lipo balancing

[Former Member]

[This posting has been removed]

[David Ashby - Moderator]

What are we going to do with you Erfolg

[Former Member]

[This posting has been removed]

[Tim Mackey]

[Mike Johnson]

Matt Hackers wrote (see)

I have a CELLPRO charger that automatically balances and charges up to 4 cells and in some cases it can restore over discharged cells.

I think the Cellpro is a charger ballancer in other words it charges through the main negative and positive lead of the battery and ballances indipendantly, although microprocessor controled this is not true ballance charging.

 As explained earlier a true ballance charger charges through the ballance leads without the main negative and positive leads connected too the charger, they are in effect seperate chargers for each cell, microprocesser controled to ensure each cell is ballanced as it is charged though its own lead, I hope that is clear.

 Mike

[Matt Hackers]

Mike

The CELLPRO charger does charge through the balance leads, in fact it is the only way you can connect a battery to it.

Matt

[Matt Hackers]

Mike

Check out the charger by going to  www.aurorra.co.uk

Matt

[Mike Johnson]

The Cellpro charger on the above link has positive and negative connectors on the front case, why does it need these if it charges through the ballance leads?  Please do not think I am trying to be awkward I just want to know how many true ballance chargers are out there.

 Mike

 EDIT:  Sorry you have the 4S which does look like a true ballancing charger, so we now have the Tenergy, Cellpro and Orca, it seems more and more are becoming available, its a shame that they are all only capable of charging four cells.

[Matt Hackers]

Yes , it is a shame but at the present time my maximum cell count needed is only three cells so I don't have a problem at the moment but in the future, maybe???

Matt

[Matt Hackers]

Mike

That 10S charger at AURORRA will charge either a pack of 10 cells or two packs of 5 cells. I think you will find the connections for the balance leads on the charger are in the righthand end white coloured the same as on the 4S. I don't Know what the connections on the front face of the charger are for.

Matt

[Mike Johnson]

Matt

 It looks like they are for charging through the main leads and the ballancer is just a microprocessor to ballance whilst charging, its the same with all of the chargers over four cells at the moment, my Bantam 902 will charge 12S in any combination of packs and it links to the PC, you can check individual cell voltage either on the charger by scrolling through or on the PC screen, its as good as any of the others out there at the moment maybe a little bit better as it also charges A123's which I use as Rx packs in my bigger planes.

 Will keep looking for a ballancing charger rather than a charger ballancer, strange how the description gets confused by lots of manufacturers.

 Mike

[Ultymate]

At the end of the day I can';t see that it matters so long as they are both charged and balanced and personally i don't see it as of major importance that the cells are balanced every single charge

[Erfolg]

Before buying my present balancing charger (IMax 6) iused a lipo charger with an inline balancer (Overlander).

The inline charger definitetly charged via the balance lead, as there was no other way.

I did not see this as very satisfactory, certainly not the answer to a maidens prayer, for the following reasons.

• On large capacity batteries +2000mah batteries took to long. Three or four hours, not spectacular on small capacities 500mah either.
• The final balance between cells was not as good than the IMax 6.
• Balance method often did not reach 4.2 v per cell.

I am quite happy with these balance chargers that use the power leads in addition to balance lead.

I balance every time because it is almost as quick at 1C to balance as not balancing.

Regards

Erfolg

[Mike Johnson]

Ultymate

Once you get above 5S the inballance of the cells after discharge needs to be addressed, even though the cells are all of the same C rating they can have slightly different discharge charicteristics, IMO on my 10S packs it is essential to ballance on each charge, if only for piece of mind because of the cost of replacement.

Erfolg

As you say most modern LiPo's will take a 1C charge rate, therefore it should only take a maximum of an hour to charge any pack with that capability, if the charge is going through the ballance leads the ballance is done automatically and therefore will not take as long as a charger that does it as an afterthought, that's why it took three to four hours to chage your 2000mah batteries. Most packs should not be discharged to thier fully flat state and so they will charge quicker than an hour at 1C, personally I only charge at 1C in the field, back in the hanger I charge at 0.5C, treating them with respect I still have a pair of 5000mah 3S2P from FlightPower that is gigantic, heavy and has a carbon cover, but still serviciable after 4.5years and 250 cycles, can't say the same for the cheaper branded ones though.

Mike

[Mike Johnson]

Perhaps a further explanation is in order:

 On a charger that chages through the main leads and has a ballancer either attached or internal, the over charge that causes the inballance is already in the pack, the ballancer acts as a voltage dump to take excess voltage out of the overcharged cell to equalise with the other cells being charged, this is normally disipated as heat, in most cases the over charged cells are not receiving any charge during this process, hence a longer charge period waiting for the dump to finnish before re commencing charging.

On a charger which charges each cell individually through the ballance lead only, each cell is monitored through an individual microprocessor for its voltage and if one or even two cells get in front of another cell in voltage terms those cells get a reduced charge rate untill the under voltage cell catches up, quicker and more efficient.

