Wiring questions (need for multiple BECs)

[YeeP]

So I am trying to understand how to setup the wiring on my rig. Currently, I have a CCBEC in driving my hitech steering servo. I want to eventually add another steering servo to the back axle, as well as some lights. The lights will come first. Do I need to add a BEC for each of these? If so where do they all plug in (all of my plugins in the current ESC are full). Sorry if this is a silly question, I am just trying to understand how all of this stuff can be added. I am looking at multiple lighting ideas, it would be nice to have a powersource "plug in" that I can use for lighting, but keep them on a separate circuit (share battery with everything else). EDIT: Also currently running a Ready Winch that plugs inline with my battery.


Thanks!

[Axial Rose]

The easy answer involves calculating the maximum amps and then get a BEC to cover it

The formula for Amps is Watts divided by Volts

Castle Creations has a 20 amp ESC --> LINK

The information for amp draw isn't usually available for servos - which will vary drastically based on load, voltage, and other factors - servocity.com does list the current drain - stall for many of their servos

For example, a Hitec HS-7950TH servo has a 4.8 amp stall rating at 6 volts - so a ten amp BEC would cover two of those running at 6 volts (but just barely if they were both stalled, pulling max amps)

You could use two of those servos --> LINK --> because they are designed to run directly from 2S lipo's - no BEC needed - and then use either a BEC for the lights or use a very small 3S for 12V light systems (since they usually don't draw many amps)

Have you considered a two battery system? I have "way long" runs using 3S 2200 mAh battery packs with my crawlers - these batteries are light weight compared to many other batteries used for crawling so I could add add another small 2S battery pack and still have a reasonable total weight for battery packs

One other thing to consider - when I run quads with LED's I use a home-brew connector: 1 connector splits off and goes to the LED's, the other connector goes to the ESC's. You could do the same with crawlers if you were using 3S batteries with a 12V LED light system and if your ESC would take 3S. The best thing about Castle Creations BEC's and ESC's is the stupid-simple easy way to program them using my computer - I can control voltage to the motors, to the servos, and I can run 2S or 3S, and I can run brushed motors or brushless. What's not to love about that?

Sorry if this doesn't help

[YeeP]

That does help, I was trying to avoid running dual batteries for the weight added, but I guess I should consider it.

I am running the 7950TH with the 10amp BEC set at 7.4 volts. I guess I could bump to a 20 amp BEC. How can I calculate the amperage at 7.4 volts? I do have a nice DVOM at home and can put it in line to get an amperage reading I guess.

I will take a look at those smaller batteries. I was trying to save the second battery space/weight for a camera I am building out of a raspberry pi zero. Thanks for the tip.

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[Axial Rose]

Originally Posted by YeeP

How can I calculate the amperage at 7.4 volts?

ServoCity.com is the best source I've found for stall amps, theoretically, should be the maximum encountered

If your servo isn't listed at their website, then find one that's close and use those amps as a "ball park" and go conservative

I can't imagine the 20 amp BEC from Castle is going to ever get maxed out, even with two power-hungry servos, a boatload of LED's, and using the winch without stressing/stalling both servos

[YeeP]

Originally Posted by Axial Rose

ServoCity.com is the best source I've found for stall amps, theoretically, should be the maximum encountered

If your servo isn't listed at their website, then find one that's close and use those amps as a "ball park" and go conservative

I can't imagine the 20 amp BEC from Castle is going to ever get maxed out, even with two power-hungry servos, a boatload of LED's, and using the winch without stressing/stalling both servos

Ok. The winch is on its own circuit pulling directly from the battery anyway..

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