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Old Jan 02, 2007, 02:47 PM
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Hoppy; I've been through this particular drill (disch..unbalanced...slow chg...balanced...normal charge) many times, watched the voltages during charge and I have yet to see a cell go over 4.2V. Not to say that it can't or won't happen. I just haven't seen it happen. One of my packs has had a harder life than the others and I'll be watching its terminal voltages pretty closely, especially since this dicussion...that's assuming that the snow finally clears off and I get a chance to fly again!

Hal...you ought to remind us once in a while...what the heck is a voltage clamp? You let us in on that once, but as I recall, it's not the sort of thing that just jumps off the shelf.
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Old Jan 02, 2007, 03:10 PM
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it's my best kept SECRET about charging LIPOs, too bad U guys will never find one or even know how to use one to stabilize the voltage at higher energy level outputs even lower IMPEDANCE levels than normal
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Old Jan 02, 2007, 03:24 PM
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Quote:
Originally Posted by roidspop
Hal...you ought to remind us once in a while...what the heck is a voltage clamp? You let us in on that once, but as I recall, it's not the sort of thing that just jumps off the shelf.
You mean to tell me that you did not bookmark Hal's famous series of 'LIPO Tricks'?

Or, you could use a pair of vise-grips and adjust the screw thingy so that the pack is clamped, thus preventing the voltage from puffng the pack.

Bill
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Old Jan 02, 2007, 04:05 PM
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U guys need to think low Z ( impedance ) and how to condition the cells for that and not be overly concerned about hi-C discharges
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Old Jan 02, 2007, 08:14 PM
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[QUOTE=roidspop]Hoppy; I've been through this particular drill (disch..unbalanced...slow chg...balanced...normal charge) many times, watched the voltages during charge and I have yet to see a cell go over 4.2V.

QUOTE]

Let me see if I understand you - Assume that we are starting with a pack that is unbalanced at discharge but balanced when charged with no operator or charger intervention. Are you saying you have balanced a pack like that ,with say a blinky, when it was in the unbalanced discharged state, then charged it, and at the end saw that it was still balanced?

I think you are saying that an unbalanced pack will balance itself during charging if it was balanced to start out with. On that I agree.
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Old Jan 02, 2007, 11:28 PM
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These compound/complex sentences make my brain hurt.

Yes. That's what I've seen.

No...I didn't generally balance with my TP205 BEFORE charging...I used it while charging.

For some time now, I've been charging without using a balancer at all; simply monitoring the voltage state (and IR) of the cells and doing what seemed necessary. If a discharged pack was balanced when I checked it, I charged at 1C. If it was out of balance by 0.03 or so, I'd slow charge for about fifteen minutes, or until cell voltages hit about 3.7, and if they were within 0.01 V, I'd run the rate up to 1C and finish the charge. In every case, the packs have reached full charge in an apparently balanced state..."apparently" because the only thing I know to do to measure pack balance is to use a DVM and check cell voltages. Other posters have different ideas, but I can't see what it is that we're supposed to measure to tell us if this state they're talking about has been reached or not.

I admit this is just experimentation on my part, and I may very well wreck a cell or two doing it. It is odd to keep hearing people declare that I'm not seeing what I'm seeing or that I'm wrong about this "balance" thing. Well, so far it's working and it doesn't seem to care what anybody thinks about it. Anyway, it's created a sort of minor cottage industry... should advertise them as "Nature's-Way Organically Balanced lipo packs".
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Old Jan 03, 2007, 10:02 AM
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Ok, I see what you are saying and I don't disagree with your observations or conclusions.

The question in my mind concerns what would happen if the pack that was unbalanced discharged/balanced charged was balanced with a non-charging balancer before charging. Would the low voltage cell(s) (prior to balancing) end up being high V cells at the end if a non-balancing charger was used.
I'll run the test and report back.
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Old Jan 03, 2007, 11:32 AM
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ANY overcharge, of any cell, will not give maximum life of the pack.

Any undercharge, of any cell, WILL give maximum life of the pack.

That covers all the charging conditions. Period.
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Old Jan 03, 2007, 11:38 AM
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To fully charge a 10 cell pack requires 10 isolated peak chargers, or a stepping from one cell to the next and being able to only finish charging the undercharged ones until all are charged.

Period.
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Old Jan 03, 2007, 11:40 AM
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2 posts were needed to seperate the 2 DIFFERENT end resuts.

Enjoy.
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Old Jan 03, 2007, 12:31 PM
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Hoppy; experimentation is the way to go. I'm going to predict that the outcome will be a balanced pack with all cells within a hundredth of a volt or so of each other.
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Old Jan 03, 2007, 01:07 PM
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Quote:
Originally Posted by hoppy
Ok, I see what you are saying and I don't disagree with your observations or conclusions.

The question in my mind concerns what would happen if the pack that was unbalanced discharged/balanced charged was balanced with a non-charging balancer before charging. Would the low voltage cell(s) (prior to balancing) end up being high V cells at the end if a non-balancing charger was used.
I'll run the test and report back.
Yes, they will regardless of the rate.
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Old Jan 03, 2007, 01:17 PM
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Look at the graph of Lipo voltage in various state of charge, and estimate how many mAh makes the difference of certain voltage and vice versa. You can expect high voltage difference for equal mAh at both ends of graph, but very low in the middle.
(e.g. 50mAh charged in will result in neglible REST voltage increase around the half of the charge,
but it results in much higher voltage increase for empty cell as well as for allready full one.
Experiments should be used to support theory, or they should be at least explained after observations - everything has its reason and this is not so complex..
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Old Jan 03, 2007, 02:36 PM
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Just to be perfectly clear about the question-
Pack is unbalanced when discharged, but balances when fully charged.

Hypothetically, assume the pack in discharged condition has voltages of-
3.7, 3.7, 3.6V
Balancing this pack with a blinky brings the voltages to:
3.6, 3.6, 3.6V
Now you guys are saying if this pack is charged the voltages will be:
4.2, 4.2, 4.2

My feeling is that they will be:
4.15, 4.15, 4.3

The next time I discharge/charge batteries I'll check it out.
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Old Jan 03, 2007, 02:45 PM
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Experiments and observations are what theory arises from, and they are used to to put theory to the test, even to pull it down, but not to support it. If support comes from experimentation, that's great, but if the intent of the experiment was to uphold a theory, then it's very likely that that's exactly what it will do, even if the experimenter has to "adjust" the results to fit.
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