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Old 09-08-2005, 09:12 AM   #106
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Quote:
Originally Posted by andsetinn
MobileIT, I think you're too pessimistic. I expect you're pleasantly surprised at every evening to have survived through the day with all limbs intact . I've carried GSM cellphone now constantly for over 10 years, as have most of my friends. None of us personally knows anyone whose cellphone has exploded, none of us knows anyone who personally knows anyone whose cellphone has exploded. I'm thinking it's kind of like the Mark Twain death story ("this report on my death was an exaggeration"), only very few explosions, maybe even just the possibility of explosion. On the other hand, I personally know two people whose disposable lighters exploded.
For the soldering and size issue. That's your problem. I have no difficulties in soldering AAA cells. I expect you wouldn't either if you practiced a bit.
For the cost issue the solution might be more rules. There is already a rule that limits how much motors are allowed to cost. If there were similar rules that limited cost of batteries and ESCs then the cost of racing would most likely decrease. But knowing people I expect those who have money to spend, to spend it on other go faster gadgets.

I think that longer mains would help the sport a lot, letting the drivers face the challenge of longer mains would put the emphasis on driving skills, not equipment and luck. It takes lot of skills to finish longer race with the car intact and still have some charge left in the batteries.
Re: Cell phones and Laptops, etc.

These are very "controlled environments." The chargers are well designed, and the devices themselves are factory made -- no "home brew cellphones". Even still, batteries have poofed. Nokia acknowledged the fact, pointing out that the problem is generally caused by 3rd party cheap batteries. Moreover, when Apple brought out their first LiPo based laptops, they recalled them all before they sold them -- right back from the stores that were about to start selling them, because they had a potential fire problem. No problem arose after sales because they were very careful.

You guessed correctly that I do not personally know anyone who had a LiPo catch fire or explode, however, I can say that if I talk on my old Sony cell phone with its big battery, it retains heat so much that the phone is hard to hold after a couple of minutes of actual talking. It is probably *very* close to the edge in that respect.

Keep in mind that none of these uses involve competition machines, that are home built by amateurs, with mixed parts from manufacturers, or anything close to 30 Amp draw applications.

Last edited by MobileIT; 09-09-2005 at 01:18 PM.
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Old 09-08-2005, 09:18 AM   #107
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Longer races = bigger $ investment. Prices are out of control and is what is keeping this hobby from growing. Not everyone can afford a new set of 3700 batteries along with a stockpile of motors or a brushless system and they shouldn't have to. Once the hobby starts growing again I would be all for a tech type class with longer races but in the mean time there should be more focus on sportsman type classes that would appeal to a broader audience.
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Old 09-08-2005, 09:19 AM   #108
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LiPos have 3 times the power density of NimH, I know you are scared of it, but as andsetinn said, I suspect you must be in a contant state of "fight or flight" (just as the republicans want you to be). Be scared of everything and you won't have time to realize how bad this administration is. Ah.....better now.

And are you sure you're talking about LiPos (Lithium Polymer)? Not the older (few years ago) Lithium Ion, which were slightly more dangerous?

Another benefit of LiPo, is the stupid simply charging method, you can build you own charger for a few $s of parts. No more $400 Turbo 35s! No more dragging huge power supplies around with you.

Anyway.......there is no significant weight savings that I know of under the current racing rules. So I am simply throwing the rule book out and thinking outside the box. How can we make this cheaper and easier?

One of the main consumables on a 1/12 scale is tires. How can you make tires last longer? Half the weight of of a normal car. If this works, then a new 1/12 scale design can take advantage of the lighter power system and make an even lighter car.
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Old 09-08-2005, 09:23 AM   #109
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EDIT

Last edited by jamescam; 09-09-2005 at 02:26 PM.
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Old 09-08-2005, 09:51 AM   #110
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Quote:
Originally Posted by MobileIT
...Can someone post the charge time requrired for a pack of 3700 mAh, and a pack of 3800 mAh batteries?

Also, what are the discharge times?

Also what were the times for the 2000 and 2200 mAh batteries that have been mentioned?
Just do the math 3.7Ahr / 4A = .925hr * 60min/hr = 55.5min.
3.7Ahr / 30A = .123hr * 60min/hr = 7.4min
3.8Ahr / 4A = .95hr * 60min/hr = 57min.
3.8Ahr / 30A = .126hr * 60min/hr = 7.6min
2.0Ahr / 4A = .5hr * 60min/hr = 30min.
2.0Ahr / 30A = .066hr * 60min/hr = 4min.
2.2Ahr / 4A = .55hr * 60min/hr = 33min.
2.2Ahr / 30A = .073hr * 60min/hr = 4.4min.

Of course, actual numbers will vary but this is a starting point of where the charge and discharge times would be. In fact just look at the numbers on the 3700 and 3800 battery. Almost a full hour to charge a pack!! Wow!!

So how do you make it fun and less costly? Keep it at 5 - 6min per race and bring out a a 2500nimh pack that can charge in 30min. Have less classes and bigger tracks that can handle larger grids (10- 15 cars) which is now possible because most guys are using Spektrum. Change from 27T to 23T to help make gearing easier. Then all a guy has to do is bring one car, two packs a charger and radio. Nowadays people are bringing to much gear to the track. A guy is suppose to have fun at these events not break their backs lugging extra gear.
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Old 09-08-2005, 10:06 AM   #111
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Generally you charge 3300s at 5-6 amp so it's not as long as you say. Plus you don't need to discharge them after each heat/race, just let it cool down and charge it up again, so the charging won't even take 30 minutes probably. If you feel like you need to tray the batteries, do it during the week.

