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Old 12-28-2005, 06:10 PM   #91
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Danny

What do you mean when you said that LiPo couldn't take the draw of NiMh cells?

I heard that the LiPo's could sustain a 144 amp draw for 10 seconds, and a 250 anp draw for a few miliseconds.

Can you please inform me of what you know about the LiPo's.

Thanks,
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Old 12-28-2005, 07:26 PM   #92
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Quote:
Originally Posted by Vahe
What do you mean when you said that LiPo couldn't take the draw of NiMh cells?

I heard that the LiPo's could sustain a 144 amp draw for 10 seconds, and a 250 anp draw for a few miliseconds.

Can you please inform me of what you know about the LiPo's.
I'm not Danny, but I can help... Your question is relative to the pack you are speaking of- If it's a 7.2 volt pack with 4000mah and is rated for a 10C discharge, then it supposedly can handle a 40 amp nominal discharge and usually a 60-80 amp spike.

There's a lot of talk about LiPo not having the low internal resistance they first claimed, but personally I'm not convinced. When speaking of battery energy release, internal resistance is to blame for much of the energy lost in heat. If that were the case, then doesn't it seem that cells with poor internal resistance would create waaaaay too much heat when discharged at a 20C rate? Lipo's can't handle that kind of heat. However, there are more factors than just resistance, but this isn't the time nor the thread....lol

Keep up the good work Danny- and thanks for the great information and assistance on the threads.
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Old 12-28-2005, 09:42 PM   #93
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Hi Danny,
will the new IB 4200 have the crazy voltage like 1.2+++ what is your team tested result will it better than the IB 3800 or the power are same just increase run time? thanks
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Old 12-29-2005, 01:33 AM   #94
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Quote:
Originally Posted by dakrat
i really doubt it. my 3300s are dumping at the last 2 minutes of 8 min. in order to run two 5 mins. it better be at least 6600s mah. maybe you can get away with it but would you risk it?
At one of my local tracks, last year when everyone was running 3300's, they tried 10 min mains in stock and mod. Hardly anyone ever dumped. This was offroad however, so the amp draws are a bit more concervative.

But there was a good size tripple that you needed to line up just right for to make even with a fresh pack on the first lap. I was able to clear it on the final 37th lap, after 10mins.

I think it may be possible in stock with the 3800's. Infact, I would bet you could do it no problem onroad.

We also used to run 7 min 19t heats and mains onroad, at a fairly big outdoor track. Again, I never had a problem making runtime even with 3300s.

But lets not start the longer heat and main argument.......
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Old 12-29-2005, 01:57 AM   #95
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Quote:
Originally Posted by Guo Chean
Hi Danny,
will the new IB 4200 have the crazy voltage like 1.2+++ what is your team tested result will it better than the IB 3800 or the power are same just increase run time? thanks

The IB4200s have the same average voltage as the IB3800s with 20-30 extra seconds of runtime. Based from the track testing done so far they perform as good as the IB3800s.
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Old 12-29-2005, 08:06 AM   #96
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Quote:
Originally Posted by Danny/SMC
The IB4200s have the same average voltage as the IB3800s with 20-30 extra seconds of runtime. Based from the track testing done so far they perform as good as the IB3800s.
will you think that i will be better than IB3800 in future?
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Old 12-29-2005, 08:28 AM   #97
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Quote:
Originally Posted by Guo Chean
will you think that i will be better than IB3800 in future?
Maybe not now, but in the future... I'm positive
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Old 12-29-2005, 11:37 AM   #98
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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.
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Old 12-29-2005, 12:11 PM   #99
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Quote:
Originally Posted by pony klr
unfortunatly once some one allows 4200 in say stock oval they will feel compeled to buy because of the increased voltage trap a 3800 at 240 then a 4200 at 240 with a 35 amp discharge or 30 what ever and the 4200 will have more thats been around for 20 years voltage means power!
VOLTAGE DOES NOT MEAN POWER.
Power is defined as the rate of DOING WORK.

To get POWER out of a motor you have to develop TORQUE, and TORQUE is PROPRTIONAL to CURRENT, not VOLTAGE.
Every motor has a Kt constant. This constant will tell how much TORQUE the motor will develop at a certain CURRENT

Voltage means higher rpms.
CURRENT DEFINES POWER in electric motors. Without the current, you can have as much voltage as you want, yet your motor will not move.

For example: In a stock motor you only gain 3.6 RPM's / millivolt. So if you have a 1.190 battery v. a 1.200 you only gain 36 RPM /cell or 144 RPM for a 4 cell pack.
At 4.8 volts this motor will turn 17,280 RPM
At 4.76 volts the motor will turn 17,136 RPM
These are NO LOAD RPM

Assuming Kv=3.6

VOLTAGE = RPM
CURRENT = TORQUE

You need torque to get a motor to accelerate and POWER (WATTS) to keep it going.

POWER in a motor is the product of TORQUE multiplied by rotational distance per unit time (either in RPM or rad/sec) or better known as the angular velocity.

P = M x w

where:
P=Power in WATTS
M=Torque
w=angular velocity
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Old 12-29-2005, 12:50 PM   #100
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Yeeesshhhh....you seem like a nice guy but geezzzz...STEP AWAY FROM THE SLIDE RULE!

Look, in evey increase in battery capacity we have seen an increase in performance. That increase may be that the motor does not fall off as quick or that our laptimes do not increase towards the end of our run. Bottom line for those whom are not Engineers is we get a little faster.

See....wasn't that easy?
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Old 12-29-2005, 01:44 PM   #101
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Last edited by cr250; 10-19-2013 at 04:04 PM.
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Old 12-29-2005, 02:10 PM   #102
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I hear you but the "regular" guy is getting buried in the BS.

Two well known facts that most people ignore:

Increase the voltage you increase the RPM and .02 volts don't mean jack.

Most people here don't have an Engineering degree so explaining "Power" as work will not help anyone. Keeping it simple will help the newbs and the non-engineers understand what is going on. For those of us that have had some education in the matter.....we already know the two well known facts stated above.

My comments are in no way a slam on Issac. I'm just trying to keep it REAL.
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Old 12-29-2005, 02:14 PM   #103
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Quote:
Originally Posted by cr250
Batt_Man is an incredibly nice person and I believe he is only trying to clear up an ongoing misconception; that battery packs by themselves make power. Sometimes it is necessary to go back to the original math derivations to convince the disbelievers. I've recently been reading other posts on this forum and as well as other websites about how much more "power" the IB cells make. It all starts when someone asks why they are seeing a drop in motor performance after a minute or two into a race with an IB pack. Typically someone representing IB replies with a statement similar to this; "the drop in performance is due to the increase in power the new IB cells make That statement is misleading, untrue and flies in the face of the true relationship between enegry and power.

Please give me your explanation as to why the motors heat up more when using IB cells ? If it's not the ability of the cell to provide more power then what should it be called ?
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Old 12-29-2005, 02:23 PM   #104
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........

Last edited by cr250; 10-19-2013 at 04:03 PM.
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Old 12-29-2005, 02:45 PM   #105
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I found it fairly easy to understand and I cannot recall the last time I stayed at a Holiday Inn Express. It seemed very straight forward to me. Thanks Batt_man. There are books available on all of this. If only I spent the time reading up and taking the time to understand it I just might have my name in a magazine with the word "WINNER" in big print under it.


Damn, if there was such a medium in which I could search the world for information on all this..
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