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Balance vs Non-Balance Charging

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Old 02-17-2011, 11:47 AM
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Default Balance vs Non-Balance Charging

The Best Investment ... E-flite Li-Po Cell Voltage Checker ~ EFLA111

LVC(LowVoltageCutoff) is a crutch for those who will not land before running out of juice.
All that really matters is OPEN VOLTS AT END OF FLIGHT!!!!!!!!Open /resting/no load volts per cell must be a minimum of 3.3 volts per cell and 3.7 is much kinder to the cell (everydayflyer rcgroups 7/25/2005)
3.7v per cell is most desirable and evidence of a healthy Li-Po in tip-top condition

Always land before reaching a stock ESC’s LVC of 3.0 volts per cell. Elite pilots have enough flying experience to know by the planes performance, when say a 3-cell lipo is approaching 9.6 volts (3.2 volts per cell) under aggressive flying so they know it’s time to throttle back and bring it in for a landing. When you throttle back from full throttle the Li-Po voltage actually bounces back up giving you sufficient time to bring it home. The other thing is that the additional flying time between 9.6 volts and 9.0 volts is very, very short at full throttle. Actually, the flying time between 10.0 volts and 9.0 volts is just a few seconds with aggressive flying. Even if you’re soaring a sailplane seeking thermals (very conservative flying) it’s still/more important to use a LVC of 9.6 than 9.0 because a slow discharge drains capacity with possibly less bounce back voltage. You could possibly cause more grief to your Li-Po with a very slow conservative throttle drain vs a fast aggressive drain with a LVC of 9.0 volts when it comes to achieving an eventual resting bounce back voltage of 11.1v (3.7v per cell). Can take as long as 30-60 minutes.

Ideally, you want to see RESTING voltage at 3.7v/cell. Many people find this confusing because it seems the cell is still almost full. Lipos and rechargeable batteries do NOT discharge on a linear curve. (flydiver rcgroups 6/28/2010) ... see graph below
So, one advantage of E-flite’s Li-Po Cell Voltage Checker is keeping track of the bounce back voltage of each cell which translates to the overall health of your Li-Po. One of the best ways to compare the health of each cell in a Li-Po is to periodically check the bounce back resting voltage of each cell after touch down, then again 15-30min later. It can take up to 60min before reaching 10.8-11.1 volts depending on LVC, flying pattern, flying time and condition of Li-Po.

I've been using 2s lipos in planes for years before they came out with balancers or balancing taps. I've probably got 20 packs ranging from 2s 180mah-2200mah and 3s 340mah-1850mah. I still use them, and get the same performance from them. Just don't discharge them too far, charge them only at 1C, and you'll get plenty of life out of these batteries. (cfwdude rctech 2/2006)
So here’s the KICKER: Some experienced pilots have always charged their top brand Li-Po’s thru the larger discharge connector. They have never used a Blinky, a CSRC Cell Spy or ever periodically balanced charged their Li-Po’s thru the smaller white multi-pin connector. Nor abused or misused their expensive Li-Po.

As a matter of fact there was a Li-Po distributor several years back that stated that having to balance charge Li-Po’s was so much malarkey … that balancers came into existence because too many motorheads were misusing and abusing Li-Po batteries AND some questionable Li-Po manufacturers had poor quality control when it came to mating cells of equal character into each Li-Po pack. Then there are a few who believe that because of the inherent chemistry and unique individuality of each cell in a multi-cell Li-Po pack (no matter how good the quality control) it is actually better not to balance charge a perfectly good Li-Po. For example it may not even be necessary to balance charge a 3-cell Li-Po with a bounce back resting voltage of say 3.68v, 3.71v, 3.69v. However, if the bounce back resting voltage after 30-60 minutes is 3.49v, 3.75v, 3.65v you’ve got a not-so-good Li-Po, and even though balance charging should bring out the best of each cell it will not necessarily cure your Li-Po’s woes. It may be a cheap pack having cells of unequal specification OR the pack may have been damaged (misuse/abuse). In either case a pack of ‘cell inequality’ should be balance charged thru the smaller white connector.

