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e-Electric Batteries & Chargers > Rapid Charge & Discharge Cycles of Lipo Packs
 
 
HeliMan Dave
Senior Heliman
Location: Chicago

My Posts This: Topic  Forum		I'm wondering what the "experts" say are the current "best practices" for rapid charge and discharge of multi-cell lipos?

I'm currently doing the following with my (3) 6s 5000mAh packs...

1) Charge at 1C (from 60% storage charge) the night before flying.

2) Fly each pack only once on flying day.

3) Recharge all packs that night if flying within the next 2-3 days

(If not, each pack storage charged until the night before next flying day.)


This is very limiting however I do NOT want to shorten the life of my 6s Lipos by field charging while they're still warm. They take about 30-40 minutes to cool on the outside but internally I'm sure they're still warm so I don't recharge them for at least 3 hrs. (which is no longer at the field)

Have any of you battery technology experts tested and confirmed that it's "ok" to quick-charge a warm pack at 1C (or 2C) immediately after its been discharged?

I'd rather not "just do it" without knowing for a fact that it's not going to degrade the lipo pack in doing so.

Logo 500 3D / E550 Raptor / E325 mini-Titan / T-Rex 250 / Blade CX-2 / Blade mCX
10-28-2009 01:16 AM
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TJinGuy
Elite Veteran
Location: Socorro, NM - USA

My Posts This: Topic  Forum		Everybody has their own way of doing things. Some push the limits and others are overly careful. That said there are some things that are pretty well universally accepted.

The one that stands out on your list is the once per day thing. There is nothing wrong with running a pack more than once a day, even 10 times a day.

How you get to more than once a day is up to each individual pilot. Most people think it is bad to charge a warm pack but I do not believe that. I believe there is no problem charging a warm pack IF it has cooled off sufficiently by the time the charge is finished. In other words it needs if it takes 30min to cool off, then you shouldn't charge it any faster than 2C. Otherwise the pack will be undercharged. But remember that is my belief and many others do not share it.

- Chris

TJinTech
Team New Mexico
10-28-2009 02:10 AM
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fenderstrat
rrProfessor
Location: Aston,Pa

My Posts This: Topic  Forum		I'm with CHRIS,there is no reason to wait for a lipo to cool to ambient to re-charge.if your packs are really hot after a flight just let them sit for a few min(if they are that hot you have other issues)10-15 min is plenty,lipos do not heat up while charging therefore they will continue to cool during the charge cycle.

This is my direct experience with about 4000 cycles of 2 and 3 C charging,3s and 6s lipos.

oh and if i have a whole day of flying,my lipos get flown and charged back to back all day long,and i have been getting at least 200-250(several packs much more) cycles out of every lipo,so no performance or cycle life problems

PerformancePlusRC field rep
COMPASS helis field rep
Mini Titan/SE
HBK2
Futaba FASST
10-28-2009 03:34 AM
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zaw
Key Veteran
Location: Lebanon, NH - USA

My Posts This: Topic  Forum		With my Gaui 425 running 2x 2200 30C keep the packs pretty warm, I charge them a few min after I remove them from heli. They cool down as they charge. I fly them soon as they're charged. Days are getting Shorter!

They also fly give you more punch hot off the charger.

ಠ_ಠ HBK2 built with inexpensive parts! ٩๏̯͡๏)۶ Gaui425
10-28-2009 06:56 AM
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eclipso
Heliman
Location: Tucson,Az.

My Posts This: Topic  Forum		I agree. the temp. of a lipo is relative and it should only get as hot as it will get during discharge but if it does over heat during discharge or charge then something is wrong. I currently only fly one 3s pack four to five times if im lucky to have that much time to fly in one day and battery is holding up great for almost a year now.

Wished I had a sponsor.
10-28-2009 08:41 AM
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Richardmid1
Key Veteran
Location: Leeds, England

My Posts This: Topic  Forum		I think with the new 30C+ packs that only get warm during discharge it is ok to put them straight on the charger after a flight. I was doing this at the weekend with one of the Hyperion 35C 6s 2200mah packs and charging it at 10amps aswell (14-15mins), the pack was still warm after charging from the flight before! 4x longer life apparently! Lets see!

