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My LiPo's are dying

#1
I bought and have been using (2) 2200mah 3cell Lipo's. I've probably flown (and recharged) with each battery 15 times and now both are pretty much dead and won't recharge. Since this has happened with both batteries my guess is that error is with me. I do not have the voltage alarm setup on my KK2 but I also dont run the lipos until they completely dead. Once I start to loose some power I recharge.

When I recharge some of the time I choose the 2amp setting and the rest of the time I choose 1amp. (this is my charger http://radientrc.com/Primal/ )

Since I'm new to the hobby I do tend to crash from time to time which I'm also wondering if thats a factor.

(yesterdays crash...I under estimated the wind)

[video=vimeo;91122770]https://vimeo.com/91122770[/video]
 

xuzme720

Dedicated foam bender
Mentor
#4
I think Cyber has hit it. Waiting for the packs to get low enough to notice loss of thrust is taking them way low, probably close to or below 3v per cell...
 

Cyberdactyl

Misfit Multirotor Monkey
#5
Also I would ask if you're balance charging (using the balance plug).

If you're running them down to where the quad is slowly sinking, and not balance charging them, I could well imagine the life of them would be drastically reduced.
 

FinalGlideAus

terrorizing squirrels
#6
If you are flying until power stops you are way over draining your batteries and as a result they are dying after only a short time. This should highlight the importance of the use of a voltage alarm such as in a KK2. Here is how you can kill a lipo.

Overcharging which you are not doing
Charging at higher than 1c rating which you are not doing
Discharging at higher rate than the C rating of the battery can handle which you are not doing
Over discharging the battery past the lowest voltage it likes which you ARE doing.

Lipo's are great batteries but unlike the trusty old Nicad's of yesteryear they don't like being mistreated. The voltages I will give are 'per cell' so please multiply by the number of cells in your pack (in your case 3 cells). A fully charged lipo cell has 4.2volts. Above that and you will hurt it. A smart lipo balance charger will stop this from happening. The balance plug is used to measure each individual cell to ensure they all stay the same voltage so as not to accidentally damage one cell that starts off at a slightly higher voltage than the others when charging.

A fully drained lipo is at 3.3 volts. Going lower than this can permanently damage the cell. Go below 3 volts and the cell will die straight away. Airplane ESC's are designed to cut out power at 3.3 volts but this could be bad for a Multirotor so that feature is removed but you run the risk of over draining the battery without an alarm. Even draining the cell to 3.3volts each flight can vastly reduce its service life as it taxes the cell badly. If you want to look after it then only drain it to about 3.7 volts and the battery will last a long time.

Also, lipo's must be stored at a correct voltage which is 3.8volts. If left fully charged they will puff and die. I try not to leave my batteries fully charged for more than 24hrs. Storing it at 3.3 volts can have the same effect and if the voltage drops below 3 volts over time the cell will die. If I know I'm not going to use the battery for a week or more then I charge the batteries to 3.8volts. Problem is the cheaper chargers don't have a storage charge option but you can charge the batteries and set the KK2 to 3.8 volts per cell and discharge it to that voltage.

In summary (voltage per cell)
Don't over charge past 4.2v
Don't discharge past 3.3v but recommend not past 3.7v for long service life
Below 3v and cell will die
Don't charge over 1c charge rate
Don't discharge higher than the batteries c rating
Put batteries to 3.8v storage voltage when not using for a while.

Hope that helps
 

colorex

Rotor Riot!
Mentor
#7
In summary (voltage per cell)
Don't over charge past 4.2v
Don't discharge past 3.3v but recommend not past 3.7v for long service life
Below 3v and cell will die
Don't charge over 1c charge rate
Don't discharge higher than the batteries c rating
Put batteries to 3.8v storage voltage when not using for a while.
I got this PM today from someone at RCGroups.

