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Old 12-14-2007, 08:27 PM   #16
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I don't race 1/12th scale but couldn't you run a 3.7 volt lipo and a little hotter motor and achieve the same performance as 4.8 and 27t. How about 3.7 and 19t or something like that. With brushless run 10.5 instead of 13.5 or 13.5 instead of 17.5.

Has anyone run a lipo yet that is reading this thread?

How much slower is it?

A bunch of us are running 13.5 and Lipo in sedans at CEFX, that combination works fine (it's really fast). By the way, we are all running the same weight,1525 grams, no matter what type of cells are used.
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Old 12-14-2007, 08:28 PM   #17
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Originally Posted by gurumods View Post
It wouldn't be if someone would make a cutoff for 1/12.What is so hard about knocking the voltage down from 7.4 to 4.8
Not hard at all if all you need to power is the receiver and servo drawing maybe 1 amp. To handle a motor drawing 40+ Amps, you would need a pretty big (translation: heavy) bunch of electronics.
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Old 12-14-2007, 08:32 PM   #18
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NiMH won't go away in the highly competitive STOCK class, where everyone is looking for the slightest edge over the other guy. LiPo's just don't have the peak voltage of NiMh, yet...

As for modified racing, I think LiPo will be the clear winner once approved with LiPo's greater amperage capabilities. Rick Howart already touched on this as well in the Reedy LiPo battery thread.

I'm not too sure how to equalize this argument, but as long as NiMh have a voltage advantage, they will remain the choice for competitive stock racing. For me, I'll take the consistency over a 5-minute race and save money compared to the NiMh guys. I don't have to win to enjoy racing.
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Old 12-14-2007, 08:37 PM   #19
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You dont wan to run a single cell lipo, that means having a RX battery pack and the lower voltages may cause problems in the ESC. The BEC is a voltage regulator circut, not a DC-DC convertor. Then you have your onboard circuts, designed to run on the 4.8V to 6V from the BEC.

To me it just seems logical to compromise and rasie the 4-cell voltages just a little and drop the 6-cell voltages a little. Look how easy it was for Novak to wind some brushless motors to equate a 7.4 lipo to a 4.8V NiMH. Surely the 21.5 motor on 6.6V would be close to a 17.5 on 4.8 in oval and 1:12.
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Old 12-14-2007, 08:47 PM   #20
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my 3.2r is the only thing keeping me from being nimh free!
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Old 12-14-2007, 08:50 PM   #21
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Look at the popularity of LiPo two years ago. Look at it a year ago. Look at it today.

Every new chassis that comes out has special provisions to make sure LiPo fits. If that's not progress, I'm not sure what is. Be patient, things are moving right along. There's no need to taunt NiMH users, or push the issue, these things just take time. Remember all the resistance to brushless in the past? Now you can't give your lathe away for free.
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Old 12-14-2007, 09:04 PM   #22
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The problem w/ sub c cells is that you have to push them to their absolute max to get the best performance out of them. This is not true for lipos. I do not want to race in an inviroment where a guy can spend $500 a week on batteries & actually gain an edge because of it. Instead I want to race in an enviroment where your top of the line $200 lipo pack can be set up to perform at the max and then be re used 500+ times, not a 10 amp charge for 3 cycles and then trash them.
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Old 12-14-2007, 09:28 PM   #23
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Quote:
Originally Posted by party_wagon View Post
The problem w/ sub c cells is that you have to push them to their absolute max to get the best performance out of them. This is not true for lipos. I do not want to race in an inviroment where a guy can spend $500 a week on batteries & actually gain an edge because of it. Instead I want to race in an enviroment where your top of the line $200 lipo pack can be set up to perform at the max and then be re used 500+ times, not a 10 amp charge for 3 cycles and then trash them.
Amen to that. I've seen some deep pockets do just that.
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Old 12-14-2007, 10:13 PM   #24
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Originally Posted by Ted Flack View Post
I don't race 1/12th scale but couldn't you run a 3.7 volt lipo and a little hotter motor and achieve the same performance as 4.8 and 27t. How about 3.7 and 19t or something like that. With brushless run 10.5 instead of 13.5 or 13.5 instead of 17.5.

