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Old 10-18-2007, 12:12 PM   #586
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When you RC car accelerates out of a corner and it's pulling 50-60 amps, the lipo cell will has less IR and thus a ton more voltage.
Then why does my car have more power with a NiMh than when I test (back to back) with a LiPo?
Shouldnt the LiPo be faster based on your statement above?
Or is the advantage only at amp draws we will never see on the track in stock and 19turn?
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Old 10-18-2007, 12:14 PM   #587
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Linger: So basically your saying that a Lipo pack will have better acceleration than sub-c cells so this means a Lipo should be as fast if not faster in stock and 19t.

Since you have allot of knowledge about Lipos what do you think about IR increasing over use ?
Danny,
A lipo will not have better acceleration in the 13.5/stock class. Those motors simply cannot pull enough amps. The lower voltage of lipo at low amp draw is a handicapp in this class. With 10.5/19T it's pretty close between Nimh and Lipo. In Mod, there is no question - a good lipo will accelerate much harder than even a brand new NiMh pack. Top speed with mod might be a hair less since the motor isn't pulling much amps at top speed.

IR increases almost linearly with capacity loss with most lipos. If your lipo loses capacity at a very slow rate - then the IR gain will be slow as well.
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Old 10-18-2007, 12:21 PM   #588
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So if we can design a Lipo pack that has more power than current models and still have acceptable cycle life than it would be a good thing.

I don't think anyone really needs or wants a 1500 cycle life pack. If a 500 cycle life pack has great performance with some of the benefits of Lipos then it could be a good alternative over the sub-c packs. I'm not sure if we can come up with such a pack but our supplier has been informed that we need more power and so far the response has been that it can be increased but will take some time.

Wouldn't it be funny if SMC the bad company for Lipos would actually help out the situation and make Lipos more competitive against sub-c.
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Old 10-18-2007, 12:24 PM   #589
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Then why does my car have more power with a NiMh than when I test (back to back) with a LiPo?
Shouldnt the LiPo be faster based on your statement above?
Or is the advantage only at amp draws we will never see on the track in stock and 19turn?

What Lipo packs have you compared to your sub-c packs ?

How much slower were the lap times ?

Thanks.
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Old 10-18-2007, 01:11 PM   #590
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Danny, 500 cycles would be plenty. That would be approx 10 cycles per week. If I could get a year out of a lipo battery for $150 or less with great performance then that would still be a much better value then nimh.

As for lap times Im about the same (maybe even a little faster) with an Orion 3200 then I am with nimh. Here is the catch with lipo. While a fresh well taken care of nimh might be faster do we all take great care of our packs all the time? No, so the lipo stays pretty consistent over time while the nimh falls off. So while nimh laptimes might be faster week 1-5 with a battery the lipo will start to become faster somewhere after that. All unscientific observations but I assume scientifically it would prove true.
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Old 10-18-2007, 01:14 PM   #591
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It's amazing that SMC spouts facts and figures about their lipo packs when they obviously don't know much about their own lipo packs or other lipo packs beyond what the company they contracted to make their packs tells them.

Also, mis-stating facts about kokam cells because you misread their charts isn't confidence inspiring. I realized that you misread the kokam charts, but what would be the point of catching your error?

Danny and Jack, please hire Linger to teach you about lipo packs.
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Old 10-18-2007, 01:23 PM   #592
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It's amazing that SMC spouts facts and figures about their lipo packs when they obviously don't know much about their own lipo packs or other lipo packs beyond what the company they contracted to make their packs tells them.
billjacobs - be nice.

SMC is going through the LiPo learning curve. It's their first shot at distrubuting lipos so some bumps are expected. As more and more companies start selling LiPos, they will go through this process as well.
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Old 10-18-2007, 01:27 PM   #593
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Originally Posted by billjacobs View Post
It's amazing that SMC spouts facts and figures about their lipo packs when they obviously don't know much about their own lipo packs or other lipo packs beyond what the company they contracted to make their packs tells them.

Also, mis-stating facts about kokam cells because you misread their charts isn't confidence inspiring. I realized that you misread the kokam charts, but what would be the point of catching your error?

Danny and Jack, please hire Linger to teach you about lipo packs.
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Old 10-18-2007, 01:33 PM   #594
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Well the crying avators shut me up. I'll go away now and leave the discussion to the grownups.

SMC- please hire Linger or someone with similar knowledge to teach you about the products you are selling.

I design and sell software for a living. If I gave my users the same answers that SMC gives racers, I wouldn't be in business.
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Old 10-18-2007, 01:53 PM   #595
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Old 10-18-2007, 02:07 PM   #596
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Well the crying avators shut me up. I'll go away now and leave the discussion to the grownups.

SMC- please hire Linger or someone with similar knowledge to teach you about the products you are selling.

I design and sell software for a living. If I gave my users the same answers that SMC gives racers, I wouldn't be in business.


