SkyRC imax B6AC v2 and a Battery Question

[Spork]

Moz, get off my lawn you little whippersnapper.

 

[Gyro Doctor]

Moz, my hobby experience goes back even further, I was referring to my professional experience

I think you're misunderstanding the use of the word "balance" when it comes to the charger. It refers to the final charge on all cells. In a 2s battery, the two cells are "balanced" so as to have an identical charge on each one.

I know full well what the term "balance" means, thank you very much !

Naturally some cells will draw more current, especially if they are starting at a slightly lower charge. That's why you need to start them all out within about .2v of each other, so you don't have the higher-charged cells start dumping current into the lower-charged ones at a high rate.

That is EXACTLY what I mentioned in the third paragraph from the end of that dissertation.

If your final charge on a 2s battery is 8.2V, the charger balances the cells so that each one is exactly 4.1V, not one at 4.0 and the other at 4.2, or something like that.

That is correct.

Same for the second cells in parallel. So all cells in all batteries end up exactly 4.1V. Balanced.

WRONG !!! ... The bulk charging plate only shows the balance charger the first CELL of each PACK (according to the sales rep, and even if that's not the case more on that later) and therefore the charger treats the (e.g.) three four-cell packs as if it were a single three-cell pack ... The charger really has no idea whatsoever what the voltage is on any other cells unless the rep was wrong, to which I wouldn't be surprised, given he should know how that board works but even if this board behaves like any other THAT IS NOT a BALANCED pack.

Repeating myself again, my argument is not that all the batteries aren't getting the same "charge" (more specifically voltage) it's that the cells in those batteries being charged are NOT being actively balanced.... FYI a balance charger monitors EACH CELL in a (single) pack and applies a drain to the higher cells holding them from an overvoltage condition while the weaker cell catches up. THAT yields a balanced PACK because each cell in the pack is at the same voltage. As I said in my conversation with the salesperson on the website, in order to actually balance multiple packs' cells (what you want) you would need the balance leads to be connected to each cell in each pack (not currently possible) and not just to each battery (like his board supposedly does) which only balances the packs on the boards to each other, NOT their cells, which results in (guess what ?) charged packs WITHOUT balanced cells. Even "high end" para-boards (which should have separation fuses in place between each battery) that DO monitor "every cell" in the several packs in parallel use their balance leads to "see" the COMBINATION of all the second cells, third cells, etc. on each of the balance lead's lines ... This relies upon the "self balancing" of each of these cells (by virtue of being in parallel) and therefore is also not ideal either because, once again, you're not monitoring each cell but the summation of the cells that occupy the successive positions of the balance leads.
To use your own words with respect to what balancing actually does:
"If your final charge on a 2s battery is 8.2V, the charger balances the cells so that each one is exactly 4.1V, not one at 4.0 and the other at 4.2, or something like that." ... One balancing line "looking" at two, three, four or more cells cannot possibly balance them !
One line handling one cell can balance that cell with respect to the other cells in that pack, but one line looking at several cells from several packs simply leaves them to their own devices and (according to your very own words on the understanding of what balancing is) does not balance those cells.

Also, remember that the cells are in SERIES (in each pack) so what you actually have is a series parallel circuit ... SOoooo, after you've mastered the understanding of the behaviors of series versus parallel circuitry, you should then study Thevenin's Theorem if you'd like to derive equivalent circuitry and then do some peak current math to determine whether or not I'm just "blowing it out my ass" when I say that it's not a good idea to perform unregulated charging (which basically is exactly what gang charging is).

Can you do it ? Certainly ... Should you do it ? That's up to you, but I certainly don't recommend it ESPECIALLY TO NEWBS (There's just too many precautions needed and understanding required to do it safely) e.g. plugging in the charge leads first so you don't smoke the board or melt the balance leads because there's too dissimilar potentials on the bats ... the need for understanding and performing the calculations to determine safe current levels ... the need to check each cell's voltage on each battery before charging ... understanding and performing calculations to determine power ratings required so you don't smoke your charger or the board, etc ... And when it's all said and done the charge per battery yielded is less accurate given it's bases upon AVERAGES of cell counts spread over the number of bats ganged with the accuracy diminishing with the higher the number of batteries charged simultaneously ... AND, as I've said all along, you only really have control over individual cells for purposes of balancing when you are monitoring and controlling individual cells not the summation of any number of cells strung on whichever line !

