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Old 07-26-2012, 03:35 AM
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thailazer
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Default LiPo Life

I am new to electric flight, although I did fly an electric plane for a while two years ago. I was recently given an ESKY Hunter coaxial helicopter and it has been a lot of fun. The original LiPo puffed up after about 12 flights so I bought a new one at the LHS. They told me to not take it out of the heli and to avoid handling the battery. Okay, had not heard that before and the new pack has about 30 flights on it and flight times are about half of what they were when it was new. Is this loss of flying time typical after 30 cycles? I am using the balancer/charger that came with the Hunter. Seems like batteries should last many hundreds of cycles with no degradation.
Old 07-26-2012, 03:58 AM
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Default RE: LiPo Life

I dont know so much about hundreds but it should be better than 30 flights thats for sure. Battery life is directly proportional to 3 things, in order of impact.

1. How low its discharged to each flight. If you wait till there isnt enough power to fly every flight, what you're seeing is typical.
2. How hard its run during flight as far as sustained loads versus the battery C rating, keeping in mind that C ratings are often optimistic
3. How many amps you charge at
Old 07-26-2012, 04:52 AM
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Default RE: LiPo Life

There is a problem though; you let your batteries away for a while and you will find that they degrade and inflate. so this idea that shelf life is long to me is just a lie, all of my bateries end up this way after a while (lets say a month or two theyget inflated).
I do not know if this happens to all brands, but at least all that I have bought have this problem, so just take care.
Old 07-26-2012, 04:58 AM
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Default RE: LiPo Life

Thanks Andy. I do tend to fly until it is unable to climb well so that is probably what is going on. Did not realize that limited the LiPo's life. Live and learn!
Old 07-26-2012, 06:12 AM
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Default RE: LiPo Life

General consensus is to remove LiPos for charging.
The fire danger is slight but real.
If it catches fire do you want to lose your model also?

Not handling I've never heard of.

I prefer a charger where I can see what is happening.
Hobby King has many inexpensive chargers that are
programmable with digital readouts. This is the best way
to know what is happening with your battery.

Puffing is somewhat normal, it seem to happen to all of us.
I have quit worrying about it.

Good Luck,
KW_Counter
Old 07-26-2012, 06:26 AM
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Default RE: LiPo Life

If you store your lipos fully charged, they will puff
Pete
Old 07-26-2012, 06:51 AM
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Default RE: LiPo Life

Store them at 70% then top off before flight
Old 07-26-2012, 09:19 AM
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Default RE: LiPo Life

Most surface ESCs have a configurable low-voltage cutoff; is this not common in the 3d realm?

I've got my car ESCs set to cut at about 3.4V/cell; shortens the runtime a bit but won't overdischarge the battery....

Old 07-26-2012, 02:39 PM
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Default RE: LiPo Life


ORIGINAL: BarracudaHockey

I dont know so much about hundreds but it should be better than 30 flights thats for sure. Battery life is directly proportional to 3 things, in order of impact.

1. How low its discharged to each flight. If you wait till there isnt enough power to fly every flight, what you're seeing is typical.
2. How hard its run during flight as far as sustained loads versus the battery C rating, keeping in mind that C ratings are often optimistic
3. How many amps you charge at
I can agree with number 1 and 2 posted here. I believe that 1 is key to the OP's problem of reduced capacity in only 30 cycles especially since he knows the flight times are getting shorter. For number 2 , a good bit of info would be the actual flight time when new and now after 30 cycles.

I'm gonna guess that the battery you bought was a bit better quality than the original AND if you were to buy an even better one it would live a better life than the replacement you got.

Old 07-26-2012, 03:18 PM
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Default RE: LiPo Life

Over amp charging isn't any better for them. Even batteries that advertise higher than 1 or 2 c charge rates benefit from not pushing all those amps while charging them.
Old 07-26-2012, 03:22 PM
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Default RE: LiPo Life

I have not noticed ANY decline in using faster charge rates. This coming from one who badly abuses the charge rate and top voltage, yet doesn't abuse the discharge rate or bottom voltage.
Old 07-30-2012, 01:10 AM
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Default RE: LiPo Life

Update: I got another three flights in and those were rather short with the last one not allowing a climb above a meter. The battery is done. So..... less than 35 flights on the last battery. I am a bit of retro-grouch and I think I will stick with fueled aircraft. In one month I have used up two batteries and now have to dispose of them. Do electric fliers buy a lot of batteries?
Old 07-30-2012, 02:35 AM
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Default RE: LiPo Life

Nope! I suspect you are over discharging them or discharging them at an excessive rate? Often the C ratings are exaggerated so a large safety margin is needed...
Old 07-30-2012, 06:36 AM
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Default RE: LiPo Life

"Not handling LiPo battery packs" - I can only imagine someone said that implying that you run less risk of "dropping" the battery perhaps... people handle the LiPos all the time.

