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Old 07-03-2014, 08:50 AM   #1
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Default Best battery for 17.5t blinky

Hi I am wandering what every one prefers in 17.5t blinky tc
Weight vs large 7600
C rating watts
If anyone has done bk to bk testing with shorty and full size
or brand vs brand
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Old 07-03-2014, 10:24 AM   #2
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I've been switching back and forth between a R1 Wurks 7200 90C lipo and a Turnigy Nanotech 5300 30C lipo. With the turnigy lipo, my tc is perfectly balanced left to right, and is only 4g overweight. The R1 Wurks lipo is ~30g heavier, so it disrupts the balance, and also makes my car heavier on the right side. Here is how I found it to affect the car:

-I consistently post a faster fast lap with the lighter nanotech lipo due to the better balance and less weight.
-I post the same number of laps in qualifying with both lipos even though a can post a faster lap time with the nanotech lipo, likely due to the R1 lipo not falling off as much by the end of the race.
*note: my car was more prone to traction rolling with the heavier lipo. I had to make adjustments to the setup to compensate for the extra weight.

If you can run the better lipo without being a bunch overweight and without disrupting the balance, go for it. However, if the bigger lipo is going to make your car overweight and/or disrupt the balance of your car, it may not be worth it. At least that's what I found. Your mileage may vary.
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Old 07-03-2014, 10:49 AM   #3
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Quote:
Originally Posted by tcboy1983 View Post
Hi I am wandering what every one prefers in 17.5t blinky tc
Weight vs large 7600
C rating watts
If anyone has done bk to bk testing with shorty and full size
or brand vs brand
Voltage is extremely important in spec racing. Larger batteries offer more voltage throughout the run, and lead to better lap times late in the race AND less wear and tear on the motor due to less heat being generated. Use the largest battery you can get, and redistribute the weight on the chassis to get your car balanced and as close to minimum weight as possible. It'll take some work, but it's well worth the effort.
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Old 07-03-2014, 11:02 AM   #4
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If you're going to be 30gr heavier, the extra voltage might not compensate for it. If you're also out of balance, this can't help either.

In actual fact, I don't believe the extra voltage will actually show at the motor end at all under load. It's the C rating that counts, but I think the ratings advertised are at best optimistic mainly because of the internal resistance of the battery. That said, you'll never need one gazillion Amperes unless you're trying to tow the Moon behind you. most batteries will give enough current for a 17.5. And if you're still in doubt, check out what the champions run.

Lastly, you didn't mention how long is your race? 3 minutes? 5? 7? 15? Though frankly, both your batteries should last well enough even for 15 minutes.
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Old 07-03-2014, 11:11 AM   #5
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The one situation where additional weight would be counterproductive is when there's no minimum weight specified. Most Lipo-ready cars need additional ballast to meet weight requirements if the rules specify a minimum weight; in these situations adding capacity also assists in bring the chassis up to your club's racing standards. If balance becomes an issue, work towards moving the battery closer to the centerline of the chassis.
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Old 07-03-2014, 12:01 PM   #6
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1000% correct !!! I would like to add that it's best to have a much lighter pack(thunderpower 3300 .. 208 grams) , and add the extra weight flat on the chassis, in order to lower the Center of gravity(no traction rolling)... That's over 120grams less than the R1 wurks pack, and the weight is sitting lower inside the lipo case too.... Huge capacity and weight is just not good in corners, and you'll be able to gear higher with the 3300mah pack too, since it won't deliver too much energy to the motor compared to the 7600mah pack.... Remember, the 17.5t powerband is around 8300rpm. Higher gearing is key here....
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Originally Posted by DBM View Post
I've been switching back and forth between a R1 Wurks 7200 90C lipo and a Turnigy Nanotech 5300 30C lipo. With the turnigy lipo, my tc is perfectly balanced left to right, and is only 4g overweight. The R1 Wurks lipo is ~30g heavier, so it disrupts the balance, and also makes my car heavier on the right side. Here is how I found it to affect the car:

-I consistently post a faster fast lap with the lighter nanotech lipo due to the better balance and less weight.
-I post the same number of laps in qualifying with both lipos even though a can post a faster lap time with the nanotech lipo, likely due to the R1 lipo not falling off as much by the end of the race.
*note: my car was more prone to traction rolling with the heavier lipo. I had to make adjustments to the setup to compensate for the extra weight.

