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Old 03-13-2008, 02:20 PM   #46
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How does this http://www.westmountainradio.com/CBAAmplifier.htm test a pack? Does it drain the pack at 120A continuous? If so, why don't a company that sell battery packs get one and do some tests.
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Old 03-13-2008, 02:59 PM   #47
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A big thanks to all the battery sellers posting on this thread. Some good info!
We all know sales have to be made, but intergity will make the long haul.
As a racer, I want a lipo that will give me the same or better race performance as my NiMh (along with the pros of Lipos). I only need it to last for 5 minutes, but I want the punch of the NiMh right off the 10 amp charger.
P.S. I also want a car made for Lipos!
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Old 03-13-2008, 03:33 PM   #48
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How does this http://www.westmountainradio.com/CBAAmplifier.htm test a pack? Does it drain the pack at 120A continuous? If so, why don't a company that sell battery packs get one and do some tests.
I think an independent third party needs to do the testing. If a manufacturer listed the results, it could be considered biased.
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Old 03-13-2008, 06:04 PM   #49
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Regarding the useful service life of lipos, based on the available info please remember that not discharging them all the way makes a big difference in every respect. How much voltage they maintain under load, capacity they retain, and how well they stay balanced. Staying above a 20% charge level helps a lot, with more improvement if kept above that. And given the relative capacity, brushless systems efficiency, and the drastic reduction in the number of batteries you need, this seems like a ridiculously small price to pay IMO.
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Old 03-13-2008, 06:30 PM   #50
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Originally Posted by 403forbidden View Post
Just a few months ago we kept hearing from "industry leaders" about how lipo would blow up in your face.

Now those same "industry leaders" are trying to get on the lipo bandwagon because they know NIMH is (or will soon be) DEAD for for the future of racing.

Always beware of the bias and agendas behind the the statements!
403,

It works both ways, the original bandwagoners also said LIPO and to some extent BL will create equalness, and fairness and be simplier. Now that we have lived the "life" for a little while can you honestly say that everything is better. I feel bad for the nubes, wading through all the hype and fluff has got to make things even worse for them.

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Old 03-13-2008, 06:44 PM   #51
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I think an independent third party needs to do the testing. If a manufacturer listed the results, it could be considered biased.
I agree, but the manufacturer could post some true numbers and then decide if they would or not sell the pack. If the maker of the cells claim a 25C and the seller finds out it's a true 20C pack then just do it like that. Cheapbatterypacks.com does something like it, but I'm not sure if they do test their packs with a CBA. There's a guy in rcgroups that has done some tests with his CBA.
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Old 03-13-2008, 07:09 PM   #52
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can you honestly say that everything is better.
yes! more people joining the hobby (and more importantly sticking with it) and more fun then juggling batteries and motor maintenance.
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Old 03-13-2008, 07:14 PM   #53
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yes! more people joining the hobby (and more importantly sticking with it) and more fun then juggling batteries and motor maintenance.
More people joining than leaving, not in my area. I like BL motors, LIPO so far has done nothing for me. I will also state that I did not like the recent bad NIMH period either. The LIPO stuff needs to get under control a bit. Industry standards would help. BTW I was taking about from the newbie perspective anyways.

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Old 03-13-2008, 07:18 PM   #54
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More people joining than leaving, not in my area. I like BL motors, LIPO so far has done nothing for me. I will also state that I did not like the recent bad NIMH period either. The LIPO stuff needs to get under control a bit. Industry standards would help. BTW I was taking about from the newbie perspective anyways.

Steve
Its great for the newbies. Makes the hobby more affordable long term. Once you have the stuff you are set for a long time. You can get away with 1 battery and 1 charger. Its really helped grow the hobby locally and kept people around.

lipo is under control. Its the hype that some spew that isnt.
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Old 03-13-2008, 07:28 PM   #55
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Come on guys, have we forgotten how flaky nimh are already? And again, we are talking currents that are far higher than they have ever been, with motors that use less. From batteries that are far more stable, especially for a new kid that wants to recharge NOW. IMO the sky is staying up there pretty damn well.

I love the new stuff. Well it was fun to be able to charge nicads in 12 minutes or whatever back in the day, but other than that....

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Old 03-13-2008, 07:43 PM   #56
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And hey, I'm as guilty as anyone. My apologies to Danny for hassling him earlier in this thread.

And like I also said earlier, I do support the efforts to continue to improve the product, support that I will continue to provide the only way that really matters, with my wallet. These things have improved dramatically in a very short time, will probably only get better.
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Old 03-13-2008, 07:46 PM   #57
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the real bug is not in C rating but who will buy 1000 pack and more at 25C when 1 month later the 35C is spirit to leave and your 25C cell is out of date

for 4 months later the pack more hot pack had 20C and now I see 33C in production soon

And for the price The lipo is not very good +- 100 cycle for racing and +- 200 for bashing very low lifecycle

Ok yes it was very powerfull and light

But when i test lifepo4 cell at 20C rate and 2C charge and after 100 cycle the capacity is same and more i think change for it soon


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Besides possbile lasting more cycles than LiPO, there is an advantage that is clear to having a slightly lower votlage.

