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Old Jun 30, 2006, 08:03 PM
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A123 Systems Li-Ion, CBA+10X Amp. Graphs

MaxAmps donated this cell and the manufacturer's application sheet.

Because of the 10X current amplifier, all the amperage and mah figures are low by a factor of 10, so it's necessary to mentally move the decimal point one place to the right.

The voltage figures are correct as shown.

- RD
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Old Jun 30, 2006, 08:05 PM
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Charges were @ 1C.

Higher charge rates, multiple maximum rate discharges and condition checks to follow.

- RD
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Old Jun 30, 2006, 08:19 PM
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Do you have any plans for pulse discharging? IMO, those continuous-current graphs aren't the best...
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Old Jun 30, 2006, 08:52 PM
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The West Mountain Radio CBA system is software controlled and there is no provision for varying the amperage during a discharge.

- RD
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Old Jun 30, 2006, 10:51 PM
Spokane Washington
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RD,

What rate did you charge the cell at? From the spec sheet it states you can charge at up to 10 amps. That is pretty impressive quick charging.

As far as weight/capacity, its not great but I think that it has some upsides to NIMH also like the fact that it has a hard case instead of soft. They are kinda big as far as the form factor goes. I would love to hear some comments on if we should bring this cell in or not...

-Austin
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Old Jun 30, 2006, 11:37 PM
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Mr. Blakesly, am I reading that graph correctly and the beige line is discharge at 3C or is the decimal on the Amps misplaced?
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Old Jul 01, 2006, 04:59 AM
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RD - Lomcevak has a point; there is a goofed up decimal place in all of those discharges, no?

Brad
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Old Jul 01, 2006, 05:13 AM
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Austin, See post #2 - I'll be doing higher charge rate tests shortly. As to commercial viability for eflight, this thread might help you decide:
http://www.rcgroups.com/forums/showthread.php?t=537359

The A 123s do accomodate greater power demand, in and out, than the contemporary generation of Saphions.

Speaking for myself, graphing LiPos has never been stress-free for me. They are too unforgiving of a mistake and voltage MUST be monitored, IMO. I do not agree with the staement on FMA's website with respect to their automatic LiPo charger: "Plug and Play and Walk Away".

It would be nice to rely on the digital readout of my CC/CV P.S., (I didn't do that while graphing, of course) without need of worrying about a little inaccuracy or drift, because of the non-critical nature of the A 123 and Saphion charging algorithm.

- RD
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Old Jul 01, 2006, 05:23 AM
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Guys, when The West Mountain Radio 10X amplifier is used with the CBA, the decimal point must be mentally moved one place to the right on readouts of charging amperage and discharged AH, pending a software patch to be done by W.M.R. shortly (I hope). I should have mentioned that at the outset, sorry.

http://www.rcgroups.com/forums/showthread.php?t=528314

- RD
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Old Jul 01, 2006, 06:31 AM
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Quote:
Originally Posted by RD Blakeslee
Guys, when The West Mountain Radio 10X amplifier is used with the CBA, the decimal point must be mentally moved one place to the right on readouts of charging amperage and discharged AH
'S okay - just don't do it again!

Brad
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Old Jul 01, 2006, 01:55 PM
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Anyone else notice the interesting thing about the higher discharges (20C & 26C)? After the initial dip, the voltage actually increases throughout the entire discharge almost right to the end. Heating effects - suggesting a high optimum operating temp?

ps - thanks for all the work, RD
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Old Jul 01, 2006, 09:02 PM
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You're welcome, Neil.

Re high Temperatures: note that the manufacturer specifies a maximum operating temperature of 185F (85C) quite a lot higher than LiPos will tolerate.

- RD
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Old Jul 01, 2006, 10:36 PM
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How much are these cells? If they are cheap enough I will try some in my ducted fans.
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Old Jul 02, 2006, 01:26 AM
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We dont have the pricing from the supplier nailed down yet. I will let you know what it will be if we decide to bring them in.

-Austin
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Old Jul 02, 2006, 08:50 AM
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Thank you RD for the testing. While we sometimes disagree in threads, your time and effort spent doing cell testing, considering the risk you take is appreciated.

Some observation from being around at this stage in the introduction of Lipo for RC:

- Gen 1 Lipo's were good for about 5C, now we have 15C and claimed 20C Lipos.... if A123 improves simiarilly over time the energy density delta to Lipos may disappear.

- Saftey...... I sure hope it's true...... but in the early days of Lipo's we were told they were the safest cell type yet.... worst case they would just swell up and you could throw them away.... yeah we sure know better now.

- Cycle life.... remaims to be seen at +20C but local RC boat racers here in Florida love the A123's. They usually have to throw away a Nimh pack (GP or IB cells) after around 10 cycles to remain competative. They have yet to see the need to toss a A123 pack.

Now if only A123 would put out a +3500mah cell at around 100g I would be a very happy heli flyer.

Brad
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