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JR-Spektrum . E-flite . HeliDirect

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e-Electric Batteries & Chargers > What is currently the best brand/model LiPo battery
 
 
misskimo
Veteran
Location: Alaska 12 years before , mississippi for 31 y

sounds like a charger problem to me! over charge will result in short life span, what charger you useing ?

Do-Yo-Thang! !:~) Team ThunderPower & Spartan Gyros
05-10-2008 01:48 AM
 
 
rexxigpilot
Senior Heliman
Location: florida

I use 3 different chargers - TME Extrema, Triton and CommonSense. FP V-balancer is used with the Extrema and Triton. The CS has a built in balancer. I also check voltage after charging with a separate meter. Packs are always right at 4.2V/cell after charging.

I will try the AirThunder (in T-Rex 450's) and A123 (in 600E) packs next. Can anyone who uses the A123 setup in a 600E provide feedback please?
05-10-2008 07:40 AM
 
 
rexxigpilot
Senior Heliman
Location: florida

OK, hopefully I found the problem. My Extrema charger has a defect. Voltage input went berzerk during multiple battery charging (one battery after another) this past weekend. While charging the second battery, I witnessed an input voltage fluctuation of between 3-18 volts on an 11.1 V battery.

TME was notified of the situation via e-mail. They acknowleged that this is a serious problem with some of their units and requested that I send my charger in for repair.

I congratulate TME for having the integrity to admit there is a problem. I hope they do something to compensate me for the batteries destroyed.
05-20-2008 12:52 AM
 
 
Wyn
Senior Heliman
Location: Oregon, USA

Was the output voltage affected when the input voltage indication fluctuated?

Wyn
VoltMagic
05-20-2008 01:31 AM
 
 
pgoelz
Senior Heliman
Location: Rochester MI

Quote 
I do store my packs fully charged but from what I have read I refuse to believe that full charge storage can be blamed for a high internal resistance failure in less than a year or two. As a compromise I am now storing my packs in a small refrigerator in the basement (usually fully charged). Storing them partially charged is not logistically realistic so the fridge was the best solution I could come up with.
Oh crap! I just read that since the maximum safe cell voltage decreses with decreasing temperature, I am supposedly damaging my packs by putting them fully charged into a 35 degree refrigerator. I can't win.

So that eliminates the one viable solution for pack storage if it is impractical to discharge charged packs prior to storage. The only other thing I can think of is to reduce the end of charge cutoff voltage from 4.2V/cell to 4.1V/cell. That is possible on the Cellpro if you can fool the temperature sensor into thinking it is always cold. Like finding it and replacing it with a fixed resistor.

A123s are looking better and better, even if they are heavier.

Paul

Paul Goelz
Rochester MI USA
http://www.pgoelz.com
05-21-2008 02:13 PM
HOMEPAGE  
 
 
naked painter
Senior Heliman
Location: Mid glamorgan uk

I wonder why manufacturers havin't started producing A123 packs suitable for helis?
05-21-2008 03:07 PM
 
 
pgoelz
Senior Heliman
Location: Rochester MI

I would imagine because they would only be attractive to those who A) have had a bad experience with LiPos, B) want the increased cycle life / longevity and C) are willing to lose some capacity and power/cost/weight ratio.

Not everyone considers LiPoly to be ultimately unsuitable for our use. Not even me. But I'm getting there pretty fast. If my current crop of LiPos dies, I'm done with LiPo for a while.

Paul

Paul Goelz
Rochester MI USA
http://www.pgoelz.com
05-21-2008 05:15 PM
HOMEPAGE  
 
 
rexxigpilot
Senior Heliman
Location: florida

I couldn't agree more Paul! Last month I responded to a survey from Tower Hobbies that inquired about my future Lithium battery purchases. Basically, they wanted to know if I would consider using A123 cells within the next year. I answered that I would if the price and weight came down.

Since that survey, I have had more bad incidents with LiPo's and their manufacturers/suppliers. I recently contacted FlightPower regarding one of my batteries that went bad due to internal resistance problems. I spoke to tech representative Steve. He was far less than sympathetic! He kept telling me I should charge the batteries twice. He said that the last charge or even the complete charge should be at a low rate (1/8± C) to get full capacity. I explained to Steve many times that full charge was not the issue. He didn't seem to understand, but boasted how experienced he was in the field of RC (5 years) and how he makes his living on his knowledge of batteries.