Bottomline: Get a Li-Po Cell Voltage Checker to keep tabs on your Li-Po’s bounce back resting voltage before recharging. This will give you the best indication of your Li-Po pack’s overall health. Then it’s up to you to decide whether you want to recharge your Li-Po thru the larger unbalanced discharge connector or through the smaller balanced multi-pin connector.
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Old 02-17-2011, 02:39 PM
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Default RE: Balance vs Non-Balance Charging

It sounds as if you are saying that the cell "bounce back" directly has something to do with "balance". Are you saying that the more cell voltage recovery the worse the balance?
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Old 02-17-2011, 06:52 PM
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Default RE: Balance vs Non-Balance Charging

Are you saying that the more cell voltage recovery the worse the balance?
No Way! The usual expected 3-cell Li-Po resting voltage recovery with a LVC of say 9.6v (or even 9.0v) should be at least 10.8v and preferably 11.1v (3.7v per cell) with a 3-cell Li-Po in good condition.

The resting time period (after flight discharge) doesn’t have an adverse affect on a Li-Po pack’s cell balance during bounce back. If anything the most noticeable difference in each cells voltage would be 5 minutes of pedal-to-the-metal aggressive flying just before and right after the LVC. During a longer resting recovery period of 30-60 minutes the cells will tend to even out somewhat.

So, for the sake of an example let’s compare 3 cells in a 11.1v Li-Po in fairly good condition. At a LVC of 9.0 volts let’s assume each of the 3 cells lowest cutoff voltage was 3.20v, 2.80v, and 3.00v = 9.0 volts. After a resting recovery period (bounce back) for 30-60 minutes the same 3 cells will be closer together in comparable voltages … let’s say 3.71v, 3.69v, and 3.70v = 11.1v for the sake of this comparison. In other words discharging a Li-Po over 5 minutes with aggressive flying will magnify any inequality among the pack’s individual cells. Whereas, during 30-60 minutes of resting recovery (bounce back) a weaker/poorer cell will get some residual benefit from a stronger/healthier cell. However, there is the possibility that having done this one too many times the middle cell may gradually weaken to the point where the resting recovery voltages at most may be closer to 3.65v, 3.55v, and 3.60v = 10.8v.
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Old 02-19-2011, 06:12 AM
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Default RE: Balance vs Non-Balance Charging

OK, so maybe I'm making too much ADO about the bounce back of a perfect Li-Po that has never experienced a LVC below 9.6v or 3.0v per cell. However, we don't fly in a glass house, or from an ivory tower or live in a perfect world.

So, which is better when it comes to balancing a 3-cell Li-Po pack having cell inequality?

A: Pack balance charged to a voltage of 12.45v with each cell having 4.15 volts, BUT with cells with the followiing voltages at LVC of 2.76v, 3.10v and 3.14v = 9.0v.

B: Pack balance charged to a voltage of 12.35v with each cell having the following voltages of 4.16v, 4.10v and 4.09v, BUT with each cell having the same voltage of 3.2v = 9.6v at LVC.
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Old 02-19-2011, 06:26 AM
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Default RE: Balance vs Non-Balance Charging

I'm rather confused still as what it is you're trying to get at exactly.

Which is better "for what" ?

Pack A (seems the voltage check was taken imediately upon hitting 9 volts) , but still depends on how fast it got there. If it got there fast (10 minutes or less) then it has unmatched IR and/or capacity. If it got there very slowly (60 minutes or more) then it has mismatched capacity.

Pack B (says balance charged) by definition wasn't balanced really. With the readings given we can conclude that the pack has either mismatched capacity and/or IR (again depending upon when the readings were taken at both ends.


This helps me think of these things when talking about lipos. Keep these terms seperate:

Balance
Capacity Match
IR match
cell IR (directly related to voltage bounce)

I tend to keep very tight tolerances on balance when full , check balance when discharge only as a "capacity match" and very rarely concerned about IR let alone individual cell IR since it all adds up anyways. The only thing here that most of us can do anything about is the balance. The others can't be changed easily by the user. I guess another way to say it is "it is whatever it is"


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Old 02-21-2011, 03:03 PM
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Default RE: Balance vs Non-Balance Charging

Pack B (says balance charged) by definition wasn't balanced really. With the readings given we can conclude that the pack has either mismatched capacity and/or IR (again depending upon when the readings were taken at both ends.
A Li-Po pack having exactly the same balanced voltage in each charged cell of say a balance charged 3-cell pack, even with a $200 Li-Po balance charger still isn't a true/good indication of a pack's equal balance charged cell capacity(mAh). That's the main reason why all ESC's should use a LVC of 9.6 volts instead of 9.0v (see previous Pack A example above).

