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Ripmax Pro Peak Prodigy II Charger Question - A123 Ready?

Old 10-23-2007, 02:28 AM
  #1  
Rickochet
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Default Ripmax Pro Peak Prodigy II Charger Question - A123 Ready?

I have one of these, about a year old (v2.0) and noticed it has separate selections for Lipo or Li Ion. It doesn't mention anything about A123 in the book. When selecting LiIn it gives me voltage selections of 3.6, 7.2, 10.8. 14.4 & 18.0 and I can select settings of up to 5 amps in 100maH increments. Does anyone know if this charger can handle A123 as is?

Rick
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Old 10-24-2007, 07:52 PM
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compflight
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I believe you can use the Lipo settings as these cells are far more tolerant.
can anyone confirm this?
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Old 10-24-2007, 08:20 PM
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Rickochet
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Since I posted this I got a reply back from Globalhobbies, the US distributor. They could not recommend this charger for A123 use as they had never tested them and termination voltage was in the 4.2v range. I did get a reply on RCGroups that suggested that although 3.7v was a perferred termination voltage for A123, they have charged them to 4.2v many times with no apparent problems. I think I might watch mine at first on LiIo setting and manually terminate the charge at 3.6 or 3.7 per cell.
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Old 10-29-2007, 07:21 AM
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kgfly
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Depends.

a) You can charge A123 above their nominal 3.6V charge limit so long as you terminate the charge quickly (within a few minutes) of them going over 3.6V/cell

b) You can charge using a different cell count to get close.

Code:
-------------------------   ---------------------------  ---------------
A123                        Closest Lipo                 A123 over/under
No. cells   charge cutoff   No. cells     charge cutoff  volt per cell
-------------------------   ---------------------------  ---------------
   1            3.6               1            4.2            0.60 
   2            7.2               2            8.4            0.60
   3           10.8               3           12.6            0.60
   4           14.4               4           16.8            0.60
   5           18.0               5           21.0            0.60
   6           21.6               5           21.0           -0.10
   7           25.2               6           25.2            0.00          
   8           28.8               7           29.4            0.08
-------------------------   ---------------------------  ---------------
Clearly the best match is 6s lipo for 7s A123 with 7s lipo and 8s A123 close enough too. You other option is to get an A123 LipoDapter (aka Dapoter) which lets you charge A123 packs using the NiCd setting on your charger. The Dapoter device goes inline between the constant current source (your charger set to NiCd mode) and the A123 pack and terminates the charge when the pack voltage reaches 3.6V/cell. This will only 90% charge the pack since it leaves out the CV charging phase normally needed to top off the last 10-20% capacity. It also doesn't balance the pack so you would need a separate balancer.

What size packs are you planning on using ? There are several chargers around that do a good job on A123 packs for not much money. The Cellpro4s ($75, 50W output) for 2s-4s or the BalancePro for 2s-6s ($105, 240W output) are both great options.
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Old 10-29-2007, 12:38 PM
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Rickochet
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Good info Kgfly, thanks. I have since picked up a used Astroflight 109 with the A123 chip.
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