Has anyone run a lipo yet that is reading this thread?

How much slower is it?

A bunch of us are running 13.5 and Lipo in sedans at CEFX, that combination works fine (it's really fast). By the way, we are all running the same weight,1525 grams, no matter what type of cells are used.
thats a good idea,i thoght about the same
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Old 12-14-2007, 10:22 PM   #25
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I know I heard that up in Nor-Cal some guys were testing w/ 1/12th scale and single cell lipo voltage (3.7) using the Low wind B/L motors (ie:3.5's) and I had heard a 3.5 on single lipo ran about like a 19t/4 cell.

This would be a very viable option for 1/12th scale.
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Old 12-14-2007, 10:24 PM   #26
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Default lipo voltages.

hiya folks,

Its unlikely that LIPO cell manufacturers will ever change the voltage per cell any lower. It is entirely possible, but will not happen, why? cos the hobby business is microscopic compared to what lipos are typically made and sold for... consumer electronics!

mobile phones, pdas, laptops etc, they all run off a standard voltage, which over time has been set to 3.7v or multiples of that.

manufacturers have also designed their cells around these markets, not the hobby business, we are really just an incidental occurance, a pleasant side revenue, if you must.

no lipo manufacturer will deliberately design cells at 1.5v or 1.2v per cell.

lipos, are the way forward, but it takes time for more battery manufacturers, such as orion, reedy, trackpower, core creations etc to pick up on this technology before it will be legal.

japan is infamous for business protection, so it's not surprising that they, of all people, would still cling to brushed motors and nimh batteries for many years yet.

already, 23T brushed motors have evolved into a more competitive class with the new rules. i really dunt see nimh and brushed motors going the way of the dodo just yet.

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Old 12-14-2007, 10:34 PM   #27
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Originally Posted by party_wagon View Post
The problem w/ sub c cells is that you have to push them to their absolute max to get the best performance out of them. This is not true for lipos. I do not want to race in an inviroment where a guy can spend $500 a week on batteries & actually gain an edge because of it. Instead I want to race in an enviroment where your top of the line $200 lipo pack can be set up to perform at the max and then be re used 500+ times, not a 10 amp charge for 3 cycles and then trash them.
oh man these are wise words,thx man u spoke my mind.
you go out and buy a $65 battery ok,what are u willing to do to that pack to win that trophy race?i ll tell u.,u charge it at 10 amps and u will be fast,vfast,but dont count on any special performance from that pack again,so u go out and buy another $65 pack,now how many of us can do that?
you gonna always be faster than ur mate as long as u keep buying new packs providing that u and him of the same skill.
and in case that pple dont know that when u put 4-5 cycles on ur new pack,it will go out of match and if u dont have a matcher to moniter evey cell,u are racing a bad pack.
i always hear this in my clup:why is this guy faster then me,my lines are better,he must have a special motor or hes cheating.well he simply have better newer packs,dont put 8 cycles on ur packs and say oh..but my packs are new,u make me laugh.
i am not expecting when using lipo in a competitive racing to have 50 cycles but at least 20 cycles without a drop in performance now that would make a diffrence and the fast guy with deep pocket or battery sponserd wont always be the fastest,cheers
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Old 12-14-2007, 11:04 PM   #28
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There are 1.5V LiFeS2 cells out there that are designed with high rate discharge and saftey. They are used in mining head lamps where other Li-Ion cells are deemed too risky.

There are 2.0V Ag-Zn used in aerospace for their saftey track record

There are 3.2~3.3V LifePO4 used in high-rate discharge: powertools, larger laptops, EV's

There are 3.7V Li-Ion used in lower rate discharge: Laptops, light duty cordless.

It is just a matter of picking a chemisty and sicking with it.

I am saying no to LifeS2(too new), Ag-ZN(too expensive), Li-Ion 3.7V(Voltage too high).

