Debate on Lipos. To balance or not?
03-24-2014, 02:23 PM
#26
I balance charge every time. While it may not be necessary for the health of the battery, it incorporates a very large number of really neat safety features. The most obvious is that by allowing the charger to "know" the voltage of each cell you eliminate the possibility of over charging one of more cells.
Some important background: LiPos are charged using the constant current to constant voltage method. That means the charger will charge at the specified current until it reaches the correct voltage. The correct voltage is typically 4.2 volts per cell - so a 3 cell pack would charge to 12.6 volts. You knew all that right?.?.?
Now say you begin a non-balance charge on a pack with damaged cell. Say the voltages for each cell are 2.0, 3.6, and 3.6. Notice the total voltage for the pack is over 9 volts. Below 3 volts per cell most chargers will not charge. In this case the charger will see 9.2 volts and begin charging. It will continue charging until it sees 12.6 volts for the pack. But as we said, one of the cells is not going to charge. The only way to get to 12.6 volts with one of the cells at 2 volts is for the other two to charge to 10.6 volts or 5.3 (!) volts per cell. This will cause a fire.
Had you simply hooked up the balance lead and selected balance charge, the charger will not allow any cell to exceed 4.2 volts. Period. You will still have a damage pack, stuck at 10.4 volts, but at least you won't have a fire.
I'm not going to tell you how to live your life, but given the option, I balance charge.
Clear as mud?
Cheers,
Bill
Some important background: LiPos are charged using the constant current to constant voltage method. That means the charger will charge at the specified current until it reaches the correct voltage. The correct voltage is typically 4.2 volts per cell - so a 3 cell pack would charge to 12.6 volts. You knew all that right?.?.?
Now say you begin a non-balance charge on a pack with damaged cell. Say the voltages for each cell are 2.0, 3.6, and 3.6. Notice the total voltage for the pack is over 9 volts. Below 3 volts per cell most chargers will not charge. In this case the charger will see 9.2 volts and begin charging. It will continue charging until it sees 12.6 volts for the pack. But as we said, one of the cells is not going to charge. The only way to get to 12.6 volts with one of the cells at 2 volts is for the other two to charge to 10.6 volts or 5.3 (!) volts per cell. This will cause a fire.
Had you simply hooked up the balance lead and selected balance charge, the charger will not allow any cell to exceed 4.2 volts. Period. You will still have a damage pack, stuck at 10.4 volts, but at least you won't have a fire.
I'm not going to tell you how to live your life, but given the option, I balance charge.
Clear as mud?
Cheers,
Bill
Last edited by wjvail; 03-25-2014 at 05:50 PM.
03-24-2014, 02:26 PM
#27
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I balance charge every time. While it may not be necessary for the health of the battery, it incorporates a very large number of really neat safety features. The most obvious is that by allowing the charger to "know" the voltage of each cell you eliminate the possibility of over charging one of more cells.
Some important background: LiPos are charged using the constant current to constant voltage method. That means the charger will charge at the specified current until it reaches the correct voltage. The correct voltage is typically 4.2 volts per cell - so a 3 cell pack would charge to 12.6 volts. You knew all that right?.?.?
Now say you begin a non-balance charge on a pack with damaged cell. Say the voltages for each cell are 2.0, 3.6, and 3.6. Notice the total voltage for the pack is over 9 volts. Below 3 volts per cell most chargers will not charge. In this case the charger will see 9.2 volts and begin charging. It will continue charging until it see 12.6 volts for the pack. But as we said, one of the cells is not going to charge. The only way to get to 12.6 volts with one of the cells at 2 volts is for the other two to charge to 10.6 volts or 5.6 (!) volts per cell. This will cause a fire.
Had you simply hooked up the balance lead and selected balance charge, the charger will not allow any sell to exceed 4.2 volts. Period. You will still have a damage pack, stuck at 10.4 volts, but at least you won't have a fire.
I'm not going to tell you how to live your life given the option, I balance charge.
Clear as mud?
Cheers,
Bill
Some important background: LiPos are charged using the constant current to constant voltage method. That means the charger will charge at the specified current until it reaches the correct voltage. The correct voltage is typically 4.2 volts per cell - so a 3 cell pack would charge to 12.6 volts. You knew all that right?.?.?
