I know charging LiPos over 1C rate drastically reduces their lifespans. I've been charging my 2200 maH LiPos at about 1.4 C (3A) for quite some time now. I know people who charge LiPos at 2C (and even 3C). How much can we exceed the 1 C limit safely without affecting the lifespan of the LiPo too much?

What charge rate do you use?

if you got normal battery packs, 1C is the best!! but if you want the lipo for more cycles charge with something like.4-.5 C !! and if you want fast charging you can go for turnigy nanotech which you can charge at higher C ratings!!

regards,
JK

Well for good results i suppose its best to charge at 1-2.5 Amps on a 3 Cell lipo...... it charges well and does not take too long....

I charge my lipos max at 0.7C

@swapnil,
I use 6 Zippy Compact 3s 1000mah every Sunday.
2 of the older ones died after 2 years.
One is really dead, one has one bad cell.
Been charging them at 1C, ie, 1A. Normally takes about 30 minutes as i avoid going below 11.4v.
If flying gently, i land after 5 minutes.
If doing aerobatics, i land after 4 minutes.
On rare occasions, i charge initially at 1.5-2C, then 0.5C, if in a hurry.

One lipo shows full at about 11.7 (3.9 each) on 1C charge.
Gets upto 12.4-12.5 at 0.5C.

Moral: Do it as slowly as you can!

Correct KKIyer. Slow charging is much kinder to your batteries. I never exceed .5C and I still have batteries I purchased 5 years ago. I also rotate my batteries and don't use the same ones over and over again. This way they all carry the load. I've not been flying for some time due to ill health and I expected my batteries to suffer because of it. I did give them a storage charge prior to having my operation and it seems it worked. I spent half a day doing nothing but testing them all then fully charging them. Only one cell tested as a little down compared with it's adjoining cells.

The secret is mostly looking after them. I use a padded bag (insulated) to carry them to the field and try not to subject them to rough handling. The extra time I spend on them pays off in the long run. Subjecting them to fast charging does lessen their life. How much, I've never bothered to find out. But it does make common sense. Oh yes, I also avoid running them down too far and all of my "low power" beepers are adjusted for 3.4 volts.

By the way KK, the correct full charge should be 4.2 volts per cell. Your charger isn't charging correctly, Maybe it needs calibrating. On a 3S Battery you should show 12.6 as a top charge. As for your 11.7 battery, I suggest you have just one bad cell. Check each cell individually and see if I'm right. If it is one cell I advise against using it in any aircraft which can't glide. Happy Flying.  Stu

Quote from: K K Iyer on January 18, 2015, 09:21:16 PM
...
Been charging them at 1C, ie, 1A. Normally takes about 30 minutes as i avoid going below 11.4v....

I let them drop to 11.1V. Is 11.4V the safe lower limit then?

@swapnil,
I'm talking about the resting voltage, checked after landing/removing the battery.
If you have used a wattmeter, you would have noticed that after running the motor for a while (depending on capacity) the voltage will often go below 11v, perhaps even 10.5v, on opening the throttle.

I'll give an example. Using one of my Turnigy 2830 1000kv with a 9x5 and a Zippy compact 3s 25C 1000mah, after a 5 minute gentle flight in a trainer, the voltage will typically be around 11.7.
The same setup flown aggressively in an aerobatic model usually shows 11.4v after a 4 minute flight.

Since i'm not monitoring the voltage realtime during the flight, i prefer to have enough reserve to be able to abort the landing, pull up fast and come around again, without the battery going below say 10.5v during the manouvre.  . After each flight, i usually have enough juice left to do one or two circuits and bumps.
My guess is that if the resting voltage is 11.1, it may be going below 10.5v during any open throttle manouvres towards the end of the flight.
(The other important thing is to ensure enough cooling airflow, and not have the battery wrapped up completely in sponge. I only use hard sponge/foam in front as a crash precaution)

Rai saheb usually uses bigger motors and batteries in heavier models than mine. Mine are typically below 1kg, his usually over 1kg. You should ask him too how far down he runs his batteries.

Edit:
Using one of my Turnigy 2830
Needs a plural. Hence corrected to
Using one of my Turnigy 2830s,

Hi Swapnil, please forgive me, I made a mistake, I meant 3.4 volts per cell, not 11.4volts per 3s battery. A lapse in memory, I do apologize.

I know you didn't mention it in your post but I understood that. Still, isn't 3.4V per cell a bit low? Or do you let it drop to that much only in extreme cases?

Iyer sir,

my telemetry module reports 10.6V in flight for a resting voltage of 11.2V. I've been landing when the telemetry shouts 10.6V. Have I been pushing it? Should I land at 11.1V in flight or 11.1V resting voltage?

@swapnil,
If you are monitoring it realtime, you should be ok with 10.6 under load.
(Assuming each cell is at ~3.53, and not 3.7, 3.7, 3.2!)

Guess i'm conservative. Prefer to have reserve left for one circuit and bump, rather than eke out an extra 30 seconds. BTW i'm mostly using 1000mah. Larger lipos may be more tolerant.

No having a minimum of 3.4volts per cell is OK as long as it doesn't go below that. The amount of times I've even been that low I could count on one hand. My plane of quad is landed well before even 3.6 or even more. If my beeper goes off it's only because I've been distracted, which is rare.

Some people like to cut things fine and have their voltage set really low and others are more conservative. I guess it's an indication of your character, at least that's what I've found. Those who fly like a mad man tend to like taking chances and tend to like leaving everything to the last minute. Those who fly sedately usually land their craft a lot earlier. If you fly in a club setting, take a look around at those flying and see the way they fly, then ask them when do they land their craft. After many years of flying you'll be able to pick them straight away.

It's like alarm clocks. If I have to go anywhere early the next morning I'll set my alarm to wake me accordingly. But I'm always awake before my alarm goes off. Maybe it's an inbuilt alarm. It's the same after you've been flying for some time, you get to know when it's time to bring it home. Having a new aircraft can mess things up a little and it takes a few flights until you get to know when the time is up, but then I'll always make sure the craft doesn't stray too far when it's new and I may even adjust the beeper to go off early.

Maybe it's old age, but my flying would be classed by the younger guys as sedate. I tend to do a lot of low throttle or no throttle flying if the plane allows for it. Therefore I'm not pushing the battery to supply masses of power. It pays off in flight times and the overall life of the battery. I was only giving my low battery levels and what I'm comfortable with. If you're new and unsure of what you'll get from a battery then you should keep the low level a little higher and fly with what you are comfortable with.

The fact remains, everyone has a different idea of what the think is a safe minimum level. I found out a long time ago it's best to not tell people what's right or what's wrong. I much prefer to say what I use and leave it at that. As for "under load" settings, I've heard other flyer's beepers going off under really hard throttle and yet they can still fly around for quite some time afterwards. As long as the beeper isn't going off continuously, keep flying. After all that, to answer your question, Yes, maybe 3.4 volts is too low a setting for you. Ignore what everyone else is using, just fly with something you can live with and then there's no panic when your beeper goes off. If a pilot is continually worried he won't have a good flight. After many years of flying you'll know when it's time to land without needing beepers or telemetry. :-) Have FUN, that's the most important thing.