Battery on FPV Setup

[Ace2317]

So I'm an FPV noob. Here's my question. I want to run my FPV equipment off of the same flight battery that flies my multirotor. What size battery will I need to step up to to run both and have a decent flight time?

Flight setup
Bat Bone tricopter
Suppo 2208-14 motors
3s 2200mAh 20C battery
8x4.5 props

FPV setup
FatShark 250mw 5.8 Video Transmitter

Any other advice is also welcome. Thanks!

 

[William A]

Use the fatshark 'balance plug tap' to power the video Tx. You can use the battery you have now.

 

[Ace2317]

Use the fatshark 'balance plug tap' to power the video Tx. You can use the battery you have now.

Awesome! How badly would that affect my flight times? Right now I get about 6 minutes. Or do you have any idea?

 

[William A]

Haven't done any testing, but I didn't notice a change in flight time.

 

[William A]

Looking up Tx specs on Immersionrc's site, they list the 600mw model as a 3w power consumption. So....

 

[Ace2317]

Wow. Cool. Thanks a lot for the help!

 

[joshuabardwell]

The FatShark 250 mW vTX is rated at 330 mA @ 7.4 volts. You are feeding it 3S = around 12 volts, so there may be some additional loss in the voltage regulator, depending on if it is switching or not (I don't know). A typical board camera running at 5v will pull about 60-80 mA. The FatShark 250 mW vTX has an in-built switching regulator for the 5v camera feed, so that should be very efficient--perhaps as little as 15% overhead. Let's estimate that all in all, you're at under 0.5 amps.

You have a 2.2 Ah battery, which means you could run the FPV setup alone for about four hours on one pack. If you had a flight time of ten minutes, you would use 0.5 amps * 10 minutes / 60 minutes-per-hour = 0.08 Ah, or 80 mAh over the course of one flight. If one flight consumes 80% of the battery's capacity, that's 1,760 mAh. 80 / 1,760 = 0.045, or about 5%. 5% reduction in flight time over ten minutes is 30 seconds.

To sum up, the camera and vTX's current draw is so small compared to the draw of the motors that you will probably not notice the difference at all.

 

[Ace2317]

Wow. Awesome. Thanks for that. And now I can actually figure it out on my own. Thanks for the lesson! You guys rock!