Other uses for a BEC?

[danhikeski]

Hi, i have a been in rc for decades, but never used a bec, but think it might fit the application I need to step voltages down. I have an on/offroad motorcycle and want to use a 7.4 volt lipo for a battery system to charge my gps, cell phone, ipad, whatever I want, can run off of 5 volts.

If I have the battery hooked up to the bec and a usb plug, could it work in this regard? Does the bec need other input to work from the reciever? It'll step the voltage down for a servo, why not here? I had originally had the idea of using a voltage regulator off the battery, but this idea came to me.

[The Violator]

I use a BEC in my 4pk radio so I can use a 3s lipo to power it. I have ruined a lipo by leaving it on, so a way to monitor the battery voltage would be nice.

[danhikeski]

So it seems like it would work, what about wiring it into a 12 volt car battery system to get an output of 5 volts, for usb use. Do they work with lead acid batteries?

[losikid]

Originally Posted by danhikeski

So it seems like it would work, what about wiring it into a 12 volt car battery system to get an output of 5 volts, for usb use. Do they work with lead acid batteries?

Yea that will work just fine...if you run it to a lipo though make sure you have a lvc or alarm

[ClassicGMJunkie]

installing a switch between the battery and the BEC to break continuity will keep you from d/c'ing a lipo from leaving it plugged in on the tx.

[federally]

A BEC doesn't require any input from anything except a battery. A lot of guys wire them from the battery directly to the power leads of a servo, skipping the Rx entirely. Which is the same basis thing you're looking to do.

The only things you need to consider is that you don't put too many volts into the BEC, a 12v battery being charged by an alternator puts out about 14.5v so make sure the BEC can deal with that much juice.

Also remember the larger the step down the more heat the BEC will generate and they can overheat and when they are made the manufacturer is expecting them to receive some airflow for cooling. So you'll need to do something, maybe wire a little fan to either it's input or output to blow some air across it.

Lastly low voltage alarms can be had for very cheap on Ebay. I have one that works on 2s or 3s, plugs in to the balance tab and sounds a 120 decibel alarm when the battery starts to get low. You're gonna need something like this.

[heyok]

I use a BEC in my 1:1 truck to run a PIC circuit I built to flash some LEDs to make it look like there is a "Real alarm system" running (yes, it's lame).
Anyway, I was just using resistors to drop the voltage to a usable level for the circuit but the resistors ran fairly hot - see federally's post where he mentions the heat issue. I used one of my switching type BECs to do the job as it doesn't get hot like a linear type voltage regulator does.

I guess the bottom line here is to use a BEC that has a switch mode regulator in it so that you don't need a huge heat sink or fan. The BEC I sell, losikid's power supply upgrade to the GT3b transmitter and the Castle BEC are examples of switch mode regulators.