All 3 cells in say ... a 3-cell 1300mAh Li-Po pack are rated/sold as having the same mAh, but that doesn't mean cheap or even moderatley priced Li-Po's actually have the same exact mAh cell capacity. As an example for this discussion let's say ... Cell #1 has a capacity of 1300mAh, cell #2 has a capacity of 1285mAh, and cell #3 has a capacity of 1325mAh. Then as you pointed out IR(internal resistance) is another factor that will somewhat affect each cell's discharge, even if each cell suppposedly has the same capacity (1300mAh in this example).

"it is whatever it is"
That's my point ... not all Li-Po cells are exactly equal in cheap or even moderately priced Li-Po battery packs. Therefore, the LVC setting on ESCs (especially sold with ARFs and RTFs should be 9.6 volts instead of 9.0 volts (see previous Pack A example) for 11.1 volt 3-cell Lipo batteries.
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Old 02-21-2011, 05:41 PM
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Default RE: Balance vs Non-Balance Charging

It seems that you are calling "balance" what I called "match"

I don't like the word "balance" , but we're stuck with it and I define it to mean cells at exactly same voltage (and this should really only be at 4.2 volts

I refer to "match" as cells having exactly the same capacity and if they are "matched" then they will also be "balanced" at the discharged state. I've seen some of the best quality cells have terrible capacity match , yet have also seen many low quality cells be perfectly "matched"
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Old 02-22-2011, 11:14 AM
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Default RE: Balance vs Non-Balance Charging

I've seen some of the best quality [Li-Po] cells have terrible capacity match , yet have also seen many low quality cells be perfectly "matched'
Thanks, appreciate your Li-Po feedback. Yes, need to differentiate between a Li-Po pack’s voltage balance and capacity balance(or match). Just so we/others understand that I/we first need to clarify that your use of capacity match refers to the manufacturers fully charged ‘mAh’ cell capacity rating and not an inferior, older or wounded pack’s capacity ‘imbalance’ between cells during discharge. Even though a pack’s fully charged voltage is 12.6v(4.2 balanced volts per cell) and the cells are ?supposedly-capacity-matched? … it’s still probable that during discharge each of the cell’s mAh will experience an imbalance—more likely closer to and even moreso at LVC.

So, one indication of a Li-Po pack’s capacity imbalance during discharge may be reflected in a greater inequality between cell voltages of the pack; especially more noticeable between 10.0v to LVC. So, one could assume that if the cells IR(internal resistance) and any other variables are all equal … then the cell with the least voltage at LVC has less mAh capacity and the cell with the highest voltage at LVC has the most mAh capacity.

The mAh ‘imbalance’ capacity problem I’m concerned about on this thread is with the use, care and any unfortunate treatment of a Li-Po pack that can further exacerbate an existing capacity imbalance even though each mAh cell capacity in the Li-Po pack is supposedly ‘matched.’ Mistreatment (abuse/misuse), improper storage, and continuous use may exacerbate any mAh capacity imbalance between cells that originally were of matched mAh capacity.

Among other questions I would like to discuss with respect to: Balance Charging vs Non-Balance Charging … of say a 3-cell Li-Po is the following for starters. First, though let me quote you as I think we all can agree that what you stated is common understanding.
...I define it to mean cells at exactly same voltage (and this should really only be at 4.2 volts
Question One: So, will a 3-cell Li-Po that is charged at 1C through the non-balanced discharge connector to 12.6 volts (4.2v per cell) be just as balanced (voltage wise) as another 3-cell LiPo that is charged at 1C through the smaller 4-pin balance connector to 12.6 volts (4.2v per cell)? What, if any, difference is there in 'balance' between a 3-cell Li-Po charged to 12.6v via the discharge connector and one charged to 12.6v via the smaller white balance connector.
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Old 02-22-2011, 05:13 PM
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Default RE: Balance vs Non-Balance Charging

I can go along with all you have stated above.

