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New Lipo battery problem

Old 02-16-2010, 12:00 AM
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Lightning Fan
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Default New Lipo battery problem

Anyone had a new lipo not take a full charge? I have a 350 mAh Flitepower battery that is giving me only around 100 mAh.
Thanks guys!
Old 02-16-2010, 01:44 AM
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jdetray
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Default RE: New Lipo battery problem

How may cells is the pack, and what is the voltage of the pack after charging?

A fully charged lipo pack should measure 4.2V per cell. That's 8.4V for a 2-cell pack and 12.6V for a 3-cell pack. If your pack is much less than 4.2V per cell, then for whatever reason, your battery is not being fully charged.

- Jeff
Old 02-16-2010, 09:08 AM
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jzrf6c
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Default RE: New Lipo battery problem

Try cycling the battery. Discharge then charge. Also, remember, if this is a new battery you just received it is partially charged. So, it may not take but 100 mah to "Top-it-off".
Old 02-16-2010, 12:10 PM
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jdetray
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Default RE: New Lipo battery problem

In general, lipos do not need to be cycled. If you do it, be careful not to damage the battery. If you discharge a lipo too far (below approximately 3V per cell) you will permanently damage the pack.

Like jzrf6c said, if this was a brand new lipo, it would have been partially charged when you bought it.

You can know for sure if you simply measure the voltage. If it is 4.2V per cell, it is fully charged.

- Jeff
Old 02-16-2010, 03:12 PM
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ceejay007
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Default RE: New Lipo battery problem


ORIGINAL: jdetray

In general, lipos do not need to be cycled. If you do it, be careful not to damage the battery. If you discharge a lipo too far (below approximately 3V per cell) you will permanently damage the pack.

Like jzrf6c said, if this was a brand new lipo, it would have been partially charged when you bought it.

You can know for sure if you simply measure the voltage. If it is 4.2V per cell, it is fully charged.

- Jeff
3V/cell is inviting disaster. LiPo batteries are generally void of any useful charge at 3.6V/cell. To promote battery longivity, most use the 80%
discharge rule which is about 3.75V per cell.

Old 02-16-2010, 09:04 PM
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Matt Kirsch
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Default RE: New Lipo battery problem

More importantly, how are you determining that you're only getting 100mAh?

There are quite a few reasons why you'll see what you're seeing...

If you are flying to LVC, and then the charger is only putting in 100mAh, your battery is too small for the load being placed on it.

The battery is not really discharging. Its voltage is dropping due to the excessive load being placed on it by the motor/prop combination.
Old 02-16-2010, 11:40 PM
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Default RE: New Lipo battery problem

Well, let me start by making an apology for my stupid question. I thought I had supplied more info in another post.
Also, the issue is fixed, so if you want to move on, forget this.

The ESC is a XP-12A, motor is unknown make from Truerc.com, 100W and 1000 kV. Battery is Flightpower 350 mAh, 3S, 25C. The battery has been flown 10 times with only 2 min flight times from the start. Max current draw is 6A in the plane, with most flying at 4 A or less.
Using eFlite wattmeter, and test setup is set throttle to 3.0 amps and record.
The battery continues to only put out around 100 mAh after a full charge. I tried it on a Celectra Pro and a Hobbico Quick Field charger with inline balancer - same results.
Today I received two new batteries from HK in the mail, 350 mAh, 3S, 30C. Same test setup with the new battery, and I shutdown at 350 mAh with 10.7 V showing.

Obviously there is a dead cell in the Flitepower battery, and always has been. I got it from Tower, so back she goes. No swelling in the battery, although the middle seam looks a little wrinkled.

Sorry for the trouble, and thanks for the quick responses.

Regards to all.
Old 02-20-2010, 06:40 AM
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Default RE: New Lipo battery problem

Matt or anyone else I have a question about Lipos connected in series. I connected (2) 7.4v 2200 mah batteries in series with an EC3 series harness and get 514 wp with 34.04 ap on the voltmeter and I think it will be just enough power for the large super cub which weighs between 7-8# but would like to get closer to 100 watts a pound so I tried a 11.1v 2200mah + (1) 7.4 v 2200mah battery which I thought would give me 18.5v. When I tested it I had a drop in power to 386wp and 28.11 ap. They were both fully charged but the 11.1v battery is an older battery do you think this is the problem or did I do something wrong. Thanks Terry
Old 02-20-2010, 10:18 AM
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Default RE: New Lipo battery problem

Responding to Terry....

I'll give this a shot. Hopefully I'm not boring you with stuff you know.
Let's assume that the motor was propped in the two different setups so that you got constant watts out of each one. Since the higher voltage setup will lead to a higher RPM, you would need to reduce pitch or diameter or both to achieve this condition.
OK, so this would mean that Watts(Low Volt setup, 514W) = Watts(High Volt setup,386W), or 14.8v * 34 amps = 18.5V * X amps. Solving for X we get 27.2 amps. You say you get 28.1 A, on this 18.5V setup, which gives 18.5V * 28.1 A = 519.8W. But you also say your measured watts is only 386W. 386 does not equal 519, so even if you left the same prop on the two setups ... something is wrong.
Since you measured watts and amps in the high volt setup, we should be able to calculate battery voltage with some confidence, 386W / 28.1 A = 13.7V. Whew! That is a long way from 18.5v! 18.5 - 13.7 = 4.7v ... how old did you say that 11.1v battery is?

