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Old Mar 29, 2006, 10:24 AM
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Formerly Denver. Now West Bend, WI
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Are my lipos dead or just unbalanced?

I'm having a power system issue with my Blade CP heli. At first I thought my motor was bad and replaced it. The new motor seems to be running very hot too and lacks sufficient power to climb like it used to. I did break in the new motor too.

I am running the recommended pinion and blade combinations and I have never over discharged either of my two TP 1320 3S lipos... I kept a very detailed cycle log for each pack so I am very confindent about my discharge/charge history with each pack. On average I discharge them to approx 11.1v. I never charge them over 12.56 volts. I use a Vision Peak Ultra AC/DC Charger to charge them.

One TP 1320 has 65 cycles on it and the other has 60 cycles on it. I have never used a balancer on them.

When I started to notice the decrease in performance I immediately checked the resting voltage after flight and it was the same as usual... 11.1 volts.
Resting voltage after charge was the same too. 12.41vs.

Seeing that I have replaced my motor I believe the culprit is my lipos. My question is....... Are they dead, or are they just unbalanced?

Should I go out and buy a balancer from my LHS, or should I just buy new packs?

Thanks for any help with this as my fun money budget is very conservative these days.
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Old Mar 29, 2006, 10:31 AM
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Haralson County GA. USA
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Are the TP 1320s ProLites ,as in do they have balancing leads / connectors?

What is the normal flight times and how many mAh does it take to recharge them?

Has the decline been steady? Is it possible that you have became a better heli pilot and you are merely oushing them a little harder than befor?

Have you ever used an in- line watts meter or clamp on amp meter to check max. amp draw?



Charles
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Old Mar 29, 2006, 10:51 AM
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Quote:
Originally Posted by everydayflyer
Are the TP 1320s ProLites ,as in do they have balancing leads / connectors?

What is the normal flight times and how many mAh does it take to recharge them?

Has the decline been steady? Is it possible that you have became a better heli pilot and you are merely oushing them a little harder than befor?

Have you ever used an in- line watts meter or clamp on amp meter to check max. amp draw?
Charles
"Are the TP 1320s ProLites ,as in do they have balancing leads / connectors?"

I believe they are. They do have the balancing leads and a date of 01-09-06 on the label.

"What is the normal flight times and how many mAh does it take to recharge them?"

Normal flight time is 14 minutes. I could fly for 18 minutes max, but I wanted to pamper them so I cut my times short. I'm not sure how many mAH it takes to recharge them. How do I figure that?

"Has the decline been steady? Is it possible that you have became a better heli pilot and you are merely oushing them a little harder than before?"

It started about 15 flight ago and seems to be getting more noticeable. I have gotten much better with my flying skill, but I'm not pushing it any harder than I have in the past.

"Have you ever used an in- line watts meter or clamp on amp meter to check max. amp draw?"

Nope. I was hoping I could trouble shoot the source of the problem without having to buy more "do dads"
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Old Mar 29, 2006, 11:09 AM
Southern Pride
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Well with 14 min. flights you are only averaging approx. 4C discharge rate so amp. load should not be an issue.
Many chargers have a display which shows how many mAhs or Ahs goes into the battery during the charge.

TPs with Balancing leads and connectors are ProLites.


Quote:
Resting voltage after charge was the same too. 12.41vs.
Is on the low side. 12.48-12.54 is more normal with most chargers but they do vary.
Have you noticed this voltage decreasing with time / cycles?
If a LiPoly stsrts to develop a higher internal resistence (IR) the charger (most) will terminate the charge with a resulting lower open / resting voltage.

If your flight ties have deminished by 5-10% then I would say this is normal and is due to cycles and capacity lose.



Charles
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Old Mar 29, 2006, 11:31 AM
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Quote:
Originally Posted by everydayflyer
Is on the low side. 12.48-12.54 is more normal with most chargers but they do vary.
Have you noticed this voltage decreasing with time / cycles?
If a LiPoly stsrts to develop a higher internal resistence (IR) the charger (most) will terminate the charge with a resulting lower open / resting voltage.

If your flight ties have deminished by 5-10% then I would say this is normal and is due to cycles and capacity lose.
Charles
When they peak on my charger is says 12.48-12.53, but after letting them sit for 20 minutes the resting voltage is normally 12.40-12.42. When they were new the resting voltage was the same.

