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E-Revonut
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10.17.2010, 04:23 PM

Quote:
Originally Posted by molak View Post
Even if this pack do hold a 150 c discharge...(almost impossible)

WHAT´S THE POINT ??

There´s no motor/ESC that will pull that much Amps on 4s ... Is like killing a cockroach with a V2 missile...
I disagree. The point of a higher C rated battery is that as your current climbs you put more stress on a battery, diminishing it's life cycle. A battery that can handle a very high discharge will not be stressed nearly as much when pulling 150-200 amp spikes if it can handle 900amp spikes. My RC8T truggy on 5s geared for less than 40 had a peak of 167 Amps. Even with good quality cells that I was using (RC-Monster 25/50C) they did get warmer than I would have liked, even though they held about 3.4V/ cell under that load, the heat that they generated did tell me they where getting stressed. If that battery had been a 50/100C it may have been 10-15 degrees cooler because I wouldn't have been stressing it as much.

I doubt that these lipos from MA are 150C constant, that may be their burst C rating, so maybe they are actually a 40C continuous, which would still be a great battery.

As it's already been stated we really need an industry standard for measuring C ratings. Such as it needs to hold 3.4 volts at load or 3.5 or whatever, as long as it's a standardized value we would really be able to make an accurate assesment on the batteries we purchase


RC-Monster RC8T 1515 2.5D/MMM/5s RC-M 4500mah
SC10 MMPro 13.5T 2s NeuEnery 5000mah
RC18T Mamba 25/5400kv 2s lipo + 6s NiMh
   
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  (#62)
sikeston34m
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10.17.2010, 11:08 PM

Quote:
Originally Posted by thzero View Post
Go for it. Better to be more transparent than the next guy. Formulas, unless wrong, are hard to argue with. Numbers and claims can always be manipulated.
Each cell is 4.2 volts and if we discharge at 975 amps, we get 4095 watts.

4.2v X 975amps = 4095 watts (Note: this would make a 4S pack, capable of 16,380 watts of power.

1 electric horsepower = 746 watts of power

This would make a single 4S pack capable of producing 21.96 horsepower!

22 electric horsepower would not only start your car, but it would be enough to push a small car fairly well.

The Industrial Lift Trucks I mentioned earlier have a 6.6kw drive motor. That's less than 9 horsepower and the truck weighs almost 10,000lbs. Top Speed of 9.5 mph, but still ALOT of weight.

All Batteries have an amp hour rating or on the smaller types of batteries we use, a mah rating.

Mah rating is amp hours divided by 1000. Since Mili means 1000.

A 6500 mah pack can also be called 6.5 amp hours.

The "hour" term is added to show how much amp draw it can sustain in 1 hour. A 6.5 amp hour pack can hold a 6.5 amp discharge for 1 hour.

As long as we know this, we can play with the numbers and calculate how long the pack can sustain any rate of amperage discharge.

The same pack can sustain a 1 amp discharge for 6.5 hours.... and so on.

Now, how do we calculate how long it can sustain a 975 amp discharge?

6.5 amp hour pack / 975 amp discharge X 60 (discharging minutes) X 60 (discharging seconds) = How long the charge will last at that level of discharge.

6.5 / 975=.006666666666666666666666667 X 60 = 0.4 X 60 = 24 seconds

You can play with this formula any way you like, for any size pack, for any amp draw rate.

So, in conclusion. If the 6500mah of charge ONLY lasts for 24 seconds. This should change the warranty to pretty much an unconditional warranty as far as the discharge rate is concerned.

No more should anyone hear "Well your gearing was wrong and it was too much load on the pack".

Because evidently, if you don't discharge the ENTIRE charge in less than 24 seconds, you are safe within the confines of the discharge rating.

I'm very sure this kind of amperage is enough to smoke and cook every FET from the power board of ANY ESC if the esc fails and the powerboard goes into runaway meltdown.

Last edited by sikeston34m; 10.17.2010 at 11:52 PM.
   
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  (#63)
redshift
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10.17.2010, 11:42 PM

^ Blah blah facts..... blah blah math....why so negative???

   
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sikeston34m
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10.17.2010, 11:57 PM

Quote:
Originally Posted by redshift View Post
^ Blah blah facts..... blah blah math....why so negative???

All the Blah blah facts and comparisons point toward something........

A "True 150C" continuous rating is NOT possible from these "little" Lipo packs and these little wires.
   
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redshift
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10.18.2010, 12:05 AM

I think you know that was sarcasm...

