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Old 12-23-2005, 08:29 PM   #16
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Quote:
Originally Posted by BATT_MAN
ALL motors have a Kv constant, right?
So what does that mean? Well, if you have a motor with a Kv of 3.5 (3500 RPM/volt) like a typical stock motor, that motor will turn 4095 (NO LOAD) rpms at 1.170 volts and 4200 rpms at 1.200...a difference of 30 millivolts (0.030volts) and a total NO LOAD RPM INCREASE OF ONLY 105 rpms.
Since we run 6 cell (tc) wouldn't that actually be 630 RPMs in your example?

It apples and oranges anyway. You are comparing average discharge voltage, while they are pointing out a difference in nominal voltage.

Back to topic...

Given the weight savings with this LiPo, did the guys testing add lead to rebalance their cars? Lotta Lead? lol
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Old 12-23-2005, 08:35 PM   #17
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Quote:
Originally Posted by Rick Hohwart
Therer is a difference between the types of batteries that can never be changed. Even if the capacity of a NiMH pack equals that of a LiPo pack, performance will still be inferior.

We have charged the Platinum pack at 10 amps and have seen no ill effects.
If they are charged at such a high rate what tempature will be reached inside the battery. We know that high temps will damage any battery so how long will it last in other words how many time can it be recharged? 1000 times?
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Old 12-23-2005, 10:14 PM   #18
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Quote:
Originally Posted by JKA
Since we run 6 cell (tc) wouldn't that actually be 630 RPMs in your example?

It apples and oranges anyway. You are comparing average discharge voltage, while they are pointing out a difference in nominal voltage.

Back to topic...

Given the weight savings with this LiPo, did the guys testing add lead to rebalance their cars? Lotta Lead? lol

JKA - Nominal voltage equates to average voltage... If the nominal voltage is higher the average voltage will be higher.

I have tested and continue testing LiPo's and the Vaverage is even higher when compared to NiMh because they have a completely different discharge curve.
Different chemical reaction, different power/weight ratio...way too many differences.

Like Rick said, they are different!!!

and you are right...back to the LiPo issue.

Isaac

Last edited by BATT_MAN; 12-24-2005 at 09:48 AM. Reason: splling :0
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Old 12-23-2005, 10:55 PM   #19
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If nothing else they will be good for practicing, you can change your setup a couple times and still get plenty of laps after each change. Might have to add some weights to make the car handle the same as it would with ni-mh cells though. I'll wait for someone else besides Orion to release them before I consider a purchase though.
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Old 12-24-2005, 01:31 AM   #20
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It would be great to organize 20 minutes races with 19 turns motors, has Ryan tried the Element 19 turn V2 with the Platinum ?

Now we could make 5 min qual. 10 min 1/4 final 15 min semi and 20 min finals !
Like in Nitro.
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Old 12-24-2005, 01:44 AM   #21
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More track/race time will be cool...

BATT_MAN... great information (it's about time )...
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Old 12-24-2005, 08:54 AM   #22
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One problem if every race heat was 10 min long you would stay there for about 12-14hr assuming you have 3 quals and a main.
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Old 12-24-2005, 09:17 AM   #23
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Quote:
Originally Posted by TadehI
One problem if every race heat was 10 min long you would stay there for about 12-14hr assuming you have 3 quals and a main.
Thats not true...how long does it take to get through a Nitro Sedan club race? Only the mains are longer. Qualifiers are still 5 min and the mains are 15 min to one hour.

We could do the same. 5 min qualifiers and 10 min mains.

I bet that in 2 years (with brushless and LiPo) we could run a 30 min main non stop.
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Old 12-24-2005, 09:43 AM   #24
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My theory was only if qualifiers and mains were 10 min I have no problem with that theory AdrianM. I believe that that would be the way to go. Battery prices would have to go down but personally I would rather by a Lipo and run it in offroad and maybe stock or 19-turn touring and just have one pack. I wonder if sedan designs will change due to less weight on the batteries side?
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Old 12-24-2005, 10:40 AM   #25
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Quote:
Originally Posted by TadehI
My theory was only if qualifiers and mains were 10 min I have no problem with that theory AdrianM. I believe that that would be the way to go. Battery prices would have to go down but personally I would rather by a Lipo and run it in offroad and maybe stock or 19-turn touring and just have one pack. I wonder if sedan designs will change due to less weight on the batteries side?
Club races here can be 50-100 entries so 10 min quals would be a big problem. 5 min quals and 10 min mains would be ok.
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Old 12-24-2005, 10:57 AM   #26
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Quote:
Originally Posted by TadehI
My theory was only if qualifiers and mains were 10 min I have no problem with that theory AdrianM. I believe that that would be the way to go. Battery prices would have to go down but personally I would rather by a Lipo and run it in offroad and maybe stock or 19-turn touring and just have one pack. I wonder if sedan designs will change due to less weight on the batteries side?
JRX would be ok I guess, the rest I would guess you could just add weight to the battery side to equalize the chassis without redesigning it.