So the "normal" capacity loss is causing my excessive motor heat and loss of power? The power loss is very noticeable. My heli will still hover for 14 minutes, but just barely and the motor is super hot. When I check the resting voltage after a flight the battery still reads 11.09-11.1 like it used to after 14 minute flights. Does this mean that my batteries are working fine and are balanced? If so, the motor must be the culprit then.

This is a new motor, so I guess I could have gotten a lemon. I just thought an unbalanced lipo might cause similiar symptoms to a bad motor.
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Old Mar 29, 2006, 11:36 AM
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Well the LiPoly sound fine and the motor could very well be the problem. Hot is a very broad term and I have no idea what normal would would be with your setup. I do know that to much motor heat will weaken the magnets which will cause the motor to lose power and draw more amps than it should.


Charles
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Old Mar 29, 2006, 11:45 AM
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Quote:
Originally Posted by everydayflyer
Well the LiPoly sound fine and the motor could very well be the problem. Hot is a very broad term and I have no idea what normal would would be with your setup. I do know that to much motor heat will weaken the magnets which will cause the motor to lose power and draw more amps than it should.
Charles
I'll buy a new motor and see if that solves my problems. What are the symptoms of an unbalanced battery then?
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Old Mar 29, 2006, 11:51 AM
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In broad terms decreased performance due to greater than normal capacity lose.

If all cells are balanced at 12.48 open volts all cells are 4.16 volts which is approx. a 96% stae of charge.

If they are out of balance then they could be 4.2 / 4.2 and 4.08. Two at 100% and one at approx. 79%. The low (under voltage) cell reduces the available capacity of the pack.


Charles
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Old Mar 29, 2006, 11:56 AM
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what is the discharge capacity of the pack ?
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Old Mar 29, 2006, 12:05 PM
Southern Pride
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Quote:
Originally Posted by hall woo
what is the discharge capacity of the pack ?
Good question hal but since he has no means to measure how many mAh are going into the pack and really does not want to by electronic do dads , I bet he has no idea.
His resting volts would suggest approx. 1100 mAh used per flight.

Charles
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Old Mar 29, 2006, 12:36 PM
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check the voltage of each cell - either use a digital voltmeter - pretty cheap normally or connect to your charger and it will tell you the voltage if it will do single cells. You may need to make a lead that connect to the balancer lead.

Mike
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Old Mar 29, 2006, 12:49 PM
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there is no other way to verify pack integrity other than to take the TIME to do a diminished capacity discharge test, ONLY WAY
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Old Mar 29, 2006, 01:37 PM
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I take it that the information that I have provided thus far is not sufficient enough to determine if it is my lipos. The motor is new so my initial thought was that it couldn't be the motor, but its possible I got a lemon for a new motor. I intend to buy another motor to test that theory.

Mike Payne,

I plan on buying a digital voltmeter so I can test the voltage of each cell. What is the safest way to connect the dvm? - OR - What should I use to make a lead to connect the dvm to the balance plug?

hall woo,

How do I do a diminished capacity discharge test?
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Old Mar 29, 2006, 02:54 PM
aka Michael In Mukilteo
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Quote:
Originally Posted by LuckyDuc
What are the symptoms of an unbalanced battery then?
Iím going to jump in here if you guys donít mind. Many people donít realize the dangers of an unbalanced LiPo pack and why it can be such a big deal. The safe limits for a three cell battery are 9 volts on discharge and 12.7 volts on charge but this is only true for a perfectly balanced pack. The real limits are 3 volts per cell on discharge and 4.235 volts per cell on charge. If the pack is out of balance the imbalance will quickly snowball and get worse and worse.

On discharge the cell with a low voltage can get below 2.5 volts while under load and then the chemistry starts to die. On charge, the now damaged cell can cause the other cells to go over voltage if the charger is not a balancing type. A cell that is over voltage can burst into flame even if the pack voltage is safe.

So in short: flames bad, balancers good.

Michael in Mukilteo
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Old Mar 29, 2006, 03:09 PM
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Diminished Capacity Discharge Test

can easily be done with the AF 109 after a 1C normal charge @ ~ 1AMP or connect pack to a 1 amp lite bulb load and thru a whattmeter and also a voltage guard for 3S by FMA
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