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Matched Cell Problems.

Matched Cell Problems.

Old 01-16-2007, 10:06 PM
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Originally Posted by Mosc_007
Looks like I will have to buy some matched cells from you. At that low a failure rate I will be very happy. So far I have had %100 failure with matched cells bought recently.


Charles

This is interesting, You say that you would buy cells from Canon besides the fact that on page 1 he said he had thousands fail during the matching process.

Feral and Harris both sell great quality products at very competitive prices.
In the almost year now that I have been running Harris matched 4200's I had one cell die in the first 2 weeks, it was replaced straight away.
So after 10 months of having these cells they are all taking above 4300mah and consistantly around the 1.2v on the label besides the fact that I have been charginh them at the potentially fatal rate of 5.5amps.
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Old 01-16-2007, 11:24 PM
  #152  
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IB 4200 matched "chinese" cells yield awesome punch in my tamyia mini and thats a fact
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Old 01-17-2007, 02:13 AM
  #153  
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Dear R/C Racers,

It seems that the Japenese have found another way to beat the Chinese!! They used to do it back during war times too, Disinformation


Mosc_007, Can you please tell the whole racing community how the Sanyo 3600 cells can perform better then IB4200SHV or WC cells again please?

Its just that i must be a lowly, no nothing.

I work for a multi-national power tool company, and therefore no nothing about cell technology. I have 10,000 IB cells that we are in the middle of testing and have found the quality of the product meets or exceeds specs.
We currently use Sanyo and Panasonic cells and i can asure you that they are made in Japan, not China. Oh and we only use 1,500,000 cells in production per week....

You asked what the teminal temp would be for a cell, Well we found it with repeated results. The IB4200SHV terminal temp is 102.23+ degrees celis on no less than 20 odd occasions or above. The outside temp was 75+ on each occasion. The terminal temp on Sanyo cells (sorry cant tell specs Confidentially reasons) was 99.56+ on over 20 odd occasions outside temp 75+. But have you forgotten?? That the internial temp will continue to rise up to 30+ mins after you have stopped putting a charge into them. And that is the time that most likely an incident may occur?

The IB cells have handled 10c and over discharge rates with no problems. Now 10C equates to 42 amp hr per a cell. So 6 IB4200 cells wired in series would equal what? Thats right 252 amp hr at constant discharge and would have to do that to meets safety standards constantly.

Now the cells availible today are far superior to days gone by, as well as the specs on the motors we use today. You suggested just to gear up the car, Bad move! Overheats the cells, motor and ESC. That will do damage!!
The correct battery/motor/gear ratio will minimise any problems.

"True, But you have failed to mention he was using a Temperature sensor. And when using a Temperature sensor it doesnt matter what value you use for the -ve Delta V as the Temperature sensor will stop the charge at a safe level." Um no, read above!!

Oh and we have equipment availible to us that can do upto 100amp per cell charge and discharge rates, and we use it!! Nicd cells will handle more abuse tha Nimh. I could go on for days here........

But when its all said and done, Use Common Sense!!!! The cells are just as good as the Japanese counterparts and will withstand a fair bit. To a point.

Simon
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Old 01-17-2007, 02:36 AM
  #154  
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Simon,

I was waiting for you to appear to give us the full technical info.

The answer from you: Game, Set and Match ...... thanks


BTW ... I dont like that name in your sig
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Old 01-17-2007, 02:52 AM
  #155  
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There is no sense arguing about batteries I have purchased over min 50 plus packs from Harris and beleive it or not I have had 1 pack let go and that was due to charging poorly as they say if you match at 35 you end up with a better quality pack and I am not being bias that is a fact.
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Old 01-17-2007, 03:16 AM
  #156  
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I'd just like to throw a comment in here:

Thanks to all for this thread!!! I've been soooo disappointed with the lack of reading material on rctech since the xmas break started, but this thread has singlehandedly provided enough bullsh*t to keep me amused for hours!!

