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Old 09-17-2006, 10:44 AM   #1
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Default Why Buy Matched Cells?

Nowadays theres a lot of emphasis on charging and discharging equipment that does cells individually in a pack. The idea is that charging and discharging individually tailors to each individual cells characteristics. So given that, what is the point in putting together matched cells?

Aside from that most of the cells coming from today's factories are being produced to a more tighter tolerance such that the variance from one cell to another is very minimal. Yes, this could be debated but manufacturing technology for batteries has much improved since the early days of Sanyo 1200s.

Will such technology(ie Spintec ICC, Much-More, etc) eventually put the "matcher" out of business?

Please share your comments constructively.
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Old 09-17-2006, 11:56 AM   #2
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Actually the cells have more power than ever but the actual consistency within a case of cells isn't that good. We see a 40 second spread at 35amps. The voltage and IR is more consistent but there are some low voltage and higher IR cells within a case.

The price of loose unmatched and zapped cells is lower than matched packs but not much lower. You can get mid level packs from every matcher at a real good price and they are matched.
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Old 09-17-2006, 02:47 PM   #3
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You need to come match a few cases of cells......you will see how big the spread in voltage and runtime is.....

You will also to get to see the occasional cell that is so bad, its not even funny.....


Matched cells allow your pack to discharge during the run at the same levels.....give you the same feel from start to finish....no random drops you would see from unmatched cells.

All the new equipment does is allow you to maintain your batteries to keep them as close to the labels as possible.....and charged to optimal levels. No charger out there is going to turn a bad or medicore cell into a great one......the charger can only get it to its peak level.....if thats 426 seconds.....than thats what you will get, which won't give you optimal performance if the rest of the pack has 440 cells....

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Old 09-17-2006, 06:49 PM   #4
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With the batteries we have now a days (High voltage low IR)I don't see the point of really getting matched cells, There is a very minimal advantage of running a matched cells. I can't really tell the difference between my matched 3800's and my unmatched 3800's when running them,they both run consistent thru out the run with the same lap time. You just need to properly discharge and charge you packs. In a long run your expensive matched packs will become unmatched.
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Old 09-18-2006, 12:24 AM   #5
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Personally I used matched cells, but just the lowest voltage, so that they all dump around the same time, so you dont end up killing one cell by repeatedly having the voltage drop to 0.0v under load.
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Old 09-18-2006, 12:43 AM   #6
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Hi all,

I was wondering...How many cycles do you go through (average) to get the matched cells unmatched??
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Old 09-18-2006, 09:09 AM   #7
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Quote:
Originally Posted by Jochim_18
With the batteries we have now a days (High voltage low IR)I don't see the point of really getting matched cells, There is a very minimal advantage of running a matched cells......
Matched cells benefit everyone because the grading and matching processes quantifies a pack's performance. With all other things being equal a matched pack will typically run stronger throughout its discharge cycle and run more consistent from one charge/discharge cycle to the next, whether it be racing on the track or bashing around the backyard.
What about runtime? You don't mention it as a performance parameter and it is extremely important! In any given batch of cells, lets say IB4200SHV's; it is possible to see at least a 60 second (at 35-Amps) difference in runtime between cells throughout a batch. If assembled as an unmatched pack those same cells will charge and discharge with destructive disparity. During a charge cycle the cells will charge unevenly by 200 to 300 seconds or more. Then during the discharge cycle a similar relationship will occur with cells unevenly discharging by at least 60 seconds. Since it is a fact that more battery packs are destroyed by over discharging than any other factor, it follows the more closely the cells in a pack are matched the less likely any given cell will be damaged during the discharge cycle. Once a cell is damaged its capacity is reduced thus adding to the discrepancy noted above and the problem worsens with each additional cycle.
Quote:
Originally Posted by Jochim_18
In a long run your expensive matched packs will become unmatched.
Sure, it is inevitable. In one word, Entropy!!!! Thatís the way the universe operates. However it is always better to start out with a pack with closely matched performance parameters. When a matched pack ages and the individual cells finally do change, what does that pack eventually become? An unmatched pack. As for how many cycles that takes, thatís open to discussion as there are far more variables involved than I want to discuss here. Unmatched packs by their very nature are more prone to change with each charge/discharge cycle then matched packs. So why not get as much of a head start as you can on the inevitable order-to-disorder transformation?

Last edited by SPC; 09-18-2006 at 09:53 PM.
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Old 09-18-2006, 09:27 AM   #8
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If you can search around the average price of a OK matched pack of 4200...it is around $40-50 each (6 cells)........for that kind of a price, I would let them to MATCH the cell for me instead of me buying 100 cells and find only 30-40 of them are able to be matched and the rest are for nothing...

