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Old 03-14-2007, 04:15 PM   #1
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Default LiPo Awareness

As more racers discover the benefits and convenience of using LiPo batteries in R/C cars, clubs and other racing venues find themselves under further pressure from their racers to allow these batteries in races. LiPo batteries raise concerns about safety, and unfortunately, there's a lot of misinformation being passed around about these batteries, which often causes them to be dismissed as "too dangerous." This is clearly not the case, as these batteries are used in everything from cell phones to laptop computers to toothbrushes.

My hope with this thread is to create awareness about LiPo batteries, and clear up many of the common misconceptions about their safety. Ideally, this could become a resource for track owners that are considering whether or not to allow the use these batteries as well as racers that have concerns about them.

To get things started, I'm going to repost some information provided by R/C Tech member "linger" a few days ago. He is what you may consider an industry expert, and has a lot insight on the topic.

IF YOU READ NOTHING ELSE IN THIS THREAD, PLEASE AT LEAST READ THE NEXT POST SO THAT YOU MAY BETTER UNDERSTAND LIPO BATTERY SAFETY.
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Old 03-14-2007, 04:15 PM   #2
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HARD CASES ARE GOOD FOR LIPOS!
The internal construction of the high discharge type lipo that we use in RC cars/planes are essentially a bunch of little lipo batteries stacked together in parallel. These batteries are constructed with layers of copper graphite coated anodes and aluminum metal oxide coated cathodes and they are separated by a very THIN polyethylene film. Itís extremely important that the seperator maintains integrity or some of the cathode/anode layers will short out. A LiPo cell is MOST vulnerable at the edges where the seperator is not continuous. A dent on the side of a Lipo may move the seperator and cause an internal short. Sometimes the short burns off a little material, creates a little gas, and you have a puffy cell with less capacity. Othertimes, the short can melt enough of the seperator which causes shorts in other areas of the cell and the chain reaction causes a flame situation. A hard case prevents dents, which prevents internal shorting, which prevents a dangerous situation.

I canít make general statements covering all Lipo distributers, since itís usually impossible to find out exactly where each distributor gets all their cells (sometimes from multiple sources and judging from MaxAmps pricing, they get most of their cells from China), but I can share some insight over the price difference:

ďWhatís the difference between an expensive Lipo from a top tier manufacturer and an ďinexpensiveĒ Lipo (usually from China)Ē

Iíll address three areas: Quality, Performance and Safety

QUALITY CONTROL
Quality control is a joke in most China factories. Incoming material inspection, statistical process control, in-process measurements, Hi-Pot testing, six sigma etc are completely foreign concepts. In a lipo cell, the main source of failure is from internal shorts. In most cases, an internal short burns off a little material, creates a little gas, and you have a puffy cell with less capacity. Othertimes, the short can melt enough of the separator which causes shorts in other areas of the cell and the chain reaction causes a flame situation. These shorts may be prevented in manufacturing with good control over contaminants and manufacturing burrs. All the top tier manufacturers will have automated Hi-Pot testing where a large voltage is applied (200-300 volts) before the electrolyte is applied and the resultant current is measured - high current means that something is shorted out. The China factories donít do this. The top tier factories will have specialized equipment to transfer material without exposing it to the environment thus reducing contaminants. The China factories literally use cooking pots and scoop them out manually. I could write a whole book about what the China manufacturers do wrong with respect to quality control, like how they measure coating thickness on a moving roll with a micrometer!!!, but I wonít bore you guys with that.

When asked about their failure rate after manufacturing Ė the China sales rep was proud to say that 0.3% of their cells swell up just sitting on a rack after manufacturing due to internal shorting Ė who knows how many cells are close to shorting out internally. Out of only 1 million cells Ė thatís 3000 failures. I asked a top tier manufacturer the same question Ė they produce 4 million cells a month Ė in 1 year, or 48 million cells later Ė they had a total of 0 cells swell up by themselves after manufacturing. 3000 cells out of 1 mil failure or 0 cells out of 48 million cells failure Ė thatís what you are paying for.

PERFORMANCE
Current Rating Ė Most of the top tier manufacturers are fairly close to their published current rating. I find that most all the manufacturers are a little optimistic in their C-rating. Some of the China cells do live up to their C-rating, but Iíve tested some 20C rated cells from China that are virtually destroyed at a modest 10C discharge rate. Basically, there is no guarantee that a 20C cell from China can really do 20C. Some of the cells from China actually can do 20C and they hold a higher voltage than the top tier manufacturers - due to more volatile cathode chemistry, but at the expense of safety (see the safety section).

Cycle Life Ė the cycle life of the top tier manufacturers is stunning. Iíve tested many cells that perform just as good on their 400th cycle as they did their first. For whatever reason Ė every China cell has a degrading profile, where the capacity drops slightly every cycle. The rate of degradation varies depending on manufacturer. Some donít last 100 cycles, while others are about 80% capacity at 300 cycles. The bottom line is that the cycle life is virtually guaranteed with a top tier manufacturer and itís a crapshoot when you buy a cheap cell.

SAFETY
The first step in safety is a top quality cell construction (see quality control). The elimination of contaminants and internal shorts is good prevention. Iíve tested enough cells to know that there is not a single Lipo cell on the market that can take an extreme overcharge condition without going up in flames. The distributors that show a little video about how the cells ďcanítĒ be ignited through overcharging are sending the wrong message. Give the cell to me, I guarantee you that I can ignite it (except for the A123 Li-Ion cell). The next step in safety is the cell design itself. Most of the China cells use pure LiCo2 coating on the cathode which is the most volatile and also the most powerful molecule. That way, they have a great looking discharge curve for the first few cycles. Most of the top tier cells will have other additives that greatly reduce the volatility and also suppresses voltage slightly. This means that the cell can take a higher temperature before it reaches thermal runaway, and even if it does reach thermal runaway, the resultant flame is much less. Iíve purposely overcharged and ignited China Lipoís and all of them turn into immense flamethrowers that burn for about 30 seconds. When I purposely ignited a Kokam cell, itís chemistry self extinguished in about 2 seconds Ė the flame was an order of magnitude less than itís China counterpart. Furthermore, the Kokam cells use the negative tab as a built in overcurrent fuse. If you short out the cell, the negative tab vaporizes and creates an open circuit.