 Mike

[Erfolg]

I sence the thread is in danger of totally loosing any direction or cohesion.

My main concern is what works effectively in practice.

If charging at 1C or 1/2C has any practical advantages it certainly can be achieved using a balance charger with additional balance lead. It is not necessary to charge only by the balance lead to do this.

My original set up charged by the balance lead only, and I saw no advatages from the set up. Given the limit of current that it is practical to pass via the balance lead, I found that my charger balancer would sit there all afternoon  charging. Some would say fine, no problem. In my opinion if you have 3 or 4 battery packs it can be seen to be impractical, if eqaully effective, yet faster methods are available.

Does limiting the rate of charge have any significant effect on life of the battery? I do not know. Although reading various publications, the rate of discharge is known (and many modellers can testify to the fact) to have a significant effect.

Less if any thing has been written about charging at less than 1C.

For myself, a balance lead and power lead charger are a practical solution. With no documented negative attributes. Where as the in-line balance lead charger, was the first solution, to the charging the lipo in balance problem, the power lead with balancer lead seems to be the latest solution. The effective balance seems to be a function of the particular balance charger rather than the method.

Erfolg

Erfolg

[Tim Mackey]

Mike Johnson wrote (see)

Your right, it was the other chap answered in the same post, and as I am not allowed to go back and edit on this forum I can't hide my mistake.

 Mike

Thats OK, I will go and change it

[Mike Johnson]

How are we loosing direction and cohesion, we are talking about "LIpo Ballancing" which is the theme of the Thread.

 Dumping excess voltage through heat and the ballancer is old technology and not the latest solution, the most effective way to ballance a pack of cells is to charge each cell individually with a cross link microprocessor controlling the power into each cell to ensure they are all charged equally, the only problem with this latest technology is the expence of making a charger capable of doing this with more than four cells.

 If you are happy charging your cells through the power lead and dumping excess voltage through the ballancer then fine, carry on I have been doing it that way with my ten cell packs for a couple of years, because there is no alternative.

The only reason for discussing the latest technology of charging through the ballance leads was to inform others of a more effective way of charging LiPo packs, if the manufacturers finally produce the right charger we will be able to charge each cell at up to 3amps each as the ballance lead is connected to each cell and the cables used are quite capable of taking that sort of load, so a three cell pack could be charged at 9amps if the battery is capable of taking that sort of charge rate, just think what this could mean for a ten cell pack at last we could get a charger that will charge at over 5 or 6 amps, mind you it would have to be a 1500 watt device, I wonder how much that would cost?

 As to charging at a lower rate, talk to Ian at FlightPower due to the demands of the show circuit his ten cell packs are fast charged and only last approx 50 cycles, he recommends always chaging at a lower than optimum rate if possible, of course the disscharge rate has the greatest effect on the life of the battery and should be kept within the C value of the pack if you want it too last.

 Mike

[Mike Downs]

Hi all,

Its balance plug time again! After reading last monthd RCM&e about balance chargers I went and got a Lipro plus 5......guess whar none of my batteries will fit any of the sockets provided! The overtec kokam ,s do not fit it I went on overtec sie and they do not mention in the battery specs the balance charger ,plug type........The charger has XH ports. Any ideas anyone? Cheers JD

[Mike Johnson]

Your best bet is BRC Hobbies, they have all the convertor leads in there range, what you need is a JST XH too your Kokam battery ballance lead, sorry I don't know what type of lead is on the Kokam.  At the moment BRC Hobbies advert is at the top of this page.

 Mike

 EDIT: the Kokam ballance lead is the same as Graupner and Robbe, other than that I can't find the spec, give BRC a ring they will be able to help.

[Erfolg]

Mike

I am quite happy about loosing some of the energy as heat during charging, as it does not effect the max desired voltage required.

As to the concept of efficiency I doubt if the energy saving is significant in  the real world. I guess you are suggesting that the new chargers are charging and monitoring all the cells simultaneously. This will require more processor power compared with the inline balance lead charger that I used. Which may use more power. The single in line cell charger, switching cells, take many hours to charge a 3s battery, I guess that the power consumed by the step down transformer is far greater than the energy wasted in loosing small amounts of energy required to achieve balance with a power and balance lead charger (off my set up).

During my training as a Professional Engineer, we students (undergraduates) undertook some calculations of systems, to provide an understanding of why Perpetual Motion is not possible and the efficiencies of systems needs careful analysis. I became aware (as intended) that many energy savings are never  realised in the real world, often because the whole system has not been analysed, or real world conditions have not been assessed as they occur (not as the promoter presents them). This is happening today with many of the Governments initiatives (Condensing Boilers, light bulbs, housing insulation).

