Imax B6

[Gary Manuel]

Posted by Biggles' Elder Brother - Moderator on 29/06/2018 23:20:59:

We'll just have to agree to differ then Gary.

BEB

Yes we will

The main thing is that people can use their balance chargers with confidence, knowing that their batteries are being properly balanced - thanks to the clever internal circuitry.

[Biggles' Elder Brother - Moderator]

Oh dear. If you like Gary.
Obviously you have a cupboard entirely stocked with perfectly balanced batteries? No? How's that then?
You seem to think I am contesting that these chargers have circuitry aimed at achieving balance, I'm not. What I'm saying is that in practice, it doesn't work except in cases where the imbalance is tiny. This is what I mean, they do not charge individual cells, they attempt to address the problem indirectly and they fail.
If a charger fails to balance then no matter how much circuitry it has in it in my view it's not a balanced charger.
BEB

[Nigel R]

BEB.

The B6 chargers can balance cells.

You stated very clearly that you believed they don't.

Then you gave the example of an expensive charger beingsomething that is a balance charger. This will balance cells in exactly the same way as a B6.

You also gave the example of the turnigy balance widget. This to will balance cells in the exact same way as a B6.

They all do it by switching in a resistance in parallel with the a high cell.

Is not that complicated. By doing that you can simultaneously discharge one cell whilst charging another.

This is balancing.

If it helps to lend credibility I work with lipos and balancing chargers for a day job.

Regards

[Craig Carr]

I always understood chargers such as the B6 monitor each cell and then used fets/gates per cell to keep switching current on and off individually to each cell to achieve a balance?

I don’t think it’s correct to say they don’t balance charge.

[Alan H]

The Imax B6 and most other balance chargers work by applying a resistive load across any cells which are higher than the lowest one. The effect of this is to reduce the charging current in the high cells by around 200mA. Depending on the degree of out of balance the pack may or may not end up fully balanced by the end of charge. For badly out of balance packs connecting them to a stand alone balancer is good practice. To say balance chargers do not balance the pack is simply incorrect.

[Don Fry]

Thank you all for an informative if tetchy discussion. Now I am a glowhead. I, like most of the world use leccy planes in the smaller sizes.

A restoration I am doing of an exqistite example of a Storch, has just caused me the invest in three 4500 40c 6S batteries, as a glow motor just didn't fit.. The batteries are lovely, expensive, and I want them to stay that way. Now I know the rules as to looking after these things, balance changing, storage chages, cooling.

So to keep them balanced, should I spend a few quid on a balancer as BEB suggests.

[Nigel R]

Don

They will undoubtedly be fine and stay well balanced under normal use with any charger that can balance.

[Former Member]

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[Gary Manuel]

I'm pleased we are all sorted and that engineering / science has prevailed over gut feeling.

Batteries currently on charge (balance charge of course) after a rather windy days flying.

[john stones 1 - Moderator]

No comment.

[Biggles' Elder Brother - Moderator]

Posted by Gary Manuel on 30/06/2018 22:10:58:

I'm pleased we are all sorted and that engineering / science has prevailed over gut feeling.

Batteries currently on charge (balance charge of course) after a rather windy days flying.

Says who?

BEB

[Gary Manuel]

Posted by Biggles' Elder Brother - Moderator on 30/06/2018 22:39:18:

Posted by Gary Manuel on 30/06/2018 22:10:58:

I'm pleased we are all sorted and that engineering / science has prevailed over gut feeling.

Batteries currently on charge (balance charge of course) after a rather windy days flying.

Says who?

BEB

Sorry BEB.

I should have said that we are NEARLY all sorted.

If you take the trouble to study the schematic diagrams in conjunction with the video links I posted, you may see the light. Let's put the "E" back in "RCM&E".

[Biggles' Elder Brother - Moderator]

OK, if we can have a sensible debate - without trival jibes, I'll continue and try to explain my view - which is different from yours.

Don't knock gut feeling Gary, reality counts for a lot more than theory.

I had a lot of PhD students that thought like you, here is a theory, it "works" like this. So I say, "Does it work?" Oh yes, they say, it must do, the theory says so. Well, let's do an experiment then - let's prove it works. Suddenly everyone isn't quite so confident. Then the experiment doesn't give a clear endorsement to the theory, instead it raises questions. And that's how we learn!