Since the battery in question was put into service in November of 2007, I asked about warrantee repacement. My good buddy Steve informed me that the warrantee is only good 90 days.

FlightPower has a crash replacement policy for half price. When I asked Steve about replacing the battery under that policy, he said that I had to send him pictures of the crash damaged battery and AIRCRAFT. What a loser! I am done with FlightPower!!!

On a good note, I found a reasonable supplier of A123 cells. I ordered 14 - 2300 mAH cells at about $15/cell. I figure at that price I can make my own A123 packs for less than the cost of any major LiPo manufacturers' approx. equal capacity/voltage packs.

Also, I doubt that storage at a cold temp would be a bad thing for any battery. Your maximum discharge rate will certainly drop at colder temperatures. This is because all chemical reaction rates (what is happening inside a battery under charge and discharge) drop with a decline in temp due to lowered Gibbs' free engergy. As long as you don't charge them at cold temps you should be OK.

Another good thing is that me Extrema charger can charge A123 cells just fine.
05-22-2008 12:26 AM
 
 
pgoelz
Senior Heliman
Location: Rochester MI

Quote 
Also, I doubt that storage at a cold temp would be a bad thing for any battery. Your maximum discharge rate will certainly drop at colder temperatures. This is because all chemical reaction rates (what is happening inside a battery under charge and discharge) drop with a decline in temp due to lowered Gibbs' free engergy. As long as you don't charge them at cold temps you should be OK.
I am constantly frustrated with a near total lack of information from the actual cell manufacturers. All we get is heresay and second hand informaiton, which gets quoted and re-quoted and partially quoted but which we all take as the last word on LiPos. From the little I can find, the maximum voltage before permanent damage occurs goes down with decreasing temperature. It is 4.2V or a bit more at room temperature. But at 0 degrees C, it is less than 4.2V. How much less, I am not sure. The Cellpro stops at 4.1V at something like 55 degrees F. The result is that if you charge to 4.2V at 20 degrees C and then cool the cell to 0 degrees C, the cell can be damaged because at 0 degrees C, 4.2V is more than the maximum safe voltage. At least that is what I synthesize from what I have been able to find.

$15/cell isn't TOO bad but it bugs me that not too long ago they were available in DeWalt packs for 10 for $130 or $13/cell.

Not sure how my Trex would fly with three.... or worse, four A123 cells. My Mini Funtana might be OK with it but I love it at its AUW with a 3S 2200 LiPo.....

Paul

Paul Goelz
Rochester MI USA
http://www.pgoelz.com
05-22-2008 12:44 AM
HOMEPAGE  
 
 
Pistol_Pete
Elite Veteran
Location: Tampa Bay non-Buccaneer

seems like the eagle tree would be the cheapest route to go...nothing like actual flying data.

<><>...the lunatic is in my head...<><>
05-22-2008 12:53 AM
HOMEPAGE  
 
 
rexxigpilot
Senior Heliman
Location: florida

Paul, the peak pack voltage will drop when you lower the pack temp. For example, I placed a mostly depleted 3S pack measuring 11.92 V at 72° F. in a freezer at 3° F. After 4 hours the voltage drop was 0.12 V. The frozen pack measured 11.80 V. As I said before, you can charge to full at normal (room) temp and place in freezer without any problem. Don't charge a cold pack to a full 4.2 V/cell and then allow to warm to room temp. That's when you will have a problem!

It's actually quite simple, cold packs gives less voltage and power -warm pack, within operating tolerances, gives more voltage and discharge rate. This is a chemical/physical law. No manufacturer's claim can change this.

Pistol, I agree that data recording is best. However, static measurements are close to (above) continuous discharge rates. The Eagle tree data recorder is great for us geeks that just want to know with absolute precision what is going on. But, this does not explain the enormous failure rate of current technology LiPo's.

I personally think that the manufacturers have pushed the envelope with LiPo's to provide the highest C value possible. This is similar to car batteries versus marine batteries. The marine batteries have much thicker plates and are, as a result, far more damage resistant than the typical thin plate car battery that boasts huge cold cranking amp ability.
05-23-2008 01:06 AM
 
 
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e-Electric Batteries & Chargers > What is currently the best brand/model LiPo battery
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