Mick - you're spot on... it's like a scab, although I'm trying to resist picking it! Frankly I can't believe he got so many responses, when clearly he's so far from the mark.

But, hey, bring it on I say!! It's great for a giggle
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Old 01-17-2007, 04:07 AM
  #157  
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Originally Posted by kimbalion7
Dear R/C Racers,

Mosc_007, Can you please tell the whole racing community how the Sanyo 3600 cells can perform better then IB4200SHV or WC cells again please?

Its just that i must be a lowly, no nothing. Simon
I dont beleive I have ever said the Sanyo cells can perform better than IB4200 cells on the track or in overall performance.

I ask you find any post were I have said such a thing !.


The only time they have an equal average discharge voltage is when comparing Raw cells at a 10 amp discharge. This is just a quirk of the Sanyo cells, But they start to drop off over the 10 amps discharge rate.

That is all I have said over and over again. And for some reason people keep on assuming I am saying they perform better than the IB4200. Again, I ask you to quote any message were I have said they perform better.

I accept the Race experts experiance that the IB4200's are the fastest battery on the track. I do however have some quality issues with them.

You will have also noticed that I have said I would use IB4200's during races and that I would also purchase some from feral.

I wish people would STOP putting words into my mouth and just take what I am saying exactly as written.


Charles
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Old 01-17-2007, 04:10 AM
  #158  
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Originally Posted by ford_racing
This is interesting, You say that you would buy cells from Canon besides the fact that on page 1 he said he had thousands fail during the matching process.
I said that after he said his failure rate is about %5. So if he has had Thousands of them fail that just means he has sold around 50,000 of them that have been fine.


Charles
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Old 01-17-2007, 04:20 AM
  #159  
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Originally Posted by ford_racing
So after 10 months of having these cells they are all taking above 4300mah and consistantly around the 1.2v on the label besides the fact that I have been charginh them at the potentially fatal rate of 5.5amps.
By taking, I assume you mean taking in, as in charging capacity ?

That is not too bad. At Fast charge currents the battery takes about %110 of its discharge capacity. So if they are taking in 4300 then they are putting out about 3900.

About %93 capacity. That is about the best you can expect from most rechargable cells. Its very unusual you ever get the full rated capacity as rated by the manufacturer. Some honest suppliers give the Max and Min capacities you can expect. IE, Sanyo RC3600HV's are 3300-3600. And most often the Min is what you get.

I have however got one IB4200 Stick pack that got 4222 mAh when discharged at 20 amps. The other stick pack was 4065 mAh. %97. Still very good.

You only need to look at the powertech batteries that Jaycar sell. Powertech advertise their older AA cells at 2500 mAh. When jaycar tested them %80 were only 2400 mAh. So jaycar told Powertech to re-label them as 2400 before they would sell them. Jaycar now has a new one which is labeled as 2500. (Powertech call them 2600).

I have tested the Powertech 2400's and I get 2200. Again about %92.


Charles
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Old 01-17-2007, 04:22 AM
  #160  
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Originally Posted by Z-Mann
IB 4200 matched "chinese" cells yield awesome punch in my tamyia mini and thats a fact
I have no doubt that is true. And I have never said I didn't believe this.


Charles
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Old 01-17-2007, 04:30 AM
  #161  
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Originally Posted by kimbalion7
The IB cells have handled 10c and over discharge rates with no problems. Now 10C equates to 42 amp hr per a cell. So 6 IB4200 cells wired in series would equal what? Thats right 252 amp hr at constant discharge and would have to do that to meets safety standards constantly. Simon

Sorry, But you are confusing Parrallel with series and how to calculate the current.

In Series you Add the voltage but the current is the same. In Parrallel you Add the current but the voltage is the same.


If the cells are in series, No matter how many cells. Its still 42 Amps in each cell.

If the cells are in parrallel then with 6 cells it would be 252 Amps. IE, 42 Amps in each cell.

Like I said before. Do the maths with an average Internal resistance for a cell at 252 amps. The terminal voltage would be around 0.2 Volts.