I never go under 3.8V/cell, meaning ~11.5V total...You will damage your batts if you go that low...
Although in my experience the longest flight time is at 11.2 volts - I wouldn't mind flying to 11 or 10.9 volts for the extra minutes. But indeed 3.3 volts per cell is def to low. It's what the voltage alarm sounds at, but still, it's too low.

I used to fly down to 10.5 but now some of my batteries are a bit puffy :(

Are your LiPo's puffy?
 

jhitesma

Some guy in the desert
Mentor
#8
At a bare minimum I'd suggest getting a cheap volt meter and checking your voltage after flying. But setting up the voltage monitor on your controller board or getting a voltage beeper that plugs into your balance port is an even better idea.

I notice when I hit 3.7-3.8 per cell on my packs (3 different manufacturers 2 styles/capacities from one of those manufacturers so 4 types all together) at that point the quad still flies...but starts taking more throttle to stay airborne. Same thing when I fly my fixed wings and my micro helis at 3.8v per cell I can feel a noticeable difference and by 3.7v I'm feeling it enough I land. I've flown to 3.5-3.4v per cell and it's VERY obvious to me that the voltage is sagging by that point - keeping my quad from falling out of the sky is tough by that point.

I've had very mixed results with the voltage beepers though. The cheapies that are set to 3.5v with no option to change them I've had the best luck with...but I don't really like going that low before getting an alert. The ones that let you program a voltage point I like since I can set them to warn me at 3.8 - but I've had big issues with them starting to alert me after just a minute or two of flying when one cell sags a bit under load...land and check and all cells are at or above 4.0 but take off and it starts beeping almost immediately. I figured it was just that my packs are 2 years old and have had a good bit of use (and one of those packs did just loose a cell entirely a few weeks ago) but even the 2 new packs I picked up back in November started doing the same thing after just a week or two - and none had been taken below 3.5 per cell and always charged at 1C in balance mode. Yet after just a few weeks of use they started setting off my warning beeper prematurely.

Maybe that particular voltage beeper was the culprit...it had been through a few crashes and had it's case knocked off a few times. Then after one particularly bad crash it got really quiet as the beeper itself was damaged and I gave up on using it. Now I just rely on a combination of my ability to feel when the packs hit 3.8, the timer in my TX which I have dialed in to where it was matching the beeper almost perfectly before the beeper started acting up, and the voltage monitoring in my MW (though I'm not at all impressed with the MW's voltage monitoring and don't trust it at all...plus since I don't have a beeper on my FC I can only monitor that using the app on my phone or the OSD when flying FPV....so it's not a method I really rely on - though as I'm doing more and more FPV I really want to get it reporting more accurately.)
 

FinalGlideAus

terrorizing squirrels
#9
This lipo alarm has worked well for me.
http://www.multirotorsuperstore.com/accessories/26/lipo-battery-voltage-alarm.html
Programmable to any voltage and shows each cell voltage on the screen 2s-8s. Even with an OSD something like this may save you if flying FPV and you have a cell go bad. You won't notice it on the overall voltage on the OSD but that little alarm will warn you. It happened just like that recently to a friend.

When flying hard acro and pushing the cells so there is a voltage say I just drop the alarm voltage down by .4v as it is the resting voltage that is the key voltage to watch for so long as you're not dipping below 3v.
 

chaos23

Senior Member
#10
sounds to me like its not altogether his fault, that charger he uses could be at fault from what hes saying, how many of you have mistreated a battery (be honest) and still got more then 15 cycles out of it. it takes alot to puff a lipo from bad discharging. but bad charging can puff them in one cycle.

colorex... at what point did your lipos start to show signs of puffing? if you over discharge it will start to puff after the flight but if not and it was puffed after you charged it then it could be a fault in the charging process.. just a thought?

also what brand lipo are you using and what is the total flying weight, KV of motors, amp draw of each motor, watt of each motor and what props are you using? if any of these are mismatched even slightly you could be staining your lipos C rating
 
#11
I see a lot of people here talk about minimum voltage of a Lipo. I have been told that I should watch how much current I put back into the battery while charging and to try to adjust flight time so that I am only putting 80% of the battery capacity back in during charging (others say I should only discharge 65%). So, on a 1000mAh battery, I do not want to discharge to where my I put more than 800mAh (or 650mAh depending on who you listen to) when I charge the battery.