Now say you begin a non-balance charge on a pack with damaged cell. Say the voltages for each cell are 2.0, 3.6, and 3.6. Notice the total voltage for the pack is over 9 volts. Below 3 volts per cell most chargers will not charge. In this case the charger will see 9.2 volts and begin charging. It will continue charging until it see 12.6 volts for the pack. But as we said, one of the cells is not going to charge. The only way to get to 12.6 volts with one of the cells at 2 volts is for the other two to charge to 10.6 volts or 5.6 (!) volts per cell. This will cause a fire.
Had you simply hooked up the balance lead and selected balance charge, the charger will not allow any sell to exceed 4.2 volts. Period. You will still have a damage pack, stuck at 10.4 volts, but at least you won't have a fire.
I'm not going to tell you how to live your life given the option, I balance charge.
Clear as mud?
Cheers,
Bill
03-24-2014, 02:56 PM
#28
Yes i know all of this. That is why i always load check the volatge of each cell. It is hard for me to balacne charge due to the location of the battery in a new plane im building. So if i check voltage and it is off i will balance, buit if not i will not. Chances are that i wont need to balance more often than i will need to.
Err.. You did know they make balance lead extensions, right? http://www.progressiverc.com/balance-extensions.html Route the balance lead of your battery to some place where it's easy to balance charge. Job done. Spend 5 bucks and then your (dads) house won't catch fire.
It's really pretty simple... and I really don't care what you do. If you jumped out of plane every day and some asked you do you want a reserve parachute, would you tell them no - I check the primary myself and I've never had a problem before - and I find putting it on inconvenient? If you've got a charge system in place that allows you to sleep at night, do it. Me, I'm saying yes to the reserve question.
Bill
Last edited by wjvail; 03-25-2014 at 07:24 AM.
03-24-2014, 04:28 PM
#29
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I read this full thread before deciding to "contribute".
An Rx battery should be treated like any other - install it some place where you can get to it. Remove it to charge it. Balance charge it.
A 97" Hangar 9 Cap 232 with a 3W75i deserves all the "best practice" you can put into it.
Assuming you are using a SINGLE battery for all of your Rx/Servo chores, if a cell puffs and drops out during flight, you have a crash.
An aircraft that large falls into the double-precaution category for many of us.
An Rx battery should be treated like any other - install it some place where you can get to it. Remove it to charge it. Balance charge it.
A 97" Hangar 9 Cap 232 with a 3W75i deserves all the "best practice" you can put into it.
Assuming you are using a SINGLE battery for all of your Rx/Servo chores, if a cell puffs and drops out during flight, you have a crash.
An aircraft that large falls into the double-precaution category for many of us.
Last edited by Bob Pastorello; 03-26-2014 at 04:24 AM. Reason: new info from OP regarding application
03-24-2014, 05:17 PM
#30
[QUOTE=hoverlow44;
.Unless i add extra long balancing leads. But i dont want to modify the pack
[/QUOTE]
I am sorry but something here makes no sense. OK so you don,t ever remove the battery and your balance lead is buried but yet you say you are checking your cells in the post just above and early on the first page, so how are you doing that?
If I am gonna use a Lipo in any airplane for any purpose you can bet it will be removable and will be balance charged or if not easily removable I will definitely change my lazy ways. I was nearly taken out by a careless Lipo operator while fueling my gasser with a gallon of fuel in my face when his battery and airplane lit off in very close proximity.
John
.Unless i add extra long balancing leads. But i dont want to modify the pack
[/QUOTE]
I am sorry but something here makes no sense. OK so you don,t ever remove the battery and your balance lead is buried but yet you say you are checking your cells in the post just above and early on the first page, so how are you doing that?
If I am gonna use a Lipo in any airplane for any purpose you can bet it will be removable and will be balance charged or if not easily removable I will definitely change my lazy ways. I was nearly taken out by a careless Lipo operator while fueling my gasser with a gallon of fuel in my face when his battery and airplane lit off in very close proximity.
John
03-24-2014, 06:22 PM
#32
If he buries the battery and the balance plug is or will not not be assessable as he indicated early in this thread (see the quote) then he cannot easily check individual cell voltage. Sorry SRT, not trying to argue at all however it would seem this fellow is only using this forum to rationalize his becoming an irresponsible Lipo Operator.
