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bcuzau
12-19-2005, 07:36 AM
I've been into RC's for a awhile(7yrs) before I took a long break from the hobby(6yrs).. Well I've brushed the dust off my old equipement and now I'm back into this great hobby just because of the Kyosho H8..

Anyway.. Lipos and brushless are new to me..

Brushless seems a little fast for me(old school :) ) but I was just wondering what are Lithium polymer batteries? Will they benefit someone running a standard 7-cell HF ESC? Is that possible? pros, cons?

Thanks,
Nam

hrtln
12-19-2005, 08:06 AM
Cool Avatar. ;)
I just got into Lipo's within this past month. And brushless to boot. I wasn't planing on doing eather one, but it is the ticket w/ these things. IMO anyway.

bermbuster
12-19-2005, 10:17 AM
the li pos are smaller (in some cases) and definitely lighter. They also have the ability to store more power. They can discharge a lot of power too.
Lipos cannot be discharged too low so with a brushed setup you will need a low voltage cut off to protect your battery pack. You also need a charger that can specifically charge lipos. Improperly cared for packs will self destruct (bloat and can possibly catch fire). United rc makes really awesome lipo packs for the H8.

GP1100/Intellect1200 (nimh)2/3a cells can discharge a lot of power also. With 7 cells and a brushed esc using them will not be so bad. Easy on the wallet too.....not that this hobby really is.......... :cool:
Hope I didnt confuse you more........

Hawk
12-19-2005, 05:57 PM
I will post about this again with the fear that it may be tiresome to some out there.I am not a battery expert and have never played one on television. I have read about them extensively and have used them for my needs successfully. Don't trust me nor my words. Go find out for yourself. There are many untrue 'truisms' out there that can cause harm.

LiPos have their particular problems. There is hyperbole running rampant about them and some true but flashy videos of their ability to end in a dramatic way when abused.

LiPos have a much higher energy density then NiCad and Nimh batteries. The size and weight to produce the same amount of power is much less than the Nickel based technologies. One of the better features of LiPo batteries it their voltage curve is much flatter until they are near cutoff. That means it starts at 7.1v and stays there or near there until it is time to stop using it.

As to the cutoff issue, LiPos have a cutoff voltage, lower than which may cause damage or be disabled to charge. Nimh and Nicad have a cutoff voltages also. The exact result of going below cutoff voltages is different depending on the technology. Storage condition, charge status, is different for different technologies also.

Lipos major issue with powering cars especially high end, high amp cars is they have to be higher mAh and larger. You have to look not only at the mAh rating but the cont. discharge ratings usually in C or a number times the mAh rating. 1200 mAh at 10C is 12A discharge rating. The higher ratings, 15C and above are not as common and are more expensive. This becomes apparent in brushless motor setups and low wind brushed motors. They require high ampere flow to work as they are designed.

Another issue with LiPo is voltages are different. Not a bad thing but different. Nimh and Nicad cells are 1.2v per cell and the industry has standardised around that. Most things electrical are based on x number of cells or a voltage that turns out to be evenly divided by 1.2v, Nimh, Nicad voltages. LiPo cells are nominal 3.7v per cell so a 2 cell is rated at 7.4v. a nice fit with many electronic equipment ratings. This is usually not a real issue except in some very specific situations.

Charging is an important issue to examine. LiPos being charged can be spectacular, either in their ease of use and performance or in their self destruct cycle. This is a very dangerous situation if you don't use the correct, LiPo specific charger or have injured the battery case in a crash or through other abuse. My sugestion, find a battery manufacurer that you like or that suits you situation. Read their info about the technology you are considering. If they don't offer information about use, abuse, charging and storage care, they are not a manufacurer, they are dumping product on the people silly enough to buy from them.

In the end, you need to find out the limitations and benefits of a power storage technology and see what best suits your needs. Don't take talk around the boards and at the track as gospel. I have heard lots of just plain wrong information given out. Find out through a little research. There are bad outcomes with any kind of energy storage technology that you may not be aware of until you are injured by it.

Last thing I want to say:
Don't carry battery packs or cells in you pocket, period. The one time you do and it shorts and causes painful injury is not worth the convenience.

pimpsmurf
12-19-2005, 06:34 PM
Sounds great to me man.

