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Author Topic: Two batteries connected to receiver  (Read 233 times)

dpbarry

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Two batteries connected to receiver
« on: July 22, 2020, 06:47:51 PM »

Hi folks


Just learning a bit about ESCís as Iím more of a nitro person and have a wee query  :embarrassed:


I was working out in Ďofficeí and connected up a motor, esc and receiver. I had the LiPo battery connected to the esc and connected the bec lead from the ESC to the receiver but also connected a 4.8 volt battery to the receiver. Not sure if it was weird things happening or just me but esc kept beeping at me and not doing anything so studied the layout a bit more.


Having studied it, I wondered why I should have a battery attached to the receiver if the ESC BEC was supplying power to the receiver so I disconnected everything then reconnected all except the receiver battery an all seemed to work fine.


I did further online research on connecting up ESCís, BECís and motors and realised that if I connected a dedicated receiver battery I should disconnect the positive wire from the BEC.


I suppose, shortening the story, have I (or could I) damage the ESC (or anything else) by having the two batteries feeding power into the receiver?


Declan
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gribeauval

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Re: Two batteries connected to receiver
« Reply #1 on: July 22, 2020, 07:33:33 PM »

Either just use the bec from the esc OR a separate 4.8v supply with bec disabled(remove the red wire between the esc and receiver).
Receivers do very weird things with two power sources!!!
Mike
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justboatonic

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Re: Two batteries connected to receiver
« Reply #2 on: July 22, 2020, 07:36:22 PM »

The short answer is you could have damaged one or both components if you'd set off for a fast or prolonged sail. Presumably, you were testing in a shed and didnt try running the esc at full chat for a prolonged period? That being the case, you are probably ok but will need to test.
I always run with a separate rx power supply and motor batteries so it's best to use what's called an Opto esc with this set up. It's designed so you dont have the situation you ended up with. Alternatively, as you mentioned, remove the red wire from the esc if it has a BEC. However it's best to read the instructions before doing so.
Never cut the lead either. if you're careful, you can withdraw the wire and pin from the plug. Tape out of the way and that way, you can re insert it if you ever decided not to use a separate rX power supply.
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dpbarry

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Re: Two batteries connected to receiver
« Reply #3 on: July 22, 2020, 07:43:18 PM »

Cheers Guys


It was just momentary on/off in the shed - no prolonged use and since removing the receiver battery, No magic smoke witnessed or anything Weird like that.


All a learning curve for me now with new man cave  {-)

[/size][size=78%]Declan [/size]
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JimG

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Re: Two batteries connected to receiver
« Reply #4 on: July 22, 2020, 08:57:43 PM »

When you checked it out the first time where was the throttle stick? Powering up with the throttle at full generally sets the esc into programming mode and it sets up a sequence of beeps, the esc then doesn't power the motor.
Jim
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dpbarry

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Re: Two batteries connected to receiver
« Reply #5 on: July 22, 2020, 09:53:40 PM »

Hi Jim.


From memory, Had throttle at low, got beeps then went high, more beeps (different pattern. Musical tune) then worked fine - after sorting battery issue out. Itís a Turnigy 30A ESC



Declan


When you checked it out the first time where was the throttle stick? Powering up with the throttle at full generally sets the esc into programming mode and it sets up a sequence of beeps, the esc then doesn't power the motor.
Jim
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malcolmfrary

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Re: Two batteries connected to receiver
« Reply #6 on: July 23, 2020, 10:12:37 AM »

If an ESC 5 volt BEC is connected to a 4.8 volt battery it will try to charge the battery at 5 volts.  It might or might not be OK, depends on lots of things.  A fully charged 4.8 volt battery might be more than 5 volts, the voltage regulator might not like it, the battery might discharge through it, or not.
The load imposed by the battery might overload the BEC.  You might find any weak connections. The voltage that the receiver gets might not be stable, and a stable voltage is what RC elecronics depend on for correct working.
Use the Battery ELIMINATOR in the ESC, save the extra weight, save having to remember to charge an extra battery, put up with it working as it should.
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