Now don't get me wrong, I like theories and mathematics and models and simulations as much next next man - probably more than most. And I spent a good deal of my working life dealing with them. But I never lost sight of the fact that the only truth is reality - everything else is less than that.

So, today I didn't go flying - been flying 4 times this week already and due to go tomorrow too! - insead I pottered about in the shed and I thought while I was there I'd do a little experiment. I took some batteries - a small sample admittedly but I just wanted to try something. Some of the batteries are pretty well balanced - one was not. Let's see what the "balance" charger makes of them shall we?

All the batteries were charged on the balanced setting, at 1C and with a 4 hour "time out" cut off, ie if it isn't balanced after 4 hours stop anyway. Let's have a look at the results:

BAT 1: 4s 4000mAh,

Pre Charging 34%, 15.20V. Cell 1: 3.800, Cell 2: 3.802, Cell 3: 3.801, Cell4: 3.806. Imbalance: 0.008V

Post Charging 99%, 16.79. Cell 1: 4.189, Cell 3: 4.199, Cell 3: 4.197, Cell 4: 4.211. Imbalance 0.022V

Charging Timed Out after 4 hours.

Comments: A well balanced battery returned slightly less well balanced than we provided it! Still it's acceptable as an outcome.

 

BAT 2: 6s 3000mAh,

Pre Charging 36% 22.85V Cell 1: 3.805, Cell 2: 3.811, Cell 3: 3.806, Cell 4: 3.812, Cell 5: 3.813, Cell 6: 3.807

Imbalance 0.008V

Post Charging 99% 25.23 Cell1: 4.203, Cell 2: 4.199, Cell 3: 4.201, Cell 4: 4.210, Cell 5: 4.198, Cell 6: 4.219

Imbalance 0.012V

Charging terminated by the charger.

Comments: A simailar result to battery 1, a well balanced battery is resturned charged and basically still balanced.

 

Now, let's give this charger a bit of a test!

BAT 3: 6s 5000mAh

Pre Charging 72%, 23.84. Cell 1: 3.795, Cell 2: 3.947, Cell 3: 4.204, Cell 4: 4.165, Cell 5: 4.026, Cell 6: 3.708

Imbalance 0.495V

Post Charging 76%, 23.99 Cell 1: 3.805, Cell 2: 3.962, Cell 3: 4.227, Cell 4: 4.185, Cell 5: 4.059, Cell 6: 3.761

Imbalance 0.466V

Comments: An out of balance battery is returned to us after 4 hours of balanced charging,...an out of balance battery. Any improvement is absolutely marginal.

This is not in my view a defective battery, the voltages of the low cells are low yes, but they are at fail level. But the "balance" charger, for all the theory and the Darlington Pairs and microprocessors fails to make any meaning impact. Balanced charger? I think not in reality.

BEB

Edited By Biggles' Elder Brother - Moderator on 30/06/2018 23:23:43

[Former Member]

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[Gary Manuel]

BEB

On my way to bed, so feeling a bit tired, but I'll have a go at addressing the results of your tests.

Battery 3 has obviously been subjected to some form of abuse for it to be so far out of balance to start with. I suspect that it has either not been balance charged regularly, or has been loaded via the balance leads in order to set up your test conditions. It may actually have faulty cells, but I'll assume not.

Cell 3 is the highest voltage cell and cell 6 is the lowest, both before and after your 4 hour balance charge. The difference between these two cells has reduced from 0.496V to 0.466V during the process. You have therefore improved the balance of the cells - but not by much.

Here is the reason why:

• A fully charged LiPo cell has a voltage of 4.2V - which is roughly what your cell 3 measured to start with.
• Cell 6 measured 3.708V, which equates to less than 15% charge.
• Cell 6 therefore needs 85% of 5000mAh = 4250mAh to catch up with cell 3.
• As the charger works by discharging the HIGH voltage cell, to bring them down to the LOW cell voltage, it needs to reduce cell 3 down to the same capacity as cell 6. It therefore needs to reduce cell 3 charge by 4250mAh.
• The balance rate of B6 chargers is 210mA according to the schematic diagrams (or greater than 100mA according to specs?).
• At 210mA, it will take 4250/210 = 20.2 hours for the cells to balance - assuming that the charger spend 100% of it's time loading cell 3. It then needs to charge the cells back up to 4.2V which will be additional to the 20.2 hours and will be at a lower rate due to the charger reducing the charge rates as the cells near completion. It could potentially take up to (say) 30 or 40 hours total.
• The charger cuts out after 4 hours, so it cannot cope with balancing batteries with this range of imbalance in one pass.
• It should improve with each pass.