So I say again, if a product works as intended in the real world, any conceptual improvement, needs to provide a real benefit. Much is sold on momentum these days, I believe in cell balancing, I can be convinced on lower than 1C charging rates (but at the cost of more energy, for the transformer), I may yet be convinced on simultaneous battery cell charging (but without irrefutable significant figures of total energy saving) it will not be on the grounds of saving energy. I also believe that high discharge rates reduce the life of the Lipo.   

So I will not be dumpimg my IMax6, to go back to a multiple version of my Overlander balance lead charger.

As to loosing the subject of the thread, it is "should I balance Lipos" not t"he best charger". Or so I thought.

Erfolg

[Mike Johnson]

With due respect, it seems that there is no way of convincing you that dumping excess current as heat is inefficient?

 During my formative years I was always told to keep an open mind to new and exciting posibilities and not be blinkered by old trusted technology, but to embrase change and evolution.

 As to loosing the subject of the thread, discussing the different ballancing methods that chargers have is right on the money of the subject of this thread, so I don't understand your comments on loosing the subject matter.

 Mike

[Erfolg]

Does your transformer not emitt heat?

Is heat not a by product of the inefficiency of the voltage reduction process.

Does the heat emitted from your microprocessor not indicate inefficiency of the device.

With out quanifying how much energy is being wasted at each stage and for how long, I remain open minded.  But I will not be hood winked into considering one aspect of a system and believing there has been a substantional improvement.

There has been dialog within the magazine of my institution regarding aspects of energy saving, one concerned the energy saved by converting to Flouresent lighting from Tungsten filaments. Some found it hard to believe that for "on-off" lighting situations, Tunsten lights had a lot going for them, in energy terms, compared to Flourescent Lights, particularly when immediate lumin values are concerned. There have been many other discussions on similar lines, all very illuminating.

As I keep saying how much energy is used to charge a particular value Lipo, by the various means. That will easily tell you how efficient each method is. As we all know the transformer and processor IC in our computers, give of substantal amounts of heat energy in doing there work. If any system takes longer or requires substantial processor power, to achieve its goal, It probably is using more power than that shed in balancing cells.

Charging at low rates will almost certainly use considerably more power than charging at a faster rate. This is almost certainly more significant than shedding heat from balancing cells. My balancer does not get warm, that is noticably (without measurement with thermometer). Where as the transformer does, requiring a fan to cool it.

The big question is, "does it really matter" or is the saving trival. Perhaps one less coffee or E-Mail is more important from an energy reduction perspective.

Our problem is that many of us just deal in opinion and not measurement. That includes me.Timbo does some excellent real work in quantifying performance of a number of systems/devices. All else is conjecture and guessitmates.

As many of us used to say, "do not take one fact and then stretch it like elastic".  

Erfolg 

[Mike Johnson]

Erfolg wrote (see)

I sence the thread is in danger of totally loosing any direction or cohesion.

Erfolg

I see what you meant now.

Energy reduction was not my point, the relative efficiencies of balancing Li Po's in different ways to achive a ballanced pack was.

Putting to much power into a cell and then taking it back out again can not be as efficient and as kind to the battery as charging to the correct value individually. This is a basic concept that should be easy to grasp and even easier for someone as educated as you tell us you are.

 Mike

[Erfolg]

Mike

To clarify the efficiency of a system it is not unusual to keep things very simple

energy out / energy in = efficiency

This will tell you if you have seen any improvement

By taking the  black box approach it is possible, by sleight of mathematics or units, to fool yourself into believing that you have improved things. The black box or function approach is very useful in analysis. What you have not quantified is at what price is the extra processing coming at.

I do not know, but I suspect that the approach taken is, to

1. Measure voltage across cell.
2. If less than max value required charge cell at predetermined rate for a predetermined time.
3. If equal to required range, do nothing
4. If greater than required value then reduce voltage
5. Set a flag to either true or false (full charged and overcharged or underchargedt)
6. Go to next cell
7. Repeat operations 1 to 5
8. When flags indicate all cells are charged (true) then stop process.

I would not expect the sequence of 4 to be occuring for very much of the charge sequence.

I still suspect that the time taken to effectively charge your battery is more significant than the energy removed from the battery, in determining efficiency. That transformer again.

One question that you raise may be significant. Does it matter that the cells are potentially taken to a point above a set value? I guess that depends on what the setting is. Also it it suggests that the battery may be set to be charged to less than the theoretical maximum. Does this matter?

As I am no expert on the electro chemistry of Lipos, I will leave it to others who are to tell me and others what  the maximum voltage is and how narrow a band  it is. 

I think we only have to look at the various technology lead consumer wars/battles in retailing to see that often, the benefits of one approach relative to another are products of the marketing departments, the differences of the technologies not really mattering to most people. Apple mac/ Windows, Betamax,  the MP3/i player etc. as the list is almost endless.

In short I do not think the differences in charger types is worth dying in a ditch over. I certainly do not think the energy saved is worth worring about. I still need to be convinced that the maximum voltage achieved by either method is worth getting excited about.

Erfolg