For your question ,  my first thought is that there's absolutely no difference.

We may make some assumptions though first:

Pack A originally started out perfectly balanced before it was used. (when recharged thru the discharge lead it will be perfectly balanced again)

Pack B I have a question: Did you mean to charge using the outer two pins (non-balance charge?) OR Did you mean to use the 4 pins and "balance charge" it?


ps How do you split quote? I find it makes responses very clear.
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Old 02-22-2011, 06:56 PM
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Default RE: Balance vs Non-Balance Charging

For your question , my first thought is that there's absolutely no difference.
So, if the primary purpose of a balancer is to fully charge each cell to 4.2 volts (and according to previous and current thinking we aren’t suppose to balance individual cell voltages before charging) then WHY is it necessary to balance charge a 3S 11.1v Li-Po via the smaller white connector even if the three cells are imbalanced by 0.25 volts after a cool down resting bounce back recovery of say 15 minutes. Let’s assume for the sake of example the individual cell voltages of this So-So Li-Po after a 15 minute rest are: 3.45v, 3.70v, and 3.65v = 10.80v.

With a 1C charge why wouldn’t each cell get as full as possible whether charged through the larger discharge connector or the smaller 4-pin white connector over a period of 45 to 60 minutes?
Pack B I have a question: Did you mean to charge using the outer two pins (non-balance charge?) OR Did you mean to use the 4 pins and "balance charge" it?
Well … actually I made up a two pin connector to individually top-off the voltage of each cell after they were non-balance charged via the discharge connector to approximately 12 volts or 4.0 volts per cell. Because Cell #1 had what I thought to be more IR or less capacity or both or whatever I charged it to 4.16v and the other two cells to 4.10v and 4.09v. This hopefully, allows it to somewhat recover or at least not exacerbate the poorer health of Cell #1 thus extending the number of charge/discharge cycles.

ps How do you split quote? I find it makes responses very clear.
Just highlight copy and paste the sentence you want. I do all my editing on Microsoft word and then copy and paste into the reply. Even then I find I have to go back and make a few corrections.
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Old 02-23-2011, 03:35 PM
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Default RE: Balance vs Non-Balance Charging

It is not necessary to balance charge the pack. Normally it will be perfectly balanced if it started out that way before use. (try it once and see)

Your example is a bad difference , but none the less you are correct. It would be a bad idea to balance the pack before charging (if it started out perfectly balanced before use)

Here's an example that may illustrate that capacity,IR,voltage, ect has nothing to do with cell balance.

Let's build a pack with grossly differing cells

a old 1300
a new 1500
a new 5000
a cheap ebay 3900
a High IR 1200
an unknown cell

This pack is perfectly balanced at the full mark can be used normally (down to the lowest capacity cell's minimum) within tolerances. It will be severly imbalanced when 1000 mah has been used. It can then be recharged thru the discharge lead without balancing and will be again in perfect balance. This can be done again and again. I am convinced that varying rates of self-discharge and Damage are the two things that "throw a pack's balance off"
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Old 02-24-2011, 09:24 AM
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Default RE: Balance vs Non-Balance Charging

Gotcha ... me thinks we're pretty much on the same page ... good learning exercise for me to bounce around ideas. Much appreciate your willingness to participate ... a kind inquisitive person with patience.

Your above example with respect to a cheap pack or a moderately damaged(but still useable) pack with unequally matched cells needs a little more explanation/exploration so I fully get it/understand. Again, lets take an EXTREME example by dismantling three packs(mental brainstorming only) that have seen better days, but the cells still have useable punch for this point of discussion being ... how much can one expect a good LiPo balance charger to accomplish through the 4-pin balance connector that can't be accomplished through the discharge connector with a charger like say the Vision Peak Ultra charger with an Astro Blinky. So for this EXTREME example let's compare a Vision Peak Ultra/Blinky combo with one of the more popular LiPo Balancing Chargers in the $100 to $200 price range (parameter for this discussion is more concerned with only 3S LiPo batteries).

