Tiger72

iTrader: (1)

Hi everyone, I've just recently got back into R/C but am racing now in VTA. Prior to this I was just a basher so I never paid much attention to batteries.

So, the question is: I have a used rig and batts that are rated at 3300 mAh, w/ a 27T motor. In VTA they provide 3 battery motor combos and the only brushed option is 27T w/ 4600 mAh NiMh. I've found info relating the mAh rating to a gas tank ie the larger the rating the longer you run. So if I can still finish the race w/ my 3300's is there an advantage to switching to 4600?

I know lipo's are much better and lighter but acording to the rules I'd have to switch to brushless and right now that's too much coin.

I did very well in my first race. I qualified 2nd in the B Main and finished 1st in the B also. I noticed a HUGE gap in lap times between the A and B Mains - almost 2 sec average per lap! Just wontering if the battery is the key.

Thank you for the time.

Cpt.America

iTrader: (52)

What matters most, is their voltage output. More volts = more punch and more speed. Their mah rating will only dictate how long they run.

Duster_360

iTrader: (21)

The 4600s would give you higher voltage for a longer period of time than the 3300s. There is a diff, but how long the higher voltage would last with the 4600s is hard to say since it depends on how your driving style demands current from your system.

I suspect there is some batt diff in the lap times, but its not the only factor involved in that lap time diff.

racer1812

iTrader: (31)

How old are your 3300's??
+1 for Dusters comment

Tiger72

iTrader: (1)

Regarding your statement about batt diff in lap times - are you talking about the batt making the car slower as the race goes on or that the 4600's may be faster w/ more punch?

Tiger72

iTrader: (1)

I'm afraid I don't really know how old the batts are. They take a charge well and last more than the full race before tanking. I know age and number of charges takes a toll on the batts life expectancy and do plan on getting some new ones when I can afford them.

Tiger72

iTrader: (1)

I'm not sure if you guys race VTA or not but how can I go faster? I know driving is a big part and practice is well worth it. My car handels well - seems to keep the line I want and doesn't push or slide. I'm tied to the 27T and 4 cell 4600 mAh batteries (when I the batts), and have to run specific tires and offsets. My final drive ratio is with in the VTA recomended ratios - 5.81.

Are those guys in the A Main faster by the 2 sec just because they are running brushless? I thought the VTA motor / battery combinations are ment to be equal and competitive.

Don't get me wrong, I know I have to put my time in for the B Main before I can get to the A but I was told my lines are pretty good and my lap times are all within 0.6 sec of each other in the race. I just can't get what the gap is due to.

Thanks for the comments.

Duster_360

iTrader: (21)

The 4600s will hold high voltage longer than the 3300s. You know when you 1st start out and how much punch you have - the 4600s will give you a little more time with that extra punch before they start falling off. Yes it may may you a little faster, how much don't know. Can you borrow a 4600 pac for a practice session? That would be the best way to get an idea of what 4600s would or would not do.

A little of that 2 sec faster lap times for the A Main guys may be due to batts - if they're running NiMh, they are prob maintaining them at optimum condition by discharging and conditioning. But most of that 2 sec time difference is their skill level vs yours.

Tiger72

iTrader: (1)

Thank you,
Borrowing a 4600 is a good idea. I can run a run 20 laps or so with my batts then the same with the 4600 and compare the averages, sounds logical to me.

I know I have much room for improvment with my driving skills. Theres guys there that conststantly run the exact same lap times, mine do have variance to them but there pretty close suprisingly.

JR007

Without knowing a single thing about you, i'd say the difference was more to do with driving. Coming in to racing after one event and being 2 secs off the fastest racers is no mean feat.
There may be a batt difference, but 27 Turn motors are hardly battery-suckers....

racer1812

iTrader: (31)

I agree, it's easy to be just a tick off on your set-up with a VTA or any on-road car and you'll easily be 2 sec. slower. Your 3300's don't help but they're not the whole story.

iambored

Every person is coming up with good solutions. Nice to be associated with this forum

JeromeK99

iTrader: (3)

A 3300 is an older cell than a 4600 of course. There are a couple of things I think that people are slightly mistaken on or perhaps just didn't explain it clear enough.

A good matched 3300 can hold just "as high" of voltage as a good 4600. The peak voltage before it levels off is about the same and lasts for about the same amount of time given the same draw. The difference however is the amount of time that the larger capacity battery (4600) will have that level power. It is longer of course.

There is also a big difference in weight.. the 4600 for its higher capacity will weigh more... thus slowing the car down. This you really can feel when racing.

Now.. with all that said... if your batteries are old and used back when they were the newest cell out.. well.. go for new ones.. You'll more than likely need them anyway.

Good luck!

Jerome

Tiger72

iTrader: (1)

Thank you, I didn't know the 4600's would be heavier. They looked the same size. I guess I could go either way since I should buy new ones. However I could save the weight by using the 3300's because they still allow me to finish the race w/ what seems to be full power.

RC Dad

iTrader: (26)

One other factor not mentioned is the lower IR or AR rating on the 4600's. My ProMatch 4600's have 1.2 to 1.3 Internal resistance compared to 3.0 for my best matched 3300's (long gone now). That rating is the rough equivalent of the C rating on lipos. It determines how hard/fast the cells can dump power. I don't have the math for it, but the 4600's will definitely offer noticably more punch than the 3300's regardless of voltage and run time.
They are slightly larger though, but IMO the added punch easily offsets the weight but you may have to enlarge your battery tray and strap to accomodate them. My XXXS and XXX4 both needed the battery strap and chasssis slots dremeled to fit the larger cells.
Another tip is to make sure the cells are warm, freshly peaked or re-peaked immediately before the race. (That was the single best tip I ever received for stock motor racing.) And make sure you've replaced any stock white Tamiya connectors with Deans/Traxxas/Losi type connectors to allow the power to pass.