How much difference do 40C batteries make??

[mm123521]

I ran my boat today.

First run: 5S 30C Flightmax.
Second run 5S 30C flightmax
Third run 5S 40C Turnage

The third run looked much faster than run 1 and 2 (no GPS).
Do the 40 C batteries make that much difference??

My fourth run was 6S, 25C Flightmax and it looked slower than run 1,2, and 3.
The 6S should have been a lot more RPM, but it looked slower?? Did the 25C make the run slow?

Boat is a Aeromarine SprintCat 40 (34.5 inch long).
All batteries are 5000 Mah.
Twin motors are castle 1520 1600KV.
Two batteries in the boat for each run, borh batteries in parallel, feeding both motors.

Does battery quality make that much difference??

Mark

[keithbradley]

You could have a bad battery, but the batteries WILL make a big difference if you have a fairly high current draw.
Besides the C rating, the wires are usually smaller on the flightmax than the turnigy. That just adds to it. I have seen 20C Turnigys with 10 awg wires outperform 40C flightmax batteries with 14 awg wires!

[Chilli]

For me 30C to 40C made a noticable difference. No difference when I went up to 45C. I also had some high quality packs that really lost allot of power after two seasons even thought I took good care of them and they balanced well.

[Make-a-Wake]

Your 40c batts are putting out 200 amps constant and your 30c's 150a. The thirsty 1520 is maxxing out the 30c's. 40c will run cooler too............

[Fluid]

There is considerable misunderstanding about what the "C" rating actually means. It is a relative measure of the internal resistance of the cells. It is not a direct measure of the maximum amperage a cell will deliver, it tells you what is safe to draw. For example, a 5000 mAh pack with a 40C rating can safely supply 200 amps continuously. The cells can deliver far more than that but you will overheat and damage them. This is where the "maximum C" rating comes in, it signifies the maximum draw for a short time: 5 to 10 seconds usually. A 5000 mAh pack with a maximum 80C rating can deliver 400 amps for a very short time without damage to the cells.

The problem with the "C" ratings is that different sellers measure them differently. It is a value that is almost impossible for the consumer to verify, so some unscrupulous sellers will "up-rate" their packs to sell them at a higher price. This means that two packs with the "same" C rating from two different makers can perform a lot differently.

But the short answer is that yes, with a relatively high-draw system like the OP has the higher the C rating the faster the boat runs. With low-draw systems like a 'spec' motor "C" rating is less important but can still make a difference. On my FE30 I ran 1-2 mph faster with a 45C pack than I did with a 35C pack pulling an average of 100 amps.

Another answer has to do with the history of the pack. A pack with just 5 cycles will deliver higher power than the same pack with 50-100 cycles.


.

[SweetAccord]

"It is a relative measure of the internal resistance of the cells." That sentence by Jay is the most important sentence in his statement which all the rest of his statement is baised off of.

[mm123521]

Thanks everyone!

Trying to get my boat dialed in.
Today, I ran 4, 3S, 5000MAH, packs in my boat.
2 batteries on each side for 6S
2 batteries were 40C Flightmax and 2 batteries were Turnage 30C.

Also moved the CG back a little.
Also bumped the timing up from 3 degrees to 7 degrees.

Wow! did that boat fly!
This was the first sucessful 6S run.

Now I dont know whether the great run was from the different batteries or the timing or the CG shift.

The motors were really screaming this time. Gained at least 10MPH. When I ran the 6S 25C packs, i didnt get these RPM's.
Could it be the timing change?

ESC's are T180's
Getting long run times, 6 minutes or so, so I know the average current cant be that high.

What happens when the timing is set too low?
Do you get a loss of RPM's on the high end?

Also the boat can really make a "hole shot" now, the bow lifts up 6 inches or so on a hard acceleration. Much better than before.

All battery packs are new, except one had 5 runs on it.

What about the timing?

Mark

[Brushless55]

I would love to see a video of this monster!!

[Old Sloppy]

What happens when the timing is set too low?
Do you get a loss of RPM's on the high end?


Mark

Yes.

low timing is for low rpm's
mid timing is for mid rpm's
high timing is for high rpm's

multipole motors require higher timing


Harry
from Atlanta