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Old Feb 03, 2010, 07:42 AM
Southern Pride
everydayflyer's Avatar
Haralson County GA. USA
Joined Oct 2004
34,546 Posts
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Do Not Balance discharged LiPolys/ PowerLab8 monitoring/Thunder Power PP45 Charge#3

Most every thing in the title and on the graph.

I have posted for years that good LiPolys do not require much if any balancing and that they should never be balanced while discharged.

I have read hundreds of post where an Astro Flight Blinky or other such stand alone balancer is routinely used on discharged LiPolys. All this does is pull the higher voltasge cells down more which makes them more out of balance when they are charged thus the balancer has to work harder.

Graph also shows that a high quality LiPoly does not die after a few cycles. This is the same TP PP45 which I tested for 300 cycles ,charged at 5c and discharged at 18C.

Graph also shows one of the neat functions of the FMA Cell Pro Power Lab 8. Sure is nice to be able to run one charge and have graphs of cell voltages all through out the charge as well as cell IRS (these were 3.9 / 2.8 /2.8) ,pack voltage ,amps, capacity and a few other very handy details. PL8 can also be used in the Monitoring Mode while battery is being discharged with another device or being charged on another charger(?). I love all my neat toys!

It sure is great having my 4 year old Compaq Persario XP Home back up and taking care of busness again. I could write a book on my computer adventures during the past 3 months. Reader's Digest version . Compaq started acting up, purchased an E machine with Win.7 (64 bit) and found out some RC software (being at the bottom of the tech food chain )will not run on it. Faught with Compaq computer,revieved it to only have it die again , over and over , ordered a Dell Latitude D610 Laptop with Win. XP Pro and another e machine with Win. XP Home. So I have gone from a dieing desktop to a revived desktop,an addational new in service desktop,a laptop and a spare desktop ,just in case. All that remains now is restoring over 4 years of data. Sure glad I believe in backups and had external HDs with all but a few files on them. I am now running a continuious backup / recovery system ,just in case.

Charles
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Old Feb 03, 2010, 12:37 PM
Registered User
Virginia
Joined Mar 2007
32 Posts
Then when is the best time/way to use a stand alone balancer?

I use an Equinox balancer and a non-balance charger (Accu-Charger) on my
3s batteries.

I usually have 20% or more left in batteries after use.

What process of balance/charging do you recommend?
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Old Feb 03, 2010, 02:23 PM
Southern Pride
everydayflyer's Avatar
Haralson County GA. USA
Joined Oct 2004
34,546 Posts
With 20% or more left in them they should be at 3.8V per cell if they are in good condition. It is OK to balance at this point and above. If the 3S measures 11.1 or above I would connect the balancer and start the charge.

You could wait until the Lipoly is around 4V per cell (12.0V) and connect the balancer then however some balancers with little current bleeding / balancing power may have a hard time keeping up if the cells are to far out.

If the balancer is having a hard time keeping up as in the LEDs are mostly on then reduce the charge rate. Many wait and balance after the CV stage starts (cells at 4.1> or even after the charge.

My point about not balancing a discharged LiPoly is that say the cell are out of balance and a 3S has cells at 3.5 . 3.8 and 3.7 (11.0V total) and you connect a balancer and let it set and balance. Well the balancer drop the two high cells to 3.5 and when you start the charge the weak celll (3.5 one) will climb the fastest and the balancer will struggle trying to keep the other two down.

Snip from a 5 year old post of mine.

Quote:
Discharged pack to 8.76 @ 1.25 Ah on AF109.
Added taps and checked voltages.
3.67
3.45
3.67
Difference 0.22 volts

Charged at 0.9Ah (0.75C) on Triton to 12.3(Li Ion setting.
4.09 plus 0.42
4.05 plus 0.60
4.09 plus 0.42
Difference 0.04 volts.

Charged each cell to open resting voltage of 4.2 volts using Apache 2500.

This is an old generation E Tec 1200 mAh (6-7.5C)Classic purchased 6-17-04 and has approximately 100 flights on it. Flown on Fancy Foam Edge 540, Hi Max 2015/4100 ,6.6:1, 12X6 prop. Many flights to LVC of 7.2 v ,soft cutoff.

Note cells and setups were much different back then. If you discharge newer LiPolys that deep they may not last long but then who really knows.


Charles
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Last edited by everydayflyer; Feb 03, 2010 at 07:04 PM.
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Old Feb 04, 2010, 07:55 PM
Registered User
Massachussets
Joined Nov 2005
233 Posts
I had been charging 5s 5000mah batteries using a Thunder Power 1010c and one of their balancers. The balncers were doing a lot of work and would get pretty hot. I ruined two tp balancers in the process. This summer I stopped balancing. The batteries remain balanced at the end of the charge. They're usually balanced within 0.02v, once and awhile a little greater.

I think the balancers were chasing their own tail when heating up and going out of calibration. This issue probably gets worse at higher charge rates and higher capacity cells as well as when trying to balance cells that should really be imbalanced when only partly charged.

I haven't heard anyone complaing about chargers with built in balancers, so I'm assuming they're up to the job. Can anyone confirm this?
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Old Feb 04, 2010, 09:26 PM
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USA
Joined Jan 2002
4,530 Posts
This is a bug in the firmware. The firmware should have a threshold to determine when balancing is required and as well as when it's not required and when it's making things worse instead of better. Sounds like a little intelligence can be added here.
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Old Apr 03, 2010, 05:43 PM
どうもありがとうミスターロボット
Wrend's Avatar
United States, IL
Joined Jul 2009
3,063 Posts
Quote:
Originally Posted by wingster View Post
...

I think the balancers were chasing their own tail when heating up and going out of calibration. This issue probably gets worse at higher charge rates and higher capacity cells as well as when trying to balance cells that should really be imbalanced when only partly charged.

I haven't heard anyone complaing about chargers with built in balancers, so I'm assuming they're up to the job. Can anyone confirm this?
I don't think it's so much an issue that they should be imbalanced when only partially charged, but more that they just are through slightly varying levels of capacity and/or internal resistance.

I like to balance charge my packs up to storage voltage levels or when I fully charge them to help maintain closer concistancy between cells in a pack. Whether or not this really has any noticeable beneficial effects, I can't say. I don't see any reason to balance below storage voltage levels.

I use a balance charger that also does discharging, and it seems to be holding up just fine so far.
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