PDA

View Full Version : Cell Balancers?


Bob_CO
12-12-2005, 03:32 AM
This one has me puzzled. Maybe someone here can help me understand this. It seems to me that for a single pack all of the new access paths to the single cells doesn't really do anything.

Yes you can charge each cell individually and yes you can see if a single cell is bad but what benefit does that give over a pack with the series wires.

My thinking is that by charging all 2 or 3 cells at the same time will result in the pack being nearly as fully charged as if they were done seperately. The cells will equalize themselves by just sitting there too right?

everydayflyer
12-12-2005, 04:41 AM
Series charging a LiPoly does nothing to balance it other than most cells are more closely balanced when charged as opposed to when discharged.
THe useful voltage range of a LiPoly cell is between 3.7 and 4.2 volts. If a single cell is 0.1 volts out of balance as in a 3S pack then it can have 20% less capacity. If a cell is charged above 4.2 it is damaged. A 3S is charged to 12.6 which should be 4.2 per cell. If one cell charges to 4.0 then the other two could be charged to 4.3 each and be damaged. If two cells are charged to 4.1 then the third cell could be charged to 4.4 volts which is a very dangerious and harmful point. Balancers increase the life,safety and useful capacity of LiPolys.



Charles

Bob_CO
12-12-2005, 06:11 AM
Great and thanks. So there is a need to do it for more that just a tad more performance.

I guess the next question is if there are cells that are out of balance for some reason can the situation be corrected? If so, how long does the fix last?

I currently have all Apogee packs so I don't have anything to compare them to. Are the plugs the same for say Polyquest, TP Apogee?

everydayflyer
12-12-2005, 03:47 PM
Some will stay balanced loger than others, some will stay balanced longer after being rebalanced than others. You must check them to determine each packs pattern. I find it easier to balance than to check each cell. A good balancer does the checking and balancing if necessary.

Hyperion & PolyQuest use the same .025 Sq. pins and .100 spacing and also the same balancer connections and wiring. Apogee use the same size and spacing but does not skip connections same for VAMPower packs.. AF Blinky (balancer) uses same size pins and spacing and does not skip connections. Thunder Power uses connectors different from all others.
AF has a Blinky to TP adaptor available part # 549. The Blinky will work with Apogee and VAMPower LiPolys without modifications. It will work with TP PL with adaptor and with PQ and Hyperion if you move the packs taps connections.Tanic sells Tanic taps to TP adaptors.


Charles

Matt Kirsch
12-12-2005, 04:13 PM
The reason NiCd and NiMH packs "self-balance" to a certain degree is because they have rather high rates of self-discharge. All the cells are seeking a particular level, so to speak. Fresh off the charger a NiCd or NiMH's voltage will read signifigantly higher than after it's been sitting for a few minutes. A LiPoly stays at whatever voltage it was charged to, in contrast.

jmtdmt
12-20-2005, 03:15 AM
I have several 2s and 3s packs that range from 1320 to 2220 MAHs. Since I live less than five minutes from my flying field I bring the batteries home to charge them. I do not have a balancer but when I charge any of my batteries I never charge above .2A (200 MAH's). Would this be considered a low enough charge to balance the cells in the pack without a balancer connected ? I use either a Trition or a Minron Mobile to charge my batteries where I manually set the charging current.

Matt Kirsch
12-20-2005, 01:51 PM
Charging at a lower rate will not balance LiPolys. Only charging each cell individually, either by a manual process or with one of the available cell balancing systems on the market will bring the cells to the same voltage.

In fact, there is little to no advantage to charging the cells at any less than a 1C rate. That's one times the pack's capacity in mAh. Some chargers, like the Astro 109, actually depend on you setting it for a 1C charge rate to properly detect the number of cells in the pack.

Rugar
12-20-2005, 03:54 PM
Some chargers, like the Astro 109, actually depend on you setting it for a 1C charge rate to properly detect the number of cells in the pack.

