R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Reply
 
Thread Tools Search this Thread
Old 07-03-2014, 07:48 PM   #16
Tech Elite
 
Join Date: Jul 2010
Posts: 2,306
Trader Rating: 9 (100%+)
Default

I just went through this same conundrum when upgrading from turnigy packs to something of higher quality 7000+ vs 6000.

Decided to drop my bikkies on LRP 6000mah packs (55/110C) due to better weight balance. I run 13.5T and I'm not expecting (hoping) any drop off as I was seeing it with the 5800 turning packs (45/90C)

Hopefully they arrive before next race meet!
cplus is offline   Reply With Quote
Old 07-03-2014, 08:13 PM   #17
Tech Master
 
samnelso's Avatar
 
Join Date: Aug 2011
Location: Fitchburg, MA
Posts: 1,751
Trader Rating: 1 (100%+)
Default

Get the best possible pack. Lots-o-Cs. 5mm plugs if you can. If the mfg has options of different capacities in the same pack size, steer away from the highest mah and get the one just below. From my exp, the packs stuffed with mah tend to puff more.
__________________
Team Associated | Reedy | Airtronics

RC Excitement: Fitchburg, MA | RC Madness: Enfield, CT | Horsham RC
samnelso is offline   Reply With Quote
Old 07-03-2014, 08:21 PM   #18
Tech Elite
 
Join Date: Jul 2010
Posts: 2,306
Trader Rating: 9 (100%+)
Default

Quote:
Originally Posted by samnelso View Post
Get the best possible pack. Lots-o-Cs. 5mm plugs if you can. If the mfg has options of different capacities in the same pack size, steer away from the highest mah and get the one just below. From my exp, the packs stuffed with mah tend to puff more.
This was also my thinking. LRP offer a 6000 and 7500 in the same range.

Volker and co use both depending on the track it seems. Only last year they were using 5200-5700 packs as well, so should be awesome for my 13.5 races.

I've gone with two packs, I think that's good for rotation. Three would be better/ideal, but that's too much coin.
cplus is offline   Reply With Quote
Old 07-03-2014, 08:33 PM   #19
Tech Champion
 
RedBullFiXX's Avatar
R/C Tech Elite Subscriber
 
Join Date: Mar 2003
Location: Intergalactic Planetary
Posts: 6,542
Trader Rating: 34 (100%+)
Cool

Quote:
Originally Posted by cplus View Post
This was also my thinking. LRP offer a 6000 and 7500 in the same range.

Volker and co use both depending on the track it seems. Only last year they were using 5200-5700 packs as well, so should be awesome for my 13.5 races.

I've gone with two packs, I think that's good for rotation. Three would be better/ideal, but that's too much coin.
Mod guys don't care much about voltage or punch, they have more than enough with motor and boost, so they can run lighter packs for better balance, hence the 5700-6000 LRP packs
Most won't even charge their packs fully
__________________
--> 12th scale Information Source <--

"Men do not quit playing because they grow old; they grow old because they quit playing."
― Oliver Wendell Holmes Jr.
RedBullFiXX is offline   Reply With Quote
Old 07-03-2014, 08:40 PM   #20
Tech Adept
 
Dread Pirate's Avatar
 
Join Date: Jun 2010
Location: OC/RC Raceway
Posts: 248
Trader Rating: 15 (100%+)
Default

Quote:
Originally Posted by RedBullFiXX View Post
Most won't even charge their packs fully
Yep, saves even more weight
__________________
"We face each other as God intended. Sportsman-like. No tricks, skill against skill alone." -Fezzik
Dread Pirate is offline   Reply With Quote
Old 07-03-2014, 10:17 PM   #21
Tech Master
 
evochick's Avatar
 
Join Date: Dec 2011
Location: Sydney AU
Posts: 1,537
Trader Rating: 5 (100%+)
Default

Quote:
Originally Posted by cplus View Post
I just went through this same conundrum when upgrading from turnigy packs to something of higher quality 7000+ vs 6000.