I started building power supplies and DC to AC inverters when I was 14 years old. I built my first computer from scratch before they were even commercially available and the
"Windows" operating system had not even been invented yet. I am perfectly capable of both designing and building a battery charger that would actually perform the tasks we
are discussing here should I be so inclined, so you can either choose to believe me when I say these boards DO NOT do what you think (and what "they" would have you think) or not
because it is, repeating myself again, nothing more than utter bullsh*t and marketing hype that is preying upon the ignorance of those who do not know any better.
By the way, I've got some beachfront property for sale in Arizona if you know any one who's interested. .... I shall not beat this dead horse further.

 

[Gene_Drone]

I appreciate all of the insights here and how people can disagree and still be civil.

Can I take one of the connectors that came with the imax and take a connector from an old lost battery and solder it? Thanks

 

[Jeff Neese]

Moz, my hobby experience goes back even further, I was referring to my professional experience


I know full well what the term "balance" means, thank you very much !


That is EXACTLY what I mentioned in the third paragraph from the end of that dissertation.


That is correct.


WRONG !!! ... The bulk charging plate only shows the balance charger the first CELL of each PACK (according to the sales rep, and even if that's not the case more on that later) and therefore the charger treats the (e.g.) three four-cell packs as if it were a single three-cell pack ... The charger really has no idea whatsoever what the voltage is on any other cells unless the rep was wrong, to which I wouldn't be surprised, given he should know how that board works but even if this board behaves like any other THAT IS NOT a BALANCED pack.

Repeating myself again, my argument is not that all the batteries aren't getting the same "charge" (more specifically voltage) it's that the cells in those batteries being charged are NOT being actively balanced.... FYI a balance charger monitors EACH CELL in a (single) pack and applies a drain to the higher cells holding them from an overvoltage condition while the weaker cell catches up. THAT yields a balanced PACK because each cell in the pack is at the same voltage. As I said in my conversation with the salesperson on the website, in order to actually balance multiple packs' cells (what you want) you would need the balance leads to be connected to each cell in each pack (not currently possible) and not just to each battery (like his board supposedly does) which only balances the packs on the boards to each other, NOT their cells, which results in (guess what ?) charged packs WITHOUT balanced cells. Even "high end" para-boards (which should have separation fuses in place between each battery) that DO monitor "every cell" in the several packs in parallel use their balance leads to "see" the COMBINATION of all the second cells, third cells, etc. on each of the balance lead's lines ... This relies upon the "self balancing" of each of these cells (by virtue of being in parallel) and therefore is also not ideal either because, once again, you're not monitoring each cell but the summation of the cells that occupy the successive positions of the balance leads.
To use your own words with respect to what balancing actually does:
"If your final charge on a 2s battery is 8.2V, the charger balances the cells so that each one is exactly 4.1V, not one at 4.0 and the other at 4.2, or something like that." ... One balancing line "looking" at two, three, four or more cells cannot possibly balance them !
One line handling one cell can balance that cell with respect to the other cells in that pack, but one line looking at several cells from several packs simply leaves them to their own devices and (according to your very own words on the understanding of what balancing is) does not balance those cells.

Also, remember that the cells are in SERIES (in each pack) so what you actually have is a series parallel circuit ... SOoooo, after you've mastered the understanding of the behaviors of series versus parallel circuitry, you should then study Thevenin's Theorem if you'd like to derive equivalent circuitry and then do some peak current math to determine whether or not I'm just "blowing it out my ass" when I say that it's not a good idea to perform unregulated charging (which basically is exactly what gang charging is).