Eden George born 10/03/08, future 3D Masters winner!
10-28-2009 11:06 PM
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Band1086
Senior Heliman
Location: Kennewick, Wa. USA

My Posts This: Topic  Forum		Clint at FP once told me it's ok to charge as long as the temp isn't over 120 degrees, because he said as was said in earlier posts on this thread, they cool as they are charging. My new 5000 6S TP 45C and VX's never even come close to 120 degrees. Even dumping them in 4.5 mins, I've yet to see them hit 105...They are the best I've ever seen!
10-29-2009 03:41 AM
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Band1086
Senior Heliman
Location: Kennewick, Wa. USA

My Posts This: Topic  Forum		By the way hyperion says "It is especially harmful to store lithium packs fully charged, and should be avoided for more than a day or two at most."
10-29-2009 03:55 AM
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TomC
Veteran
Location: Gold Coast, Queensland, Australia

My Posts This: Topic  Forum		Dave,

Assuming you are never discharging more than 80% capacity, your packs don't get above ~120 deg F after discharge, and you always charge/balanncing your packs, then your approach maybe a bit conservative, but at least your packs should last a long time!

Personally, I don't recharge a pack until it has cooled to body temp (~100 deg F). In the bad old days when I was flying my 90 sized Ion-x on 32 x 3700GP Nimh packs I found that these Nimh packs lasted a lot longer if you waited ~24hrs between recharges. Also, these packs put out a lot more power if you recharged them just before you used them. Man, life has gotten a lot simpler with good quality Lipo's!

Best cheers,
TomC

CX2 2s
Logo10- 3D 5s
Trex600 10s HC-Rigid
2x Ion-x, 1x15s DS, 1x10s SS
10-29-2009 04:15 AM
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HeliMan Dave
Senior Heliman
Location: Chicago

My Posts This: Topic  Forum		Thanks for all the input. My goal is to get more flights at the field. With the cost of my good Hyperion 6s VX 5000's ($220 ea.), I want to take good care of them so they last as long as possible.

I balance charge them at 1c (or .5c) on a Hyperion 0615i Duo 3 charger every time.

My packs are just warm after 5-6 min flights and I follow the 80/20 rule so since it seems ok to recharge as soon as they cool a little I will consider doing that.

I will have to buy a good (super quiet) generator for the field and they (Yamaha and similar) are pretty expensive. The one I'm looking at is $700.00

Logo 500 3D / E550 Raptor / E325 mini-Titan / T-Rex 250 / Blade CX-2 / Blade mCX
10-29-2009 06:08 AM
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TJinGuy
Elite Veteran
Location: Socorro, NM - USA

My Posts This: Topic  Forum		Sounds to me like you are be very gentle. Assuming you store them properly, like not in a hot car, and that you don't physically damage them, you should expect to get long life from the packs.

That said, you are not likely to damage the packs noticeably if you were to push things a little, like charging them faster when you are in a hurry. Remember the reason you own the packs is fly them, not set them on a shelf and admire them, so use them and enjoy them! And if you do a little more than the bare minimum wear on them in the process, so be it

- Chris

TJinTech
Team New Mexico
10-29-2009 06:24 AM
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Dr.Ben
rrProfessor
Location: Richmond, VA, USA

My Posts This: Topic  Forum		I flew this past weekend in temps of about 60D F with a good wind. I kept the packs warm in my car on the way to the field and at about 74D F or so. They cooled a bit outside before I had airspace, but after the flight they were at 78D F. I went ahead and recharged because the packs were not much warmer than they were in the inside of my car (or what they would have been in my pocket). And yes, they were pretty cool by the end of recharge being pushed no harder than 1C in my case.

Ben Minor

Representing
MRC Hirobo Helicopters and Team Futaba for Radios
Morgan Fuels
OS Engines
10-29-2009 06:29 AM
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Band1086
Senior Heliman
Location: Kennewick, Wa. USA

My Posts This: Topic  Forum		What Chris is saying is exactly right. I used to do what your doing Dave, but these are a consumable item. Battery tech is increasing rapidly, and I still have older gen batts which I don't like to fly because they don't put out the power with the low temps. So, I have good batts which I don't use any more...I should have used them up.
It would have been a better use of my investment!
10-29-2009 06:59 AM
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UPSguy
Heliman
Location: Toledo, OH USA

My Posts This: Topic  Forum
Quote 
By the way hyperion says "It is especially harmful to store lithium packs fully charged, and should be avoided for more than a day or two at most."

