how much current (mA) does a typical radio system use?

[raytam]

how much current (mA) does a typical radio system use? I'm wondering if a 7.4v lipoly batter will mess up the receiver or servos? If yes, has anyone attached a resistor to bring down the voltage to acceptable levels? If so, how many watts and ohms is the resistor?

I believe it would be easier to use a NiMH battery pack, but lipolys are more compact and save a little weight.

Thanks

Ron

 

[Kez]

how much current (mA) does a typical radio system use? I'm wondering if a 7.4v lipoly batter will mess up the receiver or servos? If yes, has anyone attached a resistor to bring down the voltage to acceptable levels? If so, how many watts and ohms is the resistor?
I believe it would be easier to use a NiMH battery pack, but lipolys are more compact and save a little weight.

Thanks

Ron

Ron,

It depends greatly on the type of servo used AND the load on the servos. The higher the load (ie larger the boat and faster the boat) the higher the current.

You do not want to add a resistor to drop the voltage. If you look at Ohms law, V = IR, adding a resistor in series will act to limt current. What you want is either a Zener diode or a 5V regulator.

It is more simple to use Ni-Cad...or NiMH if you are not pulling high loads.

Hope this helped.

kez

 

[photohoward1]

how much current (mA) does a typical radio system use? I'm wondering if a 7.4v lipoly batter will mess up the receiver or servos? If yes, has anyone attached a resistor to bring down the voltage to acceptable levels? If so, how many watts and ohms is the resistor?
I believe it would be easier to use a NiMH battery pack, but lipolys are more compact and save a little weight.

Thanks

Ron

Ron,

It depends greatly on the type of servo used AND the load on the servos. The higher the load (ie larger the boat and faster the boat) the higher the current.

You do not want to add a resistor to drop the voltage. If you look at Ohms law, V = IR, adding a resistor in series will act to limt current. What you want is either a Zener diode or a 5V regulator.

It is more simple to use Ni-Cad...or NiMH if you are not pulling high loads.

Hope this helped.

kez

They sell voltage regs to drop it down to 6v. The receivers are not rated for 7.4v.

 

[raytam]

how much current (mA) does a typical radio system use? I'm wondering if a 7.4v lipoly batter will mess up the receiver or servos? If yes, has anyone attached a resistor to bring down the voltage to acceptable levels? If so, how many watts and ohms is the resistor?
I believe it would be easier to use a NiMH battery pack, but lipolys are more compact and save a little weight.

Thanks

Ron

Ron,

It depends greatly on the type of servo used AND the load on the servos. The higher the load (ie larger the boat and faster the boat) the higher the current.

You do not want to add a resistor to drop the voltage. If you look at Ohms law, V = IR, adding a resistor in series will act to limt current. What you want is either a Zener diode or a 5V regulator.

It is more simple to use Ni-Cad...or NiMH if you are not pulling high loads.

Hope this helped.

kez

They sell voltage regs to drop it down to 6v. The receivers are not rated for 7.4v.

You guys are great! Thanks so much.

 

[moparbarn]

radio shack has what you need. i use them to replace the horribly inaccurate mechanical voltage regulators in the dashboards of my old mopars. just be sure you check the output voltage, as i have bought 1 or 2 that were off. haven't seen one change with age, just not correct voltage out of the box.

 

[J Solinger]

Did you make a regulator using the LM7805 like the one in this scematic? I would like to use lipo too.

 

[Kez]

Did you make a regulator using the LM7805 like the one in this scematic? I would like to use lipo too.

LM7805 is a 5V regulator. The schematic would work. You might not even need the capacitor.

A Zener diode would work too but the regulator is a more elegant approach.

 

[Rigged]

i use a 7.4v lipo in my boats with a Align 6v regulator. Its a 1650mah 10C pack...doesnt seem to last any longer (runtime wise) then the 1400 and 1600mah NIMH's i use as well.

Now the 11.1v 2800mah Lipo i use in my TX...i will never use anything else again. Go 4-5+ months without having to charge it.

 

[John Kubitz]

i use a 7.4v lipo in my boats with a Align 6v regulator. Its a 1650mah 10C pack...doesnt seem to last any longer (runtime wise) then the 1400 and 1600mah NIMH's i use as well.
Now the 11.1v 2800mah Lipo i use in my TX...i will never use anything else again. Go 4-5+ months without having to charge it.

Just checking that you have the regulator between the switch and the reciever. Some people put them between the battery & the switch. (the regulator always draws some current) I only use a 600ma LI-PO and get as much run time as I did with 1650ma NI-MH.

