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Old Mar 20, 2012, 02:50 PM
Static Model Collector LOL
Katy, TX
Joined Dec 2009
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5S lipo 2 cells lagging ???

Got some new 5S 3000 30C Turnigy packs

1 of them have 2 cells that lags behind while charging
Why?

Using an iCharger 208B. Balance charge mode

Thanks

FCA

Any chargers on the market that has the capability to charge an individual cell?
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Old Mar 20, 2012, 03:38 PM
characters welcome!
Mark Wood's Avatar
United States, CA, Bear Valley Springs
Joined Feb 2000
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Simple. Because that pack has two crap cells.

mw
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Old Mar 20, 2012, 03:42 PM
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So. Cal.
Joined Oct 2004
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Quote:
Originally Posted by FLAME747 View Post
1 of them have 2 cells that lags behind while charging
What do you mean by 'lags behind'? Are all cells at the same voltage upon completion of a balance charge?

Have you used your 208B to check internal resistance of each cell within your packs? Knowing usable capacity and individual cell internal resistance can go a VERY LONG WAY in determining the health of a series connected lipoly pack.

- Other Mark
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Old Mar 20, 2012, 04:30 PM
Static Model Collector LOL
Katy, TX
Joined Dec 2009
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I think both Mikes are right

@ 2nd Mike Yes at the end all cells were completely charged, however after cells 1,2,& 3 were at 4.20V, it took an additional 32 minutes for the last 2 cells to be fully charged. charge rate was 1C

FCA
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Old Mar 20, 2012, 07:29 PM
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Melbourne
Joined Aug 2010
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What settings are you using on the charger for the following

Balance always, storage or CV
Balance speed

You can terminate the charge a little earlier to cut down some time 4.18v or so

Cheers
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Old Mar 20, 2012, 07:45 PM
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Haralson County GA. USA
Joined Oct 2004
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First off it is far more likely that two cells are not lagging at all but are running ahead. The cells which charge the fastest are the ones which require the most balancing and the most common reason is that they have less capacity thus fill up faster.

With a new LiPoly of less than prime quality then it is possible that some cells are indeed bad or of lesser quality than the others.

Do a couple or three slow 1/2C(or less) charges and whatever discharge rate your charger can manage. No point is dischargibg below 3.5 per cell. Often a few cycles will improve the over balancing.

I test a lot of LiPolys and it sure is great to have the massive balancing power of the FMA Power Labs when dealing with packs such as this one.

A few days a go my son had a new 3S 1000 that a charger with 300 mA balancing power was have an extremely difficult time with . Two cycles on one of my Power Labs and all is well with it.

Charles
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Old Mar 21, 2012, 06:01 AM
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flypaper 2's Avatar
Kingston, Canada
Joined Jun 2004
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Had that happen with new batts. After a couple of cycles you can"t tell which were the low ones.
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Old Mar 21, 2012, 08:33 AM
Static Model Collector LOL
Katy, TX
Joined Dec 2009
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Hi everydayflyer,

I will try that later tonight.
Changing subject - can the FMA charger be used to break in new lipo's, discharge at 7 amps?

Some that I've spoken to argue that a charger will not accurately discharge a pack at 7 amps

Let me know if this unit is up to the task, will be even better if I can tell it to discharge a given pack at 7A, down to xxx mAh

Thanks,

FCA
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Old Mar 21, 2012, 10:38 AM
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Haralson County GA. USA
Joined Oct 2004
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PL8 will do up to 100 watts internal discharge so yes up to a 3S at up to 8A.

PL6 50 watts internal so half as much.

Regenerative Discharge up to 40A if your Pb bttery can take it.

Discharge to volts per cell can be set over a wide range..I use 3.3 to 3.7 depending on how deep capacity wise I wish to discharge them and it will do cycles also.
No X amount of mAh settings.

Charles
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Old Mar 21, 2012, 12:19 PM
Static Model Collector LOL
Katy, TX
Joined Dec 2009
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Quote:
Originally Posted by everydayflyer View Post
PL8 will do up to 100 watts internal discharge so yes up to a 3S at up to 8A.

Charles
Charles - You lost me, sorry

Can the PL8 discharge a 6S pack at 7A.

I recently cycled some new XPS 2500mAh 65C packs with a motor and small prop, kind of a pain, the whole light discharger to me is even more of a pain, to build/make one anyways

Thanks again,

FCA
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Old Mar 21, 2012, 01:19 PM
Expo/DualRates = Lack of Skill
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San Diego, CA
Joined Mar 2009
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6S x 4.2V x 7.0A = 176.4W

6S x 4.0V x 7.0A = 168W

6S x 3.7V x 7.0A = 155.4W

By itself, the PL8 can discharge at 100W. The above example is too much power attempted.

100W ( 6S x 4.2V ) ≈ 4A

100W ( 6S x 4.0V ) ≈ 4.15A

100W ( 6S x 3.7V ) ≈ 4.5A

The PL8 will discharge the 6S at about 4A for the entire discharge. Any higher current setting and the PL8 will initially lower the current to keep the discharge at 100W. As the voltage drops, the discharge current will increase until the set value is reached, or the discharge is terminated.
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Old Mar 21, 2012, 01:24 PM
Expo/DualRates = Lack of Skill
typeRA's Avatar
San Diego, CA
Joined Mar 2009
789 Posts
By powering the PL8 with a large lead-acid battery, you may enable regenerative discharging. If regenerative discharging a 6S (22.2V) battery into a 12V battery, the current into the 12V battery will be about double what you are pulling from the 6s battery.
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