If you can run the better lipo without being a bunch overweight and without disrupting the balance, go for it. However, if the bigger lipo is going to make your car overweight and/or disrupt the balance of your car, it may not be worth it. At least that's what I found. Your mileage may vary.

Last edited by bertrandsv87; 07-03-2014 at 12:13 PM.
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Old 07-03-2014, 02:19 PM   #7
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I will be a little partial to fantom packs. But in testing and cycling my batteries recently ranging from 6000mah to 7200mah, I found the 6000 to have the lowest internal resistance and higher average voltage. I do have some 7600packs, but have not tested them yet. The 17.5 blinky cars are only going to pull so much and create so much heat. The heat lowers internal resistance thus allowing more volts to the ESC. I feel the larger MAH packs would be great in MOD, or something that will really demand higher current flow, but in stock, we really are not working them. Weight balance can be a factor as well. But I think there is only about 10grams difference between my 6000 to 7600.
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Old 07-03-2014, 02:45 PM   #8
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The lightest 2s pack for racing is around 168grams(thunderpower 35C 2700mah lipo), and after I tested one, I can say that it offered great handling at the minimal cost in punch out of the turns, in a six minute run, but I found that the 3300mah 65C gives a better compromise...
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Old 07-03-2014, 03:34 PM   #9
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The issue is that you want all of the weight of your car to be useful weight, mass that serves a purpose. If your car is under weight or off balance, get something, ANYTHING that will help it go faster instead of just adding sticky weight strips. With all else being equal meaning two packs of the same internal resistance and voltage profile the one which is a bigger pack, more milliamp hours, will make your car more powerful over the run and therefore go faster. Also, as a rule with everything else being equal, a larger pack will have less internal resistance because it has more area to source electrons from. So, when you yank the trigger and put a big load on that battery coming out of the corner, your tiny pack drops from 8 volts to 7, where as the big pack drops from 8 to 7.5, just that HALF of a volt means 15% more power, and 15% will get you a car length or more over the course of the lap.

Think about it this way: Did ANYBODY in the A-main of the 17.5 nationals think to themselves 'I want a smaller battery (for any reason) and just make up the difference with lead'? Hell no, massive packs all around. Make your cars weight work for you instead of hold you back.
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Old 07-03-2014, 03:42 PM   #10
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The issue is that you want all of the weight of your car to be useful weight, mass that serves a purpose. If your car is under weight or off balance, get something, ANYTHING that will help it go faster instead of just adding sticky weight strips. With all else being equal meaning two packs of the same internal resistance and voltage profile the one which is a bigger pack, more milliamp hours, will make your car more powerful over the run and therefore go faster. Also, as a rule with everything else being equal, a larger pack will have less internal resistance because it has more area to source electrons from. So, when you yank the trigger and put a big load on that battery coming out of the corner, your tiny pack drops from 8 volts to 7, where as the big pack drops from 8 to 7.5, just that HALF of a volt means 15% more power, and 15% will get you a car length or more over the course of the lap.

