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HomeRC & PowerAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › A123 Failure Mode ?
03-06-2012 03:25 PM  6 years agoPost 1
Four Stroker

rrElite Veteran

Atlanta

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Some of you guys must have had A123 packs long enough to have a failure. My question is what happens ? Does a cell short out and give 0 volts ? open and dump you in the dirt ? gradually degrade in capacity ?

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03-06-2012 04:13 PM  6 years agoPost 2
BarracudaHockey

rrMaster

Jacksonville FL

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I've got them in a couple of 50cc and 1 100cc plank and I haven't had any issues with them at all and I have a couple coming up on 2 years old.

Andy
AMA 77227
http://www.jaxrc.com

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03-06-2012 04:53 PM  6 years agoPost 3
Four Stroker

rrElite Veteran

Atlanta

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I think they will last forever charging and discharging at 1C for RX's. I will be long dead if they last a 1000 cycles like FMA says. On the other hand if one cell dies you hit the dirt with digital servos.

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03-06-2012 05:37 PM  6 years agoPost 4
JKos

rrProfessor

Redondo Beach, CA

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Ok, so it doesn't answer your question... But while doing some searching trying to find the answer to your question, I came across this and thought it was an interesting read: http://www.evworld.com/library/prius_fire_forensics.pdf

It does have some interesting Battery Pack Design Safety Guidelines from A123 Systems starting on page 30.

I can't seem to find an answer of whether they fail open or short chemically. All I can really find is physical failure (such as some of the failures in the above article) which would cause an open. But that only happens under extreme situations.

- John

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03-06-2012 06:09 PM  6 years agoPost 5
rexxigpilot

rrProfessor

Florida

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I've had one die. The pack charged up to full voltage OK. However within an hour or so the pack was 3 volts down. The bad cell was slightly warmer than the other cell. It seems like A123 cells short internally at the micro scale level like a NiXX when they get dendritic.

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03-07-2012 03:12 AM  6 years agoPost 6
Crashr30

rrApprentice

DFW

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They do not last forever. At 2 years you should start getting suspicious. An A123 dies with no warning.

Team Synergy RC, Team Bobby Jacks, PowerMaster Fuels, Team Scorpion, YS Engines

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03-07-2012 04:08 PM  6 years agoPost 7
JKos

rrProfessor

Redondo Beach, CA

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> At 2 years you should start getting suspicious.

Crashr30,
Is that with light, medium, or heavy use? Independent of use? How are you charging them?

All my A123 cells are well over two years old now and still going strong. I have them in everything from a handheld o-scope, to a portable guitar amp, to some of my helis. Just curious for more details from you.

Thanks,
John

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03-07-2012 04:32 PM  6 years agoPost 8
Four Stroker

rrElite Veteran

Atlanta

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Does that mean that hybrid cars have to replace the battery pack every two years ?

It is my suspicion that they will last a long time if you charge/discharge at a few C and always balance charge and never over discharge. Also there are clone knockoffs out there! There are also rejects from A123 for sale in the hobby industry - not grade A.

I bought presumably grade A authentic A123 with tabs. Several people told me I was a fool and payed twice what they did.

So did you buy from the lowest price and solder directly to the cells ? If you bought a "professional" RX pack from say NoBS or EDS and it croaked after two years, I want to hear about that!

The best RX packs that I have ever built were Sanyo RC 2400 cells when they were available fresh (used in cars). After about 5~10 years they fail shorted. You can still land on 3 cells. With A123, if a cell opens or shorts, you hit the dirt.

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03-08-2012 02:39 AM  6 years agoPost 9
Crashr30

rrApprentice

DFW

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My cells were true A123 cells. Not the "cheapest". They were charged somewhere between 2-3c depending. Cycled the battery from time to time to check them. If you were using Sanyo packs in a 4 cell pack then you must have been using Li-Io pack. A123 chemistry is LiFe. Now an A123 pack is slightly different from the LiFe flat packs that you can buy. It is both packaging and a slight difference in chemistry. LiIo packs would suddenly fail too.

The theory that automotive packs would die in 2 years is not an apple to apple comparison. ONLY the chemistries are similar. There construction, charging and cooling are completely different. At this very moment in time the only mfr using A123 is Fisker. A123 has had some other contracts but they have fallen through. Not sure why. The "old" Prius uses NiMh and the Volt use LiIo. All of which in model use has neither "100,000 mile" 10yr life spans.

When my packs failed, it was in flight and the cells dropped fast. Backwards inverted, 2 sudden piros, backed off collective, throttle hold and piro auto. Broke the skids. Back at the bench by the time I got there, I had a little over 2 volts per cell. Charged before the flight. Charged after this and they would not hold a charge for 10 minutes. Just all of a sudden.

Team Synergy RC, Team Bobby Jacks, PowerMaster Fuels, Team Scorpion, YS Engines

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