Lithium power is a pretty fantastic technology (I don't charge my cell phone for 3-4 days most of the time!)

For larger scale r/c cars, it can cause more trouble than smaller scales.

With a high performance motor, you can pull serious amperage. FAR about the manufacturer's stated limits. The 1.66Ah Apogees from United RC only provide 10.5C of constant current, which amounts to 17.43 amps. That is more than enough to run a mamba brushless motor (provided it isn't over geared) at top speed. I quote Castle Creations "once up to speed you're only drawing around 4-5A"

However the cells should get be hot by the end of the run. This is mostly because the pack is only rated for 23.24 Amps maximum discharge. Mambas can pull more than twice that off the line. You will loose life cycles of the cells, and risk overheating because of this.

Did I mention Castle Creations is releasing a mamba for 1:10 scale cars, trucks, and monster trucks?? Hopefully the Mamba Monster Max will handle 2 motors. =)

-JNY

bcuzau
12-19-2005, 11:24 PM
Thanks for all the replies..

Lipos sounds very good, If i want to switch to a brushless set-up. But is there anyone using lipos with a standard esc and a brushed motor? is that even possible because of the extra current?

bermbuster
12-20-2005, 02:53 AM
the lipos you would use with the stock esc would be a 2 cell pack 7.4 volts. that voltage doesnt get the 400 sized brushed motors moving.......
the next option would be a 3 cell lipo(11.1v) which is way too much voltage for the stock esc and a brushed motor.......
You could possibly put a 1/10 scale esc that can handle 10 cells and use the 3 cell lipo but i dont know of a brushed 400 motor that is up for the task.......
i have a brushed set up using the united sport packs 9.6v and the x speed motor with the stock esc......it is not as fast as a brushless but it goes about 20mph. maybe a bit faster. With the lipos you will get to about 35mph plus.....

Trickpatrick
12-20-2005, 03:25 AM
I was using a tekin g10 pro ESC, Li-pos 3cell 11.1, and the Xspeed motor with a 12t pinion.

I raced this for a couple weeks and I recomend it very nice balance of speed and weight.
I am sure the Xspeed wasn't intended for this but it works fine not too hot but I only ran it for under 10 min at a time which is plenty for racing.

Not for bashing to little run time but makes a good poor mans race car.

mOOsE
12-20-2005, 03:50 AM
wow, 11.1 on a brushed motor! impressive. I tried running a 3cell lipo to a tuned 300 one time but it spun so fast the armature ripped apart :D

pimpsmurf
12-20-2005, 07:47 PM
You should look at the Novak Spy Mini ESC. They have a basher (with reverse) version, and a faster no-reverse option. I believe it can handle 3 cell lipo and up to 14 volts or something. I forget.

-JNY

Trickpatrick
12-20-2005, 09:07 PM
The novak ESC is a good unit but I would look at thier site for voltage limits.
Before purchase!

RURC
01-03-2006, 12:05 PM
I have been running (without fires or explosions) lithiums for about 5 years and an so impressed with their performance that they are all I use. From my 1/24 mini z's to my 1/6 project from hell car. If you can use more than 1/2 your brain power you should not have any problems. HAWK has said the same things I have said in many forums and even in the first days of this forum. They can be dangerous. They can distroy your craft. They destroyed my friends shed that he had for his RC work. I have been in RC for 25 years and I have never before seen something that has and will continue to change the sport more than the combination of Lithium and brushless technologies. As with any cutting edge technology there are some lessons. When I make a Lithium pack (for cars) I wrap it in latex foam rubber to try to soften any blow to the pack. I also charge them in a fire proof Battery Bunker. I charge them as slow as possable (generally about an hour for 2000 maH and as long as 6 hours for 8000 maH). An 8000 maH battery in my B4 under race conditations will run for almost 2 hours.This is with full brushless setup. This dose come at a cost though. The battery is $250. They are 15 C batteries which means that you can do constant draw of 125 amps with a peak of 160 for 10 seconds. Now the numbers I saw for the Mamba from pimpsmurf although generally correct they still lack a little. Ask Shaun about the peak draws seen in Mini T's. Peak draws of greater than 100 amps happen. Although these are momentary draws, that power has to come from somewhere. Do not buy cheap off brand packs. Get the biggest maH rateings you can. 2000 maH packs with 15 "C" rateing or better are what I reccomend. That is 25 amp continous. Most 15 C packs I see have a peak of 20 or 22.5 C, that is a big differance over the 10 C packs out there. Finally in keeping with the scare tactics of videos watch the video linked at the end of my note. This is what can happen. But if you use at least 1/2 your brain you can avoid any problems.
http://www.helihobby.com/videos/LithiumBattery.wmv

