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Old 12-29-2005, 08:23 PM   #121
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Quote:
Originally Posted by cr250
Great explanation Isaac!!!! I was trying to avoid going into such detail as the anti-engineer comments had already started.
No joke

cr250, HAPPY NEW YEAR

Isaac
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Old 12-29-2005, 09:33 PM   #122
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Has anyone factored in the weight of the cell? Everyone is talking about heat build up in motors caused by IB's. Could it be that the cell is slightly heavier? Seems logical that if the car is heavier that the motor has to work harder to get it around the track. From my experience it's not so noticable in touring but in a 1/12 scale weight is noticable in acceleration mainly.

What is the weight difference between the GP and IB cells?
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Old 12-29-2005, 10:33 PM   #123
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Originally Posted by Anthony Yuen
If the average voltage keeps the same, but runtime has extra 20-30 seconds that means the IB4200 cell discharge profile is still higher than the IB3800s. I hope you can understand the mathematics behind.
I understand were you are coming from and it makes sense, however I doubt the voltage will be higher even though you are averaging over time (dv/dt).

If you look at a discharge curve the only thing that needs to change to maintain the same average voltage without an increase in overall cell voltage is the slope of the curve. IB cells have two critical slopes, one during the first 2300mah (+/-) and then the remaining (for IB3800s).
The difference between these two slopes is the rate of change.

Besides, most of the IB3800 cells that we are matching at Axxis Racing are in the 4150 mahr range, with about 5% of them above 4200mahr. That is very close to the nominal 4200mah.

Danny stated that the IB4200s have around 430 seconds at 35 amps, that equates to 4180mahr...that is within limits of what we are seeing in the best IB3800.

Untill I test the cells and see the actual discharge curves I will not speculate or pass erroneous information, but I am going under the assumption that the two cells will be very similar in their discharge and voltage characteristics.
This is based on the results that I have seen on the last few thousand IB cells that we have matched.

Last edited by BATT_MAN; 12-29-2005 at 10:53 PM.
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Old 12-29-2005, 10:48 PM   #124
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Issac,do you deal direct with dealers?if so please email me [email protected]
thankyou
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Old 12-30-2005, 07:22 AM   #125
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Quote:
Originally Posted by wvince
Has anyone factored in the weight of the cell? Everyone is talking about heat build up in motors caused by IB's. Could it be that the cell is slightly heavier? Seems logical that if the car is heavier that the motor has to work harder to get it around the track. From my experience it's not so noticable in touring but in a 1/12 scale weight is noticable in acceleration mainly.

What is the weight difference between the GP and IB cells?
Certainly there is a point of diminishing returns when it comes to additional weight of our energy or power supply in a RC vehicle. In most types of racing where acceleration, deceleration and lateral acceleration are important, an optimum motor size prevails. This can be attributed to many factors including but not limited to motor mass and related centrifugal forces. Have we reached this point with batteries in RC vehicles? Good question. It will ultimately be answered by lap times.

Does the additional weight of today’s cells force the motor to work harder thus creating more motor heat? Absolutely. As a test, record your motor temperature immediately after an eight minute, 1/12th scale race while running a good set of GP3700 cells. Then with another set of good GP3700 cells, add the weight difference between 4, GP3700 cells and 4, IB3800 cells to your car. If you want to be really precise, equally spread the additional weight laterally across the battery pack to simulate as closely as possible the mass distribution change the car would experience. Again record your motor temperature after an eight minute run. There are numerous other factors that could affect the motor temperature so try to be as consistent as possible from the first run to the second. If anyone can put in 2 consistent runs for test purposes it would be you.

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Last edited by SPC; 12-30-2005 at 07:40 AM.
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Old 12-30-2005, 03:39 PM   #126
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Hi Danny,
thought this might be a good place to ask...

There seems to be some contention over here in the UK over the IB's.
Someone on another forum was commenting that the elegibility officer was concerned over the IB's supposedly expanding under charge.

My question is this, have you experienced this with any of your cells?

Apparently the 38's will be fine, it's the 42's that (a few) people are concerned over... I personally see no reason why the 42's, if they are the same size as the 38's, would not be legal, especially if the 38's are approved.

It all smells a little fishy to me... but we'll find out in a few days when the BRCA approval list is published.

Cheers
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Old 12-30-2005, 06:24 PM   #127
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you beat me to it Ed??


danny this was cut & pasted re;IB38`s over GP37`s

tell that to the person who's homolnogating them as he was the person who told me there maybe an issue with cell size and i tend to believe him a tad more than yourself, if the cell is expanding under charge then they will not be made legal

this is IB3800 expanding bigger then the GP37 after charging
true or false

this guy also thinks the IB is bigger then GP (wrong)

IB3800 is smaller & lighter then the GP3700 yes?? no ???

(i know yes!!)

get it sorted
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