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A Slight Puffy Lipo and ESC Question: GP Evader JET

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A Slight Puffy Lipo and ESC Question: GP Evader JET

Old 05-19-2015, 06:13 PM
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Electriceddie
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Default A Slight Puffy Lipo and ESC Question: GP Evader JET

Hi Guys,
I am a longtime RC’er with Glow but I am new to electrics. I have a New (but small) GreatPlanes Electric Evader Jet with an 14.volt 2200mAh ElectricFly battery poweringup the motor & the radio. I noticed that the sides of the battery arepuffed out just slightly. Kind of like there was a little air pumped into the oppositesides of the battery. The battery is only about 8 months old and never used inflight and works fine when I run up the motor. I charged it and discharged itmaybe 3 or 4 times it the last month or so and it seems to work fine. In fact Itook the plane out this past weekend for its maiden flight and it flew verywell after I got it trimmed out. I flew it for about 5 or 6 mins and broughther in. I made a trim adjustment and a Throw Rate adjustment and went back upagain. After about 4 mins of flight while running at wide open throttle themotor abruptly pulled back on its own. I raised the throttle and it took offagain and it happened about 45 seconds later. If I am correct this is the electronicspeed controller kicking in and warning me that the battery is getting low? Isthis correct? And is the slight puffiness on the sides of the battery anythingto worry about?
In fact I took the plane out this past weekendfor its maiden flight. It flew very well after I got it trimmed out. However itwas extremely fast and everything happens very fast. It was a Great Thrill. Arefreshing thrill that after 45 years of flying was a nice reminder of how muchfun and how thrilling this Hobby/Sport can really be. It’s easy to see and understandhow that after a number of years of the same old plane, doing the same old repetitivething how it’s easy to get into a rut of flying doing the same old thing. But byjust getting something totally new and different like a fast electric Jet whichwill keep you on your toes can really bring the thrill back…..

Thanks

Ed


Old 05-25-2015, 06:22 PM
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Extreme_RC
 
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Did you store the battery charged during those 8 months? Storing lipos charged will cause them to die, the oxygen inside the cell pouches comes as a byproduct of the lithium plating itself to the anode, usually this happens from overdischarging, running them down too far at high amp draw, and storing them fully charged. The pack could be a year old before you got it too, which will exacerbate these problems once you start using it and if you store it fully charged.

If the motor cuts out likely the LVC is set to hard cutoff, this is good if you are comfortable with it happening, it tells you the pack is low, best thing is to cut throttle, bring the model round and land immediately. I set my ESC's to the highest cutoff setting, 3.2 or 3.3v usually, and hard cut, this way the modern batteries are more protected. Most modern lipo cells will maintain voltage until around 90% discharge, this of course means if your LVC is set too low the cell will be completely drained before hitting LVC, this kills packs very quickly.

Best to fly to a timer, if you got 4 mins set it to 3.5 mins and use it, otherwise you will be replacing batteries more often than you would like!
Old 01-22-2016, 10:49 AM
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BD5wingnut
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Hey Extreme

I know this is an old thread, but. My charger has a Storage setting, about 85% of capacity IIRC. I have a couple of packs that are slightly puffed as described by Ed, they seem to be fine lots of power and reasonable time available. I have been in the hobby for many decades but continue to learn about the newer gear, I have almost given up on Nitro and Gas flight, but still hold onto the stuff just for the halibut. LiPos and brushless gear is a godsend. Man, I remember the old NiCad Brushed motor days, don't have much of that gear since it sucked so much. My biggest disappointment with LiPos, is the short shelf life.

What charge-state do you recommend? It seems 85% is doing good.

Peace, Wolf
Old 01-22-2016, 12:08 PM
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BD5wingnut
I am not sure I recognise a 'short shelf life' with LiPo. With the correct storage charge level (between (about 40%) and storage temperature conditions their 'shelf life' is measured in years.
They do have a relatively limited working life - say 500 cycles under ideal conditions. Their biggest weakness is they are sensitive to how they are charged and discharged. High discharge rates and discharging below 70% capacity are likely to significantly shorten their useful life.
A situation made worse by some questionable manufacturer claims on maximum discharge rates. They avoid mentioning what state the battery might be in if used at the claimed maximum rate!

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