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Old Jan 19, 2007, 01:19 PM
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FlyingW's Avatar
Long Valley, NJ, USA
Joined Dec 2001
1,733 Posts
Charging a 10s2p A123 Pack w/Astro 109


I am nearing completion of a large plane that will require a large motor battery. the power system includes an Astro 60, MAT H-1500 belt drive, and 22x12 prop.

I looked at several alternative batteries, from 36 NiMHs to 10s-11s Emolis to 12s2p A123s.

I like the 12s2p A123 option, but there is no solution available yet for charging with Astro 109s, an I can't get 12s2p unless I buy three DeWalt packs!

I figured out that a 10s2p pack could work if I reduced the belt drive ratio and lived with higher amps (I generally like high voltage and low amps, but one must consider all the trade-offs).

I've read and searched through a lot of posts in the Ezone regarding charging of A123s. I saw that Gary Goodrum once used an Astro 109 to charge 10s A123s; the 109 recognized the 10s A123s as 9s LiPos.

The Astro 109 final charging voltage for 9s LiPos is 37.8 volts. 10s A123s need to come in at 36 volts. Using the Astro 109 will result in a slight over charge of 1.8 volts for the pack or 0.18 volts per cell.

I think that 0.18 volts extra charge should not damage the cells, either short or long term. Any opinions on that?

Also, the Astro 109 specs show that it can charge 9s LiPo at up to 4 amps. This would give about a 1.7C charge rate for the 2300mah A123 cells - should charge in less than one hour.

So, with two Astro 109s I could charge two 10s1p A123 packs, and connect them in parallel to fly at 10s2p. I wouldn't even have to reconfigure the cells after removing them from the DeWalt case, I could just solder to the first and last tabs.

Can anyone think of anything dangerously wrong with this approach?


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Old Jan 19, 2007, 01:30 PM
Southern Pride
everydayflyer's Avatar
Haralson County GA. USA
Joined Oct 2004
34,850 Posts
If you are a DIY type then the AF-109 cand also be modified to handle A123 packs.


post #39 has a 10 cell mod.
I modified mine and it will charge a 8S ar a little over 6 A.

Using the 9S LiPoly trick will work also. AF is due out with a A123 version anyday.

The Thunder Power 1010C will also charge 10S A123 at 5A.

There are several other A123 chargers available now also including the Xtrema.

You could also go the LiPoDapter route


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Old Jan 19, 2007, 02:25 PM
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747drvr's Avatar
Dundas, Ontario, Canada.
Joined Sep 2001
777 Posts
Paul ,

That'll work just fine . You could also charge in parallel but it'll take longer .

I totally relate to your avitar comment . I should do less cybermodelling !

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Old Jan 19, 2007, 02:37 PM
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supi7's Avatar
Joined Feb 2004
1,616 Posts
The e-Station 902 will charge the up to 12S Lipo / Emoli and A123.
you can also balance them with the e-Station Dual link system comprised of two PB6 units connected together.

The entire setup is available at www.TrueRC.net

You could also go with TrueRC 5S or 6S custom packs that would work with your 109 without any mods, not to mention they will cost less per mAh than cylindrical cells.
This way you could balance with pretty much any balancer and save $$ on new charger.

Best Wishes,

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Old Jan 19, 2007, 02:40 PM
Registered User
United States, MI, Goodrich
Joined Mar 2004
3,901 Posts
Or you could charge in 12-20mins with this:

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Old Jan 19, 2007, 02:41 PM
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Ft. Lauderdale, Fl
Joined Feb 2004
460 Posts
you can also buy a dewalt charge for about $40 on ebay and then charge one pack after the other within about 45 min. each. But you can use the balancing circuitry of the original pack and building the pack is also much less soldering since you don't have to do any balancing taps.
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