CARS II

My Feedback: (7)

What do you think?

Tks.




http://www.rcuniverse.com/forum/m_11562120/tm.htm

cyphur01

Charge and then Cycle to Check capacity. Only way to be sure on a123/life chemistry

CARS II

My Feedback: (7)

Can I use this to check it after each flight?

http://www3.towerhobbies.com/cgi-bin...eter&search=Go

CARS II

My Feedback: (7)

Thanks, I will do that.

CARS II

My Feedback: (7)

Should I take them down to 3.3 per cell or lower?

wfield0455

My Feedback: (7)

I would say if the pack is getting old, doesn't balance easily and takes longer to charge than it used to, get rid of it.
I had 2, LiFE packs fail this weekend only 2 minutes into the first flight of the day after being freshly charged. Other than
the packs being about 4 years old and recently starting to take longer than normal to finish charging they appeared to be fine.
I noticed the engine starting to cut out (it's powered by the receiver packs via an IBEC) and landed immediately.
Engine died while taxiing back and by the time I had brought the plane back to the pits I no longer had control of the plane. I checked
the voltage and both packs read 3.3V! I unplugged them from the receiver and recharged them and they both were back down to
less than 6 volts within an hour (no load). Just glad I was able to get the plane back on the ground without any damage. Since
my transmitter supports telemetry, you can bet all my planes with have a telemetry for receiver voltage installed before they fly again!

cyphur01

When cycling mine, I typically bring them down to 3.0v per cell. This will give you about 80-90% of total capacity of the pack. The drop off curve is steep. When bringing my planes out of winter I will do 3x cycle and find the avg capacity of the 3 cycles. if it is less than 70% of the total capacity I pull the battery for further evaluation.

CARS II

My Feedback: (7)

Wayne

You got the symptoms just right, I may have to change that pack.

I'm still working on it for now, I figure I'm learning a lot from this pack.

Thank you for al the info.

CARS II

My Feedback: (7)

3.0V or 6.0V sounds about right [&:]

cyphur01

Yes. 3.0v per cell or 6.0v total is correct

CARS II

My Feedback: (7)

The pack is now at 170 min, 7.05V, 1850 mh, 3.60 on #1 - 3.40 on #2.

rcand

Best way is to use a charger, like cellpro powerlab 8, that measures internal resustance. I have had Life batteries that charged fine and cell voltage was within limits but the IR on a cell was a lot more than the other and that cell would not produce under heavy loads.

CARS II

My Feedback: (7)

I heard that the Cellpro charger is the prefer when it comes to LI-FE.

CARS II

My Feedback: (7)

The balance spread between the two cells is 0.20 how bad is that?

CARS II

My Feedback: (7)

.

cyphur01

.2 is acceptable. Charging at only .1 amp for final balance is normal too especially if there is a measurable imbalance. I've had some of my 5000 mah 6s x 2 heli batteries take upwards of 4 hours to completly balance charge after pushing them very hard (<10% remaining) Let it finish then discharge and charge again. I bet it charges much faster next time. Plus you can check the discharge capacity.

CARS II

My Feedback: (7)

Sounds good, I will keep working on that pack to see where it goes.

madmodelman

I'm sure everyone thinks I'm crazy but been using HK life's in most of my jets for some time now at $8 a time.
Last week my new F86 went in big time. No fault of batteries but they now look like a pair of banana's!
But.....they didn't catch fire and still work perfectly, amazing!
Gary.

Jgwright

Why are you cycling your a123 packs? I have not recycled mine since I bought them. I understood cycling was only needed with Nicad batteries. I have not had problems with pack going down. Perhaps you are killing them or maybe they are not genuine a123 packs. When charging the cellpro chargers are the best for a123. They tell you what is left in the pack before you charge. Charging starts at 4 amps and reduces as it peaks. Charging and balancing only takes a few minutes.

John

derrickxp8103

My Feedback: (80)

Wayne,

What brand of LiFe battery failed??

bevar

My Feedback: (27)

I have been at the controls of two jets, one of them a twin when the Life batteries failed and the jets were lost (neither jet was mine...just flying them).

I have never flown any kind of plane, heli...name it with Li-Ions and regulators that have failed and gone in, and I was an original PowerFlite pilot back in 2001 and have been flying Li-Ion since then with thousands and thousands of flights logged.

I'll never use Li-FE in my planes.

FWIW...

Beave

Vincent

My Feedback: (61)

+1

Vin...

wfield0455

My Feedback: (7)

2, Fromeco, 3600mah IronCorp packs. These packs were getting to be close to 4 years old and I probably
had about 300 flights on them.. I normally charge at the field immediately before flying, typically fly 3 or 4
flights during the day and they normally require 1500mah-1800mah per pack to recharge them the next weekend.
This particular time I charged both packs the night before and they needed about 600mah per pack but
as I recall I only flew 1 full and 1 short flight the previous weekend so that didn't seem unreasonable.
Now, both packs seem to self discharge very quickly with no load.

OldRookie

My Feedback: (13)

Were both of the planes owned by the same person?
What brand of LiFe packs were in the planes that you crashed?
Possible problems...owner not knowledgeable on how to care for LiFe packs...cheap and/or counterfeit packs.
I don't think the age of the packs is a factor in LiFe battery failures...just worn out connectors, or failing solder joints. After 1000+ charges the pack may have served it's useful service life.
I have several A123 packs, and 3 are over 5 years old, and still working perfectly. I guess I have never seen a shelf life expectancy for the A123 or any other brand of LiFe cells.
I have never heard of a LiFe pack crashing a plane. Usually it is the pilots fault.

Greg

Chris Smith

My Feedback: (2)

CARS II ,
It is critical that we know the brand battery you are using.
Since A123 cells (known as Linp or LiFe M1) are So vastly different from other LiFe cells, the use, care, and management of your batteries will be different.

The nano plate technology is roughly 100 times more robust in true A123 cells. Therefore my comments assume you are using A123 cells since you indicated they are 2300mah size.

Keep in mind that voltage drop in a healthy A123 cell begins around 2000mah. Establishing a safe minimum discharge level, say 50% capacity is very important. NO ESV out there is sufficient for use to determine if an A123 has enough capacity to continue to fly. You must know remaining capacity percentage, not voltage, since cells drop voltage quickly below a radio's needs under load.

Since an A123 cell spread from empty to full is only .3 volts, an imbalance of more than .1 should be considered a NOGO. Let's assume you always charge using an A123 balance charger. An imbalance larger than .05 may indicate the pack was discharged too much. Either it was left connected too long or too many flights on a charge, or the balance tap continuity reached the receiver due to an install problem. Always disconnect batteries from the radio switch harness between flying sessions.

In your case since cell number one is at a higher level than cell 2, it may be that cell 1 was the cell that discharged too much. If the load such as a receiver, was seeing the balance tap it will draw cell 1 down as if it were a 1s battery. Weaker cells charge up faster. The cc/cv software sees that voltage in cell one hit max sooner and drops to a very slow charge rate that can be as low as around 100mah. This can go for a long time as the charger tries to balance the pack and get cell 2 caught up without damaging the pack.

There are little devices that can allow you to charge the cells individually and manually re balance them. But I would first find out what discharged the pack too low. Most often it is waiting too long before recharging or not balance charging every time. 4 years is not too long for an A123 battery. So age alone is not reason to retire a pack. However if you can't get that pack balanced to within .05 or so then I would not use it in an airplane. Keep it as a bench pack.