Hobbyist Forums banner

1 - 13 of 13 Posts

·
Registered
Joined
·
420 Posts
Discussion Starter #1 (Edited)
3200ma vs 5200ma 2cell, is .2 volts worth 3 oz of weight ??

question for all you racers out there. I tested a 3200ma 40c 2 cell pack and a 5200ma 40c 2 cell pack. through out the discharge curve at 30 amps on my GFX the 5200 pack is .2 (two tenths) of a volt higher then the 3200ma pack. Now normally being a guy that is always looking for the most power, I would go with the pack with the higher voltage, but the 5200 pack also weighs 3 oz more then the 3200 pack. that is about the weight of 4 dollars worth of quarters. on a pan car ,thats a lot of weight....

So the debate I have been having with my friends is
whether or not .2 volts (7.5 compared to 7.7 volts) is Worth 3oz.(4 dollars worth of quarters) of added weight ???

Please let me know what you think..
 

·
Registered
Joined
·
855 Posts
If you'd rather run 3oz heavier and run a lap and half faster, then yes it's worth it. If you'd rather run lighter, a lap and a half slower, and save a tick on tire wear, then it's not worth it.
 

·
Premium Member
Joined
·
1,227 Posts
Depends on the motor you are running and what you are actually pulling when running. If you are running and only pulling 1500 out of the pack, the lower capacity pack might be faster. Try calculating your average amp draw, then discharge both packs at that amperage. Then compare which is better.

John
 

·
Registered
Joined
·
2,685 Posts
Depends on the motor you are running and what you are actually pulling when running. If you are running and only pulling 1500 out of the pack, the lower capacity pack might be faster. Try calculating your average amp draw, then discharge both packs at that amperage. Then compare which is better.

John
RIGHT!:thumbsup:

Total Watts = AMPS X VOLTS
 

·
Premium Member
Joined
·
1,227 Posts
I plan on doing the same thing with my 25C SMC pack vs my Epic 40C packs. At 35 amps the Epic is consitently .1V better, but several fast guys at Vinton like the 25C packs in 13.5 cot. Might be the case that at 20 to 25 amps the lower C pack hits a sweet spot for voltage.

FWIW Xtreme RC did a test with different C packs and on 17.5 turn motors the difference in top speed was almost nothing, but on lower turn motors there was a difference of a few MPH. So it all comes down to your amp draw and does it push the battery to its limits.

John
 

·
Registered
Joined
·
420 Posts
Discussion Starter #7
Hey some good responses so far.
I should have specified car and class. We are talking 2 cell 17.5 pan car.
I know that in truck or touring car, 3 oz is not a big factor, but in pan car where every gram is a factor you would think it would matter..

Hi Kevin K, I appreciate the response and I do very much respect your opinion. That would also be my first thought, run the one with the higher volt. but I don't get a lot of chance to do allot of track testing so most of my testing is done on the work bench instead. So I was hoping to get a response from some of you guys that do allot of track testing.. Thanks
 

·
Registered
Joined
·
3,766 Posts
.....at 20 to 25 amps the lower C pack hits a sweet spot for voltage.
Not really a sweet spot for voltage, but for heat. The lower c pack will heat up more than a higher c pack. So that CAN make the lower c put out a higher average voltage.
 

·
Registered
Joined
·
2,707 Posts
aschwarze, is there a weight rule where you race for 17.5 2 cell? If so does your car make weight with the 3200 in it. Where I race we have weight rules, I can run my 3200 in 17.5 but I have to add weight so there would be no gain for me.
 

·
Registered
Joined
·
420 Posts
Discussion Starter #11
The minimum weight is 38 oz. My 10L4 is right at 38oz with the 3200 pack. it's 41 oz with the 5200.
I ran the 3200 last night, My car seemed a little quicker and I did run a lap faster, But, I can sure see where Kevin K is coming from, I had to move the lighter pack forward to keep the left front from lifting, but no big deal.

I guess the real underlying question is, how much weight is to much?

Hi Andy.. Rules?? Who was it that was running 2 cell lipo and a17.5 motor in our 4 cell 10.5 class ??? could it have been you.... LOL
Hope to see you one of these Wednesday nights..
 

·
Banned
Joined
·
3,250 Posts
Hi Andy.. Rules?? Who was it that was running 2 cell lipo and a17.5 motor in our 4 cell 10.5 class ??? could it have been you.... LOL
Hope to see you one of these Wednesday nights..[/quote]

True, true, but you guys with 10.5 still beat me!!! Must've been hot batteries! LOL :wave:
 

·
Registered
Joined
·
420 Posts
Discussion Starter #13 (Edited)
Just a little more thought on the 5200ma vs 3200ma pack.. I did some calculating, and what fond is this..
just to recap.
the voltage at mid 4 Minuit discharge cycle is 5.7 on the 5200ma pack and the voltage on the 3200ma pack at the same time is 5.5 volt. the 5200 pack weighs 3 oz more then the 3200 pack.
my initial question was whether the added .2 volt was worth the 3oz of added weight..

I did a power to weight ratio .
my 10L4 with the 5200 pack weighs 41 oz. 7.7v divided by 41oz = .1878.. volts per oz.
my 10L4 with the 3200 pack weighs 38 oz. 7.5v divided by 38oz = .1973.. volts per oz.
So, the lighter 3200 pack with .2 volts less has a .0095 higher volts per oz.
You may still be better off to run the heavier battery in order to help with handling.
but it just always makes me wonder when these battery companies keep coming out with the new bigger, better pack every month... at what point is the extra run time and voltage really worth the extra weight..

Just incase anyone else realy cares what I think... LOL
 
1 - 13 of 13 Posts
Top