Lipo C rating
 

G'day,
I race in 21.5 blinky(touring car) and I just wanted to know whether a battery with a really high c rating will make a huge difference to this motor.
I've been told in relation to my setup:
-Motor SP MMM pulls around 18 amps max
-ESC SP Revention with stock firmware
-Battery 5000mah/30-40c discharge=150amps constant. Sounds like plenty to me and even this is overkill. I was told that an overkill battery can't force any more power into motor, the motor pulls only what it needs.

So then why do people say that a higher c rating will make you go faster?

Been really struggling with punch out of the corners and top end speed for a while now finishing consistently in the bottom last and would really appreciate some feedback. Oh and gearing(3.25-3.40) and enbell timing(30-40 degrees)

I thank everyone in advance for any feedback.

Absolutely! A good quality High C rated battery is key to good pace in Spec classes. A good motor in spec classes is important but a high C rated battery will make that motor faster across the board.

Higher C ratings will not make your car go faster, it will keep your car going fast. The "C" stands for the current discharge rate. The higher the Cs the more easily the motor can draw the current it needs from the battery. If you use a lower C rating the motor will struggle getting what it needs to run at its full capacity, and can overheat the battery.

It looks like your set up is perfect.

C ratings are a bunch of bull since there is no testing standard of any kind so they can put whatever number they want on the label.

That being said, better batteries ABSOLUTELY DO make a difference. Yes, a lower mah, lower C battery has plenty of power to supply the motor and propel the car but a better one will see the voltage drop less under load. In other words, MORE POWER. 21.5 is such a slow and even class that even slight gains in power make a big difference in finishing positions. From what I can see, you are behind the curve in both the motor and battery area.

What you have should be plenty. I would look at reducing rotating mass (drivetrain) and also at higher quality bearings, also make sure your drivetrain rotates freely.

Also, play with your endbell timing and gearing. Possible you need to go down a tooth on your motor, and/or reduce timing. Likely 35-40 degrees is at the upper end or beyond the efficient point of the motor. Going down a tooth will increase your 'punch' and only slightly reduce top end speed.

Thanks guys these answers have been really helpfull:nod:

Follow me here - it will all make sense

High C rating is beneficial in high amperage setups, example - MOD class. If your current battery will "cover the spread" of your current set up, it will not make a difference.

Think of "C" rating as a milkshake straw. The bigger the straw the easier it is to get the milkshake. The smaller the straw, the harder you have to work to get that same milkshakethrough the straw. If you have a thinner milkshake, you can use a smaller straw ("C" raiting) to acheive the desired effect..Considering your lips as the motor and the milkshake as the battery.

There is no patent on that analogy - you may run with it at your leisure.

Trigger and Wingracer are correct. A truly higher C lipo will have lower Internal Resistance, and will provide a higher voltage under load, thus better performance.

The difference is small but clearly noticeable. Will likely only be of practical benefit if driving is up to par though.

I know it's counter intuitive, but generally with the exception of 4x4 short course, competitive stock racing requires far better batteries than modified. Modified can just use a faster motor, many use low C lipos to take the edge off of hot mod motors to make them a little more driveable even. 4x4 short course is perhaps the most common exception, they need great lipos just to survive due to the high amps required.

The difference will be most noticeable under acceleration when the current is highest, less difference at top speed but still something.

One caveat, higher C lipos are heavier, if the car is above minimum weight then the heavy battery might not be the way to go, especially on road. Off road weight is less critical, as it can have some beneficial tradeoffs in the bumpy sections and such.

There is a lot of concern regarding C ratings, some brands are pretty straight up, some not so much. That certainly complicates and muddies the whole subject.

Besides track performance perhaps the best way for the average racer to help separate fact from fiction is to invest in a quality charger that features IR measurement. Simple but generally effective way to compare packs, and track their performance over time, help determine when new packs are justified, etc.

Very creative answer Redsawacs, I like it, a bit funny too. Thanks mate.

Yeah, good point about the weight in higher C Lipo's Dave H, and thanks for the reply by the way. My Turnigy charger does have an IR measurement in it but I don't really know what is a good or bad IR reading. What should I be looking for as a good IR measurement?

cheers