Hotter wound Motors!!!!
Just the thought of runing a 21.5/LiPO to equal the speeds or greater of a 10.5/4-cell boils me. Look up the thread on OMG these Pinions. If the motors don't get to truning faster, every car will have an overdrive gearbox.

A LiFePO4's won't solve it all, but it will make the 21.5motor close to the 17.5 on 4-cell and a 17.5 on LiFePO4 will be close to the 10.4/4-Cell.


YES there needs to be standards to understanding the claimed ratings.
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Old 03-20-2008, 06:03 PM   #58
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All of this is centered around constant currents. There is nothing constant in an RC application. We drive these motors with a pulse width modulation, fancy words for saying we flick the switch on and off really fast. More on time is higher throttle. While the switch is on it is the same thing as directly soldering the battery to the motor. It delivers all the current it can and we have no control over it other than to turn off the switch. Basic I=V/R and it is basically a dead short across the battery. A little thing called back emf voltage saves our bacon once moving and why this whole thing even works and what limits spool out rpms.

So while the discharge rates we are talking about may seem well beyond the needs, that is not really true. Although the average current is 50amps to drain a 4200 in 5 minutes, a 3t Mod motors will draw 120amps with even higher short duration spikes and expose a weak battery pretty quick.

This is why lipos shine even though they have a lower voltage under light loads. They are able to provide the large short term currents that really get things moving. Unfortunately they have a pretty flat voltage response under 10amps or 50amps as compared to a Nimh that has more of a slope relative to load. This provides a higher top speed with a nimh because they hold a higher voltage under the lighter load at spool out and why all the Amain guys at the carpet nats ran Nimh... and a brushed motor.

The other major issue we have found is balance. Some batteries just do not stay balanced. That is the killer when charging and what killed many of our sample packs from various suppliers.

Now add cycle life to this discussion. Is that important?

Also consider DOD depth of discharge and the huge effect this has on life.

So discharge ratings and average voltage under a 35amp load are just part of the equation. In the end the track results and the life of the battery define the value.

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Old 03-21-2008, 12:11 AM   #59
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Now add cycle life to this discussion. Is that important?

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It's kind of strange how we have gone from one extreme to another...from 5-cycle race packs to 500-cycle race packs.

I myself (as well as probably everyone else on here) would not think twice about foregoing a 500-cycle lipo pack in favor of a 100-cycle lipo that gets me half a tenth more per lap, even for club racing. I also know that I'll probably replace the pack with the next latest greatest pack around cycle 53 anyway .

Cycle life is important to me...to a certain extent. The real reason we started running lipos over here is not because they lasted forever, but because we knew what we would get out of them when we put them on the track - something we could not get out of our NiMH batteries at the time. Ease of use, longevity, price, and eventually safety became big bonuses.

Of course, we will eventually arrive in a lipo-battery-of-the-month situation, but my big question is: Will the "leftovers" at least have good cycle life and usability, or will we eventually find a way to abuse these things within the ROAR rules in a way that turns them into NiMH batteries in plastic cases (practice packs after 5 runs, trash after 20)?
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Old 03-21-2008, 07:20 AM   #60
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It's kind of strange how we have gone from one extreme to another...from 5-cycle race packs to 500-cycle race packs.

I myself (as well as probably everyone else on here) would not think twice about foregoing a 500-cycle lipo pack in favor of a 100-cycle lipo that gets me half a tenth more per lap, even for club racing. I also know that I'll probably replace the pack with the next latest greatest pack around cycle 53 anyway .

Cycle life is important to me...to a certain extent. The real reason we started running lipos over here is not because they lasted forever, but because we knew what we would get out of them when we put them on the track - something we could not get out of our NiMH batteries at the time. Ease of use, longevity, price, and eventually safety became big bonuses.

Of course, we will eventually arrive in a lipo-battery-of-the-month situation, but my big question is: Will the "leftovers" at least have good cycle life and usability, or will we eventually find a way to abuse these things within the ROAR rules in a way that turns them into NiMH batteries in plastic cases (practice packs after 5 runs, trash after 20)?
Out here in Northern Cali most of us went lipo for the durability of the packs. We probably could have sponsored a racer for a year (travel and all) with the money we all wasted on the IB cells in the past year. We were looking for something that lasted longer than a month (some IB's didn't even go that long) The longer runtime is a plus as well. Performance is an issue too but for now most have settled for being able to club race from week to week without buying replacement cells or complete packs.
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