Regarding puffing - or ballooning - LiPo packs, boy that's a tough lesson for people getting into electric. I know it was for me. I always thought you should let re-chargeable batteries sit fully charged... but then my LiPo packs smacked me upside the head like a balloon. So I bought a AC680 charger that has a "Storage" charge cycle on it putting the packs at about 3.81V / cell. I have 6 new battery packs, none of them are showing any puffing whatsoever. I wish I had ready this information before I lost some expensive LiPo packs.

By the way, for Electric Flight (helicopters or planes), I created a mobile App called: RCcoPilot
It's available on the Apple App Store. I mention it because the app specifically has a battery log that automatically tracks battery usage and cycles along with flight logs - plus I manage my batteries via QRCode serial numbers. It's kind of nifty I must say. It allows me to see what duration of flights I'm getting, and if the battery packs are showing any degradation over time.
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Old 07-30-2012, 10:52 AM
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Default RE: LiPo Life

I have been told that you should not discharge a lipo more then 70% of its capacity - and that discharging over this will cause them to puff. I have also been told that discharging or using a battery that is not rated to give the current you want/are using will also cause puffing. This is confirmed by the guys at my field who regularly fly electric planes of a wide variety of sizes.

The problem to me is that noone tells the new e-pilot this stuff, and so their batteries puff and they usually throw them out and get new ones and those puff etc etc etc. So why does this happen- seems like most airplane escs are set to draw the battery voltages down too far - or at least far enough that they puff and can become dangerous. And a lot of experienced e-pilots know this, so why don't the companies that make and sell escs design them so the batteries don't get damaged/puff? I will bet that there are many many people who see the batteries puff and get disgusted and either never get any more batteries or they throw the whole plane in the trash - and 99% of these people forget this hobby.

Some hobby shops make sarcastic answers to these questions - seems like they know it's a problem but they expect you to magically know this stuff when the design of the escs could be changed to prevent this.

There are digital meters that are sold that tell you how much of the battery charge has been used. So its clear that the technology is out there to fix this issue - the escs need to be designed so they won't discharge the batteries too far.

What do you guys think? Right? Wrong? Some other fix instead?

Ed
Old 07-30-2012, 11:07 AM
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Default RE: LiPo Life

The rule is you don't want to put back more than 80 percent of the capacity, dropping below this will cause damage to the cells.

70 percent is a safety margin
Old 07-30-2012, 11:21 AM
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Default RE: LiPo Life


ORIGINAL: rc34074
There are digital meters that are sold that tell you how much of the battery charge has been used. So its clear that the technology is out there to fix this issue - the escs need to be designed so they won't discharge the batteries too far.

What do you guys think? Right? Wrong? Some other fix instead?
The puffing is most likely due to users not keeping the charge within the acceptible tolerances; a lot of this is caused by the fact that LiPo configurations vary significantly - so you could argue the technology is not "mainstream-friendly". That's a fair statement. C ratings are not intuitive, and without Watt Meters to monitor what your aircraft is doing - most average people have no clue if their batteries are not appropriately rated for their aircraft / cars / trucks. Or if they buy additional battery packs, they buy improperly... I know I did just becoming familiar with LiPo technology. The ESCs are pretty inexpensive, and I would say are pretty simple and don't really "care" about the LiPo capacity or characteristics. Hobby stores don't care, because they want to sell more battery packs.

Now, all that said, you simplyl cannot touch the weight advantage and power distribution from LiPo packs. So they won't be going anywhere anytime soon... just remember all you e-Pilot newbies, don't store your packs completely depleted or fully-charged for long durations (ie over the winter months). PUFFY!!!!! ;-)

Old 07-30-2012, 01:21 PM
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Default RE: LiPo Life

More expensive esc can var y the low voltage cut off. A problem with having a standad LVC is voltage sag. Under heavy current demand the voltage can sag I.e climbing. The esc might think the battery is flat/dangerously low but there is lots of cruising left.

I agree that there is a lot of mystery around lipos however having become familiar with them all you need to know could be summarised pretty briefly- possibly less skill to them than getting a glow engine dialled in especially if the low idle mix is wrong!
Old 07-30-2012, 01:44 PM
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Default RE: LiPo Life

ORIGINAL: rc34074

I have been told that you should not discharge a lipo more then 70% of its capacity - and that discharging over this will cause them to puff. I have also been told that discharging or using a battery that is not rated to give the current you want/are using will also cause puffing. This is confirmed by the guys at my field who regularly fly electric planes of a wide variety of sizes.