John
John
03-24-2014, 06:26 PM
#33
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The reality is that charging without using a balancer is riskier than charging with one.
Personally I've never used a balancer (I don't even own one) even on packs up to 5S, BUT understand that I'm taking an unnecessary risk. I minimise that risk by only using a small number of "quality" packs and only charge at 1C. What I don't have is 20-30 different no-name brand packs in varous states of puffiness with internal IR's all over the place charging at 5C.
Probably once every 6 months I'd check the balance of a pack with a voltmeter as the pack reaches the 4.2V/cell bit just to make sure all the cells are still getting to 4.2v/cell under 1C charge current at about the same time. All my 2S RX packs are charged at 1C in the plane BUT if I were going to charge my 2S RX lip-po's at more than 1C I'd definitely fit an external balancer port.
One side note is that while somebody was flying at the field one day I noticed smoke rise up from his charger and the charge leads to his plane start to melt. I quickly unplugged everything and let him know when he came back, it turned out the charger had failed and excessive current had flowed though his NiMh rx battery even melting some of the EPP foam it was wrapped in. So no matter how careful you are, in-plane charging is never risk free and made me think about fusing my charge leads just in case.
Personally I've never used a balancer (I don't even own one) even on packs up to 5S, BUT understand that I'm taking an unnecessary risk. I minimise that risk by only using a small number of "quality" packs and only charge at 1C. What I don't have is 20-30 different no-name brand packs in varous states of puffiness with internal IR's all over the place charging at 5C.
Probably once every 6 months I'd check the balance of a pack with a voltmeter as the pack reaches the 4.2V/cell bit just to make sure all the cells are still getting to 4.2v/cell under 1C charge current at about the same time. All my 2S RX packs are charged at 1C in the plane BUT if I were going to charge my 2S RX lip-po's at more than 1C I'd definitely fit an external balancer port.
One side note is that while somebody was flying at the field one day I noticed smoke rise up from his charger and the charge leads to his plane start to melt. I quickly unplugged everything and let him know when he came back, it turned out the charger had failed and excessive current had flowed though his NiMh rx battery even melting some of the EPP foam it was wrapped in. So no matter how careful you are, in-plane charging is never risk free and made me think about fusing my charge leads just in case.
03-24-2014, 06:28 PM
#34
You very well could be right John. I'm just having memories of when I was a younger man flying with my father.
the thing I line about balance charging is that you can easily track any voltage variation. If the cell voltage gets more then about 1/2 volt apart then it's an indication there could be something wrong and needs to be monitored. If it were to get worse then you can replace the battery before loosing a model due to loss of voltage while in the air or fire on the ground.
the thing I line about balance charging is that you can easily track any voltage variation. If the cell voltage gets more then about 1/2 volt apart then it's an indication there could be something wrong and needs to be monitored. If it were to get worse then you can replace the battery before loosing a model due to loss of voltage while in the air or fire on the ground.
Last edited by speedracerntrixie; 03-24-2014 at 06:34 PM.
03-25-2014, 05:44 AM
#36
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Balance charge; all upside, no downside.
LiPo for Rx pack : you can do it, but it is a pain, and more risk than its worth IMHO. go with LiFe or NiCd for Rx packs... you can charge them in the plane.. no fire hazard... and they will last you a full days flying in most cases.
You mention having to charge your Rx pack every 20 minutes or so..... can you explain this a bit more? Do you have something besides the Rx/Servos hooked up? I can get an hour or so of flying out of your typical 700mah NiCad pack and can fly for the better part of 2-3 hours on my 2500mah LiFe packs without considering charging...likely longer in many cases. I'm wondering if there is something else going on here that we could help with if you are forced to charge your Rx pack every 20 minutes.
LiPo for Rx pack : you can do it, but it is a pain, and more risk than its worth IMHO. go with LiFe or NiCd for Rx packs... you can charge them in the plane.. no fire hazard... and they will last you a full days flying in most cases.
You mention having to charge your Rx pack every 20 minutes or so..... can you explain this a bit more? Do you have something besides the Rx/Servos hooked up? I can get an hour or so of flying out of your typical 700mah NiCad pack and can fly for the better part of 2-3 hours on my 2500mah LiFe packs without considering charging...likely longer in many cases. I'm wondering if there is something else going on here that we could help with if you are forced to charge your Rx pack every 20 minutes.
