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Old 07-12-2013, 01:33 PM   #1
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Default Battery debate - Capacity vs. Weight

I'm sure this has been discussed before, but since I don't like the search engine or want to sift through thousands of threads, I'll just ask.

In your opinion what is the better advantage (assuming one uses quality packs).

Having a lighter battery pack with less capacity to increase your power to weight ratio.

OR

Having a larger capacity battery where the voltage drop isn't so dramatic.
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Old 07-12-2013, 01:42 PM   #2
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As long as there is a minimum weight limit that you can make with a heavy battery, more capacity.

One possible exception would be if a smaller battery allows for a better layout. The only problem with that is the goofy rule requiring a full size battery to fit without modification.
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Old 07-12-2013, 02:21 PM   #3
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This is a great question because I mainly race 17.5 tc and VTA.
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Old 07-12-2013, 02:54 PM   #4
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That's where I'm at too. I also race 17.5 Stock TC.

On average a 5000mAh battery is ~2oz(56g) lighter than a 7200mAh battery. It probably doesn't matter for me really. I'm not racing with the world's top drivers, but I was just curious if there's a point of diminishing returns chasing battery punch. In 12th scale, I definitely feel that the car is significantly slower at the end of the run than when I started. I'm going for a 7000mAh next carpet season.

But in Stock TC, I wonder how much the extra 2oz ends up affecting acceleration.
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Old 07-12-2013, 03:10 PM   #5
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Not positive, but I believe the "Shorty" packs are just smaller capacity 2 Cell packs

2s1p - like the bigger size "actual" 2 cell packs

The larger 2 cell packs (not sure where the cut is - but I believe EVERYTHING 5000 and up at the very least) is actually a 4 cell pack wired 2s2p.

ie: a 3300 mAh 2 cell pack = 2 3300 cells wired together for voltage

but if you took (4) of those same cells and made a 2s2p pack you'd show a 6600 mAh 2c pack (It's like running 2 packs at a time) so there WILL BE output increase w/ the larger packs - and LESS Voltage Drop under load - which will give better punch.

IF a shorty pack is actually using (4) cells in a 2s2p configuration, they've got to be some pretty SMALL cells -

(That being said - ALL I use in most of my cars are the THUNDER POWER "Sport/Race" type packs in a 3300 mAh range - and they do me just fine for a LOT less money than the big packs (But, I'd want at least ONE "BIG" pack to play with to compare..or borrow)
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Old 07-12-2013, 03:20 PM   #6
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i started out with hpi plazma 6500(301 gms) in 13.5 boosted and found the extra weight a handicap,i changed to shorty 4800(216 gms)changed over to ti screws and less paint on the shell (was 104gm now 94 not a lightweight) and the car is more responsive to adjustments and accelerates faster out of the corners ive added 25 gms in weight and weighed all four corners with some small scales and i got all four within 6gms of each other car is now just over the limit at 1353gms,it was 1440gms

and regarding battery performance ,it hasnt been affected, due to the weight loss its obviously more punchy anyway
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Old 07-12-2013, 03:35 PM   #7
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I have 78g of extra weight added to my car just to get to the 1380g minimum. That's using a 6900mAh battery. I'd gladly use a slightly heavier battery and remove some of those sticky weights. If I was already at the minimum weight without additional sticky weights, I wouldn't want a heavier battery.
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Old 07-12-2013, 03:39 PM   #8
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There isn't one answer, because it depends on

1.) how much traction you have
2.) whether your goal is to increase, or decrease traction

Some cars on some surfaces will turn better laptimes above minimum weight, in which case you are better off running your optimal weight using Mah instead of lead. On track conditions where you are trying to reduce grip, and/or are limited in HP, then a lighter pack (getting you down to minimum weight) would be advantageous.
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Old 07-12-2013, 05:03 PM   #9
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For 17.5t tc weight is more a factor than anything else... I ran all my packs in my Car and found better laptimes with my tp3300(208gram) packs instead of my tp4200(263grams) and tp5300(309gram)..... More acceleration out of the corners and a slight drop in power, but only after the six minute mark.... Remember, the pros used 3300mah nimh with mod motors for a long time and ran five minute mains...Those motors were maybe 45% efficient... Battery capacity is a business that needs to grow, whether in the C department or in the mah department..... It won't be too long before a new technology comes out to open yet again another front: less weight(50grams) and twice the energy delivery(200C) with the same capacity....lol...
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Old 07-13-2013, 03:08 PM   #10
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Default New Technology

Bertrands,
Are you speaking generally (new technology is, I guess, inevitable ), or have you heard about something new on our horizon?
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Old 07-13-2013, 05:33 PM   #11
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I was reading a while back about some university breakthrough research that emphasized on inner Cell architecture that produced impressive energy delivery with minimal voltage drop and lots more capacity out of half the size or less.... I don't think nothing will out for a while though, and don't remember what forum it was on, but it made lipos obsolete... I hope it don't blow like C4 though...lol....
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Old 07-13-2013, 05:36 PM   #12
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Quote:
Originally Posted by Cpt.America View Post
There isn't one answer, because it depends on

1.) how much traction you have
2.) whether your goal is to increase, or decrease traction

Some cars on some surfaces will turn better laptimes above minimum weight, in which case you are better off running your optimal weight using Mah instead of lead. On track conditions where you are trying to reduce grip, and/or are limited in HP, then a lighter pack (getting you down to minimum weight) would be advantageous.
DITTO HERE.
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Old 07-13-2013, 05:51 PM   #13
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My t4 with heavy electronics and a 7200mah SMC lipo is only 1295g. I still need to find 85g of weight to be legal.

When running with weight limits, it really doesn't matter, since you're probably gonna have to add weight anyway.
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Old 07-13-2013, 05:55 PM   #14
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Quote:
Originally Posted by hyujmn View Post
My t4 with heavy electronics and a 7200mah SMC lipo is only 1295g. I still need to find 85g of weight to be legal.

When running with weight limits, it really doesn't matter, since you're probably gonna have to add weight anyway.
Wow, thats with body on too?
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Old 07-13-2013, 06:13 PM   #15
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Yup, lightweight speedpassion mazda6 body. I was amazed. I knew the t4s were light but I didn't know they were THAT light.

Btw I'm running...

Stock xray t4
Savox 1251
Airtronics rx-461 receiver
HW v3 ESC
HW v10 17.5 motor
30mm fan

I still plan on adding a stiffer bumper which should help on weight too.
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