I have yet to visit a ďtop tierĒ manufacturer in China, though I admit, I havenít visited all of them, but Iíve visited enough to understand their pardigm. However, these Chinese factories are evolving at an accelerated pace. These low quality factories may equal the quality of top tier manufacturers in just a few years, but they definitely arenít there yet. Just about every China factory I visited was in the process of building another newer, better factory. Iíve referenced Kokam as a top tier lipo manufacturer. There definitely are more top tier lipo manufacturers and some even have superior manufacturing quality vs Kokam, but their pricing is the same as Kokam Ė which is nearly 4x more than their equivalent China counterpart. The top tier manufacturers admit that the RC market rates price over quality and itís obvious that the low price lipos are now dominating the RC marketplace. The good news is that some of these top tier lipo manufacturers are currently teaming up with top tier RC manufacturers to come out with high quality and high performance packs though I guarantee you that they wonít be able to touch MaxAmps pricing.

So there you have it. Other than the hard case Ė this is why the Peak/Team Orion Lipo is so much more expensive than their competitors.

Information provided by linger.
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Old 03-14-2007, 04:48 PM   #3
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I have used (and abused via racing) the Orion cells and havent had a single issue. Ive seen someone drag an Orion cell around and didnt have issues. I would be interested in knowing if ANYONE has had an issue with an Orion cell?

The Kokam site shows them both overcharging and puncturing the cells with a nail without fire. Obviously the cell is ruined but no carnage.
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Old 03-14-2007, 05:10 PM   #4
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Good stuff - informative! I've been in the lipo business since before there were R/C lipos, and I learned a lot from this.

It's unfortunate that it is very rare to see a vendor with a spine willing to tell what happens behind the advertisements.

-Adam
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Old 03-14-2007, 06:38 PM   #5
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This post is going to be great. My local track owner is looking to start alowing LiPo into some of our racing programs. He doesn't know much about them and has asked me to be the go-to guy in helping inform and help people that would like to run them or just want to know more. I'm starting by being the first guy to run them. I will lead people to this thread.
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Old 03-14-2007, 06:59 PM   #6
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Ive been running an Orion LiPo in my sedans for nearly a year and have not had a single issue. In fact I left my Orion 4800 plugged into the esc on accident once for about 2 weeks with the esc on. The voltage dropped to something around 4 volts (the standard on a safe voltage cut-off for this battery is 6.0-6.6 volts.) I went to run it and realized something was wrong when the car wouldn't even run. At first I was a little scared as I knew LiPos didn't like being over-discharged. But It wasn't swollen or hot and elicited no signs of damage, so I decided to charge it. At first my Ice wouldn't charge it as the voltage was too low. So I let it sit for about 30 minutes to self charge and tried it again. The voltage was up in the 5 volt range and the ice began charging it like normal. I'll tell you I watched it like a hawk for a good hour just in case. In the end it charged just like normal. That was over 3 months ago and I have not had any problems with it since. LiPo is all good as long as you go with quality cells.
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Old 03-14-2007, 07:40 PM   #7
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Awesome info syndr0me, Thanks
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Old 03-14-2007, 09:14 PM   #8
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The club I race at (fastlanehobby.com) has allowed LiPo (Orion only) in mixed racing for, I guess nearly a year now. I'd say more than 50% of the racers are using LiPo now, and we haven't had a single incident. We also haven't noticed any particular advantage (or disadvantage) on the track when weight rules are enforced.

In that time, we've seen NiMH explode, ESCs catch fire, and power supplies short out. No trouble with LiPo, just lots of happy faces. There's been plenty of hard crashes during that time, and not a single damaged LiPo. Nobody has replaced a pack yet either, and they're performing very much the same as a brand new pack.
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Old 03-14-2007, 10:25 PM   #9
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i would like to see lipo in 1/12
30min mains oh ya.
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Old 03-14-2007, 10:55 PM   #10
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aside from orion/kokam any other top tier manufacturers?
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Old 03-15-2007, 12:06 AM   #11
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highway, yes, but they don't offer hardcases. The only other brand with good cells in a hardcase is Duralite, specifically the 'trakpower' pack.
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Old 03-15-2007, 12:17 AM   #12
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highwayman: built up the arsenal yet?

kokam has new cells to be released in the coming months

KOKAM H5 SERIES LIPO
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Old 03-15-2007, 01:46 AM   #13
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LIPO IS SOOOOOOO DANGEROUS AND VERRRRYYYYYY BAAAAAAADDDD!!!

A Lipo battery is basically a weapon of mass destruction!!

Stay with the good ol' NiMH!!

Sincerely,
You local battery matcher
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Old 03-15-2007, 05:13 AM   #14
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very informative syndrome

I had an old 3300 almost explode on my this week, forgot the temp sensor and cell expanded enough to cause concern for me, I'm lucky but that pack has now gone to a better place
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Old 03-15-2007, 05:54 AM   #15
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I'm really pushing to have an "approved LiPos ONLY" policy. I really want this to take off and don't want some idiot to ruin it for everybody. I'll start running mine here when I get the type R and when the weather breaks and we're off road.
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