Am I understanding this correctly, if you have a lipo battery for your onboard electronics you cannot leave it charged?

the man on top of the mountain didn't fall there
10-29-2009 12:13 PM
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TJinGuy
Elite Veteran
Location: Socorro, NM - USA

My Posts This: Topic  Forum		What is charged exactly? Full 4.2V? Or anything over 4.15V? See there are no hard fast knowns with lipos. Some people leave packs charged for 2 months and they totally die, while others leave them for a year and they work fine afterward. In truth we are just working with a whole bunch of uncertainties.

The general consensuses is that leaving packs fully charged is a bad thing. So if you take that literally then no you don't want to leave your rx pack fully charged.

I personally think that one of the issues is concerning over voltage. When you charge a pack when it is cold to 4.2V and then leave it for a months, it can very likely warm up during that time and sit there over voltage. This is likely not good good for the packs. But lets say you set your charger to terminate the charge at 4.18V for this pack. Now you are only charging to about 95% capacity and you have left a little breathing room. I think that pack will ride out months of storage just fine, or at least it won't likely die from the period of unuse.

Those are my thoughts but like any others they are just theories based on a whole pile of uncertainties.

- Chris

TJinTech
Team New Mexico
10-29-2009 04:18 PM
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Band1086
Senior Heliman
Location: Kennewick, Wa. USA

My Posts This: Topic  Forum		Well, since I read that, I have not been keeping my flight pack batts. fully charged for more than a day. And I've never kept my big batts fully charged even over night. I've tried to be very careful.
Chris, why would Hyp. say it is esp harmful if it is just a matter of
possible wrong temp storage?
10-30-2009 04:45 AM
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TJinGuy
Elite Veteran
Location: Socorro, NM - USA

My Posts This: Topic  Forum		Like I said I don't understand all the possible problems with leaving the packs charged. I believe Hyperion, like all companies, states the absolute safest possible info on their stuff. It helps protect them against litigation and passes blame onto the users. It is normal for all companies to take these precautions.

I am sure there are several possible problems with storing lipos at full charge. The ones that come to mind are

- over voltage due to rise in temp
- more energy involved in the case of a malfunction or other problem
- maybe chemical breakdown IF there is such a problem, I really don't know

Whether these actually become an issue is the part no one seems to have an answer for. I personally leave all my packs charged when I know I am going to be flying that week. If it gets longer than a week then I feel the need to discharge them at least a little.

- Chris

TJinTech
Team New Mexico
10-30-2009 07:09 AM
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stanc
Key Veteran
Location: Conroe, TX

My Posts This: Topic  Forum		A little Off Topic, but how many of you guys are concerned with the temp of your packs before you fly them in cold weather?

I've read and talked to several people like Chris that say Lipos should be close to 100°F before they are used. There are a couple of guys that fly 450 size helis at our field and I've seen what happens to their flight times when they used their packs in cold weather without warming them up first. I leave my packs in the case opened, lying on the floor of my car with the heater on to keep them warm. I get the same flight times in the winter as in the summer. COLD will damage Lipos just as much as over discharging will.

TomC is right about the temp a Lipo should be before charging. They should cooled down at least to 100°F before charging and flying them. Like TomC, I've been flying electric helis a long time and have experienced what I've said above. Its not just hear say, its fact.

Stan
Logo 500
Ion X2
eStratus
eAvro90
10-30-2009 12:42 PM
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Band1086
Senior Heliman
Location: Kennewick, Wa. USA

My Posts This: Topic  Forum		I've never experienced that problem. The only thing I've heard is they don't work well down around 40 or so and never let them freeze.
But 45 or 50 and up, they've always worked well...I don't believe you have to warm then up to 100...I've NEVER done that and have always gotten good performance out of them with no problems. That's hotter than they come in on my 6min 700 (45C & 35C).
10-31-2009 03:09 AM
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TJinGuy
Elite Veteran
Location: Socorro, NM - USA

My Posts This: Topic  Forum		Some pros preheat their packs to around 120F before the flight (Jamie Robertson is one). The reason is simple, lipos are chemical devices and the become more efficient at higher temps. Is it hard on the packs to do that? Maybe but they only care about performance, not longevity.

Likewise packs become less efficient when they are cooler. I don't think you can hurt a pack by running it cold but the performance will definitely suffer. Of course as the flight progresses they will warm up and performance will rise.

- Chris

TJinTech
Team New Mexico
10-31-2009 03:23 AM
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