Can you do it ? Certainly ... Should you do it ? That's up to you, but I certainly don't recommend it ESPECIALLY TO NEWBS (There's just too many precautions needed and understanding required to do it safely) e.g. plugging in the charge leads first so you don't smoke the board or melt the balance leads because there's too dissimilar potentials on the bats ... the need for understanding and performing the calculations to determine safe current levels ... the need to check each cell's voltage on each battery before charging ... understanding and performing calculations to determine power ratings required so you don't smoke your charger or the board, etc ... And when it's all said and done the charge per battery yielded is less accurate given it's bases upon AVERAGES of cell counts spread over the number of bats ganged with the accuracy diminishing with the higher the number of batteries charged simultaneously ... AND, as I've said all along, you only really have control over individual cells for purposes of balancing when you are monitoring and controlling individual cells not the summation of any number of cells strung on whichever line !

I started building power supplies and DC to AC inverters when I was 14 years old. I built my first computer from scratch before they were even commercially available and the
"Windows" operating system had not even been invented yet. I am perfectly capable of both designing and building a battery charger that would actually perform the tasks we
are discussing here should I be so inclined, so you can either choose to believe me when I say these boards DO NOT do what you think (and what "they" would have you think) or not
because it is, repeating myself again, nothing more than utter bullsh*t and marketing hype that is preying upon the ignorance of those who do not know any better.
By the way, I've got some beachfront property for sale in Arizona if you know any one who's interested. .... I shall not beat this dead horse further.

 

[Jeff Neese]

....

WRONG !!! ... The bulk charging plate only shows the balance charger the first CELL of each PACK (according to the sales rep, and even if that's not the case more on that later) and therefore the charger treats the (e.g.) three four-cell packs as if it were a single three-cell pack ..

The IMAX will show a "Battery Connect" error if you have Balance Charge selected but it only sees the first cells. This doesn't even make sense so I think there was some miscommunication with the rep.

I think you're taking the idea of "Balance charging" in a direction that doesn't really apply here. Most quadcopter owners understand balance charging to mean that all cells across the series are equally charged. If you just apply the 12.6V across the series, there will be variation in charge between them. The balance plug monitors voltage across them and makes sure they are all exactly 4.2V. That's what balanced charge means in the world of quadcopters.

As long as your multiple batteries have a pretty close voltage, the differences in power draw between them are not something significant and there's no reason to actively monitor and control current to each cell. Not in this application.

 

[Gyro Doctor]

... One balance line per cell can regulate that cell's charging to achieve a balanced pack.
One balance line looking at multiple cells has no control over whatever any single cell wants to do.

The balance plug monitors voltage across them and makes sure they are all exactly 4.2V.

Yes in a single pack ! .... But when that balance line is looking at cell number three in four packs how the hell can it possibly control any single one of those cells alone ?!!

If you just apply the 12.6V across the series, there will be variation in charge between them.

THAT IS EXACTLY WHAT IS GOING ON when one balance line monitors more than one cell !! You get variations between the cells !!
Like you said yourself, one could be several tenths of a volt higher or lower than the other, which defies the very definition of balanced.
What part of that you fail to understand is beyond me .... but I'm not going to argue with you just for the sake of arguing.
You just don't get it ... fine ... discussion over.

 

[Jeff Neese]

... One balance line per cell can regulate that cell's charging to achieve a balanced pack.
One balance line looking at multiple cells has no control over whatever any single cell wants to do.

Yes in a single pack ! .... But when that balance line is looking at cell number three in four packs how the hell can it possibly control any single one of those cells alone ?!!

THAT IS EXACTLY WHAT IS GOING ON when one balance line monitors more than one cell !! You get variations between the cells !!
Like you said yourself, one could be several tenths of a volt higher or lower than the other, which defies the very definition of balanced.
What part of that you fail to understand is beyond me .... but I'm not going to argue with you just for the sake of arguing.
You just don't get it ... fine ... discussion over.

You really, really don't know what you're talking about. Multiple cells receiving a parallel charge will always end up with the same voltage. They're in parallel. It's series batteries that have the potential to vary. Are you even thinking about this? You definitely don't seem to understand how a battery charger works.

It seems as though both the product rep tried, and now I have tried also to explain it to you, but you're just not getting it.

 

[Gyro Doctor]

... Troll much ?