The lipo cell shuffle.

[mistercrash]

This is a post from Helifreak.com. From Finless, a very devoted, important and respected contributor to the heli hobby and to Helifreak forums. Here's what he thinks about the lipo industry. What do you think, is he right? Sure makes sense to me and if true, confirms that no matter what brand you buy or what price you pay, you might end up with crap. Only option is to pay higher to get the big warranty.

''OK so I am going to go into HOW the shuffle happens. This is manufacturing process and someone can correct me if I am wrong.

ALL manufacturing processes are monitored for quality using a bell curve and what is called a standard deviation process. As manufacturing processes get better the standard deviation from the norm gets better. In other words there is still a "bell" curve but the deviation from mean or average gets tighter and the standard deviations get tighter.

So lets look at a cell manufacturer that has a pretty tight standard deviation or "tight" process.

Lets say they make 10,000 CELLS a week and their standard deviation is 1. Pretty damn tight right? A good process with a standard deviation of 1 means for every pack they make 100 are out of spec. Understand thats BOTH sides of the bell curve. So 100 are over achieving from the average and 100 are under achieving out of the 10,000.

Now one might say... HEY I am a pack maker and I want those 100 per week that are the BEST of the crop! OK... all fine and good right? WRONG... a deviation from the norm is just that... NOT a consistent thing that the manufacturing process can deliver with any consistency! If you started a pack company and signed a contract to get the left side of the bell curve YOU would be screwing yourself in the end as that 1 deviation to the left is not a consistent process that can be sustained... It's just a fall out of the process itself!

On the other hand lets look at why what I call the "shuffle" that happens. So in 6 months the cell manufacturer makes 6x10,000 or 60,000 cells. Simple yes? Well their one standard deviation to the right now makes 6x100 or 600 cells that are no good. Over time they build up a stock of these "to the right of the curve" cells and they are not just going to toss them. THEY SHOULD and in the old days the USA or other quality companies would toss them. Unfortunately today THESE over stock cells of inferior quality get HANDED to the pack makers without them knowing it. SHAME!

Now my example above is a "tight" process with a tight standard deviation. You might say. HECK 600 cells in 6 months WHY would that cause pack makers to worry? Well what if the standard deviation was larger? lets say out of the 10,000 cells a week instead to 100 being outside the average 1000 were out of the average? That is only 1 more deviation away from mean! Now in 6 months they have 6,000 cells on the right side of the bell curve they made and are sitting on.

You can see how a pack maker could get screwed by having ONE of those cells in a pack. The cell makers ARE NOT tossing these out... They are mixing them into batches sent to pack makers. And the BAD part is they don't do this in the beginning they do this LATER to DUMP the cells. Thus what I call the "shuffle"!

A new pack maker comes along and calls up a cell maker and says "hey I want to make packs". As the new customer the cell maker sends them "possibly" the "to the left of the bell curve" cells or what are called "ringer" cells to get their business. They say "we are the best". The packer maker agrees after testing and they buy in, and buy cells to make packs. Then all things are going happily along UNTIL the day the cell makers decides for whatever reason to DUMP the "to the right" cells. Maybe they do this to the HIGH volume customer so they don;t notice? Maybe they do it to the low volume customer to LOOSE them so they can get a new customer with a higher demand? Whatever the case... THIS is the shuffle!

An thus the "shuffle" which I think has and will happen again unless the pack makers start and continue to monitor quality coming from the cell makers. It is a fact of life the cell makers are willing to do the "shuffle" to their customers. It's sad really and bad business. But when you only have 4 or 5 cell manufacturers with low competition and high demand, they will DUMP the cells to the right of the bell curve on customers when they can. Why? Because they CAN and ONLY because 99% of the pack makers are not doing quality control!

And thus the pack makers and their BRAND NAME gets hurt in the process and go out of business. YET there are many out there willing to start yet another pack and brand and live this stupid cycle. Again I cant even NAME all the pack makers and brands that have been out and are now gone in the last 5 years. Hell one of my local hobby shops just started THEIR own brand! I warned them about the "shuffle" and got a "deer in the headlights look". Oh well.... here we go again!

