.hobbyking.com/hobbyking/store/__10786__HobbyKing_HK_010_Wattmeter_Voltage_Analyzer.html)
Quote from: sanjayrai55 on September 20, 2014, 05:23:06 PM
Was called "Draupadi" by the RC Boltz cause everyone used her
sir you just made my day :rofl: :rofl: :rofl:,and where can i get "Draupadi" :rofl: in delhi or in india(online)?
Indian Hobby Shop has them for sale. Pls check with them.
is it a good idea to connect two 3s lipos of different capacity in parallel ???
will it work??? is it safe to connect them without damaging any of the two lipo??? :help: :help:
It will work for sure, - But it is not a good choice, as it is not efficient, cost wise and Weight wise .
Also there is chance of degrading of batteries faster - as the packs are not matched .
Yes you can , make sure that the packs are fully charged . If the packs have different C ratings , treat the whole pack with the lower c (3s 2000 mah 20c and 3s 5000 mah 40 c , treat the pack at 20 c)
nice information sir