I think the 3.3V LiFePO4's would make the best compromise off all the chemistries and have better power density than NiMH or Ag-Zn. Li-Ion will always have better power density but can not tollerate the higher dischrage rates.

The single cell Li-Po is a bad idea. So you are running a 3.5 motor now to make times like a 19T, what will mod racing look like? 1.5T you have to bee joking? Did you not read my post about the ESC's and needing a RX pack? I rather just have skip having extra equipment and keep it simple.

I still feel developing a LiFePO4 3.3V cell 23mm x 55mm would be a good all around compromise for all racing classes except mini/micro. Winding the motors for slower RPM would be alot easier than winding for higher rpm as with a single cell LiPo. Since Euro sedans are already using 5-Cell layouts this change could go unoticed with the voltages being very similar. For the U.S. folk, embrace the LiFePO4 it wil be cheaper in the long run since more an more industries are moving to LiFe based batteries. I suspect the cell pricing will be about the same or less due to reduction in cell failures. Since sedan guys will be buying 1 to 2 cells less that could mean up to and easy $30 a pack saved!


About the physical conversion process.
On most t-bar 1:12 cars with lengthwise battery slots the slot is alreay 55~60mm. The same also goes for most 1:10 oval cars, the batteryslots are mostly longer than 55mm. On linked 1:12 cars, well I guess you can extend the slots yourself or pony up $40 for a new main chassis. For the 1:10 sedans, the slots will have to go from horizontal to lengthwise but would be the same ballance as a 5-cell pack

With racers charhing batteries at 12amps or dead shorting I really don't think intoducing a cell the same size as a sub-c would be a good idea. It would bee too easy to place the pack into a Zero-30 tray turn that battery into a gernade the next charge. That is why I am leaning to the 23mm x 55mm size.
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Old 12-14-2007, 11:18 PM   #29
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The NiMH "punch" advantage is dispensed with if one imagines a day when our minimum car weights are not oriented around the sub c standard. Stock, 19t, 13.5, or whatever, would be more than adequate at the 1200-1300 gram mark that lipo's and chassis designed around them would permit us to run. (12th scale would run mini packs and mamba-sized brushless--I've seen it done. It rocks.) And though they seem to go together like peanut butter and chocolate--lipo's and brushless--it's frustrating that brushless has gained acceptance ahead of lipo's.

Running a lighter car is so much easier on every component, mechanical, electronic, or otherwise. Tires last longer...EVERYTHING! And I think lipo's would actually extend the competitive prospects of brushed motors because it would be significantly easier to maintain them. Speaking of, look at 12th scale. Even really competitive club racers spend a lot less time on their motors because the loads are so much lighter. Brushes and comms simply don't wear out as quickly. Yes, part of that is 4 cell vs. 6 cell, but that's really only another hallmark of the car's overall lower weight. If the brushed motor crowd had their act together, they would actually get on the lipo train and lobby for lower minimum weights. Guess what, if you're not spending money and time on sub c's, you can devote more attention to your motors, which would then require less maintenance anyway. And then one could consider the nice things about brushed motors for a change, principally the still-superior feel compared to brushless (see offroad buggies.) Do you hear that brushed motor guys (big echoing empty hall on THAT one), get behind lipo's!

Lipo's are the revolution. Electric flight has exploded, and lithium battery tech is the reason. It's insane that organized racing hasn't embraced this technology yet. Insane and not remotely to the credit of the people in charge of the show.
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Old 12-14-2007, 11:21 PM   #30
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I truly hope that all of you Lipo and brushless motor advocates are not so naive as to believe that once the majority of people are running lipo and brushless that the motor and battery wars won't start up again. I know everyone reading this knows there is someone in their basement right now experimenting with a lipo pack to get that little "extra" out of it. People are already experimenting with different com sizes turned down on a metal lathe and laptops to tweak the brushless motors. The only difference between sub-C/Lipo and brush/brushless will be the technology used to tune/tweak them.
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