Think about it this way: Did ANYBODY in the A-main of the 17.5 nationals think to themselves 'I want a smaller battery (for any reason) and just make up the difference with lead'? Hell no, massive packs all around. Make your cars weight work for you instead of hold you back.
I agree, the only thing that should be taken into consideration is the balance front to back and left to right. Most companies offer a "mid size" pack that weighs about 300 grams the offer a "large size" pack that is probably close to 330-340 and also a "small pack" that weighs about 270 ish. If your car balances out with the biggest pack then go for it. If it balances out with the medium pack then try that. I personally run the orca 6200. Its 295 and my car is balanced front to back left to right with in 3 grams I believe. Anyways very low IR as well as a balanced car. Its all about finding the power/ balance ratio.
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Old 07-03-2014, 03:59 PM   #11
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Power/ balance ratio is very important for the chassis you are running, but no engineer will want a higher center of gravity versus a lower one, and yanking the trigger causes high amp loads only at the start of the race, after that, smoothness rules....This approach gives the heavier chassis a chance to compete, but if you run a very light chassis, you'll have to make your choice... Also, the Amain guys would still make the Amain with lighter packs.......
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I agree, the only thing that should be taken into consideration is the balance front to back and left to right. Most companies offer a "mid size" pack that weighs about 300 grams the offer a "large size" pack that is probably close to 330-340 and also a "small pack" that weighs about 270 ish. If your car balances out with the biggest pack then go for it. If it balances out with the medium pack then try that. I personally run the orca 6200. Its 295 and my car is balanced front to back left to right with in 3 grams I believe. Anyways very low IR as well as a balanced car. Its all about finding the power/ balance ratio.

Last edited by bertrandsv87; 07-03-2014 at 04:11 PM.
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Old 07-03-2014, 05:03 PM   #12
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I noticed you are using r1wurks pack. I have had very good luck with r1wurks 4600 70c shorty pack for 17.5 SC. and use my R1Wurks 7200 90c for SC 4x4. FYI at ocrc I let a buddy running stock 2wd buggy 17.5 who was having issues making tripple with two other expensive brand shorty packs. I let him borrow my R1Wurks shorty and it was able to make the tripple .Also I have been able to keep up with my orion vst2 17.5 against guys who run the cheater d3.5 17.5 .... Just my two cents
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Old 07-03-2014, 05:52 PM   #13
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Originally Posted by Adam B View Post
I will be a little partial to fantom packs. But in testing and cycling my batteries recently ranging from 6000mah to 7200mah, I found the 6000 to have the lowest internal resistance and higher average voltage. I do have some 7600packs, but have not tested them yet. The 17.5 blinky cars are only going to pull so much and create so much heat. The heat lowers internal resistance thus allowing more volts to the ESC. I feel the larger MAH packs would be great in MOD, or something that will really demand higher current flow, but in stock, we really are not working them. Weight balance can be a factor as well. But I think there is only about 10grams difference between my 6000 to 7600.
Actually the fast mod guys prefer the lighter 6000 packs (or less). Some even only charge their pack 90% for certain situations. If I remember correctly, 5cell mod was faster than 6cell mod a few years back. Anyways, as stated, it's not about mah it's about C rating for mod. I think that's more important for off-road than it is for on road.

Going back to the OP. If you have a friend with a GFX charger, have them cycle your packs. Then have a look at the discharge curve over time. When I do, I look at 300 seconds (5 min), 360s (6 min), and 420s (7 min). This'll give you an idea how your pack will perform towards the end of the race. Keep track of it over time and you'll see if/when your battery is going bad and you can buy a new one. You can also check both your packs to see which is better or to save for the main if you run more than one pack per day.
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Old 07-03-2014, 06:11 PM   #14
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I have been using a 7200 331g lipo and needed to move the esc and receiver further out and add 10g of lead to balance the car.
Car was 70g overweight.
I tried a 295g 6000 lipo which allowed for balance without any lead and receiver as close to center as possible.

Power wise lighter car was faster with 13.5 boosted and the car was less prone to traction rolling.
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Old 07-03-2014, 06:41 PM   #15
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I'm quite new to RC (about a year in proper racing now) and my only advice is to invest in some good batteries. When I first started I read a lot of people saying that in stock racing it didn't really matter too much because it's such low current. Even in stock racing the difference between cheap batteries and expensive batteries is night and day, especially when you start running decent ESCs and motors.
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