Mah vs. Voltage question

[tiqueman]

I think I know my answer on this, but I want to make sure. If Im running a boat on a 3S 4500mah pack, and lets say for simplicity it goes 10mph, temps are ESC 100F, Batt 100F Motor 110F. Now If I ran the same boat on 4S 5000mah and it adds say 5mph, so Im at 15mph. HOWEVER, now my temps are pushin the limits, ESC 125F, Batt 135F and Motor 145F and Ive propped down from a 442 to a 637.

Heres the question, If I run 2- 3S's in Parallel, 5000mah would then become 10000, Am I still going at my 3S speed of 10mph??? , just with a longer run time, or am I somewhere between 10 and 15 mph???

Im sure there are variables, ie, now Im doubling the weight having 2 3S packs, Im just wondering if more mah can produce more top end?

[Steven Vaccaro]

It depends on the amperage pulled and how the batteries react to the load.

[ED66677]

two 3S5000 instead of one means more weight, probably more drag!

[tiqueman]

two 3S5000 instead of one means more weight, probably more drag!

Thats what I was kinda thinking. I just wasnt sure. So more MAH would only give me more run time and probably slow me down a bit because of the added weight.

I think I will just swap out the ESC and Motor for the BJ components. Its in a 32" Imex cat. I do not know the ratings of the ESC, and do not know what brand the ESC is. I did some homework and found the motor to be a Fusion 2045KV. The ESC has never broke 126 in any of my 4S runs on any of the props Ive tried. But the motor is screaming hot, as well as the batts on a 442. Motor got up to 150, batts at high 140s. Cant be good.

[domwilson]

That motor is water cooled? Do you have good flow of water if it is?

[mickvk]

Do you have a steerable outdrive that might be binding? A 37mm prop shouldn't be loading the motor up that bad. I'm not sure what the issue is there.

But one thing I would say is that if you're heating the battery that much, it would certainly benefit from running with another one in parallel. The weight difference is worth it. Hitting almost 150F is surely going to puff your pack.

[tiqueman]

domwilson That motor is water cooled? Do you have good flow of water if it is?
Yes and yes, its that Fusion motor in the Imex cat you helped me get handling correctly.

mickvk Do you have a steerable outdrive that might be binding? A 37mm prop shouldn't be loading the motor up that bad. I'm not sure what the issue is there.
No, not a steerable outdrive. I did however check it all out to see if it could be binding under load. I think its just that the ESC/ Motor combo cant take 4S. I can run a 440 on a 3S 4500 and it stays within safe temps. But with that, its too slow and boring.

[Ub Hauled]

Tiqueman, let me ask you this...
what is the Kv and size of the motor (i.e. 4500kv and 36mm x 74mm)

The adding mAh to your setup will add weight (no brainer) the thing is,
if your motor was being starved from amps it probably would benefit from the extra mAh... but there would be signs, maybe cogging, slow unloading of prop, etc.
You may add more cells but make sure that:
1- your ESC can take 4s and more amps
2- make sure that your motor stays within 27-32,000 rpm @ nominal voltage.
3- if the motor has a very high Kv then you'll need to prop way down to keep the amps in check or stay with 3s.
4- make sure your drive dog is not too close to the strut, under load it'll rub and may slow down or even burn your system.

my2cents

[tiqueman]

Tiqueman, let me ask you this...
what is the Kv and size of the motor (i.e. 4500kv and 36mm x 74mm)
2045 KV and 36mm by 60mm

The adding mAh to your setup will add weight (no brainer) the thing is,
if your motor was being starved from amps it probably would benefit from the extra mAh... but there would be signs, maybe cogging, slow unloading of prop, etc.
You may add more cells but make sure that:
1- your ESC can take 4s and more amps Have no idea because I dont know what kind it is
2- make sure that your motor stays within 27-32,000 rpm @ nominal voltage.
3- if the motor has a very high Kv then you'll need to prop way down to keep the amps in check or stay with 3s. Perhaps this is my answer?
4- make sure your drive dog is not too close to the strut, under load it'll rub and may slow down or even burn your system. Have a bit more than a 1/8 gap

my2cents

Every cent helps

[Ub Hauled]

your motor is fine with 4s... is it an Ammo?
your motor on 4s will be spinning at 30,000rpm... actually less then that due to Eff, slip, voltage drop, etc. It also should be able to spin a 440 no problem at all, a 442 as well... what type hull is it?
can you post a picture of the ESc, maybe someone can identify it.

[domwilson]

I would change out the motor. Perhaps the magnets are not as strong as they used to be and may be causing the heat issues. Try a Feigao 8XL with the X637 or 9XL with a X442.

[bwells]

Something seems a miss, a 442 to a 637 almost seems like a wash. What about battery C ratings? These aren't aircraft batteries I hope but he did say they are 5000MaH which seem to have a higher C rating than the 1850/2500 ones (sometimes). Could this cause his heat problems?

[Ub Hauled]

low C rating (or not enough mAh) is a heat generator...

[tiqueman]

your motor is fine with 4s... is it an Ammo?
your motor on 4s will be spinning at 30,000rpm... actually less then that due to Eff, slip, voltage drop, etc. It also should be able to spin a 440 no problem at all, a 442 as well... what type hull is it?
can you post a picture of the ESc, maybe someone can identify it.

Its a Fusion Motor in a 32" cat. I have a thread on here about the ESC in trying to determine the brand. I didnt get anywhere. I cut the factory black shrink wrap off and tried to pull some numbers off the boards as recommended by J.M. but came up w/ nothing. http://forums.offshoreelectrics.com/...ead.php?t=9446 I also contacted another site in China, Amex instead of Imex and with several emails later, I still have not heard anything from either one.

Dom, The motor is new and has maybe 10 runs on it now, so thats probably about what, less than an hour of run time. I would love a new motor but being unemployed at the time, I have to work w/ what I have.

bwells, C ratings are 20. They are Reedy 5000mah. They run fine in my BJ26. Im thinking again its just the motor/ESC combination cant take what I want it to do.

Again, I was just curious as to what happens when you double your MAH's, if its ONLY longer run times or do you get a bit more punch. The only pic I have of it with the factory shrink wrap is a bit blurry and wont do much good but here it is anyway...

I think Im just going to swap it all out for the BJ26 guts and call it done. This cat handles INCREDIBLY well, thanks to the efforts of many including Domwilson and Ub hauled. We all know how the BJ handles Running it slower cant hurt.

[bwells]

It's agreed that paralleling will double your MaH for longer run times, but the more punch or higher C ratings, there is a 50-50 split. I've been in a couple threads on this subject and there does not seem to be a consensus. Many say that you have 2 packs to draw from thus more amps available, others say the amps available stays the same.I guess I'd try the parallel thing and see if the temps go down, your only out the cost of the wye!