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Old 11-19-2008, 09:16 PM   #106
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I was away from racing from late '95 to around '2000, so I missed that... Any idea why those 2200's didn't do the job?
Not sure why the 2200s with lower IR and better voltage weren't as fast it must have something to do with voltage recovery from higher loads which a constant discharge can't show.

We have a 2200/25C pack for Helicopters and when we sent 30 and 35C packs to our test pilots they told us the higher C rate packs were better in flight with faster recovery from loading. Keep in mind that a 3D Helicopter pulls allot of amp draw they notice really notice these things. The funny thing is when we cycle the 3S packs on our GFX the 25C , 30C and 35C are not that much different on a constant load so this is why I think the GFX or constant discharge doesnt' always show you the full picture.
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Old 11-19-2008, 10:03 PM   #107
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If you only knew half as much as you THINK you do!!

EA
At least I don`t resort to insults ...


I only asked a simple question .....
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Old 11-20-2008, 04:25 AM   #108
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I think that choosing or rating LiPo packs only based on the C-value isn't the whole truth. When racing limited motor classes I think one of the most important thing is to to get as much power as possible from the battery. This means you have to get highest possible average voltage during your run. C-value usually has nothing to do with it. Like I said in previous post, when you drive 5-minute runs you can only draw average of 12C from the LiPo. Drawing more than average 12C would mean you won't finish because of flat battery Most of the LiPos are more or even twice as much.

You need highest possible average voltage during your run to get maximum power. Now we should look at the discharge charts to see what really matters. Sadly I don't have any at the moment to show you.

Basically you get higher possible average voltage from the LiPo by:
1) having the biggest capacity LiPo that can fit, is allowed, can be bought, won't make your car too heavy. Having bigger capacity battery means that after your run you have more capacity left in the battery. This means you have higher average voltage. When you run 17.5T stock you probably use only 1500mAh. If you have 5500mAh battery you'll end up with 4000mAh left in it. The average voltage from that battery will be MUCH HIGHER than using 2800mAh battery. Although both will do fine, the big capacity battery gives you huge advantage because of the much higher average voltage.
2) having the LiPo work at its optimum temperature. I think this lowers its internal resistance I do warm the LiPos up to 50 degrees Celsius before racing. This keeps the LiPo voltage higher under load. Without load it seems not to make any difference! Cool your LiPo down to 5 degrees Celsius and yuo won't get almost any power out of it, voltage drops fast with load, its quite drastic!

Like said for 5-minute run you only need to have 12C capable LiPo and most of them are. So having 20C or 25C 5000mAh LiPo really does not make any difference directly. The difference MAY come from the fact that probably the 20C LiPo has bigger IR than the 25C one which means you could get better higher voltage during your run. But I would then take the 5500mAh LiPo instead

Another thing. Higher C-valued LiPos tend to be MUCH heavier, they have worse capacity to weight ratio than lower C-valued LiPos. This probably has to do with the structure of the cell. So you should always look at the weight of the pack also! It might be better to get lighter lower C-valued LiPo with higher capacity than heavier (which might put you over the weight limit!) higher C-valued LiPo.

I think reading that EFRA will limit the capacity to 5500mAh. I think in a short time we see 2S LiPos with 5500mAh. Today there are 5300mAh and 5400mAh packs out. But then, because we need higher overall voltage during a run we still need the biggest possible capacity and we would like to get the 6000mAh battery that isn't allowed Do you see problem rising from this fact I don't know if EFRA will do testing and approval like ROAR is doing. Anyway I see manufacturers soon puting 6000mAh cells into hardcased LiPos and marking them as 5500+mAh

"New" technology, many things to consider, many wrong decisions can be made...

Please disagree with my opinion if you think I'm wrong. This is just the way I'm seeing things at the moment - running LiPo in 1/10 stock and trying to get the maximum out of the power system (motor+esc+LiPo).

Different LiPo 5-15C discharge graphs would be nice to add to this thread. Also the LiPo temperature graph with 10-15C discharge current.
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Old 11-20-2008, 04:52 AM   #109
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Capacity was how they used to rate Sub C Nicads. The GE 1000 mah cells were good, way back in the day, then the Sanyo 1200's were better. Then Bob Emott started matching batteries for runtime. I don't know if he was the first to match cells, but was among the first for sure. For a while, then, RUNTIME was how you tested Nicads. Then along came average voltage and internal resistance, and THAT was how you tested Nicads (and NIMH's)

The reason LiPO's are rated by C rating isn't because it's the "right way", it's because LiPO technology in R/C racing is still in its infancy. When the technology catches up, we'll see LiPO's rated by average voltage and IR as much as C rating. My whole reason for making comments in this thread was to hopefully get folks to want to see that information. I applaud SMC for printing discharge information on their LiPO packs.



Once again, are you sure the difference in performance was due to the SMC pack having a better C rating than the alleged 35C pack? I'd bet a year's salary that if you charged each pack on a good LiPO charger, then put each on a Turbo35GFX and discharged them at 30 amps down to 7 volts, the SMC would show higher average voltage and lower IR than the alleged 35C pack...

Trips I did just that....I bought every race 3800-4000 race pack available about 2-3 months ago and ran 4 cycles thru every pack and smc pack had the highest voltage and lowest ir.

