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ESC, motor DYI setup basically

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Old 06-07-2018, 11:25 PM
  #1  
Ralhar01
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Default ESC, motor DYI setup basically

I took a busted 37" majesty 800 s duel prop and gutted it. I don't have a lot of money so I took 2 goolrc 2430, 7200 kv motors and 2, 60 amp water cooled ESC'S and I'm trying to figure out my battery situation. The esc's can take up to a 4s lipo each. The motors are only rated for 8.4 max volts each. I have an R-line, 1300 mAh 11.1 ( or 8 ) volt 75c 3s lipo. Can I run both motors off the one battery without burning them up? I am trying to build an in your face, yes I can build one you local ***** holes that race at the lake boat lol. I have a Y connector for the ESC's to run off of one receiver but I want power without the weight of a giant battery or even 2 giant batteries. Any suggestions?

There are some insanely smart posts here. Never knewkne could be this complicated but been hooked ever since my first drone rebuild.

I even decided to install my own servo and rudder so no power would be lost during turns. Took the parts off of a mini Lagos boat. I think once I figure out how to power it and keep the weight down this enormous yet light weight beast could be a contender.

Any help would be greatly appreciated.

Thanjs
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Old 06-08-2018, 12:48 AM
  #2  
mfr02
 
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Motors take what they can according to the loading (prop size and configuration), volts available, the ability of the ESC to pass the current and the ability of the battery to supply the current.
A small, light battery is like a small fuel tank. The large, light boat might go fast, it won't do it for long before the battery flattens.
It is very possible to run a motor over volted to get more RPM from it, but it must be lightly loaded and you mustn't expect a long life from it. It might also take more current than expected. A 1300mAH battery should give several seconds of run time. Running two motors off one battery, the limiting factor is not the motors, it is the C rating of the battery that decides whether the system will work without damaging the battery. e.g. a 30C 1300mAH battery should safely deliver 39A (19.5A per motor), but at 30A, only for 2 minutes. Less a bit for the current used by the controls.
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Old 06-08-2018, 03:51 PM
  #3  
Hydro Junkie
 
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I have to agree with mfr02, this is going to be a balancing act. To get light weight and fast is possible but at the expense of run time. What you really need to to think about is which of the following do you want to have:
1) a top fuel dragster
2) and indy/F-1 style racecar
3) a NASCAR style racecar
A lightweight boat with a small pack will give you what amounts to a dragster. It will be fast but only last a lap, two at best
An indy car is heavier than a dragster but will run further. By adding a second battery pack, in parallel, you will be able to run further, but not as fast, The added weight will lower your top speed but give you roughly twice the run time, three to four laps
A NASCAR is the heaviest of the examples I listed, but also the longest running. By sacrificing a bit more weight in bigger packs and maybe better motors and ESCs(yes, I know, funds are limited), you would be able to run more laps and still have respectable speed.
What it comes down to is do you want to dazzle everyone for a lap or two, be faster than the rest for three or four laps or be able to run with everyone for a full heat?
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Old 06-09-2018, 05:37 AM
  #4  
Ralhar01
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Default ESC, motor DYI setup basically

So your saying run each motor off a 1390 mAh 30 c.while keeping it at the correct voltage per motor rating. Correct? Don't use the R-line 65 c to run both. Use separate power to each motor?
i suppose the weight is just going to have to happen, no way around it.

And the 60 amp ESC,'s . Are good,
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Old 06-09-2018, 06:39 AM
  #5  
mfr02
 
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In electrical engineering, when drawing up specifications, it pays to be a bit pessimistic.
You don't run motors on too high a voltage, and you don't give them more prop than they can handle.
You have ESCs that really can handle the expected current that the motor will take at the voltage that the battery will offer plus a safety margin,
Similarly, the batteries should be specified to give rather more than the plain numbers imply because theory and practice often disagree, and practice usually wins. And, of course, while battery sellers do state the right voltages, they might be a bit lax on occasions regarding actual capacity and C rating.
Assuming that the hull can actually give the performance wanted, it must be remembered that performance comes from power, and power and money are almost the same thing, but it doesn't always work going the other way. Extra money doesn't guarantee either the power or the resulting performance.
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