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Old 12-24-2005, 12:00 PM   #27
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Quote:
Originally Posted by RKeasler
JRX would be ok I guess, the rest I would guess you could just add weight to the battery side to equalize the chassis without redesigning it.

Rod
All cars will have to add weight. Even the JRXS....we all still have to be 53oz on rubber and 50oz on foam.

Eventually car weights will come down,LiPo packs will get a lot smaller and chassis will be re-designed.
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Old 12-24-2005, 12:52 PM   #28
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LiPo Battery info, characteristics, advantages, and disadvantages

Characteristics
Lithium is the lightest of metals and it floats on water. It also has the greatest electrochemical potential which makes it one of the most reactive of metals. These properties give Lithium the potential to achieve very high energy and power densities in high power battery applications; therefore, they are GREAT for r/c cars.

Lithium batteries have now taken their place as the rechargeable battery of choice for portable consumer electronics equipment. Though they were expensive when introduced, volume production has brought the prices down. In the near future, we will see the Lithium batteries overtake the r/c market.


Some Advantages
In many ways Lithium is almost the perfect cell chemistry. They have many attractive performance advantages which make them ideal for high power applications. Just what we need for r/c cars...

High cell voltage of 3.6 Volts means fewer cells and associated connections.
Flat discharge characteristics
Very high energy density.
Very high power density.
Low weight
Can be optimized for capacity or rate.
Individual cells up to 1000Ahr capacity available (not milliamp hour).
Can be discharged at rates up to 40C. The high discharge rate means that we can get by with lower capacity batteries that will deliver high energy rates.
Fast charge is possible.
Can be deep cycled.
The cell maintains a constant voltage for over 80% of its discharge curve. Thus, it delivers full power down to 80% DOD. This means that the battery will deliver a consistent punch (and voltage) before becoming effectively discharged.
Very low self discharge rate.
Very high coulombic efficiency (Capacity discharged over Capacity charged) of almost 100%. Thus very little power is lost during the charge/discharge cycles. NiMh batteries fall in the 80-90% range.
No memory effect.
No reconditioning needed.
Will tolerates micro cycles without affecting performance. This means that the battery does not need to be fully discharged before charging again. If we run 5 minute races, you can recharge without cycling the cell.
Long cycle life. Cycle life can be extended significantly by using protective circuits to limit the permissible DOD of the battery. This mitigates against the high initial costs of the battery.
Does not need reconditioning as do nickel based batteries (NiCd, NiMh).

Some Shortcomings
Internal impedance higher than equivalent NiCd or NiMh (contrary of what has been posted)

Stability of the chemicals has been a concern in the past. Because Lithium is more chemically reactive special safety precautions are needed to prevent physical or electrical abuse and to maintain the cell within its design operating limits. Lithium polymer cells with their solid electrolyte overcome some of these problems.
We will see stricter regulations on shipping methods than for other cell chemistries.
Degrades at high temperatures.
Capacity loss or thermal runaway when overcharged.
Degradation when discharged below 2 Volts/cell.
Venting and possible thermal runaway when crushed.
Need for protective circuitry.

Although Lithium cell technology has been used in low power applications for some time now, there is still not a lot of field data available about long term performance in high power applications (like an r/c car). Reliability predictions based on accelerated life testing however shows that the cycle life matches or exceeds that of the most common technologies currently in use.

These drawbacks are far out weighed by the advantages of Lithium cells and are now being used in an ever widening range of applications.

Charging

Should be charged regularly.
Battery lasts longer with partial charges rather than full charges.
Can not tolerate overcharging and hence should not be trickle charged.
Constant voltage Constant current
Chargers have to operate in one of these modes or use both of them.

Hope this will help.

Isaac
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Old 12-26-2005, 03:00 AM   #29
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And has anybody tried a Platinum ? Rick said they have been shipped !
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Old 12-26-2005, 10:20 AM   #30
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Not sure about the T2, but the Fk05 is typically overweight in FOAM without adding anything....



I don't think running 5 minute qualifiers and then 10+ minute mains will work very well....its gas....and racers will be required to make guesses on gearing and such to stay competive...

Racing is fine right now at 5 minutes......by the end, the top 3-5 are usually on the lead lap......in gas, yer lucky if the top two are even on the lead lap....it just becomes a car endurance war....5 minutes gives plenty of RACING......and allows the tracks to have enough entries to stay open.....

I can barely hold my arm up for 8 minutes as it is.....

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