Why do you think we don't know what were selling ?

Were selling high performance lipos for the RC market. Our Lipos meet the International safety standards and have a true capacity and C rating. As far as cycle life the standards used by most manufacturers is to have the cells hold up to 80% of there rated capacity after 50 cycles at the maximum C rate discharge which ares do. Maybe Kokam or others will do better but ours seem to meet the standards.

Sorry if I'm not a Lipo engineer. I'm sure all other Lipo distributors must be engineers.
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Old 10-18-2007, 02:55 PM   #597
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What Lipo packs have you compared to your sub-c packs ?

How much slower were the lap times ?

Thanks.
I did Lipo vs Nihm testing the last time I raced at Norcal hobbies. I used a Novak 10.5 with both packs. My laptimes were faster with the Orion 4800 lipo. I had more punch with my nihm pack (EA 4200) and this is my take on everything. The motor was hotter with the nihm pack (maybe due to the extra voltage) and maybe because of the extra bottom end I was over shooting my lines....who knows. I wasn't down on power compared to the guys running killer nihm packs. In fact if I hadn't crashed on the last lap no one would have been close to my TQ pace with the Lipo. The laptimes were only a tenth or so off each other. Art Davenport can fill you in on the testing done that day. The one thing I didn't do was add weight to the car due to the Lipo being light. The week before when testing mod I did add weight. I want to go Lipo just because I'm tired of replacing IB cells everytime they crap out in a pack. The Lipo I used has more than 1000 cycles on it and it felt killer to me. I know that these Lipos were used for two enduros and God knows what else. So for a guy like me...I'll pay for longevity and hope the performance is up to par rather than the other way around. Your rep is killer so I know you'll put out a great product once everything is all said and done. Just make sure EA get some Lipo's for me
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Old 10-19-2007, 12:16 AM   #598
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Originally Posted by Danny/SMC View Post
What Lipo packs have you compared to your sub-c packs ?

How much slower were the lap times ?

Thanks.
Hi Danny:
Here's some data of a Lipo Vs. Nimh comparison. http://duralitebatteries.com/track/p...t%20Review.pdf
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Old 10-19-2007, 02:53 PM   #599
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I have no racing experience with lipos versus sub-c cells so for thos who have tried it they need to tell us the difference.
I ran 3 hours of practice laps on rubber tires at a large outdoor track in mid-August this year with another racer. This was after having run an Enduro that day, so my batteries already had maybe 3 partial charge cycles apiece on them. I was using a Novak 10.5 with the standard sintered rotor and so was the other guy. I was using two IB4200 packs (1.5-1.7 IR, 1.241-1.243 V) purchased from Team Express at Paved Nats June 8th. I rested, discharged, equalized and recharged my IB's prior to running the practice session. The other guy was using Orion/Peak 3200 packs bought this season. We both had decent cars with smooth running drivetrains, and athough his was Tamiya and mine Corally, we were geared virtually the same (roughly 4.83 FDR).

We kept regrouping just before the back stretch every time we got apart. So we zipped down the backstretch over and over and over again, almost together. One following the other, back and forth. We had a great chance to see how our speeds compared.

With a fresh pack, I outpulled him by several feet (2-3 feet). Consistently enough we were sure I was faster.

After about a minute, the difference was pretty small. Maybe a foot in 100. It then evaporated and we were too close to tell. Sometimes I thought I was a little faster.

But as the run went on, I could tell I was losing ground. In a 5 minute race, I think it was almost too close to tell... I had the better hole shot, but he could pull me at the end.

This particular course is very open and flowing, 15' wide lanes, 120 x 70 or so.

When we have run at another track that is tighter and longer, there was more advantage to the LIPO. The NIMH2 seemed to fall off a little more. Of course they had another 2 months of runs on them. But the discharge curve of the LIPO clearly seemed flatter.

During the actual enduro, one of my teammates had an Orion 4800 LIPO. He went seemingly forever running his 13.5, way way longer than I could have, over 10 minutes, and with every bit as much punch as I think I had, until close to when he dumped, he finally fell off. Whereas my packs fell off much more markedly in comparison, slowing more and more through the run while pushing my 10.5 BL.

I never realized how much NiMH2 fell off in a race until I saw LIPO running. They fall off too, but the ones I have seen, do so much more gradually.

I realize it's not me running both types, but the subjective difference on the track was, although subtle, easy enough to pick up by watching the cars. Based on our club trophy races, I think in a race you could guess 2 out of 3 times (by watching) which drivers had LIPO and which drivers had NIMH2.

It would be interesting to compare the new 3600 to new 4600 cells. I imagine they are both pretty close when integrated over a 5 minute run, albeit with different discharge curves. Just a guess... actual test and track data would be nice....
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Old 10-19-2007, 03:18 PM   #600
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Last edited by Joel Lagace; 10-19-2007 at 03:23 PM. Reason: edit
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