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Old Jan 13, 2013, 02:08 PM
FPV Recon
Altimat's Avatar
United States, TX, Cedar Park
Joined Nov 2005
195 Posts
Discussion
Dedicated flight video battery capacity

How small of a LiPo can I safely get away with for my 1.3G 800 VTX? What capacity are you using?
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Old Jan 13, 2013, 07:48 PM
Radd Graduate '06
Mochaboy's Avatar
United States, MA, Sudbury
Joined Aug 2006
1,820 Posts
12v input supply
@ 800mw
= 66 mah

ReadymadeRC supplies 3S 450mah batteries with their starter kits, so you can use this as a baseline. You'd be looking at close to 7 hours of continuous operation under best conditions (closer to maybe 5 or 6 hours when you consider all the energy lost to heat dissipation from the voltage regulators.)

A good practice would be powering your camera off the same rail, provided they were both rated for the same voltage, so those cameras pull about 100mah-120mah. Just tossing that in case you decide to go that route.

I started out with dedicated flight batteries. I've since built my own line conditioning filters that plug directly into the battery's balance tap and provide nice clean voltage out to the camera and transmitter.



Parts list:
JST-XH male header - straight pins/through hole (just bought right angle version for the next set that I will build)
2 right angle headers
560ohm resistor
3mm T1 Red led
micro slide switch
470uf 35v capacitor (overkill - but all I had on hand)
12mm toroid with 8 turns of servo wire

Whole thing cost about $4 bucks to make.

I tucked the toroid under the pcb to save space - whole thing ways about 11 grams - not bad compared to tossing an extra battery on the rig.
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Last edited by Mochaboy; Jan 13, 2013 at 08:55 PM.
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Old Jan 13, 2013, 10:56 PM
FPV Recon
Altimat's Avatar
United States, TX, Cedar Park
Joined Nov 2005
195 Posts
Thanks so much for the informative reply Mochaboy. I wasn't sure how efficient the TX was as far as using the output to calculate current draw. Your solution looks like a good alternative, but I'm going overboard on the noise prevention after reading all the horror stories and finding the good quiet regulators cost 10X and weigh nearly as much as a small battery. RMRC was out of the little packs so they ended up shipping me 1300s that'll I'll be using elsewhere. I found 370s@ 39 grams so i guess I'll try those. Do you have a schematic for yours? Whats the JST plug and switch for?
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Old Jan 14, 2013, 09:34 AM
Radd Graduate '06
Mochaboy's Avatar
United States, MA, Sudbury
Joined Aug 2006
1,820 Posts
The simplest solutions are sometimes the best ones - not always, but in this case yes. Is this setup for a plane or for a multirotor? What are you using for a control frequency? LRS? or 2.4?

As for noise suppression - first off - you're taking power directly from the battery, not from the ESC line, so you'll see voltage sag, but not necessarily noise. If you do see noise - it will be noise picked up from an untwisted servo wire or other stray RF signals (like 436mhz from a GoPro or a keychain camera). And if by chance that gets picked up the line - the inductor (the toroid) in the line conditioning filter will reduce that dramatically, and the capacitor will smooth out the voltage delivery.

The JST-XH plug is a 3s male connector - the same type you'll find on a balance charger. That's how you plug this filter directly into your battery's balance connector. If you're running thunderpowers - you'll have to buy the male thunderpower balance taps.

This entire rail powers just 2 components - the CCD camera and the video transmitter. I have the micro switch on there to turn those off if for whatever reason I need to fly without video. Typically what happens is that, I don't like to turn on the video gear unless I know it has good airflow, so I'll wait till the last possible moment to turn video on. So I'll turn the rig on, run my preflights and set up then when I'm ready to fly, I'll turn on the video gear. The LED just let's me know everything has power
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Old Jan 14, 2013, 10:02 AM
Radd Graduate '06
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United States, MA, Sudbury
Joined Aug 2006
1,820 Posts
This is pretty crude drawing I just whipped up. From a schematic point of view - the connection are all serial straight through. From a layout perspective, the inductor is on the bottom and the capacitor on top - just to cut down on space.
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Old Jan 14, 2013, 11:11 PM
FPV Recon
Altimat's Avatar
United States, TX, Cedar Park
Joined Nov 2005
195 Posts
Wow. I saw "started out with battery" and then jumped to filter and assumed you were back to a noisy regulator with your own filter added. I missed that this is for the battery, and didn't even know there was still any need whatsoever for filtering with a dedicated battery.

I'll be flying LRS on a Spyder quad. My current plan was to isolate all video components right up front: GoPro2, VTX, battery, and FPV Cam. Will you be building any more of these?
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Old Jan 15, 2013, 12:33 AM
Radd Graduate '06
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United States, MA, Sudbury
Joined Aug 2006
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Honestly - this takes 5 minutes to slap together you don't need to go to the crazy lengths I went to...You'll spend more time getting to radioshack than you will assembling this. I just like to tinker.

The 3 main components are the toroid, the capacitor, and some servo wire. That's all that is. I used a 12mm toroid, but if you have a "noisy" system you can go bigger and fit more wire wraps in. Remember it's a dampener not an eliminator. The only way to eliminate the noise completely is to go with a separate battery. So horses for courses.

I just hate hate hate hate hate plugging and unplugging batteries - I don't know what it is but I seriously can't stand it...so I wired switches into all my harnesses. I wired in an LED because with the million things you have to remember to do between preflight checks and monitoring your ground station - it's so easy to forget that you left a camera plugged in.

It took completely draining a 3s flight battery once to teach me how important it is to idiot proof my setup. That LED is so bright in fact it hurts to look at straight on

Oh and by the way - you don't need the lc filter if you go with a dedicated flight battery. I might not have been clear on this but I use *1 battery to power my quad AND my video system, hence the need for the line conditioning filter.
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Old Jan 15, 2013, 09:00 AM
FPV Recon
Altimat's Avatar
United States, TX, Cedar Park
Joined Nov 2005
195 Posts
Got it. I'm on 4S with the dedicated battery, but I'll definitely scrounge this stuff up and try one someday! Great lesson for me too thanks. Funny I could not find a small 3S ANYWHERE so ordered from HK Int., which no says NO LIPO for EMS on shipping options. Its been a while since I ordered any from HK, and I thought I read only big LiPos were an issue, but it let the order go through despite the warning. Wonder what happens now?? Hopefully it ships EMS - it is just one very small LiPo...
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