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Jan 10, 2019, 12:27 PM
Latitudes vs Attitudes
Bob Gaito's Avatar
Discussion

Power off switch


I am planning to use two Turnigy 70 amp marine ESCs- -Can anyone tell me if I were to remove the receiver from the picture with a switch in the BEC would that disable the boat and/or prevent the batteries from depleting over time?
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Jan 10, 2019, 12:34 PM
Mmm, tugs...
patmat2350's Avatar
Switching off the BEC to the Rx won't stop current going to the brain in the ESC. It might be micro- or even milli-amps, but it's a drain.

Some ESCs have a power switch that does do the job... Mtroniks, HobbyWing, others... the switch stops juice before it even gets to the Vreg that supplies both BEC and the microprocessor.
Jan 10, 2019, 02:06 PM
Latitudes vs Attitudes
Bob Gaito's Avatar
Thanks Pat-there's nothing in the specs and I'm not set up to test it yet-would be nice to go the day at the pond without taking the deck off, if its milli-amps...I can live with that. I was hoping to put in a magnetic reed switch -drop a magnet on the "spot"and the ESC shuts off- the receiver draws very little and I was worried that the ESC drew a lot statically.
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Jan 10, 2019, 02:10 PM
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CaptCB's Avatar
Bob,

On Nellie Irene, I use a 30 amp. auto switch, between the battery (LIPO 5200, 2S) and the boat. It is "rated" at 30 amps "switching", so, that means in reality it will take a lot more amps. My brushless motors, are rated at 70 amps each, at max draw. CaptDH and I have discussed it. I have never even felt the switch get warm, We have not put a digital draw meter in the boat, so we have no real numbers. But the run time is very reasonable, and even the ESC's, only get "mildly warm", without the water cooling on.
Hope this helps some.

CB
Jan 10, 2019, 04:05 PM
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Bob Gaito's Avatar
Yea Charlie it does...you highlighted characteristics that I wasn't aware of-but I am not concerned about circuit protection. I am using two 70 amp ESCs with two 60 amp maxi blade fuses on motors that should not exeed 55 amps each. My concern is the mission profile -you know RC boaters...run the boats for 10 min, then drift the boats for 20-30 min while B.S.ing then run for 10-15min more. Raft up and B.S. or lunch or both - run some more then time to go home...I guess the batteries (two 5200 lipos) will last with the boat being constantly on and the radar spinning..
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Jan 10, 2019, 04:30 PM
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Olscuzbut's Avatar
A simple toggle or slide automotive switch as CB mentioned, works great as a battery disconnect switch. There a lots of different current handling options out there. Just have to mount it somewhere on the permanent part of the deck and disguise it as deck clutter.
Jan 10, 2019, 04:41 PM
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CaptCB's Avatar
I am only running ONE 5200 battery, and if I do your scenario, I usually won't put the second battery in. But, I have it with me, if I want to push the boat hard/fast!
Jan 10, 2019, 05:10 PM
Latitudes vs Attitudes
Bob Gaito's Avatar
Not sure yet-the numbers are mind boggling-two motors at 55 amps= 110amps but its pulsed/transient amperage ..so its like less amperage. The switches are rated to switch under load but we'd be turning them on and off at zero power so they'd take a lot more amperage and the batteries only have 14 awg wire but that works...what the heck?
Last edited by Bob Gaito; Jan 10, 2019 at 05:30 PM.
Jan 10, 2019, 05:18 PM
Latitudes vs Attitudes
Bob Gaito's Avatar
Quote:
Originally Posted by CaptCB
I am only running ONE 5200 battery, and if I do your scenario, I usually won't put the second battery in. But, I have it with me, if I want to push the boat hard/fast!
I don't know, Charlie, if it would run on one battery-I'm using two 5200 2s lipos in series...for a 4s system -the motor's min cell count is 3s..
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Jan 10, 2019, 07:50 PM
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CaptCB's Avatar
Bob,

When I design a wiring harness for a Show Car, or Race Car, this is what I use for wire sizes.

Headlights, 3, 12 ga wires, will do both headlights, WITHOUT using 1-2 relays!!!
95 amp Alternator, charging wire, 10 ga.
110 amp Alternator, charging wire, 8 ga.

And I have done all sorts of calculations of what a realistic MAX draw might be. Example: out in the rain, "requires", elec. radiator cooling fans, lights, wipers, heater/defroster, etc., etc.. Add all that up, and what size is the main wire to the fuse box??? Normally, only 12, or maybe 10 ga. in a better system.
That scenario may not ever happen, but I liked to plan for it. Beats the heck out of HAVING to call for a flatbed tow.

Just something to think about...

I have done custom auto wiring / design and fabrication, trouble shooting, and repair, since the early 1970's.
So, a lot of this "automotive type" stuff, does not spook me.

CB
Jan 11, 2019, 09:58 AM
Big Boats Rule!
boater_dave's Avatar
If you are looking for simple main power cutoff, what about breaking the positive power lead with a pair of Anderson Power Pole plugs and a short loop of wire? Pull the loop to disarm. The Anderson plugs can be configured so you won't accidentally plug a battery into them. Google search for Anderson Power Pole Arming shows a bunch.

Dave
Jan 11, 2019, 01:47 PM
Latitudes vs Attitudes
Bob Gaito's Avatar
Dave that's a great idea! simple and it doesn't take up valuable real estate..thanks.
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Jan 12, 2019, 12:31 AM
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CaptCB's Avatar
Similar amp rating to the switch I used.

With 12 ga. wire, 30 amps.
With 10 ga. wire, 45 amps.

My switch is rated at 30 amps, switching under load, and the wire from the ESC connections to the switch, is 10 ga.
Remember, max possible draw on my motors, is 70 amps each, the same as yours. I am turning 2'' dia. brass props, and the boat weighs 11+ lbs.
Jan 12, 2019, 09:02 AM
Latitudes vs Attitudes
Bob Gaito's Avatar
Charlie, do you happen to have an add for that switch with a link or just a picture?
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Jan 12, 2019, 10:10 AM
Registered User
Another option is to use a pair of Solid State relays like this.
You will lose about .3 volts across it at 55 amp but the smallest toggle switch will control it.
A reed switch would also work.

Mark


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