OK ... here's the EXTREME example of this EXTREMELY mismatched 3S 11.1v pack: Cell #1 is from a 910mAh pack, Cell #2 is from a 1300mAh pack and, Cell #3 is from a 2200mAh pack. For the sake of not getting in over our heads the order of which cell is where makes no difference, but rather that one of the cells is 2200mAh, another is 910mAh and the other is 1300mAh.

So, Question Two: Will a good AC/DC charger like Vision Peak Ultra with the inky-dinky Astro Blinky cause further damage bringing this three cell LiPo pack (each cell at approximately 3.6 resting storage volts) up to say 12.4 volts at a 0.10 C charge rate ... compared ... to the most acclaimed $100-$200 Balancing Charger set at 0.10 C. In other words (Question Two) when/what situation would call for one to employ the use of a good AC/DC Balancing Charger. So to simplify this rather ridiculous EXTREME example when would you use a Balancing Charger to balance a pack of cells of unequal cell voltages (and mAh storage/discharge capacity) due to either poor QC manufacture or slight/mild misuse/abuse.

The more cells the more important it may be to balance charge more often, so for the sake of this Middle-of-the-Road discussion let's keep it within a 3S 11.1v LiPo parameter.

Edit Additon ... forgot to ask your opinion on what, if any, difference as far as possible TLC consideration or preventative maintenance as to any advantage whether or not the charge rate on this EXTREME example is 0.10C or 1.00C assuming all three cells have the same resting voltage of 3.6 volts ... whether balance charged with the Vision Peak Ultra via discharge connector (w/Blinky) or with a $150 Balancing Charger via the balancing 4-pin connector.

Also, are you confusing our discussion with your following statement …
Here's an example that may illustrate that capacity,IR,voltage, ect has nothing to do with cell balance.
Aren’t we talking about pack balance not cell balance?
For example one would never need to balance a one cell LiPo. In your quote did you mean to say pack instead of cell? It would seem at first glance “that capacity, IR, voltage, ect” has everything to do when discussing the balancing of a 3S LiPo pack that is out-of-balance.
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Old 02-24-2011, 03:16 PM
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Default RE: Balance vs Non-Balance Charging

I thought we were on the same page, maybe not. We may be agreeing , but saying it differently. A cheap balancer, cheap balance charger, a cheap non-balance charger can be used to do this job of balancing.

There are , of course some limitations to balancer current and time limits on chargers to interfere, but the bottom line is this: Charge the cells to 4.2 resting voltage (any way you want), they are then perfectly balanced.

I define pack or cell balance like this : "all cells are 4.2 volts resting"
The charge rate is rather irrelevant as balance is all about capacity and the cells are wired in series.

Recap: I'm not sure what distinction you are making between cell balance and pack balance , to me it is the same thing since by definition all cells in the pack are at 4.2 volts (balanced) I do make the distinction between balance and capacity match, IR match.

Let's run with your example anyways just for fun.

The pack is balanced perfectly at 4.2 volts resting.
We use around 800-900 mah from it because that is about all that the smallest cell can tolerate.
The resting voltage is as follows: all estimated
2200 cell is 3.9 volts
1300 cell is 3.7 volts
910 cell is 3.5 volts
The pack now has terrible varying resting voltages (call it un-balanced if we want)
Recharge the pack without balancing it at any rate we choose (within specs of the lowest current cell)
The pack takes around 900 mah to reach full and all 3 cells are again perfectly balanced at 4.2 volts.


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Old 02-26-2011, 12:15 PM
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Default RE: Balance vs Non-Balance Charging

The pack now has terrible varying resting voltages (call it un-balanced if we want)
You are helping me to better understand the proper LiPo terminology(balanced vs non-balanced) with this extreme example. So, I now get it that when one is talking about ‘BALANCING' a LiPo pack it refers strictly to voltage, and NOT to any cell mAh capacity differences in say a 3S pack. So, a fully charged pack with each cell charged to 4.2 resting volts is ‘perfectly balanced’ according to the proper use of the phrase, “a balanced pack.” Please correct me if there is still another factor/consideration besides … 4.2 fully charged resting volts per cell as the most widely accepted definition for defining “a balanced LiPo pack.”