Another way to look at it. If you have 6 4200 mAh cells in Series you still have a 4200 mAh Pack but at 7.2 Volts.

If you have 6 4200 mAh cells in Parrallel then you have a 25200 mAh Pack but at 1.2 volts.

Notice that the mAh rating multiplied by the terminal voltage is constant For the same number of cells. Weather connected in Series or Parrallel.


Charles

Last edited by Mosc_007; 01-17-2007 at 05:02 AM.
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Old 01-17-2007, 04:36 AM
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Originally Posted by kimbalion7
Oh and we have equipment availible to us that can do upto 100amp per cell charge and discharge rates, and we use it!! Nicd cells will handle more abuse tha Nimh. I could go on for days here........
Simon
That could be part of the problem. NiCD cells will handle much more abuse that NiMH. As you have said.

Some people may be treating NiMH cells as though they are NiCD cells. NiMH cells have a much lower tolerance to temperature and overcharge than NiCD cells do. Which is probably why NiMH cells have started exploding. Which was something that never happened in the past.


Charles
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Old 01-17-2007, 04:43 AM
  #163  
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Originally Posted by kimbalion7
Well we found it with repeated results. The IB4200SHV terminal temp is 102.23+ degrees celis on no less than 20 odd occasions or above. The outside temp was 75+ on each occasion. The terminal temp on Sanyo cells (sorry cant tell specs Confidentially reasons) was 99.56+ on over 20 odd occasions outside temp 75+. But have you forgotten?? That the internial temp will continue to rise up to 30+ mins after you have stopped putting a charge into them. And that is the time that most likely an incident may occur?Simon
I am quite aware the internal temperature keeps rising for some time after the charge has finished. This explains why the cell can explode some time after charging. And since he put the pack into his Anti Static case after charging that stopped the cell from dissapating the heat. The heat was trapped and kept rising until fatal temperature was reached.

It is nice to see the figures on temperature for IB's and Sanyo. So it wasnt just co-incedence that I could charge my Sanyo's at 1C and still keep the outside temperature below 51 Degrees C. While doing a 1C charge on the GP's and IB's the outside temperature went over the 51 degree limit before they Zero Delta peaked.

Intersting to see what internal temperature they can run at. I had a real hard time searching the net trying to find what temperature a NiMH cell starts to become damaged at. I only found one answer and that was 80 Degrees C. Maybe that was the outside temperature.


Charles
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Old 01-17-2007, 04:43 AM
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Originally Posted by Mosc_007
If the cells are in series, No matter how many cells. Its still 42 Amps in each cell.

If the cells are in parrallel then with 6 cells it would be 252 Amps. IE, 42 Amps in each cell.

Like I said before. Do the maths...

Charles
Dude, I want some 42 Amp cells!! I'm gonna blow everyone away!!
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Old 01-17-2007, 04:49 AM
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Originally Posted by kimbalion7
The cells are just as good as the Japanese counterparts and will withstand a fair bit. To a point.

Simon
That is something I am yet to be conviced of. I am not saying you are wrong, I am just saying that at the moment I have my doubts that the Chinese cells are the same Quality as the Japanese ones.

When is comes to performance on the track their is no doubt the IB4200's kick the lower capacity Japanese cells. I am wondering why Sanyo dont make a higher capacity cell. My only thoughts are that above this capacity the cell starts to become more and more dangerious.

You only have to look at the Battery Powered tool market. They are Extreamly Safety orriented. Some of the Major brands have only just started using 3000 mAh NiMH cells. Untill recently the major brands were still using NiCD cells because of the very high safety margin.

Has anyone ever heard of a battery powered power tool having the batteries explode ?. The Currents in the batteries can be just as high as those found in RC racing. The Good brands that is, Dewalt, Makita etc. The Cheaps ones are using low capacity cells which by nature are pretty safe. The higher the capacity the more dangerious a cell becomes.


Charles

Last edited by Mosc_007; 01-17-2007 at 05:05 AM.
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