I would recommend putting a voltmeter on the battery side with the system loaded, and see what voltages you are getting out of each battery. Or, put a whatmeter in series with the battery, and record voltage, current, watts. If the watts and amps indications you provided for the high volt system are correct, then the voltage should be much lower than your nominal 18.5v. W = V * A.
Old 02-20-2010, 10:58 AM
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Default RE: New Lipo battery problem

Thanks for your detailed and carefully thought out answer albeit a little over my head but if I understand you correctly it may be the older 11.1v battery which is probably close to 2 years old with unknown number of flight time. I will check it alone on the watt meter. I forgot to mention that it showed 20.18v in the right upper corner of the meter with the 11.1v and 7.4v connected in series and 16.31v with the (2) 7.4v batteries connected if that helps. I borrowed the meter from a friend and obviously don't know that much about batteries -spent all my life learning medicine. Thanks again I'll get back with you later with more results. I've got a 5s Turnigy battery coming on a slow boat from China which I plan to use as well. Terry
Old 02-20-2010, 01:44 PM
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Default RE: New Lipo battery problem

Problem solved. I feel stupid for not trying that in the begining. I checked the individual voltage on the old 11.1 3s and was shocked to find that it would barely trun the Power 46 motor over. The was only 70.5wp and 7.57ap which explains what happened. Just for fun I put a 2800 mah 11.1v on it. It produced 176wp with 17.3ap and a 5000 mah 11.1v produced 257wp/21.80ap. I rechecked the 2-7.4v batteries and got 528 wp so probably just need an a new 11.1 with the same capacity to hook in series. thanks Terry
Old 02-20-2010, 02:25 PM
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Default RE: New Lipo battery problem

Well, sir, I'll say this. I am an electrical engineer (socially challenged by profession) at a company that designs and builds MRI scanners, and this affords me the opportunity to interact frequently with those in the medical profession. I've seen what you go through to get trained up, and I respect it. Engineers have trouble understanding what radiologists need, and radiologists have trouble understanding what engineers can do. If my post was not clear ... it is my fault ... it has happened before.
If I may, I'll take another try.

The principle thng we have to consider is the equation for power in an electrical system, which is Watts = Volts * Amps. We are doing direct current here, not like the current in your house, so it is easier to do the math. No matter what else is going on, that equation up there holds true. In wattmeters, all that happens is the device measures voltage, and current (amps), multiplies those values together to get watts.

If your wattmeter says 10 volts, and 1 amp, then it MUST report 10 Watts. If it doesn't, it is broken.
One might want to wonder if the esc, or motor/prop, both of which have some adjustments, could be involved in this problem. The answer is no, because you are measuring the output of the battery, which is not effected by the load (esc and motor), other than the fact that the load eats power. Theory, done.

OK, so you said that with the 2S and 3S batteries in series, you got:
"When I tested it I had a drop in power to 386wp and 28.11 ap" (first post)
and
"it showed 20.18v in the right upper corner of the meter with the 11.1v and 7.4v connected in series" (second post)

So, the math says, V * A = W, or 20.18V * 28.11A = 567 W (calculated)
But ... this cannot be, because the meter reported only 386 W.

Our options now are:
1. Your meter is broken (unlikely)
I did the math on the 2 2S battery info you gave which was V =16.3, A = 34, so calculated Watts are 554 W, which matches closely with your reported watts from the meter of 514 W. From this test, the meter looks good.
2. Your measurements are wrong (only option that is left).

What may be happening here is that the 20.18 Volts you are seeing, is when the motor is not turning. Bad cells will show great voltages when there is no load on them ... when they are not driving anything. I'll bet that if you take the measurements again, and record watts, current and voltage with the motor loaded (running), you do not see 20.18 volts. I'll bet you see 14 volts.

There is a possibility that the "lost volts" are in a connector somewhere, but based on the 2 7.4 battery test you ran, that is not likely in my opinion.
Is the 3S 2100 battery a little swollen? Can you push on the plastic on the top and have it give, like a balloon does? Are there any marks on the battery from crashes or being dropped?
Can you try the 3S battery in a plane that uses just the 3S, and measure that with the wattmeter? If you don't see 11 volts, or so, under load ... you have the culprit.

Regards,
Rikk

Old 02-20-2010, 02:30 PM
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Default RE: New Lipo battery problem

Posts are out of order just saw you found it! Great! Good luck!
Old 02-20-2010, 03:34 PM
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Default RE: New Lipo battery problem

Thanks again you have been a great help and it is nice to know someone I can turn to when I need help. You said that you were an Electrical Engineer for a company that builds MRI scanners. I happen to be a retired Physcian Assistant with 35 years in the field of Internal Medicine and I now work monitoring Cardionuclear Stress Tests so I am very familiar with the complicated work you do. Ionly have to work about 6-8 hrs a day now. Had to go back to work to support this hobby. I'll probably have more questions later as I try to build bigger and bigger electric powered planes. Seems my eyesight is not as good as it should be so they need to be bigger. Terry
ps If you got any medical questions let me know[8D]

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