My experience comes from the PREDATOR V2 RTF FPV KIT from Fat Shark.
I'm writing so others can avoid severely unbalanced battery packs on their plane/copter.
Here is the device I am writing about, it allows you to quickly plug in your FPV TX to the balance plug on your battery in order to power the device from the same battery which is running your aircraft. Other's use an independent battery pack to power the device.
Here's a diagram showing the pin to pin wiring between the black port (power to the TX) and the 3 white ports (battery connection).
This is bad with a single battery setup, as your aircraft will be equally drawing from each cell through the main connector and a leech will be drawing from a single cell causing it to lose capacity at a faster rate than the others. This will severely shorten your flight times as the total series voltage output of your battery will drop faster than it will when distributing the load of the TX across all three cells.
This is bad with a separate battery for the TX unless it is a single cell battery, as you will be continually discharging and recharging one cell while the other stays full... quickly destroying your battery.
When using this module, you gain a capacitor which will reduce the ripple - http://en.wikipedia.org/wiki/Ripple_(electrical) - on the input voltage to the TX. In practice this is covered by a high quality BEC or ESC (what's powering your receiver) and is negligible directly from the battery.
Actual Draw Readings
@ 5v the TX draws ~.42 amps
@ 11v the TX draws ~.21 amps
Roughly 2.1 watts which on a 3S battery at 11.1v would be 210mA. That's not too bad if you are drawing energy equally from all 3 cells.
However, when using the dongle/adaptor/ripple reducer you are going to be pulling that entire 2.1 watts from a single cell @ ~3.7v which is ~.56 amps. The voltage reduction rate on this single cell will be much higher (faster) in real terms and as batteries for the most part (3S, 4S, etc) wire the internal cells together in series, you will notice the voltage drop much more quickly than it should for the entire cell pack of the battery.
Normally you are drawing power equally from all of the cells of the battery by using the main connector. If for example you have a 3S battery you would be drawing 3.7+3.7+3.7=11.1v. When using this adapter you will have something like 3.7+3.7+3.0=10.4v (with the low cell dropping at a faster rate than the other 2) at which time your aircraft will report a dead battery much faster than it actually is.
Flight times will be decreased more than they should if you use it.
This cell will wear out much faster than the others, especially if you are not balance charging which will drastically shorten the life of your batteries.
As you can see from the current readings, the TX operates fine from 3.7v to 12v so you should have no problem connecting it directly to the battery. You can also use a BEC or an additional output from an ESC to resolve this problem.
I'm writing so others can avoid severely unbalanced battery packs on their plane/copter.
Here is the device I am writing about, it allows you to quickly plug in your FPV TX to the balance plug on your battery in order to power the device from the same battery which is running your aircraft. Other's use an independent battery pack to power the device.
Here's a diagram showing the pin to pin wiring between the black port (power to the TX) and the 3 white ports (battery connection).
Code:
Red to Red
Black to Black
Blue is left floating, this means that you are only using one cell of the battery.
This is bad with a single battery setup, as your aircraft will be equally drawing from each cell through the main connector and a leech will be drawing from a single cell causing it to lose capacity at a faster rate than the others. This will severely shorten your flight times as the total series voltage output of your battery will drop faster than it will when distributing the load of the TX across all three cells.
This is bad with a separate battery for the TX unless it is a single cell battery, as you will be continually discharging and recharging one cell while the other stays full... quickly destroying your battery.
When using this module, you gain a capacitor which will reduce the ripple - http://en.wikipedia.org/wiki/Ripple_(electrical) - on the input voltage to the TX. In practice this is covered by a high quality BEC or ESC (what's powering your receiver) and is negligible directly from the battery.
Actual Draw Readings
@ 5v the TX draws ~.42 amps
@ 11v the TX draws ~.21 amps
Roughly 2.1 watts which on a 3S battery at 11.1v would be 210mA. That's not too bad if you are drawing energy equally from all 3 cells.
However, when using the dongle/adaptor/ripple reducer you are going to be pulling that entire 2.1 watts from a single cell @ ~3.7v which is ~.56 amps. The voltage reduction rate on this single cell will be much higher (faster) in real terms and as batteries for the most part (3S, 4S, etc) wire the internal cells together in series, you will notice the voltage drop much more quickly than it should for the entire cell pack of the battery.
Normally you are drawing power equally from all of the cells of the battery by using the main connector. If for example you have a 3S battery you would be drawing 3.7+3.7+3.7=11.1v. When using this adapter you will have something like 3.7+3.7+3.0=10.4v (with the low cell dropping at a faster rate than the other 2) at which time your aircraft will report a dead battery much faster than it actually is.
Flight times will be decreased more than they should if you use it.
This cell will wear out much faster than the others, especially if you are not balance charging which will drastically shorten the life of your batteries.
As you can see from the current readings, the TX operates fine from 3.7v to 12v so you should have no problem connecting it directly to the battery. You can also use a BEC or an additional output from an ESC to resolve this problem.
