drop down the voltage of a two cell lipo.

[indoruwet]

Can anybody tell me how to drop down the voltage of a two cell lipo batt to around 6 volts. Would like to use the batt to power the receiver and servos, which run from about 4,8 to around 6 volts.

[Aethertek]

A diode drops about .5 volts per, a few in series may do the trick. Make sure you use one rated higher than the required amps needed. & this will eat power in the form of waste heat disipated by the diodes, not much though. another point on that is the voltage drop decreases with an increase in temperature.
Before you do this though you should check with the manufacturer / website info to determine the max voltage allowable this may not be needed.

[randy lee]

I use a single lipo to power my dlg.
berg 6g3 rx.
2- jr 281 digital sxs'
2-hs 55s'
can only use 300ma out of 450,
when it starts to loose range.
still good for about 3 hours airtime!

[Bob Baker]

You need a Low Dropout (LDO) regulator. I have used the LM2940 in the past with good results; however it is rated at 1 Amp. If you need more than this you'll have to go shopping. You will also need bypass capacitors at the input and output of the regulator- look at the part's data sheet for advice.

Using a diode for voltage drop does not offer any voltage regulation; if the battery drops by 1 volt, the output will drop by 1 volt. It would be nearly impossible to get the rx voltage to stay between 5 and 6 volts.

[alexcmag]

A 5V regulator is really a better choice.

I made a BEC for a friend who wanted to use 2 cell lipo on a glider and it was really light, about 2 grams (one LM1117-5.0 regulator, one 10uF cap, PCB and wires).

[Mr.RC-CAM]

Maybe this would work out for you: http://www.dimensionengineering.com/ParkBEC.htm

[tomskk]

Does anybody know a good LDO Voltage regulator that can drop voltage for 2 lipo's to 5.5V and still handle the current in a large scale acrobatic plane (10 servos).

[indoruwet]

Thanks for all the feedback. I realise that using a 2 cell Lipo is overkill pricewise to power the receiver end of the whole thing, but I do have three laying around.
Looks like I am not the only one trying to do this.

I think the max voltage allowed on the set up is 6 volts, from what I have been able to gleen. The equipment is Futaba receivers and Servos. I also have a Tower Hobby receiver, but I think it is the same as a Futaba in different dress-up.
I do like the servos at the higher voltage since they operate "better" (I think). It does however take higher capacity batteries.

""It would be nearly impossible to get the rx voltage to stay between 5 and 6 volts"".

I am interested in keeping the maximum voltage below 6 volts due to the "specs" of the set-up. When the volts drop down (due to usage), I should not go below the minimum of the Lipos anyway, no ??

[alexcmag]

This is a simple circuit using:

1 Futaba Conector
1 male JST conector or anything matching the battery pack
1 LM1117-5.0 voltage regulator
1 10uF 16V electrolitic capacitor

It is the simplest BEC possible and is light and reliable.

I drawed 1 layout for each regulator size.

[indoruwet]

Wow, Thanks Alex, That was a fast response.