Only way to evaluate is to use the same gfx charger and same cycle method to carefully and honestly evaluate the packs.

Thumbs up on a great product Danny. Fyi Rc Madness is about 90% smc lipo versus the competition. You can always determine the best product from the club racers that actually buy their stuff from the local shop!

Fyi big T pack was close to same performance and big O pack was way off in performance for the rating.
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Old 11-20-2008, 05:10 AM   #110
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I suspect a year from now this won't matter much. Natural selection will take place as people find the batteries that consistently win on the track (which matters most). I guess its ok in the meantime if it help figure that out faster which seems to be somewhat debatable. Good luck in the testing.
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Old 11-20-2008, 09:34 AM   #111
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IR and average voltage will tell part of the picture when it comes to a cell/pack but in my 20 years of matching and selling batteries I have seen some cases where this doesn't always work. My Sanyo 2000 versus the Sanyo 2200 is a perfect example of this. Our 2200/3S Lipos in 25C , 30C and 35C are perfect examples of this. So yes you can get a good idea from testing at a constant load but it's not giving us the total picture.

This thread is not really about who has the best performing pack it's about letting racers/customers know that you need to be careful with all the claims out there as I suspect there are many that are false. Lets take the particular 5200/35C pack I used to test in my first post. This pack in a good car with a good driver can win at any race the problem is that it's way overpriced since it's more like a 20C pack.
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Old 11-20-2008, 12:13 PM   #112
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Yet another thread as to why r/c will never be mainstream. "sigh!"
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Old 11-20-2008, 12:24 PM   #113
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Great information in this thread and I've seriously enjoyed the performance I get in my SMC packs. I just received a new SMC saddle pack last night and was kind of bummed it didn't have the numbers indicated anywhere on the packaging. Perhaps this one missed cycling?
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Old 11-20-2008, 12:53 PM   #114
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We've been discussing about C rate (and false statements) also in Italy .

Every day there's a new LIPO battery with increased C rate.... this is crazy.

You buy a battery that next day it is said to be "obsolete"....


It is a serious problem ...... this can destroy our hobby!!!!
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Old 11-20-2008, 01:15 PM   #115
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At least I don`t resort to insults ...


I only asked a simple question .....
You don't ever ask questions. You post backhanded comments and remarks. Go back and look at any post you've made.....
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Old 11-20-2008, 01:26 PM   #116
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Originally Posted by turbodog View Post
Yet another thread as to why r/c will never be mainstream. "sigh!"


LOL.. You got a point there, I do think R/C in general is mainstream but R/C racing isn't....
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Old 11-20-2008, 01:42 PM   #117
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You don't ever ask questions. You post backhanded comments and remarks. Go back and look at any post you've made.....
Ditto

Danny should be commended for bringing this issue out in the open . He is presenting facts and figures that can be easily checked by other manufacturers.
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Old 11-20-2008, 01:47 PM   #118
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Originally Posted by DavidAlford View Post
You don't ever ask questions. You post backhanded comments and remarks. Go back and look at any post you've made.....


Bull Crap Dave


I ask Danny ...
Why use C-Rating on SMC products if C-Rating`s are not use full or accurate for rating a pack ?


You can`t have it both ways Dave, condeem another company for using C-rating and then use it yourself ?


All I got back was "I miss the point"....


That`s not a answer Dave , its a dodge ......

Just so everyone knows ...


The "point" of this thread is to condemn that other company for doing just the same as SMC has been doing all along ....


O-Lookie !
here come some more insults...
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Old 11-20-2008, 01:53 PM   #119
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Default maybe you are missing the point - or I don't understand it

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...Would it make sense to choose my real car's tires based on whether they are H rated (SAFE TO 130MPH) or V rated (safe to 149 mph) when I'm driving a car that will never see the better side of 80mph? Or would it make more sense to look at skidpad numbers to comparison shop (if I'm looking for the highest grip) or mileage numbers (if I'm looking for longest life)??? Suppose I bought H rated tires that tested to be grippier than some other set of V rated tires? Would I worry that i was paying for something I wasn't getting No, because again, it's something I don't need.
What I think is meant - using your example. If you bought V rated tires but never used them over 130, but were actually sold a H rated tire that the manufacturer MARKED as V rated - that is the problem. You PAID for V and GOT H - whether you used it/needed it or not.
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Old 11-20-2008, 02:03 PM   #120
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when I came back to RC after 5years of abscent I was confused with Lipo, BL and all that but this is how I understood the Lipo and I am sticking with it.

C rating w/Mah = as same as Mah w/ 1.2V advertised by Battery manufactures (Sanyo, Panasonic, GP..etc)

then Pack should be indivisually tested and labled by RC companies (SMC, Orion, Trinity etc..)to show true racers freindly numbers. (SEC, AVE V, MAh, int)

in NIMH days I wouldnt buy a pack that only show 3300GP 1.2V sub-C.

then why would you buy a Lipo that way? cause it show 5500/55c ! ?? from non RC manufacture?

the only RC company did show the meaningful numbers was SMC and I bought a pack and very happy with it.

here is the nembers on my pack in case you never seen them.
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False Lipo advertising-smc5kpack.jpg  
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