Matt,
Unless I'm misunderstanding you here, I have to disagree.
On the Astro 109 your supposed to set the charge rate to "0" before plugging in the pack. The charger will then detect the number of cells in the pack. You need to verify the number of cells it detects Before setting the charge rate. You then start slowly increasing the amps to a 1C charge rate, or less. I always charge my packs at approx .75C when I'm at home in no hurry, and at 1C or slightly below when at the field depending on how fast I need a pack charged to fly.

flyranger
12-21-2005, 01:45 PM
I'm using the ThunderPower charger and cell balancer. The balancer will discharge the cells that are slightly higher in order to keep all cells to the same voltage. Works ok, but only with TP lipos or lipos with a compatable balance connector.

everydayflyer
12-21-2005, 03:42 PM
I'm using the ThunderPower charger and cell balancer. The balancer will discharge the cells that are slightly higher in order to keep all cells to the same voltage. Works ok, but only with TP lipos or lipos with a compatable balance connector.

Sadly that holds true for most balancers. There is no real standard for LiPoly taps/connectors. Apogee,Thunder Power,VamPower,2DogRC ,Tanic and several others,use different connectors as do many others. Poly Quest,Hyperion and E Tec use the same style connector and I believe Kokam does also. I know that PQ and Hyperion both use the same connection configurations. These configurations require a different adapter for 2S,3S and 4S packs as they skip connections which are not needed instead of using them in a sequential order. PQ and Hyperion also also uses a different connector for their 5S pack( 6 contacts instead of 5).

I have compiled a listing, drawing and photos here.

http://www.rcgroups.com/forums/showpost.php?p=3320890&postcount=29

Charles

Matt Kirsch
12-21-2005, 06:03 PM
It'll be quite some time before a standard is developed. Balancing chargers and taps are a relatively new thing to the market, and each manufacturer is putting out what it believes to be "the best" system, in the hopes that the buyers will choose their design. As other manufacturers notice that they're losing market share to this popular design, they'll come on board and adopt that as their standard.

For now, you're left choosing your own standard. Pick one and stick with it. Pay more attention to the quality and performance of the cells than the balancing system, because the balancing system can be adapted from other brands if necessary.

cyclops2
12-22-2005, 06:33 PM
Everyday and Matt . I want to thank you both for giving such accurate information about cell voltage range AND over range.
I really cannot justify $250 for a + or - 6000 mah LIPO for the model sizes and power I need.
Especially when I would be required to set up a charge and discharge system that is almost as good as NASA.
This electric flight is far from the reliability of gas or nitro power.
-
Thank you very much, Richard Petersen.

everydayflyer
12-22-2005, 08:45 PM
Everyday and Matt . I want to thank you both for giving such accurate information about cell voltage range AND over range.
I really cannot justify $250 for a + or - 6000 mah LIPO for the model sizes and power I need.
Especially when I would be required to set up a charge and discharge system that is almost as good as NASA.
This electric flight is far from the reliability of gas or nitro power.
-
Thank you very much, Richard Petersen.

Glad the info helped but I must diagree. I have flow R/C since 1963. No telling how amny thousands of flight with glow. I us to purchased 2 55 gallon drums of fue a year and used most of it myself.

Twenty years ago when I was learning to fly helis I purchased 3 cases. 12 gallons at a time and average burning better than 10 gallons a month.

I know a thing or two about Glow Engines but all of my electric are much more reliable. The only part of the electric systems that has any wear to speak of is the batteries.
I have Brushless motors withover 200 hours run time on them and they are still going strong. A glow would have had to been rebuilt sever times long before 200 hours.

Charles

cyclops2
12-22-2005, 09:31 PM
I come up with $250 battery, $250 motor, $ 200 speed control, $ 150 for a [email protected] about $ 800 . Plus I now build and fly 2 to 4 engined planes.
At those prices, it is not fun, for a toy airplane.