whats safest /max charge rate for 5s a123?  
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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> A123Racing Support >> whats safest /max charge rate for 5s a123?
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whats safest /max charge rate for 5s a123? - 1/7/2008 5:54:01 PM   
747



Posts: 252
Joined: 9/14/2003
From: Downingtown, PA, USA
Status: offline
Hi All,

I made my 5S1p 2300mah A123 pack. To charge it what is the safest yet maximum charge rate I can choose?

[I use an Astro flight A123 version charger. The charger says" Lithium Ion Charger for A123 Cells, Charges from one to ten cell A123 Lithium Ion Battery Packs. Charge rate 50 ma to 9 amps. Software v1.2".]

My questions are:

1) So is my safe max around 9amps. I have read A123 can be charged safely at >10 amps.

2) Does the no. of cells in the pack matter when choosing charge rate?

3) How fast do I increase charge rate? Manual says set in zero first,Then turn knob to desired C rate for the capacity of the pack. Can I go from '0' to safe/max rate of eg:9amps, immediately?

4) Mine are five devault 2300 mah cells so 1C rate is 2.3A right?

5) I have charged my new pack once but with 2.3A rate, took 25 mins to get to 16.7v. Why is the charging slower as the "V" in pack comes closer to full?

Thanks!
747

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RE: whats safest /max charge rate for 5s a123? - 1/8/2008 2:57:20 AM   
everydayflyer



Posts: 852
Joined: 8/21/2005
From: Buchanan, GA, USA
Status: offline 		Max recomended is 10A however I routinely charge my 3S pack at 17A average with the start- of charge at 20-30 A and ending at 7A. 2000-2200mAh into pack in 7 to 8 minutes.

Set 109 A123 ver. at max. and it will be fine. Charge decreasea as pack volts come up because charger is not capable of charging max. number of cells at max. rate.

Not AF number ,just an example. A 100 watt charger could charge a 10V pack at 10 amps. so if a 3S was close to 10 volts and rate was set at 10A it would charge at 10A. When the pack increased to 11 volts charge rate would be 100 watts / 11 volts=9.09 amps.

If rate was set at 5A it would stay at 5 amps. since 10vX5A=50 watts and 11V X 5A=55 watts both well below the chargers 100 watts max.

Charles

(in reply to 747)
       Post #: 2

RE: whats safest /max charge rate for 5s a123? - 1/9/2008 6:22:58 PM   
747



Posts: 252
Joined: 9/14/2003
From: Downingtown, PA, USA
Status: offline 		Everyday,

I noticed that the moment I stop charging[Was fast @ 9a rate!] the 5s once it reaches 18v max rest voltage, It becomes a total of 17.5v in a few mins. Is this normal? (mine is a new pack not cycled fully yet)

Also, Since there will be some imbalance at Full charge of 18v for my 5s, If I fly without balancing (since I can save on some power) after the usual 8-10mins flight is there a risk that one of the lower Voltage cells might go below the LVC?

Do I need to chrg/dischrg my new pack using my astro 109 charger/dischrgr few times and then cycle it by flying?!

[I now see that blinky balancing after I fully charged my 5s1p a123 for 18v is quicker.]

Tks
747

< Message edited by 747 -- 1/9/2008 6:24:22 PM >

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RE: whats safest /max charge rate for 5s a123? - 1/10/2008 12:48:44 AM   
everydayflyer



Posts: 852
Joined: 8/21/2005
From: Buchanan, GA, USA
Status: offline 		Yes A123 cell settle to approx. 3.45 volts shortly after charge is complete. If you reduce the charge rate near the end (stage 3) then will finish a little fuller but not enough difference to worry about.

AF 109 will not discharge at high enough drate to help conditioning (cycling) the pack. just go ahead and fly the pack but do not fly to LVC. try to not use more than around 2000 out of them. They mostly go out of balance when discharged more than 2200.

After chargin flying charging ,balancing 5-10 times you should notice them staying balance much better.Simpliest thing to do is just connect the Blinky after the charger goes into Stage 3 that way they will be balanced at end of charge.

Charles

(in reply to 747)
       Post #: 4

RE: whats safest /max charge rate for 5s a123? - 1/16/2008 4:07:19 AM   
747



Posts: 252
Joined: 9/14/2003
From: Downingtown, PA, USA
Status: offline 		Yes once the weather gets warm ,I will fly and see the balance often. Does the Astro 123 blinky go "random blinking" after balance is done?

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       Post #: 5

RE: whats safest /max charge rate for 5s a123? - 1/16/2008 4:49:39 AM   
tenmillionarie


 

Posts: 1
Joined: 12/12/2007
From: icheon, SOUTH KOREA
Status: offline 		Hello 747,

The max charge rate for A123 Nanophosphate cells is 5C, ~10A for 2300mAh cells. There is no need to cycle A123 batteries before use, but it is important that you are familiar with the performance of the cells before they are flown.

Also make sure that you are using the modified Astro 109 that is suitable for our A123 cells.

Please let me know if you have any other questoins.

Power . Safety . Life

Customer Support

(in reply to 747)
       Post #: 6

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