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Old 06-01-2007, 01:55 AM   #1
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Default Matched Li-po's?

ok lipo are gaining popularity quickly and we all know how much difference matched nimh cells make so wouldnt lipo be the same?
raises the question when will we start seeing matched lipo packs?
is it possible? how long till it happens?
cheers, josh P
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Old 06-01-2007, 03:08 AM   #2
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Quote:
Originally Posted by aus jd 2703
ok lipo are gaining popularity quickly and we all know how much difference matched nimh cells make so wouldnt lipo be the same?
raises the question when will we start seeing matched lipo packs?
is it possible? how long till it happens?
cheers, josh P
All li-po packs better have matched cells or you will see them swell up....this is why li-pos will end battery wars with bigger capacity packs that are all matched. This is why balancing is so important to keep them matched.
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Old 06-01-2007, 05:07 AM   #3
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(Originally posted by Mr. Black on lipo legalization thread)

Here is some insight:

#1 - ALL LiPo batteries are matched they have to be or they will not perform and quickly fail. Balancing does the same as matching since all LiPo's top out at 4.2v per cell. if you where to create a LiPo pack with un matched cells the pack would quickly fail this is also why you are not supposed to use cells of different lifespan as one older cell may be aged to the point where the cells will not stay matched.

#2 - Lipo batteries do come in different grades and the difference does not make them faster or slower is simply makes them safer or last longer even the cheapest Lipo will top out at 8.4V and be listed niminal 7.4V We choose what we feel is the highest level of LiPo cell in the world Kokam SLPB. Lower grade batteries will have less cycles and be more prone to going out of blance wich will further lesson their cycle life.


#3 - The advantage going forward will not be more voltage but higher C-rating, higher capcities and smaller price and size.
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Old 06-01-2007, 06:45 PM   #4
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Lipos don't "top out" at 4.2 volts, the duty of the charger to not go above 4.2 volts per cell. BIG difference. If the charger goes above 4.2 v/c, damage to the cells occurs. Hook up a lipo to a NiMh charger and see what happens. It'll go way past 4.2 per cell.

Even the Orion/Kokam info brochure that's on the Orion website is bragging about a single lipo cell that's being charged at 18 volts is not on fire like the other guys. How did it get to 18 volts if lipos "top out" at 4.2? Heck, the display in that picture is only showing 75 milliamps of current. 0.075 amps. Next to nothing. It is quite impressive that the cell isn't on fire. I'll give 'em that. Good job guys. However, I find it interesting they show a volt/time/temp/current graph of the competitors cell during this test, and not their own. And the graph shows the voltage going up, up and away.....So much for "topping out".


If the companies were "matching" anything other than IR, the companies would brag about it because it would add significant cost to the manufacturing process. And they would tout how superior there were by doing it. Nobody does anything without some sort of return on investment. Nobody.

Taking an IR reading takes seconds and the equipment is "off the shelf", a true "match" like what goes on with the race NiMh batteries we all know and love takes hours and hours and requires specialized/custom equipment. Time is money.

I want to see a white paper on how lipos are "matched" by anything other than IR. I'm more than willing to read it.

See the Eagle Picher on the front of the Kokam brochure? I used to work for that company designing/building batteries for aerospace applications. So now I'm forever cursed with a particulary sensitive BS meter when it comes to batteries.....

Here's a link to the brochure......
http://press.team-orion.com/press/av...am_quality.pdf



I have to disagree that "balancing does the same as matching". Not really, but it sounds good from a marketing standpoint, and it's way cheaper than real matching....... Balancing simply keeps the cells closer to the same state of charge. Remember the 4.2 volts per cell charger requirement? The charger (without balancer) is set for a multiple of 4.2 volts. A 2 cell in series pack would be charged to a max of 8.4 volts. Without a balancer, one cell could be 4.4 volts and the other could be at 4.0 volts. Still adds up to 8.4 so the charger doesn't know anything is wrong, yet one cell would probably be swelled, and the other wouldn't be anywhere near charged.

If the cells were truely and perfectly "matched", there would be no need for balancers because all the cells in the pack would be discharging/charging exactly the same. Maybe the manufacturing processes used today are really good.

And my experience with the small RC airplane Lipo's is that they rarely need balancing (does that really mean they are matched? Not really). If treated properly. I don't hammer the snot out of them like the heli guys and some of the airplane guys do.


And back to the original poster's question...........I'm guessing less than 1 year until we see matched by runtime lipos. We'll see. The equipment should actually be less expensive than with Nickel batteries due to the far simpler charge regime (no delta peak sensing). We'll all see in due time. Should be interesting.

Sorry for hogging so much bandwidth......
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Old 06-01-2007, 08:06 PM   #5
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Eventually, somebody will start marketing "labeled" Lipo's listing their runtime, average discharge curve, resistance, etc, etc. Guys like Mr. Black, Craps, and Wild Cherry are being optimistic when they tell you otherwise. Its always up to the consumer to determine wether a few seconds of runtime, a few millivolts of voltage or a little less resistance is worth a few more bucks. Its all about how one battery pack compares to another battery pack, not how the individual cells in a pack compare to each other. Its a marketing term called "perceived value".
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Old 06-01-2007, 08:32 PM   #6
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ITs early but once we all accept and race them.... All the sticker lables and matching will start.... (im not knocking lipo im just relistic i know that once everyone is running them no one will settle with a single pack running it for a year or more) All the competativness we see now in nihm will ocure with lipo in time... ITs racing after all
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Old 06-01-2007, 08:55 PM   #7
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In most classes the issue isn't what is better, but what is good enough. They are going to have a hard time saling something that people don't need to spend the extra money on.
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Old 06-01-2007, 09:56 PM   #8
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Quote:
Originally Posted by party_wagon
In most classes the issue isn't what is better, but what is good enough. They are going to have a hard time saling something that people don't need to spend the extra money on.
Don't you have a hard time saying that with a straight face?
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Old 06-02-2007, 12:47 AM   #9
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Quote:
Originally Posted by party_wagon
In most classes the issue isn't what is better, but what is good enough. They are going to have a hard time saling something that people don't need to spend the extra money on.

I agree with Turbo

Ok a good Nimh label reads 1.24 voltz

a bargin pack that matchers cell as practice packs are 1.22 voltz

a differance of less than 2%

Lots of Racers pay DOUBLE for that 2%

Now you're telling me that lipo's wont have a differance of 2% between packs? I for one like Lipo's and would hope they bring with them longer races, but I'm no naive enough to belive that every Lipo pack is gonna be exactly equal. Some one will find a way to weed out the "good" ones and charge you more $ for them, and guess what when some one beats you with one of these weeded out "good" packs of Lipo's you're gonna go out and buy them too.

Just my $.02,
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