Decided to drop my bikkies on LRP 6000mah packs (55/110C) due to better weight balance. I run 13.5T and I'm not expecting (hoping) any drop off as I was seeing it with the 5800 turning packs (45/90C)

Hopefully they arrive before next race meet!
Last week got 2 of the new LRP 6000's to replace my Turnigy 5600's that were going a little soft and I need 2 more packs anyway.
Their first run last week was good, a little better punch then Turnigy and no drop off, was running 13.5 blinky.

my best run I had my consistency down to 0.12 with worst 2 laps dropped, and 0.14 with worst lap dropped.

next run with them tonight...

Beth.
__________________
Unretired

2017 ACT Rally champion :)
evochick is offline   Reply With Quote
Old 07-03-2014, 10:32 PM   #22
Tech Regular
 
Join Date: Jun 2002
Location: Arizona
Posts: 466
Send a message via AIM to kyle478
Default batteries

I can tell you first hand, if you do not have a low resistance battery in 17.5 and 13.5 you will be off pace. Try the Aero-Model 7600 90C, they have super low resistance and will give you the best possible lap times the entire race. These packs weight 330-340 but its worth the weight. If you cycle each battery pack people have talked about in this thread you will find your average voltage per gram is much better with the larger packs. Keep in mind this only works if you can get your car weight down to the min. weight limit of your particular race.

If you can not get your car weight down to the min. try using a lighter pack in the 290-300 gram range. Try the Aero-Model 6000 90c pack

Im my case with the awesomatix car I can get the cars weight to 1375-1380 with using the 7600mah pack. Normally I am still under weight and have to add 20 grams or so. This is usually placed on the opposite side of the battery as people have mentioned balance is very important. However voltage is more important with the spec classes.

Kyle Bergstrom
__________________
Hacker Brushless USA www.hackerbrushless.com
Aero-Model www.aero-model.com
kyle478 is offline   Reply With Quote
Old 07-03-2014, 10:36 PM   #23
Tech Master
 
Join Date: Jun 2004
Location: SoCal
Posts: 1,099
Trader Rating: 6 (100%+)
Default

I agree with Kyle. The Aero-model packs are definitely worth it. What ever class, these cells get the job done.
__________________
Minh Nguyen
[Maclan Racing] [Xpert Servos]
trigger is offline   Reply With Quote
Old 07-04-2014, 04:44 AM   #24
Tech Elite
 
niznai's Avatar
 
Join Date: Feb 2009
Location: All over the place
Posts: 2,940
Default

Quote:
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.
Umm, no.

Heat raises internal resistance.

More current out of higher capacity batteries is another legend. Until I see bench tests run I don't buy it, and practical experience shows no correlation. Yes, some batteries have lower internal resistance and they're better, but how many have any of the people here measured recently?

Back to our friend, 17.5 would rarely see more than 15-20 Amps, most likely under braking. This means his batteries are more than alright for the class (even the lower capacity one).
__________________
Team Greasy Weasel

The best upgrade to any car is some driver skill.
niznai is offline   Reply With Quote
Old 07-04-2014, 05:27 AM   #25
Tech Elite
 
dan_vector's Avatar
 
Join Date: Oct 2013
Posts: 3,924
Trader Rating: 27 (100%+)
Default

We are all talking about low-IR here but can someone put a figure on what a good pack's IR should look like? I have the ability to see what the IR is on my Orion Advantage Pro charger and my packs are all around the 5mohms.
__________________
Serpent Viper 977e EVO2, Serpent Viper 988 GP, Serpent Project 4x, Serpent 811T-TE Truggy, Serpent 811e 2.1, Serpent SRX2-MH, Serpent SRX-2 RM, Serpent SRX-4, Serpent F110-SF2, Serpent F180, Serpent 748 Natrix WC, Serpent Cobra GT 3.1, Serpent SRX8, Serpent S811 2.2, Baja 5B Flux, Atomic AMZ 1/27th, Schumacher GT12 SS.
Sanwa, Ielasi Tuned Novarossi Racing Engines, Tekin, Hobbywing, Muchmore.
dan_vector is offline   Reply With Quote
Old 07-04-2014, 06:06 AM   #26
Tech Fanatic
 
d16dcoe45's Avatar
 
Join Date: Oct 2007
Location: Armonk, NY
Posts: 947
Trader Rating: 1 (100%+)
Default

I would ASSUME my Orca 90c 7500 has a better discharge curb than say a 6200 Orca but I have never compared back to back. It would be interesting to see the 7500 vs. 6200 (using lead to equalize weight) lap times and total race time in 17.5 sedan. Would there really be a difference in lap times? How about over 10 laps? Would the 6200 start to drop off?

