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Old 08-25-2005, 07:18 PM   #16
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Quote:
Originally Posted by Hawk6
Nobody has answered the question about weight.

For Tamiya silver can motors and 5 minute races, is the extra power of say a 3300 mAh worth the extra weight compared to a 1900 or 2400 mAh?

More power is fine, but what about power to weight ratio. Is it worth carrying around the extra weight to have power you will never use in a 5 minute race?

Thanks for any thoughts.
hawke, have u measured the weight comparison of a 3300 to a 2400? i wonder how much heavier they are?
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Old 08-25-2005, 07:20 PM   #17
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No, I haven't weighed them yet. Just wondering. Some people spend a lot of money to lighten their cars. Just wondering if all that hard earned money is wasted by putting a heavier battery in. Thanks.
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Old 08-25-2005, 07:26 PM   #18
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I would imagine the performance gained by using the newer cells would outweigh the advantages of a slightly lower weight by using 2400/3300 cells. That's just my guess, though.

Not only that, but many cars that are underweight out of the box need to be brought up to weight anyway at large races. Therefore, battery weight would not be an issue.
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Old 08-25-2005, 07:33 PM   #19
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I'm not trying to be a smart a$$, just trying to learn. What is the performance gain?

I don't have hard data, so I'm just going to make up some facts here for discussion. Again, I'm talking a Tamiya with a silver can motor.

If I run a 1900 mAh battery for a 5 minute race, I'll use 80% of the power in the pack.

If I run a 3800 mAh battery for 5 minutes, I'll use about 40% of the power in the pack. What do I gain from carrying that extra power around?

Is it that the last minute will be just as strong as the first, or will the first minute of a 3800 be faster than the first minute of a 1900?

Thanks again.
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Old 08-25-2005, 07:38 PM   #20
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What does ZAPPED mean when it comes to batteries?
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Old 08-25-2005, 07:45 PM   #21
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Quote:
If I run a 1900 mAh battery for a 5 minute race, I'll use 80% of the power in the pack.

If I run a 3800 mAh battery for 5 minutes, I'll use about 40% of the power in the pack. What do I gain from carrying that extra power around?
GP3700 and IB3800 have higher voltage then 1900 sportpacks. Besides, on a 3700 you will end the race at the begining of the discharge curve.

For stock, Sanyo RC2000 and RC2400 have nice voltages to. Maybe a good option if u consider cost/performance ratio
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Old 08-25-2005, 07:47 PM   #22
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Quote:
What does ZAPPED mean when it comes to batteries?
"Special" treatment given by some matchers that is suposed to enhance batterie voltage. I seriously doubt this claims...
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Old 08-25-2005, 07:48 PM   #23
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Thanks Itchy. I'm in this hobby with my 10 year old son - we each have our own cars. We're having a great time, I'm just trying to keep an eye on expenses since they are basically doubled. For a race day I need 8 battery packs, not just four.

Thanks.
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Old 08-25-2005, 07:57 PM   #24
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No problem m8.

Nimh batteries perform better on their second charge. For racing (not counting practices---> u can use older packs) 2-3 packs are usually enough. Just remember to let the batterie cool down for 2 hours before charging it again.

Good luck for you and youre soon
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Old 08-25-2005, 08:45 PM   #25
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Quote:
Originally Posted by imjonah
"GP3700s, for instance, are still the choice of most pro racers"

2. Tech question- Is there some way of getting more power out of a battery faster. Theoretically the ideal would be if my battery was totally drained at the end of the race.

Hard wire and use as few solder joints as possible. Less resistance means more electrical flow.

I do agree with you on the 8 minute races.
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Old 08-26-2005, 12:09 AM   #26
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Quote:
Originally Posted by Itchy
GP3700 and IB3800 have higher voltage then 1900 sportpacks. Besides, on a 3700 you will end the race at the begining of the discharge curve.

For stock, Sanyo RC2000 and RC2400 have nice voltages to. Maybe a good option if u consider cost/performance ratio
are you saying the battery performs best when it hits the beginning og the "discharge curve"? ... at what % does this occur?

i would of thought a battery that maintains its volts and amps longest will have the better performance
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Old 08-26-2005, 12:51 AM   #27
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Quote:
Originally Posted by noobie
are you saying the battery performs best when it hits the beginning og the "discharge curve"? ... at what % does this occur?

i would of thought a battery that maintains its volts and amps longest will have the better performance
IMHO, the "discharge curve" normally occurs around 75%-80% of a full charged battery. A fully charged battery will run perpendicular to the Y axis and drop down when it is completely depleted. Now the newer batteries with its added capacity such as the Nickel Metal Hydride have been proven to defy that. Sometimes, on the newer cells such as the GP3300s, "discharge curve" occured in the last 80% of the battery which theoritically means .80x3300=2640mah. Now most of GP3300 had been recorded charging beyond it's capacity and so is the Intellect batteries. My calculation theory could be off by a few hundreds of mili ampere hours but you can try measuring it by yourself by running your car, timed of course or have a friend timed it for you, until the battery starts dying. When the car start performing lower than what you started, that is when "discharge curve" starts occuring for you.

Now to answer your question about when the IB3800 is not legal: It is not legal when the race director/organizer said do. Regardless whether the regulation permits such battery or not, the final decision lies on the race director/organizer. They usually post it on their race rules on registration day way before the race so no one would ask if anything beyond what they specified is allowed.

I hope that helps
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Old 08-26-2005, 01:29 AM   #28
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Quote:
Originally Posted by Itchy
"Special" treatment given by some matchers that is suposed to enhance batterie voltage. I seriously doubt this claims...

Your typical NiMh celll will drop .2 - .3 in IR when zapped so zapping does improve the cell. Trust me we wouldn't zapp cells if it wouldn't improve the cells.
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Old 08-26-2005, 01:30 AM   #29
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Higher capacity batts produce much higher voltages longer into the discharge, so at 5 minutes, as stated the voltage of the pack will be much higher with 3300-3800 than a 1900 pack. The cells are just better.

Even 30 seconds into a run, a 3300 is going to have MUCH higher voltage than a 1900 or 2000 or 2400 for that matter. I have done extensive testing on this. Its a fact.

More voltage = faster car.
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Old 08-26-2005, 08:17 AM   #30
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Quote:
IMHO, the "discharge curve" normally occurs around 75%-80% of a full charged battery. A fully charged battery will run perpendicular to the Y axis and drop down when it is completely depleted. Now the newer batteries with its added capacity such as the Nickel Metal Hydride have been proven to defy that. Sometimes, on the newer cells such as the GP3300s, "discharge curve" occured in the last 80% of the battery which theoritically means .80x3300=2640mah. Now most of GP3300 had been recorded charging beyond it's capacity and so is the Intellect batteries. My calculation theory could be off by a few hundreds of mili ampere hours but you can try measuring it by yourself by running your car, timed of course or have a friend timed it for you, until the battery starts dying. When the car start performing lower than what you started, that is when "discharge curve" starts occuring for you.
I think cells loose their voltage very fast on the 1st 20 sec, then slowly till about 1.05v and then they drop very fast. U can see a good graph on RC Car action of august.

u can also here
Its pulse discharge, but racing isnt linear anyways. U can see cells loose their punch gradually. Thats what i meant when i said
Quote:
Besides, on a 3700 you will end the race at the begining of the discharge curve.
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