150C
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slimthelineman
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10.18.2010, 12:43 AM

whats sarcasm? ha ha sorry red couldnt help it! at the risk of stirring up another sh!tstorm i want to throw a question out there. thought of something interesting today during a conversation with a buddy. now i know these are dc batteries, but we subject them to high frequency switched loads right? seems logical to me but everything sounds good inside your own head i gues..... so my question is, to which does the "C" rating refer to? a dc constant load or an ac like switched load? i could see a battery sustaining a higher switched load than a constant one. feel free to blow this out of the water if im wrong, but i think it might be something to consider if we are tying to pioneer a standardized rating system, and since our esc's are all high frequency switches in a sense maybe this is how we should rate these packs? no? i mean lets face it we all know that even a peice of 8 gauge wire wont take more than a couple hundred amps of straight/constant/dc load without becoming a fusable link(fun to watch!) right? but go to a switched/ac load and it might hold a bit more load. any who just curious to hear what others think on the topic. LET THE STORM BEGIN! ha ha ha....
   
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  (#67)
What's_nitro?
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10.18.2010, 01:08 AM

Not to burst your bubble, but there is no AC current at the battery terminals... I think you meant to say Pulsed-DC current. I know what you're getting at, though. The C rating would refer to a constant load, rather than a pulsed load. Seeing as how our ESCs use such high frequencies, they can be taken as a constant load.


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_paralyzed_
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10.18.2010, 01:11 AM

it's dc, needs to be tested as dc, and at no point in time becomes ac.

I get what you're saying though. Your theory might work if we tested after the esc and before the motor, but simply testing the battery all we need is dc.


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  (#69)
JERRY2KONE
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Wow - 10.18.2010, 01:35 AM

Sikeston just reading through your post boggles the mind. Not working with this kind of high end electronics equation stuff leaves one speachless. Still I get what your saying pretty well, and that is exactly what I was thinking before reading your post. Having an R/C type of LiPo battery that can deliver 150C discharge just seems impossible to me. More like scinence fiction than reality. You have to wonder where in the world are the MaxAmps people are getting this idea of 150C from. Well I would like to hear their side of this explanation. So we know your reading through all of this. Lets here it Maxamps. How are you calculating a 150c draw from a 4.2volt cell? I am not getting it????


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gixxer
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10.18.2010, 01:59 AM

Quote:
Originally Posted by sikeston34m View Post
So, in conclusion. If the 6500mah of charge ONLY lasts for 24 seconds. This should change the warranty to pretty much an unconditional warranty as far as the discharge rate is concerned.

No more should anyone hear "Well your gearing was wrong and it was too much load on the pack".

Because evidently, if you don't discharge the ENTIRE charge in less than 24 seconds, you are safe within the confines of the discharge rating.
That is the exact point I was making on the car action site. Cant see anymore complaints about gearing.


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Last edited by gixxer; 10.18.2010 at 02:05 AM.
   
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slimthelineman
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10.18.2010, 02:42 AM

Quote:
Originally Posted by _paralyzed_ View Post
it's dc, needs to be tested as dc, and at no point in time becomes ac.

I get what you're saying though. Your theory might work if we tested after the esc and before the motor, but simply testing the battery all we need is dc.
rodger that! makes more sense when i see grover explaining things you guys are right, for some reason ive been preprogramed working with ac for so long i forget that it has a brother, dc who is much happier to do what you tell it to. what really throws me are the three phase wires on the motors, i see that and boom my brain sweats cause i think i got some ac excitement!
   
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  (#72)
bruce750i
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10.18.2010, 01:30 PM

If you invented the bread slicer, wouldn't you have a slice of bread to show off?
   
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reno911
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10.18.2010, 01:34 PM

So what ever happened to that guy that was on the opposing side.

He said we would get some graphs right.

I was really thinking that with his credentials at RC Car action he would pull through and give us something.

I really wish that RCMonster would let them talk for a few minutes so that we can get some of the information out of them. Every time someone gets on here from or regarding Maxamps we tear them to pieces. I want to hear their story. Are these new chemical compositions? New materials? New something?
   
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Arct1k
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10.18.2010, 03:08 PM

I think that was Friday i.e. less than 1 business day ago...

Perhaps he could have a week before the pyre burning?
   
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suicideneil
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10.18.2010, 10:16 PM

Quote:
Originally Posted by Arct1k View Post

Perhaps he could have a week before the pyre burning?
http://www.youtube.com/watch?v=UEOQqnHMSMc

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