wiring a servo to a battery direct

[cossack]

is it possable to wire a omg hdt045070b direct to a battery instead of using a bec as it is listed on there site that it can take 7.4v


Specifications
High Voltage Low Profile 7kg Brushless Digital servo
Item No.: HDT045070B
Modulation: Digital
Weight: 45g (1.59oz)
Dimensions: 40.2 x 20.1 x 25.2 mm (1.58 x 0.79 x 0.99 in)
Gear Type: Titanium
Motor Type: Brushless
Rotation: Dual Bearings
Stall Torque: @6.0V: 5.5 kg-cm (79 oz-in) @7.4V: 7 kg-cm (97 oz-in)
Speed: @6.0V: 0.06sec/60° @ 7.4V: 0.05sec/60°

i know peolpe who have done this with a hitec 7950th and had no problems


Detailed Specifications

Control System: +Pulse Width Control 1500usec Neutral
Required Pulse: 3-5 Volt Peak to Peak Square Wave
Operating Voltage Range: 4.8-7.4 Volts
Operating Temperature Range: -20 to +60 Degree C (-4F to +140F)
perating Speed (4.8V): 0.18 sec/60° at no load
Operating Speed (6.0V): 0.15 sec/60° at no load
Operating Speed (7.4V): 0.13 sec/60° at no load
Stall Torque (4.8V): 344oz/in. (22kg.cm)
Stall Torque (6.0V): 402oz/in. (29kg.cm)
Stall Torque (7.4V): 486oz/in. (35kg.cm)
Operating Angle: 45 Deg. one side pulse traveling 400usec
Continuous Rotation Modifiable: Yes
Direction: Clockwise/Pulse Traveling 1500 to 1900usec
Idle Current Drain (4.8V): 9mA at stop
Idle Current Drain (6.0V): 9mA at stop
Current Drain (4.8V): 220mA/idle and 3.8 amps at lock/stall
Current Drain (6.0V): 300mA/idle and 4.8 amps at lock/stall
Dead Band Width: 1usec
Motor Type: Coreless Carbon Brush
Potentiometer Drive: 6 Slider Indirect Drive
Bearing Type: Dual Ball Bearing MR106
Gear Type: Titanium Gears
Connector Wire Length: 11.81" (300mm)
Dimensions: 1.57" x 0.79"x 1.50" (40 x 20 x 38mm)
Weight: 2.40oz (68g)

i just wanted to know if what i want to do is safe

cheers

[Calderwood]

As long as you only ever run 2s it should be fine. What application are you using that servo for?

[cossack]

thanks for the reply buddy

it is going into a drifter with a hpi sc-15 and a 15x2 motor

cheers ian

[JokersWild]

Yep, run red and black leads to the esc power leads, take signal line and send to rx..... Done.

[Charlie-III]

Originally Posted by JokersWild

Yep, run red and black leads to the esc power leads, take signal line and send to rx..... Done.

+1.... if it's a Spektrum radio, you may want a negative from the servo to RX ground as well.

Spektrum radios seem to have more issues with grounds than other radios, but it can happen anytime.

[redsawacs]

On heavy acceleration (and heavy gearing), youre battery voltage will drop, affecting servo performance.

I would recommend you run an external BEC, you'll get more steady voltage to your servo.

[Charlie-III]

Originally Posted by redsawacs

On heavy acceleration (and heavy gearing), youre battery voltage will drop, affecting servo performance.

I would recommend you run an external BEC, you'll get more steady voltage to your servo.

I don't believe ANY hobby grade BEC's put out more voltage than they get in, thus if the pack voltage drops, the BEC output drops.

The CAP in the BEC may help out a bit, but not much.

[Calderwood]

Originally Posted by Charlie-III

I don't believe ANY hobby grade BEC's put out more voltage than they get in, thus if the pack voltage drops, the BEC output drops.

The CAP in the BEC may help out a bit, but not much.

I don't think any of the becs that we use in the crawler community do but there is definitely 1s plane stuff that includes a voltage booster.

[JeremyH]

I have tried this on some of my crawlers and didn't like it. The servo had plenty of torque, but if I got on the throttle, the servo would jump. An external BEC got rid of this...

[Whiplashdjs]

Jumping like that is usually fixed with a good capacitor.

[JeremyH]

Originally Posted by Whiplashdjs

Jumping like that is usually fixed with a good capacitor.

I'm sure the BEC I installed had one.

[heyok]

Just wondering how serious they are?

Operating Voltage Range: 4.8-7.4 Volts

Ever measured the voltage of a charged 2S Lipo? It is usually 8.4 volts.
Just something to keep in mind.