I was trying to balance out the cell’s discharge voltages at LVC of a LiPo because of a LVC discharge imbalance (due most likely to some cell capacity differences in one of my 3S LiPo. So, I got thrown off the track by thinking that most everyone has a 3S LiPo with cells of unequal quality/capacity due to misuse or a cheap LiPo to begin. This inequality becomes more evident when checking the difference in each cell’s voltage shortly before and after the ESCs LVC. As discussed previously this imbalance in capacity can result in at least one of the cells going … say as low as 2.50v or lower depending on the discharge imbalance in cell capacities. Even with a presumable safe 3S LVC of 9 volts(3v per cell), one of the cells could get drained too much (2.40v, 3.25v, 3.35v = 9.00v) with an imbalance in cell capacities becoming more noticeable as the discharge progresses to LVC.

So, even though a LiPo pack may be “Perfectly Balanced” at a 3S full charge of 12.6v(4.2v per cell) it can still be problematic if each cell’s capacity at either full charge and/or discharge is significantly different enough to result in cell voltages at LVC ... such as 3.21v, 2.56v, 3.23v = 9.0v

So, I guess the next question would be … Is a LiPo really ‘balanced’ just because each cell has 4.2 resting volts? In other words let’s assume that the whole reason for using a ‘Balancing Charger’ is because there is at the very least some slight mAh capacity imbalance among the 3S LiPo’s three cells … so that they don’t all reach their full capacity(measured at 4.2 volts) at the same time. So, in that evident a Balancing Charger should prevent one or more cells from being stressed/overcharged.

Can we concurr/agree that the main and perhaps only reason for really justifying "Balance Charging" a 3S LiPo any one of three ways: (1) Only via the smaller white 4-pin connector of a fairly inexpensive RTF balance charger, or (2) Using even a simple Blinky(connected to 4-pin) when charging via the discharge connector with say a Vision Peak Ultra, or (3) Connecting both the larger discharge connector and smaller 4-pin balancing connector into a nifty digital readout “Balance Charger” ... IS ... (1) BECAUSE UNFORTUNATELY MORE THAN A FEW LIPOS ARE MISUSED/ABUSED, (2) SOME INTERNET SUPPLIERS OCCASIONALLY SELL CEAP BARGAIN PACKS OF INFERIOR QUALITY, and/or (3) SOMETIMES EVEN THE BEST LIPO MANUFACTURERS CAN HAVE A BAD QC HAIR DAY, WITH THINGS SLIPPING THROUGH THE CHECKPOINTS.

In other words if you/us always buy quality packs and treat them right we may never(don't know about that) have to ever balance charge a 2S LiPo and rarely, if ever, balance charge a 3S LiPo. This is assuming you have an AC/DC charger like a Vison Peak Ultra or whatever with digital readout that is reliable to the end. And it surely wouldn't hurt to have a cell checker.
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Old 02-27-2011, 09:13 AM
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Default RE: Balance vs Non-Balance Charging


ORIGINAL: Swift427


I was trying to balance out the cell’s discharge voltages at LVC of a LiPo because of a LVC discharge imbalance (due most likely to some cell capacity differences in one of my 3S LiPo. So, I got thrown off the track by thinking that most everyone has a 3S LiPo with cells of unequal quality/capacity due to misuse or a cheap LiPo to begin. This inequality becomes more evident when checking the difference in each cell’s voltage shortly before and after the ESCs LVC. As discussed previously this imbalance in capacity can result in at least one of the cells going … say as low as 2.50v or lower depending on the discharge imbalance in cell capacities. Even with a presumable safe 3S LVC of 9 volts(3v per cell), one of the cells could get drained too much (2.40v, 3.25v, 3.35v = 9.00v) with an imbalance in cell capacities becoming more noticeable as the discharge progresses to LVC.

So, even though a LiPo pack may be “Perfectly Balanced” at a 3S full charge of 12.6v(4.2v per cell) it can still be problematic if each cell’s capacity at either full charge and/or discharge is significantly different enough to result in cell voltages at LVC ... such as 3.21v, 2.56v, 3.23v = 9.0v

This is not a bad idea to have "balanced" or equal resting voltages at the discharged state. It is attainable very easily by balancing "at the bottom" Ideally we want cells capacity matched pefectly so that the voltage is pefectly equal at the top and at the bottom. If I had a pack that was off by a certain amount I would like to split the difference so that it would be in balance at the 50% mark. The smallest cell would then go over voltage at the top and under voltage at the bottom.