For anykind of racing (club or major race) matched cells is a must have....I paid $100 for 3 packs of matched 4200 SHV (1.20v plus) from Hurricane Motorsport........come downs to $33.34 each, I cannot complaint for that price, and the performance are better then what I can imagine.
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Old 09-18-2006, 09:48 AM   #9
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Okay the ad for Hurricane Motorsports is over now. Everyone can pay attention again! Hah!

More opinions here:

http://www.rctech.net/forum/showthread.php?t=126971

Quote:
Originally Posted by Ben.C
Hi all,

I was wondering...How many cycles do you go through (average) to get the matched cells unmatched??
Danny/SMC, EddieO, It's be cool to get your opinions on this topic. I've always been curious.
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Old 09-18-2006, 10:00 AM   #10
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Quote:
Originally Posted by SPC
Matched cells benefit everyone ....

....So why not get as much of a head start as you can on the inevitable order-to-disorder transformation?
awesome post. there isn't much more to be said on the topic.
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Old 09-18-2006, 10:16 AM   #11
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One thing that has me a little confused is apparently, that cells tend to get a little better as time goes on for the first few cycles.

If that is the case,maybe some in a given pack will improve more than others and therefore give you an unmatched pack?

Or is there a flaw in my thinking?

(It's probably going to be the latter guys )
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Old 09-18-2006, 10:39 AM   #12
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Big difference between matched cells and un-matched cells are:

"Matched cells will give you more punch and power for the first 2mins than un-matched cells. After 2mins, matched cells performed similar to un-matched cells. so, un-matched cells is enough for club race." said by Daisuke Yoshioka
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Old 09-18-2006, 10:58 AM   #13
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Awesome posts guys but I want to narrow the point down towards the relation of matched and unmatched packs with the new crop of Individual Cell Chargers and Dischargers.

Quote:
Originally Posted by SPC
.... If assembled as an unmatched pack those same cells will charge and discharge with destructive disparity. During a charge cycle the cells will charge unevenly by 200 to 300 seconds or more. Then during the discharge cycle a similar relationship will occur with cells unevenly discharging by at least 60 seconds. Since it is a fact that more battery packs are destroyed by over discharging than any other factor, it follows the more closely the cells in a pack are matched the less likely any given cell will be damaged during the discharge cycle. ...
SPC - I agree matched packs are necessary when dealing with the pack as a whole. That is why matching was necessary in the first place. However, when charging and discharging each cell within a pack individually wouldn't it negate the need for matching?

Also, if one were to use one of those speed controls that can adjust voltage cutoff and set it for a slightly higher voltage such that to prevent overdischarging of a weak cell in a pack, wouldn't that prolong the life of the pack as well?

The question isn't about do I need matched packs, it is more like "Do I need matched packs if I charge and discharge my cells individually?"

Please comment further.

BTW, Mr. Howart, if you are out there, I would really appreciate your opinion on this. Thanks.
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Old 09-18-2006, 12:11 PM   #14
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Quote:
Originally Posted by YR4Dude
..... However, when charging and discharging each cell within a pack individually wouldn't it negate the need for matching?
The question isn't about do I need matched packs, it is more like "Do I need matched packs if I charge and discharge my cells individually?"
I don't know that it's possible to discharge cells individually except for on the bench. I'm not being sarcastic or difficult with my response in any way. How can you discharge cells individually in an RC vehicle? What about differences in IR, voltage and all of the other operating parameters among cells? What happens to those differences in operating parameters during discharge? They don't go away just because the cutoff voltage was set higher. They still exist and they still create more problems than they would within a matched pack under the same operating conditions. What about those cells that are truly bad? Yes they exist and they're more common than you think. No matter how you charge unmatched cells the potentially large difference in performance among them will always be present and that difference will always create problems during the discharge cycle. Those problems will only get worse with time, they will not improve.
When you purchase matched cells you not only get the obvious matching you also get cells that have been pre-tested, tested for duds, tested for failures and tested for weak cells. I don't know of any battery supplier selling unmatched packs who pre-tests all of the cells they sale. Do you?

Quote:
Originally Posted by YR4Dude
..... Also, if one were to use one of those speed controls that can adjust voltage cutoff and set it for a slightly higher voltage such that to prevent overdischarging of a weak cell in a pack, wouldn't that prolong the life of the pack as well?
Hypothetically, yes.

Last edited by SPC; 09-18-2006 at 02:51 PM.
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Old 09-19-2006, 05:43 AM   #15
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I'm no expert but ...
You get what you pay for.
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