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Uneven Batt voltage draw

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Old 11-28-2010, 02:59 PM
  #1
cap10b
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Default Uneven Batt voltage draw

Robert,
I have a smart fly EQ10, Smart Fly Pro, and Sport all on A123 direct with no regulator plugged into my Airtronics 2.4 10channel and 8 channel receivers and they work flawlessly. No problems noted. However I noticed on my 39% plane running 8 JR 8611a servos I was getting uneven amperage draw on one of the batteries. I decided to add another pack (I run all A123 with no regulator) and this solved the problem. Now I recently put my Smart Fly sport into use on one of my 50cc planes running all analog high power metal gear servos and again with my 8 channel 2.4 receiver. All works great but again I am experiencing uneven current draw. Is this normal ?

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Johnny Snead
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Old 11-28-2010, 03:16 PM
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Default RE: Uneven Batt voltage draw

Hi Johnny,
With A123 packs this is not uncommon, especially at low battery discharges (<30%). A123s have such a low impedance they do not equalize in voltage as well as other battery types. A123 packs MUST be balance charged and a lot of chargers do not balance the A123s well. You should consult the Fromeco website for the chargers they have tested that actually do a good job of balancing A123s.
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Old 11-28-2010, 03:25 PM
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Default RE: Uneven Batt voltage draw

Robert,
Thanks for the quick response, to be honest I do run a balancing charger and I do balance my charges almost every time. But recently I probably skipped balancing to every other charge since I do fly just about every weekend. Could this really make a difference ? My amperage draw on the big plane is usually around 4 flight total draw over 800 mah. This is what caused me to add another pack as like you said I was getting close to 1/2 my total capacity.

This has been an eye opener.

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Old 11-28-2010, 03:33 PM
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Default RE: Uneven Batt voltage draw

Hi Johnny,
About the only charger that Fromeco found that balanced the A123s well were the FMA chargers. All the other chargers did not have a strong enough balancing circuit to get the cells balanced before the charger shut off. Fromeco told me that once the A123s get out of balance they just keep diverging badly.
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Old 01-11-2011, 12:01 PM
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Default RE: Uneven Batt voltage draw

I Have the same problem, I am using The Compatition 12. The last two charges one battery draw 980 Mhs and the other was 2030 Mhs.(4 Flights of 12 minutes and 10 Hitec HS-7950TH Servos)
I have never Balanced my batteries A123 racing.
The second time that I charged had almos the same amount on each battery.
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Old 01-11-2011, 12:06 PM
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Default RE: Uneven Batt voltage draw

Hi,
This is the problem with A123s, they are very hard to get even battery draw, especially when you do not balance them with a charger that does a good job of balancing.
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Old 01-11-2011, 12:10 PM
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Default RE: Uneven Batt voltage draw

Thank You Robert, but I never had that much diference.
So, is that If don't Balance the Batteries?
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Old 01-11-2011, 12:20 PM
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Default RE: Uneven Batt voltage draw

Hi,
I honestly do not know. The BatShare in the Comp 12 is just some high-current, low voltage drop diodes. Basically it works or doesn't. Have you checked your Deans connectors on your batteries? Are these real Deans females on the batteries? We track a lot of problems down to the battery connectors.
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Old 01-11-2011, 12:27 PM
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Default RE: Uneven Batt voltage draw

I don't know about the deams female. My batteries are A123 Racing, but what I am going to do is, this weekend I will use my Fromeco batteries, to see what hapen. I let you know next monday.
Thank you Robert.
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Old 01-12-2011, 03:00 PM
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Default RE: Uneven Batt voltage draw

All,
I found that Robert was right my charger just wasnt balancing as good as I thought it was. Once I did a few nominal discharges and brought the packs back up to full and then flew my routine, the batteries were more in line with what I wanted to see. Not perfectly matched in MAH drawn ( I never expected them to be perfect) but close enough for me ( 50mah) so I'm a happy camper and trust my A123 and smart fly set up totaly now.

Thanks Robert

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