Receiver running on 7.2/7.4v?

[Stu :)]

I've got a new project idea sitting in the back of the ol' brain doing it's 'mouse wheel'. The idea will use either a standard 27MHz AM receiver or if it's too big I'll use a 72MHz park-flyer mini receiver (GWS, E-Sky, etc) a servo board as a simple ESC driving a 280 motor and micro-like servo for steering and maybe a micro servo for moving a piece of wire around, nothing too flash.
In order to save weight and volume; both of which is very critical, I was wondering if could I tap a 7.2/7.4 volt line direct into the receiver? At this moment the best fit batteries with gobs of mAh (and cheap ;) ) is a pair of Li-Ion CGR18650s.

So how Happy will the 27MHz Am and/or Park-Flyer receiver be?
...or...
Should I ask how long until they go Sad and cry 'magic smoke'?

Many thanks,

Stu :)

[patmat2350]

If the Rx is marked "BEC", or if the instructions say you're in the allowable input range, you'll be fine.

[redboat219]

I'm facing a similar dilemma on my project. I want to know if I can use a Mtronik micro viper marine 10 together with an old JR NER-327X 7ch 72 mHz Rx ( which I can't seem to find any info on) on my boat ( I know it an air frequency but legal to use over here for surface application).
I've been looking over the mtronik site. It notes that all their ESCs are equipped with BECs unless indicated. For the Viper 10 it only notes that it has a 1.2A BEC. No mention of what the output voltage is.

[Stu :)]

Brilliant! Thanks Pat. Only asked to see if anyone else had any issues...

I checked the Futaba site and their R122JE 2-Channel AM with BEC is good for up to 8.4v, wow! :eek: However before start rubbing my hands together... must finish Teaser... must finish Teaser...

Stu :)

[patmat2350]

Any BEC will put out 5v... standard.

[Stu :)]

I'm facing a similar dilemma on my project. I want to know if I can use a Mtronik micro viper marine 10 together with an old JR NER-327X 7ch 72 mHz Rx ( which I can't seem to find any info on) on my boat ( I know it an air frequency but legal to use over here for surface application).
Redboat, don't you just love living a country where 72MHz is ground legal :D Makes things SO much cheaper and easier...
I've been looking over the mtronik site. It notes that all their ESCs are equipped with BECs unless indicated. For the Viper 10 it only notes that it has a 1.2A BEC. No mention of what the output voltage is.
Now I could be wrong, but from what I've heard is that the good people of Mtroniks use a voltage regulator in the circuit, hence the minimum voltage use of 4.8 volts (unlike the mad 2 volts found on Electronize ESCs).
Best bet would be to plug the battery to the ESC with motor attached and use a multimeter to read the output voltage on the receiver plug. The red (+) and the brown (-) wires if memory serves me right.

Stu :)

[Kmot]

Guys, an old racers secret I learned a few years ago and have used ever since, is a 9V battery to power the Rx and servos.

[AndyKunz]

Nice ESC, Tom ;)

Andy

[Kmot]

Yep, they are the best! :D

[james carey]

Interesting ,Refering to Kmot's earlier post regarding running the Rx and Servo's of a single 9V battery .The system obviously works .What are the Pro's and Con's of using this set up rather than the 4 x AA battery holder that comes with the radio set? What about component life , servo speed , run time .

The Futaba 2ER 2 ch radio spec's lists the Rx as 4.8 to 8.4 V and the Servo's at 4.8 to 6 v. The 9V batt is slightly over spec for the Rx more so for the servos.

Am thinking in particular for use in a Footy Sail Boat.


Cheers,
James

[mfr02]

The 9 volt battery shown has a limited current supply capability, so the output voltage will be dropped to a managable level. If a battery manufacturer improves their product, this will become a recipe for letting the magic smoke out. If an equipment manufacturer quotes a voltage to decimal points, do not exceed that figure, or at least, avoid using a battery that has a higher nominal voltage on the label. If the voltage shown is in round figures, it probably implies a battery with that nominal voltage, but in both cases, makers are a bit shy with concrete information.
The BECs in RC use universally supply a nominal 5 volts for radio, servos and everything else that plugs into the RX.