And while smaller batteries can be cheaper, you don't want to make it close to dropping off at the end of a race. With the new IB3800 people are noticing significantly less drop off at the end of the race (onroad).

One big local race last spring, I just used one battery, kept it in the car and kept charging it! With dirt buggies I can easily carry everthing I need with one arm.
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Old 09-08-2005, 10:07 AM   #112
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I think increasing the time of a race is an excellent idea. I mean I run 60 minute mains in gas. Why not 8 minutes in electric? I'm sure it would cause a few headaches but in the end it would be better.
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Old 09-08-2005, 11:14 AM   #113
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After racing GP cars ( 10, 15, or 30 minutes ), I feel 5 minutes EP race is too quick. That y I have GP cars now.

Why some people hate Li Po batts ? Gas car use flameable liquid nitro, which is actually more dangerous substance than Li Po in terms of getting burn / explode.
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Old 09-08-2005, 11:54 AM   #114
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MobilIT. Cheer up. Life is wonderful. We all die, it's how we live that matters. People who lived in New Orleans knew about the possibility of floods but decided to live there anyway. Most of them will move back knowing that this can happen again. You most likely wouldn't but respect their right to live where they choose. There are dangers in everything we do, carrying disposable lighter, cellphones, crossing the street. Lot of people die crossing the street, but almost all can cross the streets all their lives without dying. Very, very, very few people would use LiPo batteries if they thought it likely that they might act like miniature atomic bombs. It's possible but very unlikely.

Gordon Freeman. I said that I thought he was pessimistic. I didn't say that I thought he was scared or in constant state of "fight or flight". I'm pessimistic, I'm sure USA will start another war within 20 years but it's nothing to be scared of yet.

asw7576 good point about flameability of liquid nitro.

It's no secret that I want longer mains, up to 10 minutes for on-road touring. It might slow cars down a bit but it would slow all the cars down so we'd still get as close racing as today, only longer.
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Old 09-09-2005, 01:20 PM   #115
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Quote:
Originally Posted by jamescam
You may want to rethink and edit this statement. . . .
Done.
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Old 09-09-2005, 01:53 PM   #116
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Quote:
Originally Posted by GordonFreeman
Generally you charge 3300s at 5-6 amp so it's not as long as you say.
. . .
Actually, the 4A estimate is probably closer to a real charge time when the real charge is done at 5A. Charging is not very efficient. I remember charging NiCads for about 2000 mAh at 4A to get around 1300 mAh out. I will see if I can at least provide a charge time for 3300 mAh NiMH later.

Quote:
Originally Posted by GordonFreeman
. . . Plus you don't need to discharge them after each heat/race, just let it cool down and charge it up again, so the charging won't even take 30 minutes probably. If you feel like you need to tray the batteries, do it during the week.
. . .
Well it depends. My experience with NiMH is still limited. I have actually been mainly running my 10 year old NiCads lately. According to what I have read, you do not want to run NiMH more than 2 times per day. After that you get a drop off of peak voltage (not sure about overall capacity). Also, some people believe that zeroing out the cells before every charge does some kind of good. But I have heard fairly experienced people say a lot of conflicting things about NiMH.
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Old 09-09-2005, 02:12 PM   #117
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Quote:
Originally Posted by GordonFreeman
. . .
And are you sure you're talking about LiPos (Lithium Polymer)? Not the older (few years ago) Lithium Ion, which were slightly more dangerous?
. . .
Actually, I was lumping them together and wrongly referring to LiIon as LiPo. If anything, I should actually have been calling them all generically LiIon. But Lithium rechargeables in general are still changing rapidly. Various types of LiIon may be about as safe as LiPo right now.

Quote:
Originally Posted by GordonFreeman
. . .
Another benefit of LiPo, is the stupid simply charging method, you can build you own charger for a few $s of parts. No more $400 Turbo 35s! No more dragging huge power supplies around with you.
. . .
Huh? I thought the opposite was true. I thought LiPo needed the "special chargers" compared to NiCad/NiMH. The way I heard it, you still need special chips in the batteries to make sure you do not overcharge them, and these have to be read properly and obeyed by the charger.
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Old 09-09-2005, 02:18 PM   #118
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I think we are going to try longer mains at our local track (www.fastlanehobby.com) this winter. 6-7 minutes for touring and 9-10minutes for 1/12th. right now we have 1.5 to 2.5 minutes of run time left after our current 5 minutes. you say "gear up"---we have, to the point of cooking a few of our c2 19t motors. we are running 1yr & 2yr old 3300 packs that we recently started to dead short. that added 500-750 mah to our packs and increased our voltage immensely!!!!!!!!!! NO reason to buy new packs yet!!!
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Old 09-15-2005, 12:46 PM   #119
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I just finished charging a pack of 3300 (SMC matched GP's, 399 sec. @ 30 A pack). I have to use this charge to setup a new car, so I cannot confirm the output of the pack, but the theoretical charge time at 5 A is 39.6 min. My actual charge time was 43.56 min. [that was an error, the time was 43 min., 56 sec., sorry], with a terminal surface temperature for 1 sample cell, of 66 degrees C. At rest, the surface temperature of the cell rose over roughly 3 min. to 77 degrees C, which means that the core temperature was probably over 80 degrees C for that cell.

That looks like pretty efficient charging. Unfortunately, I will not have time to do a full cycle of a good pack for a while. I am too busy right now.

Last edited by MobileIT; 09-15-2005 at 05:27 PM. Reason: Error
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Old 09-15-2005, 12:58 PM   #120
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You do need a special charger for LiPo, but the charging method is dead simple. It's just like SLA batteries, you can build a charger for about $3 in parts!
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