Ultimately we can tolerate any amount of mismatched capacity as long as we don't go out of spec at the top of bottom, right?

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Old 02-27-2011, 09:21 AM
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Default RE: Balance vs Non-Balance Charging

When we throw IR into the mix it gets a bit muddy since TIME has a lot to do with the voltage measurements. Unfortunately we can't do anything about varying IR between cells, but can view it pretty easily with a cell checker during the discharge or charge. The best way I can view it is to stare at the digital voltage of each cell DURING a heavy discharge. The only benefit to me is to allow me to point to a particular cell and say "you are the worst one in the pack" and after seeing hundreds of them I can't say that I've ever had them reverse roles in the lifetime of the pack NI or LI types. My observation has been that when pinpointing the worst cell in a pack it always will be the worst cell even after years of nomal or even abnormal use.

I would think that installing the best cells toward the middle of the pack is best , but we are splitting hairs probably.
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Old 02-27-2011, 09:32 AM
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Default RE: Balance vs Non-Balance Charging


ORIGINAL: Swift427

Can we concurr/agree that the main and perhaps only reason for really justifying "Balance Charging" a 3S LiPo any one of three ways: (1) Only via the smaller white 4-pin connector of a fairly inexpensive RTF balance charger, or (2) Using even a simple Blinky(connected to 4-pin) when charging via the discharge connector with say a Vision Peak Ultra, or (3) Connecting both the larger discharge connector and smaller 4-pin balancing connector into a nifty digital readout “Balance Charger” ... IS ... (1) BECAUSE UNFORTUNATELY MORE THAN A FEW LIPOS ARE MISUSED/ABUSED, (2) SOME INTERNET SUPPLIERS OCCASIONALLY SELL CEAP BARGAIN PACKS OF INFERIOR QUALITY, and/or (3) SOMETIMES EVEN THE BEST LIPO MANUFACTURERS CAN HAVE A BAD QC HAIR DAY, WITH THINGS SLIPPING THROUGH THE CHECKPOINTS.

In other words if you/us always buy quality packs and treat them right we may never(don't know about that) have to ever balance charge a 2S LiPo and rarely, if ever, balance charge a 3S LiPo. This is assuming you have an AC/DC charger like a Vison Peak Ultra or whatever with digital readout that is reliable to the end. And it surely wouldn't hurt to have a cell checker.
It is my observation that even with abuse,poor quality,varying quality,misuse,ect the packs still tend to stay in balance and it is time (varying rates of self-discharge) that throws balance off the most. Perhaps I don't beat on my packs enough? My consistant habits are as follows:

(This is not a recommendation)

Charge packs far faster than the recommended max rate.
Select packs that are "just barely adequate" for the job. 120 deg F max
Store them generally discharged.
Use them down to never below 3.7 volts.
If I do test them to below I charge them imediately upon coling to below 120 at a fast rate to 3.8 volts.
Never have I discharged a pack just because I didn't use it for some reason. It stay charged until use.
I have some good packs and some bad ones, used, ect. Many of my packs are way beyond when many would replace them. I simply retire them to less stressfull apps.

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Old 03-02-2011, 01:54 PM
  #18  
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Default RE: Balance vs Non-Balance Charging

guver (MacGyver) ,

Thank YOU for your good suggestions. Thanks to YOUR helpful replies, i was able to REJUVENATE all five of the following 3S 11.1v lipos that are approx. 4 years old. Used my Vision Peak Ultra AC/DC Charger, E-flite Cell Checker, and custom-made patch cord for topping off each cell individually to 4.2 resting volts. This topping-off via the LiPo’s smaller 4-pin connector was done only after a total voltage of 12.55v was reached via charging through the LiPo’s larger discharge connector. These are the five REJUVENATED 3S lipos, thanks to YOU.

1 – ElectriFly 910mAh 15C … charged at 1.5C(1.35 amps) to 12.55v and then topped off each cell
1 – CSRC 2000mAh 8C (previously swelled to 1.063” from 0.91”) … charged at 2.5 amps to 12.55v, then as above.
3 – PKZ 2200mAh 12C … charged at 2.5 amps to 12.55v, then topped off each cell to 4.2 resting volts.

