Looking for help understanding external BEC’s and why I need one

[SaltyDog]

Hello everyone! My SCX10II build is almost complete and with that it’s about time to start installing electronics (the most foreign part to me).

For a frame of reference here are the electronics I’m working with:

• Hobby Wing 1080 ESC
• Castle Creations 10 Amp BEC
• Savox 1210SG servo (7.4v 444oz/in)

What I’m not understanding is, if the BEC is wired into the battery connection, what difference is it making using it instead of the 7.4v internal BEC on the HW1080? Is it not doing the same thing? And how is this preventing my truck from browning out when using this high powered servo?

Edit:
After talking through it with people I’m beginning to understand a bit more. In my case, Installing the CC10Amp BEC is not about increasing voltage, it’s about increasing Amps. Is this correct?

[MOguy]

Voltage is the same but you will be able to draw more amps from the battery. Most internal BECs delivery 2-4 amps, an external BEC can deliver more. Some servos need more amps to run the best they can then an internal BEC can provide.

[SaltyDog]

Originally Posted by MOguy

Voltage is the same but you will be able to draw more amps from the battery. Most internal BECs delivery 2-4 amps, an external BEC can deliver more. Some servos need more amps to run the best they can then an internal BEC can provide.

I’m beginning to understand now. I’ve been focusing on Volts when that was never the issue to begin with.

[heyok]

You aren't wrong to focus on voltage.
What happens when you draw more current from a BEC that can't keep up with the load is the voltage will sag below the desired voltage. That lower voltage means less current is being delivered to the load.

[OnTheTrail]

Originally Posted by heyok

.... That lower voltage means less current is being delivered to the load.....

And that (even momentary) lower voltage can cause other issues such as a brown-out of the receiver.

[King Dork]

Originally Posted by OnTheTrail

And that (even momentary) lower voltage can cause other issues such as a brown-out of the receiver.

You got it! Repeated voltage spikes/sags can irreversibly damage any and all of the electronics as well. This would almost certainly happen with his intended setup (don’t forget a bypass adapter).

[Ots]

Historically my use for a BEC (and I prefer user adjustable ones) was to be able to limit the voltage being applied to my electronics. A 6S pack with max voltage of 25.2 is a bit much for receivers, servos and such, and so they would receive their supply from the BEC which would be set at some other voltage, like 6 for example.

It's a bit goofy when the battery packs are 2S like I'm using for my crawlers and all they have to give is 8.4V max. Do I need a BEC? I try and select receivers and servos that won't have problems being connected to 8.4V so I don't have to mess around using a BEC.

I also don't run my packs down too far. That way they are better for the system and it's better for the longevity of the pack.

[OSRC]

It's funny we still call them "BEC" - I think we're past that point now.

BEC stands for Battery Elimination Circuitry and was all the rage back in the old days. Originally, receivers and servos had their own battery pack to power them - the typical 4AA pack you still see on nitro vehicles, which is where the 6V standard comes from. Most kits came with a mechanical speed controller that could only power the motor so the 6V pack was needed. When ESC's became more popular, some started coming with "BEC" - the abilty to step down the battery voltage and supply the radio and servos with power, thus eliminating the need for the AA pack - thus, Battery Elimination. We take them for granted now, but ESC's used to be considered a HUGE upgrade to nearly any vehicle.

We still call it a BEC, though it's really just an internal/external power supply. Grandfathered in I guess. End History Lesson...

[Ots]

Originally Posted by OSRC

It's funny we still call them "BEC" - I think we're past that point now.

BEC stands for Battery Elimination Circuitry and was all the rage back in the old days. Originally, receivers and servos had their own battery pack to power them - the typical 4AA pack you still see on nitro vehicles, which is where the 6V standard comes from. Most kits came with a mechanical speed controller that could only power the motor so the 6V pack was needed. When ESC's became more popular, some started coming with "BEC" - the abilty to step down the battery voltage and supply the radio and servos with power, thus eliminating the need for the AA pack - thus, Battery Elimination. We take them for granted now, but ESC's used to be considered a HUGE upgrade to nearly any vehicle.

We still call it a BEC, though it's really just an internal/external power supply. Grandfathered in I guess. End History Lesson...

Kinda like when you 'cc' someone with a memo you wrote.