OH YEA If you do not want to dive into this because of the expence dont ever drive a car with this set up in it. Once you do you WILL spend the money. :)

mat3833
01-03-2006, 06:34 PM
now that was a good post. i completly agree. the only reason i got out of lipo is i didnt have the money to get good quality cells and chargers. i did have an explosion happen once. it was contained in a lexan container thankfully. lipo is the best thing to happen to RC since brushless (or did lipo come first....) and if you be careful you will have the ride of your life!!

Matty

RURC
01-03-2006, 07:49 PM
now that was a good post. i completly agree. the only reason i got out of lipo is i didnt have the money to get good quality cells and chargers. i did have an explosion happen once. it was contained in a lexan container thankfully. lipo is the best thing to happen to RC since brushless (or did lipo come first....) and if you be careful you will have the ride of your life!!

Matty
Mat you are makeing me crazy. LOL

mat3833
01-03-2006, 08:34 PM
Mat you are makeing me crazy. LOL

why? because i can still be friendly after you criticised me?? but seriously why am i driving you crazy??

Matty

bigron
01-20-2006, 03:03 AM
How would you reccomend charging lipo saddle packs. What I have is 2 900mah 11.1v 3cell packs wired parallel. I have a duratrax ICE charger thats suppose to be very able to charge lipos.

Thanks

RURC
01-20-2006, 11:41 AM
After going to the Duratrax web site and downloading the manuel and reading all pertinant information I have come to the conclusion that this is NOT a LiPo charger. It IS a LiIon charger. The diferance is in the output voltage max for lithium chargeing. It runs the same voltage curve that LiIon chargers do; which is too low to FULLY charge a LiPo pack. You will however get upto a 90% charge into your LiPo. Now this has its advantages. Your batteries will last much longer (number of overall charges) as compaired to full charges. This is something I have learned over the past couple of months in extensive talks to the designers of lithium batteries. I personally have been useing LiPo and LiIon batteries for many years and had been useing a LiIon charger and unknowingly not been fully chargeing. I have still been blowing by everything on the track and on the block in spite of a 90% charge. I have reascently bought the Hyperion chargers (3 of them) and I have to say that there is a diferance in a 100% full pack and a 90% full pack. The big diferance comes in the punch. I had to completely reprogram all my speed controls because of this. What I do is when I am doing beta testing and raceing I use the Hyperion chargers, but if I am practiceing and bashing I just use my old MKII chargers. I do this to increase the life of my packs (yes I do try to be somewhat thrifty). If you have this charger already and you are not very serious about raceing I would say use it. You will get almost all of the benifits but you will also increase the life of your pack. The trade off may be worth it. For me I do it both ways. But then again I am nuts. :D

RURC
01-20-2006, 11:55 AM
lipo is the best thing to happen to RC since brushless (or did lipo come first....) and if you be careful you will have the ride of your life!!

Matty


Matt
I had not noticed this comment before. I learned about LiPo's and brushless from my flying buddies at about the same time. However, finding a brushless set up that even had brakes was impossable then. So I statred running LiPo's like 5 years ago in my cars. The diferance was amazing even with my brushed setups. When I built my packs (sometimes just rebuilt) I would try to match the shape and size of normal NiMH packs. Then in tech insp they would not notice anything. At that time there was nothing in the books that outlawed them but at the same time there was nothing allowing them, I did not want to push it. In the 15 years I spent with Porsche I learned if the rules dont say it do it quietly till it dose. So for cars I had LiPo's first and the brushless came about 6 months later with Hacker and Schultz controllers. Now in my flyers and boats I have had both for the same ammount of time.