Bench discharging was done at half-throttle ranging from 8.67amps down to 6.50amps. Then as low as 1.50amps the last few seconds before LVC. However, at LVC the individual cell differences can become quite dramatic IF one doesn’t balance charge each cell to exactly 4.2 resting volts as you suggested. Also see a couple advantages to charging at a higher rate as you mentioned. So, before implementing your suggestions one of my PKZ 2200s had the following cell voltages just before LVC … 3.40v, 3.42v, 2.61v. So, at LVC of 9 volts cell #3 probably went as low as 2.20v (3.38v, 3.40v, 2.22v = 9.00v). Even after 3 hours the resting bounce back recovery voltages were … 3.55v, 3.57v, 3.08v

I then decided it was time to remove that tiny little circuit board between cells #2&3 in all three of my PKZ 2200s(see photo below). One function being when charging strictly via the 4-pin balancing connector when using the PKZ 2-3 Cell Balancing Charger that comes with the RTF Stryker 27C. NOTE: Only perform this operation if you have previous soldering experience like an electrical microscope assembler at Medtronic. Even then don’t dismantle a 3S LiPo pack unless you have a suitable work bench, mounted panavise, patience, no distractions; while, proceeding with TLC. (1) Clip and remove smallest red wire that goes to red discharge solder point; (2) Clip red wire from cell #2, and black wire from cell #3 at circuit board solder point; (3) carefully remove circuit board or leave in place; (4) solder together free ends of red wire from cell #2 to black wire from cell #3; (4) surround solder joint with non-conductive adhesive/glue; (5) Carefully replace protective wrap over area and wrap with electricians tape (see photos below). In the photo below I soldered on the red and black wires so one can see where they originally were located before clipping off at solder point and rewiring. NOTE: I was not able to balance charge cell #3 to 4.2v resting volts (only cells 1&2) via 4-pin LiPo connector and custom patch cord before making this change. As the tiny circuit was apparently defective and would not allow me to individually balance charge cell #3 to same voltage as #1 and #2 cells.

Upon completion (using my Vision Peak Ultra Charger) I first recharged cell #3 to 3.56v via the 4-pin LiPo connector using my custom patch cord so as to match the resting voltages of the other two cells. Then, charged all 3 cells together via larger discharge connector to 12.55 volts. Then topped off each cell, plus giving each cell a little extra juice; especially #3 just in case it was weakened from previous LVC of 2.22v. The resting(5 minutes after charging) voltages of each cell after topping off with a little extra juice were … 4.23v, 4.22v, 4.27v. Then as before bench discharging to 9v LVC of programmed ESC. Individual cell voltages taken with E-flite Cell Checker a few seconds before LVC were now … 3.22v, 3.15v, 3.42v. The used mAh capacity at LVC was 2177mAh or 98.95 percent of 2200 rated capacity. Thus, thanks to you what I thought was an inferior LiPo was rejuvenated. After resting for 1 hour the bounce back recovery voltages of each cell were … 3.42v, 3.30v, 3.53v. So, what I thought was a weak cell was afterall, AOK! So, it appears I wouldn't have had to give cell #3 any extra juice, but always balance charge each cell to 4.2 resting volts ... as YOU accurately stated.



ElectriFly 910 Results: Charged to 4.21-4.22v in order to secure a resting voltage 5 minutes later of 4.2v per cell … the 910mAh ElectriFly had used up 986mAh or 7.7% more than its rated capacity of 910mAh. The resting voltages after 1 hour were 3.51v, 3.47v, 3.52v.

CSCR 2000 Results: This slightly swelled CSRC 2000mAh used 1826mAh or 91.3% of its rated capacity at estimated LVC of 9.55v. Just before LVC approximated to be about 9.5-9.6v the Cell Checker voltages were … 3.21v, 3.06v, 3.37v. The bounce back recovery resting voltages after 15 minutes were … 3.55v, 3.50v, 3.57v … after 2 hours the recovery resting voltages were … 3.63v, 3.62v, 3.63v … not too shabby for a slightly swelled 4-year old CSRC LiPo.
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