Regular use of a balance charger keeps the cells balanced and would have avoided having batteries with the high imbalance that your Battery 3 has in the first place.

Apologies for any typos or mistakes in this post. I'll have another look in the morning and correct any errors.

Edit - One important factor I forgot to mention.

Cell 6 started at 3.708V and finished at 3.761V. These figures equate to approximately 15% and 30% charge respectively. Cell 6's charge has increased by 15% of 5000mAh = 750mAh. Over 4 hours, the absolute maximum balance rate would be 4 x 210 = 840mAh. The charger is actually pretty good at balancing, bearing in mind it's design limitations.

Edited By Gary Manuel on 01/07/2018 01:52:17

[Gary Manuel]

I've re-read last nights post and am satisfied with it.

Using the wording from your 3rd paragraph above BEB, it would appear that your experimental data is in fact, giving a clear endorsement of my theory without raising further questions. In effect it has proven that "it works" - and that's how we learn!

For completeness, here's the data I used for converting cell voltage to percentage charge:

Edited By Gary Manuel on 01/07/2018 09:49:00

[iqon]

Of course it`s a balance charger, it has balance leads, Just remember to select balance charge. But does it say it`s a battery balancer nothings perfect. Well not in the B6 price bracket

[Bob Cotsford]

And please remember that in the real world everything has a manufacturing/calibration tolerance. Some manufacturers tolerances are, shall we say, more liberal than others? Personally I've found American brands to have some quite amusing interpretations of quality and accuracy.

[Alan H]

I'm with Gary's analysis 100%. The higher the capacity of a LiPo the longer it will take the charger to get a pack back in balance and periodic re-balancing on a stand alone balancer is good practice. One other thought, with the Imax B6 type chargers the default mode when selecting LiPo is not balance mode. If I remember correctly you have to press the + key once to get to the balance charge mode so it is just possible the original poster was not actually in balance mode.

[Geoff S]

Just a few minutes ago my Graupner 16 charger signalled a high balance voltage and it turned out to be that one of the balance wires had broken. I repaired it and put the battery back on charge with my iCharger 308 duo. It was very nearly fully charged and rather than charging at 4 amps (it's a 4S 4AH LiPo) it was showing a discharge of 100mA as it did a final balance to within 10mv for each cell.

I'm quite convinced my iCharger does a balance by limiting the charge of high cells as it charges those which are slightly down on voltage. Incidentally, it also shows esr values and packs at the end of their life definitely shows cells with over 10 milliohms IR whereas others are still just about acceptable at 7 or 8 milliohms IR.

Balance chargers (at least the 2 I use regularly) do actively balance packs, probably using the methods suggested by Gary and Pat et al. Theoretically it's not all that difficult to do although in practice it does need some reasonably clever electronics which are probably more sophisticated in more expensive chargers like my iCharger 308 duo.

Geoff

[Former Member]

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[Former Member]

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[Gary Manuel]

Posted by supertigrefan on 01/07/2018 15:26:20:

What would you recommend for a IC flyer using non Lithium Ion who may need a capability for flight box in the future?

Edited By supertigrefan on 01/07/2018 15:28:23

THIS would take some beating for the price. It's the upgraded version, rated at 80W (10A), rather than the usual 50W (6A). Note that it runs from a 12v supply, so if you want to use it at home, you would need a power supply.

They are all pretty generic, so you are likely to get different recommendations - just go for the one you like the look of. There are also mains voltage supplied chargers.

As / if you want a more advanced charger later, there are quad channel ones available or higher power ones which allow for parallel charging at decent charge rates.

Edited By Gary Manuel on 01/07/2018 15:51:16

[Nigel R]

Gary excellent analysis on BEBs results. They do rather succinctly show the B6 to be doing a sterling job within the scope of its design limits.

Super tiger fan. Garys link looks good. Almost every B6 type charger would do the job foryou. I would myself go for one with a built in mains supply to improve the utility value of the charger. Note that the 80w is calculated internally to the charger so you can find that e g a 4 cell lipo the current maxes out at 6a. Full 10a is only available on a 2 cell battery. All of them will do gel cell 12v batteries and also 4 or 5 cell aa receiver packs.

Edited By Nigel R on 01/07/2018 16:11:12

[Former Member]

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