Bob''

[Unsullied_Spy]

Sounds believeable. Like a drug dealer giving someone "the good stuff" to get them hooked then giving them the crap once they're addicted to improve profits and get rid of bad stock?

On a side note: There are places like HobbyCity that market and sell the underachiever cells at a much discounted price. I've hooked up some friends with lipos for their airsoft guns for $10ish because they don't need particularly great cells and settled for the underdogs. I really like that, they can get rid of their junk cells and we can get a good price on a lipo. If they put their "AA" cells into a pack and sell it for, say, $50 then "A" cells for $45, and "B" cells for $35 then they can get rid of all their cells while keeping a good reputation and selling a TON of cells. IMO a good company would just toss the bad ones, this scheme would reduce the waste and costs because they can offload more of their product while maintaining a good reputation due to honest product representation and performance. I personally prefer cheap lipos in my planes, they end up being 90+ MPH lawn darts a little more often than I'd prefer and if the crash takes the lipo it might as well be a cheapy!

[TexasSP]

There is probably some validity to this but more info is needed to give conclusions for everyone. It automatically assumes that ALL cell makers act in this way and that none of the pack assemblers test the cells. Way too much assumption with way too little information for me.

As well the bell curve in quality is nothing new and not a bad thing as he implies. It really comes down to what the acceptable specs are and the tolerances allowed in the curve. Also being to the left and right of the middle doesn't mean much unless you have the acceptable tolerance numbers and more testing information.

I respect Bob's (finless) knowledge of heli's but I don't believe that he has enough research and data here to backup his conclusions.

[BrianG]

I agree with the replies here.

Also, statistically speaking, the chances of getting a B cell in an A pack are still pretty slim. Sure, it'll happen, but that's the nature of the hobby - just like getting a new ESC that bursts into flames upon first hookup. Besides, most of the time when there is a bad cell, you only know about it a few cycles down the road. How is a manufacturer going to test a cell? It's not like CPUs where they bin them by how fast they can go and be stable; there's really no easy test for lipos (without cycling them) as long as they aren't crap right off the line. The IR and voltage could be within spec, but some other unknown manufacturing/materials flaw could arise later on.

So, a consumer is left with choices; A) pay premium prices for (hopefully) A cells in A packs assuming the price reflects the quality; B) get a pack from whoever and pay for extra "insurance" (worked into the price of course) if they do get the occasional B cell; or C) get the cheaper packs knowing they may get a bad cell once in a while, but the price is low enough that buying again (or removing/replacing a bad cell) isn't a big deal.

From a reseller standpoint; they have a couple choices as well; A) offer a time-derated replacement program for extra cost; or B) cycle each cells about 10 times before assembly to hopefully weed out the bad cells (or bin them as B cells). Option B might only be worth it to hard-core racers due to the extra time/cost - not to mention each cycle just shortens a cells life by that many cycles.

[_paralyzed_]

^ it's funny that BrianG said "bin the b cells" as "bin" is across the sea lingo and he has picked it up as his own! Not really funny, but interesting as the internet brings distant cultures together. Just a sign of our time I suppose.

Anyhoo, regardless of factual statistics I believe the basic premise of finless' statement.

I will continue to buy hobbyking packs. (zippy, turnigy, etc.) I have had several packs from them with a bad cell, but the price is low enough to just buy more packs.

[BrianG]

Actually, when I used the term bin, I was referring to a process where CPU makers put the processors in bins based on their maximum stable speeds even though they are from the same silicon. Or, if demand for X processor is really high, they label Y processors as X even though the Y's actually are faster chips.

[_paralyzed_]

Originally Posted by BrianG

Actually, when I used the term bin, I was referring to a process where CPU makers put the processors in bins based on their maximum stable speeds even though they are from the same silicon. Or, if demand for X processor is really high, they label Y processors as X even though the Y's actually are faster chips.

D'oh I thought I knew something.

[BrianG]

Don't feel bad, I'm sure you know something...

[_paralyzed_]

Originally Posted by BrianG

Don't feel bad, I'm sure you know something...

Ha! I know a couple things about an e-maxx

[whitrzac]

Can someone link to the original post please?