The problem to me is that noone tells the new e-pilot this stuff, and so their batteries puff and they usually throw them out and get new ones and those puff etc etc etc. So why does this happen- seems like most airplane escs are set to draw the battery voltages down too far - or at least far enough that they puff and can become dangerous. And a lot of experienced e-pilots know this, so why don't the companies that make and sell escs design them so the batteries don't get damaged/puff? I will bet that there are many many people who see the batteries puff and get disgusted and either never get any more batteries or they throw the whole plane in the trash - and 99% of these people forget this hobby.

Some hobby shops make sarcastic answers to these questions - seems like they know it's a problem but they expect you to magically know this stuff when the design of the escs could be changed to prevent this.

There are digital meters that are sold that tell you how much of the battery charge has been used. So its clear that the technology is out there to fix this issue - the escs need to be designed so they won't discharge the batteries too far.

What do you guys think? Right? Wrong? Some other fix instead?

Ed
That is a general rule that has been spoken for many years now. It can be ignored , but a more precise rule must be followed that is to never discharge a cell to a point below 3.5 volts. Many times this can be 100% of capacity or more.

This part "discharging or using a battery that is not rated to give the current you want/are using will also cause puffing" is absolutely true.

You are correct in that an esc many times will allow the pack to be pulled down to a voltage that is too low. The problem here is that this LVC shouldn't be relied upon to tell one when to stop , but rather as a failsafe or insurance. http://www.rcuniverse.com/forum/m_91...tm.htm#9115449
Old 07-30-2012, 03:39 PM
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Default RE: LiPo Life

My point is that the escs can be designed to avoid overdischarging the lipo and causing battery puffing and other issues. So why not redesign them to eliminate the problems? The technology is out there to do it. Plus it wouldn't cost much to include chargers that have the storage charge feature included with the RTF planes from Parkzone or others.

As an engineer I'm certain it wouldn't add much cost to the escs - especially the higher priced escs. But I won't bother - the chinese would just copy it as soon as it was done, and the US government won't stop them so it would be a waste of my time to do it. So I will just do what you guys are doing and for my one parkzone mustang I will do whatever is easiest for me.

For those who really want the hobby to move more to electric this needs to be pushed HARD because as I said in my previous post I'm sure a lot of prospective e-pilots haven gotten disgusted and quit when their batteries went puffy etc. So the hobby will continue to decline unless this kind of thing is eliminated from the hobby.

A good post that clearly shows the problem is in part "Regarding puffing - or ballooning - LiPo packs, boy that's a tough lesson for people getting into electric. I know it was for me. I always thought you should let re-chargeable batteries sit fully charged... but then my LiPo packs smacked me upside the head like a balloon. So I bought a AC680 charger that has a "Storage" charge cycle on it putting the packs at about 3.81V / cell. I have 6 new battery packs, none of them are showing any puffing whatsoever. I wish I had ready this information before I lost some expensive LiPo packs." To me this is the perfect illustration of the problem - and of a pilot who was willing to bite the bullet and spend the money and time to figure it out and keep on flying - but a lot of other would just walk away and tell a bunch of others not to bother with this hobby.

Just telling the VERY small percentage of e-pilots that end up reading these threads how dumb they are might make you feel better but it won't keep them in the hobby. This is the general theme of most of the posts I have read on this subject here and on other sites - if you don't know this it's your fault. Kind if sad I think.

Ed
Old 07-30-2012, 04:48 PM
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Default RE: LiPo Life

Thanks for all the good information all. A few take-aways:

-Do not store fully charged batteries.
-Do not fly and discharge more than 80 % of capacity. (see note)
-Do not charge at too high a rate.
-ESCs do not protect batteries. (I agree with poster that said they should be redesigned to do so.)
-LiPo quality varies from manufacturer to manufacturer.

Note: How does one know this point when having a good time flying?

It sure seems that this kind of information should be in a booklet or more easily obtained rather than getting it from the school of hard knocks!
Old 07-30-2012, 05:22 PM
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Default RE: LiPo Life

I didn't Google it , but I wonder what happen when one searches for lipo care or whatever? There's usually some standard links that a lot of us (got tired of) post. Maybe these 5 points are missing from most of the lipo care and feeding instructions. For the most part I think that the site where they are purchased generally has enough info to get you going in the right direction. I know that I researched and followed info for about a year before purchasing lipos and I still had trouble with one pack where I just didn't understand cell balance and voltage. I guess I can see the point of talking about the items we talked about , but in all fairness there might be 5 more items that may be as important and may just be as unfamiliar to some. Maybe not.