I talked with the tech from Hitec @ Toledo & he said that the recievers will take up to 12volts but the servos don't like anything over 6.5 volts. The LI-PO pack in the transmitter is the best way to go. I haven't charged the one I use for my airplanes since Jan. I have over 10 hours of flight time & the voltage is still over 11.5 volts.

 

[Rigged]

i use a 7.4v lipo in my boats with a Align 6v regulator. Its a 1650mah 10C pack...doesnt seem to last any longer (runtime wise) then the 1400 and 1600mah NIMH's i use as well.
Now the 11.1v 2800mah Lipo i use in my TX...i will never use anything else again. Go 4-5+ months without having to charge it.

Just checking that you have the regulator between the switch and the reciever. Some people put them between the battery & the switch. (the regulator always draws some current) I only use a 600ma LI-PO and get as much run time as I did with 1650ma NI-MH.

I talked with the tech from Hitec @ Toledo & he said that the recievers will take up to 12volts but the servos don't like anything over 6.5 volts. The LI-PO pack in the transmitter is the best way to go. I haven't charged the one I use for my airplanes since Jan. I have over 10 hours of flight time & the voltage is still over 11.5 volts.

yes i have the regulator between the switch and reciever. Its not like i only get 1 day of running out of it... just do not get anymore then i did with NIMH's to justify the extra cost. Definetely right about the TX battery though. When i first got mine...it charged up to 12.3 or 12.4 volts.. 5 months later i finally decided to charge it, while voltage still was only at 11.7 or 11.8 volts. When i run, i just leave my TX on all day until its time to pack up.

 

[John Kubitz]

i use a 7.4v lipo in my boats with a Align 6v regulator. Its a 1650mah 10C pack...doesnt seem to last any longer (runtime wise) then the 1400 and 1600mah NIMH's i use as well.
Now the 11.1v 2800mah Lipo i use in my TX...i will never use anything else again. Go 4-5+ months without having to charge it.

Just checking that you have the regulator between the switch and the reciever. Some people put them between the battery & the switch. (the regulator always draws some current) I only use a 600ma LI-PO and get as much run time as I did with 1650ma NI-MH.

I talked with the tech from Hitec @ Toledo & he said that the recievers will take up to 12volts but the servos don't like anything over 6.5 volts. The LI-PO pack in the transmitter is the best way to go. I haven't charged the one I use for my airplanes since Jan. I have over 10 hours of flight time & the voltage is still over 11.5 volts.

yes i have the regulator between the switch and reciever. Its not like i only get 1 day of running out of it... just do not get anymore then i did with NIMH's to justify the extra cost. Definetely right about the TX battery though. When i first got mine...it charged up to 12.3 or 12.4 volts.. 5 months later i finally decided to charge it, while voltage still was only at 11.7 or 11.8 volts. When i run, i just leave my TX on all day until its time to pack up.

The other advantage with the LI-PO rec pack is that your voltage remains the same due to the regulator.

 

[Daniel's Racing]

how much current (mA) does a typical radio system use? I'm wondering if a 7.4v lipoly batter will mess up the receiver or servos? If yes, has anyone attached a resistor to bring down the voltage to acceptable levels? If so, how many watts and ohms is the resistor?
I believe it would be easier to use a NiMH battery pack, but lipolys are more compact and save a little weight.

Thanks

Ron

To second some other posts.

Most receivers will handle the 7.4 volt lipo's just fine, it is the servos that don't like the extra voltage. That is easily cured with the many purpose built 7.4 volt

electrinic voltage regulators on the market that most have switchable 5 or 6 volt output. They are fairly inexpensive and are ready to plug right in and use.

Fasst receivers will work with up to 12 volts without damage.

Daniel

 

[Sean Bowf]

Two things...

First, I think most diodes will drop 1 volt. So putting a diode in line with it might get the voltage where you want it.

Second, I think most voltage regulators require a certain amount of voltage GREATER than the voltage output you want. I thought this was 3 volts...so if you wanted to use a 6 volt regulator, to make sure you got what you wanted, you had to apply 9 volts to it. As an example, if you look at the data sheet for a 78L05 (5 volt regulator) in this data sheet, you will notice it wants an input of 8.5 to 20 volts for its nominal 5 volt output. This data sheet for a 7806 in a TO-220 package wants an 8-25 volt input for a 6 volt output (I take it you want a 6v output??)

I would think different components would have different voltage drops, and specs...so check the data sheets.

Just my 2 cents...

Sean