03-25-2014, 06:20 AM
#39
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You all know a lot of us stopped responding to these threads cause of this, glad to see you guys stepped up to it.
First of all designers when faced with problems don't ever do nothing cause it's not easy. The OP has 3 major design flaws an doesn't want to deal with it.
1. LiPO's bad choice as Rx. This is a long running argument Iam going their again just search LiPO in Tx
2. LiPO's have become safe because we are slowing learning the RULES !
3. If it's not right why do it. As the movie goes just fix the problem john
Rich
03-25-2014, 07:12 AM
#40
I really have no issue with any type of battery being used to power the RX and servos. I have models that use NiMi, LiFe and LiPoly. I just bought a couple 7.4V 5000 MAH hard case LiPoly's to go into my new 40% Extra. I will balance charge them every time and if anything unusual is noted they will be removed from the airplane and given a very good look and either replaced or if deemed OK installed back into the airplane. I'm the kind of guy that wants to take advantage of everything that the manufacturers provide us with. This includes balance plugs, they are there for a reason. My newest pylon airplane required the RX pack ( 6.6V LiFe ) be placed 4" behind the wing. I will be installing a balance plug extension. As for flying with ones father, I envy the guys who can spend that time bonding with theirs.
03-25-2014, 07:18 AM
#41
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I think I hear you chafing slightly at my reply. I suppose that's fair. I just spend 30 minutes of my life posting a reply that lectured you on things you already knew. Nobody likes to be lectured.
Err.. You did know they make balance lead extensions, right? http://www.progressiverc.com/balance-extensions.html Rout the balance lead of your battery to some place where it's easy to balance charge. Job done. Spend 5 bucks and then your (dads) house won't catch fire.
It's really pretty simple... and I really don't care what you do. If you jumped out of plane every day and some asked you do you want a reserve parachute, would you tell them no - I check the primary myself and I've never had a problem before - and I find putting it on inconvenient? If you've got a charge system in place that allows you to sleep at night, do it. Me, I'm saying yes to the reserve question.
Bill
Err.. You did know they make balance lead extensions, right? http://www.progressiverc.com/balance-extensions.html Rout the balance lead of your battery to some place where it's easy to balance charge. Job done. Spend 5 bucks and then your (dads) house won't catch fire.
It's really pretty simple... and I really don't care what you do. If you jumped out of plane every day and some asked you do you want a reserve parachute, would you tell them no - I check the primary myself and I've never had a problem before - and I find putting it on inconvenient? If you've got a charge system in place that allows you to sleep at night, do it. Me, I'm saying yes to the reserve question.
Bill
03-25-2014, 07:37 AM
#42
LIPo as rx pack-- means you with have HV servos or a regulator from batts feeding your rx.
I read this stuff and wonder a bit --
Lipos two cell packs included - have balancing plugs today - years back they didn't-
good chargers will read impedance- info really worth knowing
I use Cellpro 10S chargers for most of my batts which include 10 cell packs etc.
Wiithout even running a pack -I can tell which ones are weak by how they charge .
Lipos especially 2 cells are inexpensive today -and far better than older packs
Unless your plane is not worth having- -- it Is simply common sense to use current cells, charged always on a LiPo balancing charger .
For as long as 2.4 has been around there have been comments about which radio was superior (2.4 )
the problem 99.999 of the time is due to power interruptions and voltage depression - usually battery - regulator or BEC.
you should really spend more time learning how to use batteries - they are the heart of 2.4 operation.
I read this stuff and wonder a bit --
Lipos two cell packs included - have balancing plugs today - years back they didn't-
good chargers will read impedance- info really worth knowing
I use Cellpro 10S chargers for most of my batts which include 10 cell packs etc.
Wiithout even running a pack -I can tell which ones are weak by how they charge .
Lipos especially 2 cells are inexpensive today -and far better than older packs
Unless your plane is not worth having- -- it Is simply common sense to use current cells, charged always on a LiPo balancing charger .
For as long as 2.4 has been around there have been comments about which radio was superior (2.4 )
the problem 99.999 of the time is due to power interruptions and voltage depression - usually battery - regulator or BEC.
you should really spend more time learning how to use batteries - they are the heart of 2.4 operation.
