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Weak New Lipo??

Old 03-25-2010, 02:41 AM
  #1  
HeliScRapYard
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Default Weak New Lipo??

I Picked up some off brand BQY "chinese" Lipos planning to use them in my PKZ ME-109. Charged on up and tried it out. on the first Run the Battery did not maintain voltage under load. Dropped quickly. will this get better after a few cycles? The battery weakened and was warm after only a min of running.
The Motor i am running is a 3536-10 From HURC, 40A esc and the BQY 2200mAh 20C pack.. (Should be able to supply approx 44A constant right?) Tested on the wattmeter and this setup pulls 30-31A with the stock prop. These are what i've got http://cgi.ebay.com/2x-11-1v-2200mAh...item2a03c6e071

Look Forward to any Help or Suggestions.
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Old 03-25-2010, 03:31 PM
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cliffh
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I've never read anything about lipos getting better after a few cycles. I have read that you should not approach max power with them for a few cycles.

That said, anything can be defective. Many manufacturers tend to "overstate" the rating of their products.

My experience with lipos (over 55 of them) is this. If you are going to be pulling close to 70% or so of the max amperage, move up a notch on the C rating chart. For your use, I would have purchased a 30, 35, or 40 C rating pack.

The only lipo packs that I have ever been disapointed with are all 20 C packs. Some of my 20 packs have been pretty good though, but I never use them at over 70% of their C rating.

Noting technical here, your results may vary.....just my experience.

Cliff
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Old 03-25-2010, 04:00 PM
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flydiver
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Any pack can be defective. You said 'some' packs. Do they all do it? If so, you likely got junk lipos. One of the problems with eBay is that is often the repository of the detritus even the super cheap sites won't sell.
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Old 03-25-2010, 04:15 PM
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philipa_240sx
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I always de-rate the C rating on 'no-name' generic lipo's. Most of my packs are only pushed to about 10-12C so they fall well below the mfg's supposed rating of 20C.

Every time I pushed too hard, I either loose performance or the life expectancy of the pack is severely shortened. The mfg's specs are very optimistic on some of these. If you are going to push the limits, buy higher quality batts with a C rating much higher than you intend on using.
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Old 03-25-2010, 05:43 PM
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i bought 2 and have only tried one so far. Hopefully one is just a fluke
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Old 03-25-2010, 09:31 PM
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it looks like this is a bad time to be in need of lipos from HobbyCity All their stock is sold out.
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Old 03-25-2010, 11:17 PM
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flydiver
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http://www.valuehobby.com/ Stateside, quick, good lipos.
http://www.okhobby.hk/ Hong Kong, good lipos, relatively fast shipping
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Old 03-25-2010, 11:43 PM
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I Know Where my next lipos will be from Those sites look good. and affordable. ThAnks!
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Old 04-10-2010, 02:22 AM
  #9  
pattern14
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Hey HeliScrapyard- bought 4 of those crap bqy batteries off ebay. Only one actually works. Sent some money for postage for a replacement one which never arrived-still waiting. Thought it must have been just bad luck, but the next two batteries were junk also. the vendor sent another one free of charge, but it was also a p.o.s. Wrote to them and said not to bother replacing any more, as they were of such poor quality. They lost power from new, 3 of them would not even accept a charge. I ended up, just yesterday, charging one without a balancer just to use in a crash test dummy. Built a combat plane out of scrap foam and bits of leftovers just to test a new desigh "crash proof " battery compartment. nose dived it at top speed into the ground from about 200 metres up. Was not prepared to use a quality battery for the experiment, and I could not think of a more fitting end. Would you believe my new design worked? The wretched battery actually survived the impact ( it was a pusher motor, and the esc and rx were mounted deep in the eppfuse, at the tail). Best use for those bqy things was to cut the leads off for something else. I now have the hassle of responsibly disposing of them......
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Old 04-10-2010, 02:46 AM
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Airhead
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I don't have all that many Lipos but I have not experienced the situation that you have had. I have bought a couple from Heads up RC. They have worked fine for me and a couple from common Sense rc too. also they worked very well. Just my 2 cents from someone who is electronically challenged. ( can't spell all that well either:o)
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Old 04-10-2010, 02:59 AM
  #11  
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have decided to just purchase my batteries from hobbyking. i've had some of the turnigy and rhinos. and have been pleased. they just cost a bit more than i have to have them shipped over here, lol. they're cheap until you add shipping.

P.S. pattern, just dig a hole, big hole, and demonstrate to newbies what happens when lipos get damaged and go into flames. lol.
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Old 04-10-2010, 01:42 PM
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I cannot stand the frustration of sub-standard lipos. Going to the field to fly only to discover your lipos are not delivering the performance is never fun!

I've used CSRC, Kokam, Tanic, GP Electrifly, Zippy Flightmax, and LiPower Lites.

The Electrifly and Kokam's were pretty used and barely lasted 30 flights. The Tanic died shortly thereafter... admittedly I was pushing it a bit... about 15C and I think the pack was rated at 10C.

The CSRC lipos were good till recently. I have a 3S 1250 pack that is 5 mos. old and my Hyperion charger is telling me one cell is reading high voltage... about 4.25V. The rest are at 4.18-4.20. The battery also seems to lack some discharge duration... I'm getting shorter flight times than an identical pack that has about 70+ cycles on it.

The Flightmax have been surprisingly good lipos. I only have a few small 350mAh 2S and I run them at 10-15C rates. They easily hold their rated capacity and have remained strong after 30+ flights.

Lipower Lites are a generic brand sold by ZebraHobby in Canada. Supposedly they are ThunderPower cells. I have 3 350mAh cells and they have been very good albeit the form factor is not the greatest (2 cells side by side for a thin but wide pack).

I've just ordered up some Hyperion G3 160mAh 1S cells for the PZ UM J-3 Cub. We'll see how those fare.
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