For now I am just sticking to common sense and will continue to run the largest capacity, highest C rated cells I can get my hands on. Since I only run stock, any extra voltage is hugely welcomed!

As long as you can get down to 1380g, run the big packs. Even if you don't race ROAR rules, if you ever decide to expand your horizons and hit up a big race you will want your car to weigh and handle the same as you are used to. (Running 7200 LRP and LW Protoform bodies I could get down to 1305g in my 418 but I never ran that light)

I would choose cells that have 5mm female plugs instead of 4mm. Again, I have no proof that they are "better" but common sense tells me more surface area = less heat & less voltage loss due to resistance.

And there are ALWAYS ways to balance the big packs. In my 418 I have had to mount my 333g Orca so its almost touching the pinion gear, along with mounting the electronics overhanging the chassis plate by a good 1/2" AND mounting some lead on the electronics side. It can be done.
__________________
Jay Lestingi

Tamiya 419x/Associated TC7.1/Sanwa M12s/Xpert servos
d16dcoe45 is offline   Reply With Quote
Old 07-04-2014, 07:00 AM   #27
Tech Master
 
Join Date: Jan 2004
Posts: 1,059
Trader Rating: 1 (100%+)
Default

Quote:
Originally Posted by kyle478 View Post
I can tell you first hand, if you do not have a low resistance battery in 17.5 and 13.5 you will be off pace. Try the Aero-Model 7600 90C, they have super low resistance and will give you the best possible lap times the entire race. These packs weight 330-340 but its worth the weight. If you cycle each battery pack people have talked about in this thread you will find your average voltage per gram is much better with the larger packs. Keep in mind this only works if you can get your car weight down to the min. weight limit of your particular race.

If you can not get your car weight down to the min. try using a lighter pack in the 290-300 gram range. Try the Aero-Model 6000 90c pack

Im my case with the awesomatix car I can get the cars weight to 1375-1380 with using the 7600mah pack. Normally I am still under weight and have to add 20 grams or so. This is usually placed on the opposite side of the battery as people have mentioned balance is very important. However voltage is more important with the spec classes.

Kyle Bergstrom
They are great lipos best I have tested and used. You have to love rebranding.

The 7600 is 335g, the 6000 is 295g, previous generation 7200 was 330g.

In my case the 335g pack is enough to put the balance off and require lead to correct it.
frozenpod is offline   Reply With Quote
Old 07-04-2014, 07:04 AM   #28
Tech Master
 
Join Date: Jan 2004
Posts: 1,059
Trader Rating: 1 (100%+)
Default

Quote:
Originally Posted by niznai View Post
Umm, no.

Heat raises internal resistance.
Lipo IR reduces as temperature increases within the operating temperature range.

Hence why people use warming pads higher charge rates ect to warm the cells.
frozenpod is offline   Reply With Quote
Old 07-04-2014, 07:08 AM   #29
Tech Master
 
Join Date: Jan 2004
Posts: 1,059
Trader Rating: 1 (100%+)
Default

Quote:
Originally Posted by dan_vector View Post
We are all talking about low-IR here but can someone put a figure on what a good pack's IR should look like? I have the ability to see what the IR is on my Orion Advantage Pro charger and my packs are all around the 5mohms.
The best lipos I have tested have IR in the range of 1.2-1.5mohm per cell depending on temperature.

Poorer brand name lipos that are currently used by racers IR is in 3-5mohm per cell.
frozenpod is offline   Reply With Quote
Old 07-04-2014, 10:58 AM   #30
Suspended
 
Join Date: Feb 2011
Posts: 6,240
Trader Rating: 1 (100%+)
Smile

100% right !!!! That would also mean that the lower capacity packs would heat up more when the the max amp charge rate has been fixed by the event officials...I see that most events limit everyone to a 14 amp max charge rate, which will not heat up a 7600mah pack, but will crank the heat in a 2700mah/3300mah pack.....
Quote:
Originally Posted by frozenpod View Post
Lipo IR reduces as temperature increases within the operating temperature range.

Hence why people use warming pads higher charge rates ect to warm the cells.
bertrandsv87 is offline   Reply With Quote
Reply



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 06:48 AM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net