How doe this compare to basing flight times on minimum battery voltage? Is it better to base flight time on battery voltage or discharge current? Which method will give me a longer battery life?
 

FinalGlideAus

terrorizing squirrels
#12
Amount of battery capacity used and voltage drop pretty much go together so they both work. The 80% rule works nicely. The problem with basing your flight time off capacity used on previous flights is that if you change from hovering all flight to flying circuits you are now using more power and you will use the battery up quicker. Having a voltage alarm will warn you when it's needed no matter how hard you fly. Voltage alarms are only a couple of dollars so it's piece of mind when your protecting a $20 plus battery.
 
#13
Amount of battery capacity used and voltage drop pretty much go together so they both work. The 80% rule works nicely. The problem with basing your flight time off capacity used on previous flights is that if you change from hovering all flight to flying circuits you are now using more power and you will use the battery up quicker. Having a voltage alarm will warn you when it's needed no matter how hard you fly. Voltage alarms are only a couple of dollars so it's piece of mind when your protecting a $20 plus battery.
I guess this is one of those differences between flying a multicopter and flying a fixed wing. I forgot to look at which topic this was posted in. I primarily fly fixed wing where power usage seems more consistent. Good to know the differences.
 

Cyberdactyl

Misfit Multirotor Monkey
#14
I believe this is the same one, or a clone. I usually grab one or two every time I order from RcTimer since I misplace them often. They also fling off somewhat easily if I have them hanging free like a dongle and I spin quick or have a rough landing and I don't notice them gone.

With free shipping, you can't beat the price.

http://www.rctimer.com/product_569.html
 

colorex

Rotor Riot!
Mentor
#17
colorex... at what point did your lipos start to show signs of puffing? if you over discharge it will start to puff after the flight but if not and it was puffed after you charged it then it could be a fault in the charging process.. just a thought?

also what brand lipo are you using and what is the total flying weight, KV of motors, amp draw of each motor, watt of each motor and what props are you using? if any of these are mismatched even slightly you could be staining your lipos C rating
My setup is as follows:

Clone F450 type frame
SunnySky X2212 980kv motors
F-30A ESC's with SimonK
FC 10x4.7 SF props (banggood)
Turnigy 2200mAh 25-35C 3S (blue lipo)

They puffed when I flew FPV at 1200grams... most likely because of the extra amps.

I charge at 1C with a balance charger and that works fine so I'm confident that is not the issue. I don't have a wattmeter so I can't test amps for sure...
 

chaos23

Senior Member
#18
My setup is as follows:

Clone F450 type frame
SunnySky X2212 980kv motors
F-30A ESC's with SimonK
FC 10x4.7 SF props (banggood)
Turnigy 2200mAh 25-35C 3S (blue lipo)

They puffed when I flew FPV at 1200grams... most likely because of the extra amps.

I charge at 1C with a balance charger and that works fine so I'm confident that is not the issue. I don't have a wattmeter so I can't test amps for sure...

yeah if your running 30amp esc you should be running 4S system. you've most likely been straining your batteries.

with 1047 props those motors draw 13.2amps each 52.8 amps total ,your esc are a bit overkill but thats ok. the motors say they are 2S-3S, running 2 3S in parallel will half the current load and should solve the current overdraw on your bat. that for planes a 35C bat is loads but for a 50+amp quad 35C is not enough for optimal operation.
 

FlyingMonkey

Stuck in Sunny FL
Staff member
Admin
#20
Maybe I missed it, but I don't think anyone has mentioned the importance of a balance charger.

The charger he's using appears to just dump the charge into the batter, all cells at once.

Being able to balance the cells of a pack is very important.