[Hoghappy]

Guys, an old racers secret I learned a few years ago and have used ever since, is a 9V battery to power the Rx and servos.

Hey Tom...what is that ESC? Specs?

That is a very nice setup...but the one heartburn I have is the cost of replacing the 9 volt every time....those are not that cheap.

Capt. Crash

[Kmot]

The 9V battery is a racing secret. It weighs far less than a pack of 4 AA batteries. That's the advantage.

It does not go dead with every run. The 9V I use in my CEN Wave Shark lasts a long time. Certainly many runs, at least.

I have used a 9V on Futaba, Hitec, and CEN Rx's. Never a problem. No smoke let out.

Robert, that ESC is an RC-Hydros unit.

http://www.rc-hydros.com/

[retoabcr]

The Futaba 3003 servo works great with 9 volt and has for 11 years and 9 volts last almost 1 boating season. I have found the 3001 Futaba servo doesn't like 9 volts cause servo arm will jump around and JR servos work great too. The 4-AA batteries take up more room and like Kmot typed weigh less and easier to find room with velcro. I too use Rc hydros escs, rock solid escs for brushed motors.

[mfr02]

It weighs far less than a pack of 4 AA batteries.
But probably more than 4 AAA cells. Running in the safety margin is never a good habit. Like I said, some day Duracell will bring out their new, improved product with reduced internal resistance. The next batch of chips in servos could well have a reduced safety margin. Either of these is a magic smoke recipe.

[retoabcr]

Using 4-AAA power pack is risky and can leave boat stranded sooner than you think and swimming is totally out of the question.

[785boats]

Stu.
I believe The easiest & cheapest option is a UBEC They're small, weigh next to nothing, & cost about $8.00 (plus postage) There are many on the market from different sellers. They have a 3 amp output & can be switched from 5v to 6v. They are powered from your main battery. Input voltage 5.5v to 42v.
These are the ones I use in all my fast electrics, both brushless & brushed.
http://www.r2hobbies.com/proddetail.php?prod=rcps81706_ub
Cheers.
Paul.

[frankg]

:) Almost all ESC’s with BEC circuits will handle up to 8.4 volts input to net 4.8 -5 volt out put to the servos. They will also allow enough current flow to handle the servo outputs they have in the receiver (usually 2 or 3). The reason that you can use a 9 volt transistor battery to power up the circuit in the receiver is that the nominal voltage of the battery is 9 volts and does not go above that voltage. The 8.4 volt BEC input voltage takes into account that a 8.4 volt NI-CAD or NI-MH battery when fully charged will have an out put voltage over 10 volts for the first few minutes of discharge before it hits in nominal voltage of 8.4 volts. The 6 tenths of a volt are well within the limits of the BEC circuit. :)

[keven64]

A rechargeable 9v 'PP3' battery is constructed from seven seperate 1.2v cells - these days those are generally NiMH chemistry.

A 9v drycell battery will never operate under load at as much as 9v - and although the rechargeable version will show as around 10v on a multimeter when 'fully charged', it's voltage will drop immediately upon application af any load.

Indeed, it will never operate under load at anything more than a little above 8v.

Yes - the rechargeable 9v battery will provide enough voltage to operate a BEC receiver, as the seven cells will provide a nominal 8.4v.

BEC systems are generally intended to provide a stable 5v from a 6-cell 7.2v battery pack - as used with electric-powered model cars and such. ;)

However, battery power is rated in Amps - and 250mah is simply not enough to risk using within a Footy yacht - or any other type of radio controlled model in my opinion.

Unless, of course, you have a particular liking for an impromptu swim ! :eek:

I have been using 2S li-po batteries to power radios in my model boats ( with regulators for those receivers without the BEC feature ) for four years without a problem...

Keven. :)