03-25-2014, 07:54 AM
#43
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I am sorry but something here makes no sense. OK so you don,t ever remove the battery and your balance lead is buried but yet you say you are checking your cells in the post just above and early on the first page, so how are you doing that?
If I am gonna use a Lipo in any airplane for any purpose you can bet it will be removable and will be balance charged or if not easily removable I will definitely change my lazy ways. I was nearly taken out by a careless Lipo operator while fueling my gasser with a gallon of fuel in my face when his battery and airplane lit off in very close proximity.
John
If I am gonna use a Lipo in any airplane for any purpose you can bet it will be removable and will be balance charged or if not easily removable I will definitely change my lazy ways. I was nearly taken out by a careless Lipo operator while fueling my gasser with a gallon of fuel in my face when his battery and airplane lit off in very close proximity.
John
Its not buried, i just cant plug my balance board into it because it is too big. The balance leads stick out enough to stick my volt/load checker into it
03-25-2014, 08:26 AM
#44
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My 2 1/2 cents worth....
I also use 2S LiPos in my airborne set-ups and regulate the voltage to 6 volts.
The batteries come with the balance jack already installed so I tend to use the balancer. Not every time but fairly often. BUT I never charge in the plane. I have mine set-up so the battery sits up just under the canopy so it's simple to reach and remove/reinstall. Just a little forethought is all it takes and I'm sure you can do that too! Most that use LiPos in their airborne set-ups do that.
One other thing I often do is to check voltage after the second and fourth flights. The discharge rate has been extremely consistent so I know within .03-.05 volts how much drop each flight produces. I run my airborne and CDI from the same battery and the 2000 ma gets me 75 minutes of flight time or 5x15 flights
I also use 2S LiPos in my airborne set-ups and regulate the voltage to 6 volts.
The batteries come with the balance jack already installed so I tend to use the balancer. Not every time but fairly often. BUT I never charge in the plane. I have mine set-up so the battery sits up just under the canopy so it's simple to reach and remove/reinstall. Just a little forethought is all it takes and I'm sure you can do that too! Most that use LiPos in their airborne set-ups do that.
One other thing I often do is to check voltage after the second and fourth flights. The discharge rate has been extremely consistent so I know within .03-.05 volts how much drop each flight produces. I run my airborne and CDI from the same battery and the 2000 ma gets me 75 minutes of flight time or 5x15 flights
Last edited by MTK; 03-25-2014 at 08:31 AM.
03-25-2014, 09:45 AM
#45
Well that's helpful to have and i thank you for that.
It's become clear that the consensus is that it is a very good idea to balance charge. You don't have to balance charge every time but many (most) do.
Further, your battery installation and charging challenges have become clearer.
Some number of years ago it became apparent to me that the balance leads for most LiPo batteries were frustratingly short. Even for simple bench charging, plugging in both the balance lead and main battery lead is a stretch (pun intended). Charging while the battery is installed in the aircraft - generally not a recommended practice - only makes it harder. Using a fireproof LiPo charge bag - highly recommended - is nearly impossible with the OEM leads. With this in mind I bought balance lead extensions for my most common battery packs. See pictures. In these pictures I'm using a parallel charge board and I've connected extensions to one of the 4 ports. This makes it MUCH easier to quickly plug in and balance charge a pack.
In these pictures I've semi-permanently attached these extensions to my parallel/balance board. For a one-off installation, such as your new build, you could semi-permanently install the extension to the battery.
The extension aren't expensive but they aren't free either. At $5 a pair, adding 20 different cell count, and connector type extensions to your cart can add up quickly. Still, I consider it cheep insurance.
Bill
Last edited by wjvail; 03-25-2014 at 05:52 PM.
03-25-2014, 12:02 PM
#47
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Just order 2 packs of the 2 S and 1 pack of the 6s.
Looking to get it set up like you did. Im glad you told me about that site, i couldnt find thunder power style extensions.
03-25-2014, 07:51 PM
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Yeah, you should read the whole post. Its actually a 35% Edge with a 3w 85. And i do have bigger packs for other electric 100 Amp planes. Which i always balance. Not going to not balance $400 battery packs.