I'll take a look for those links anyways , they are always helpful if you can stand to read that much. I don't have that kind of attention span.
Old 07-30-2012, 05:33 PM
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Default RE: LiPo Life


ORIGINAL: rc34074

My point is that the escs can be designed to avoid overdischarging the lipo and causing battery puffing and other issues. So why not redesign them to eliminate the problems? The technology is out there to do it. Plus it wouldn't cost much to include chargers that have the storage charge feature included with the RTF planes from Parkzone or others.

As an engineer I'm certain it wouldn't add much cost to the escs - especially the higher priced escs. But I won't bother - the chinese would just copy it as soon as it was done, and the US government won't stop them so it would be a waste of my time to do it. So I will just do what you guys are doing and for my one parkzone mustang I will do whatever is easiest for me.

For those who really want the hobby to move more to electric this needs to be pushed HARD because as I said in my previous post I'm sure a lot of prospective e-pilots haven gotten disgusted and quit when their batteries went puffy etc. So the hobby will continue to decline unless this kind of thing is eliminated from the hobby.

A good post that clearly shows the problem is in part ''Regarding puffing - or ballooning - LiPo packs, boy that's a tough lesson for people getting into electric. I know it was for me. I always thought you should let re-chargeable batteries sit fully charged... but then my LiPo packs smacked me upside the head like a balloon. So I bought a AC680 charger that has a ''Storage'' charge cycle on it putting the packs at about 3.81V / cell. I have 6 new battery packs, none of them are showing any puffing whatsoever. I wish I had ready this information before I lost some expensive LiPo packs.'' To me this is the perfect illustration of the problem - and of a pilot who was willing to bite the bullet and spend the money and time to figure it out and keep on flying - but a lot of other would just walk away and tell a bunch of others not to bother with this hobby.

Just telling the VERY small percentage of e-pilots that end up reading these threads how dumb they are might make you feel better but it won't keep them in the hobby. This is the general theme of most of the posts I have read on this subject here and on other sites - if you don't know this it's your fault. Kind if sad I think.

Ed
Adjustable LVC esc exist , but probably are never included an RTF or TXR or BNF , ect. Some of the cheapos that many buy do include adjustable LVC , many of them don't though. Most of the esc that I own don't even have any adjustments other than perhaps truning brake on and off. They are all cheap ones , yet they all have some kind of LVC and genrally the ones I'm familiar with use a constant voltage threshold or maybe 67% of starting voltage.

As far as storage function on included chargers , I don't think that will happen because of cost.
Old 07-30-2012, 06:14 PM
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Default RE: LiPo Life


ORIGINAL: guver
Some of the cheapos that many buy do include adjustable LVC , many of them don't though. Most of the esc that I own don't even have any adjustments other than perhaps truning brake on and off. They are all cheap ones , yet they all have some kind of LVC and genrally the ones I'm familiar with use a constant voltage threshold or maybe 67% of starting voltage.
This is a very important take-away... even my expensive ESC has the LVC set far too low to be healthy for the batteries. I didn't even think about it or realize that fact until very recently. I try not to run my motor until the LVC is hit, I simply know how long my batteries should last - and then I try and land before suffering from LVC threshold. My cheap ESCs claim you can turn the brake on/off, but they haven't worked for me...

ORIGINAL: guver
As far as storage function on included chargers , I don't think that will happen because of cost.
I cannot recommend the AC680 Thunder charger enough; it has the built in STORAGE feature setting for putting your batteries at the desired voltage automatically for storage...it's why I bought this charger. And it's one of the most inexpensive smart chargers out there - coming in at $50 bucks! Comes with the temperature sensor too, although I've never had issues with charging my batteries and them becoming too warm. Not if you obey the 1C charge rule.

Old 07-30-2012, 06:19 PM
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Default RE: LiPo Life

ORIGINAL: thailazer
Note: How does one know this point when having a good time flying?
Two ways... either incorporate some telemetry functionality - which is an expensive proposition... or I created a Timer App for my iPhone that reminds me when it's time to land for the particular plane I'm flying... the mobile app is a $1.99 solution. It isn't bullet proof, but it prevents the "getting carried away while having fun and forgetting how long you've been flying" scenario. It's cheap insurance is how I look at it, and with LiPo battery backs running anywhere from $20 - $70 bucks, well you do the math. ;-)

RCcoPilot



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