Power supply for a tethered drone

[roineust]

There is a drone which I'm experimenting with and want to move from batteries to a 2-15 meters 14AWG tethered cable.

The drone voltage is 15-21 Volts and consumes up to 200 Amps.

What would be the best method of searching for and the best brand, model and condition new or used, to find a good but not expensive power supply for the drone?

 

[danadak]

https://www.digikey.com/en/products/filter/ac-dc-converters/133?s=N4IgjCBcpgrATLKoDGUBmBDANgZwKYA0IA9lANrgAMAzLACzwgC6xADgC5QgDKHATgEsAdgHMQAX2LwAbAHYayEGkhY8RUhRDwqVAAQBBFuy6QQAVWGCOAeXQBZfJlwBXfvklTtW3AFs2uCwSQA

One possibility. Or do an architecture on 10 20A supplies paralleled.


Regards, Dana.

 

[Pommie]

The fusing current for 14AWG copper wire is 166A according to this page. And a 30M (twin) cable will weigh over 1kg.

Mike.
Edit, sorry, doubled your 15M twice.

 

[rjenkinsgb]

30m (~100ft) of 14AWG would have a resistance of around 0.8 Ohms.

If you put 200 Amps through that length of cable, it would drop 160V and dissipate over 25,000 Watts!
(And rapidly become incandescent & disintegrate).

You would need to go to somewhere between 2 AWG and 00 AWG for the cable to stand 166A continuously, depending on the exact type.

At 2 AWG the cable resistance would be around 32 milliohms, so you would loose around 6.4V and approximately 1280 Watts just in the cables.

00 AWG would be around 8 milliohms, so 1.6V loss and 320 Watts cable dissipation.

2 AWG would weigh about 25lb.
00 AWG would weigh around 45lb

I just don't see any practical approach using tether cables at that voltage and current...



You would likely get rather better results using a high voltage feed to the drone, so the wires can be thinner and lighter, then use DC-DC converters onboard to power the ESCs.

I think that could be lighter and possibly cheaper than the high current low voltage supplies plus the massive cables?
eg. a 200V feed would only need 20A cable.

You are looking at somewhere in the region of 5000 Watts input power, regardless of the supply arrangement; what are you going to plug that in to??

Whatever you do, it's a massive amount of power if anything goes wrong, with serious risk of fire and injury.

 

[roineust]

What are the chances that the following ebay unbranded power supply, would be a bad choice?

Adjustable Variable DC Power Supply Output 0-30V 0-200A Power 6000W AC110V/220V | eBay

Output current: 0 -200 A. Digital display: LED digital tube. Display resolution: +-1% + 2 words. Accessory: Power cord.

www.ebay.com

 

[rjenkinsgb]

How much weight can the drone stand to lift, for the power cables etc?

 

[roineust]

Currently and for months ahead, i will use only 3 meters cable, which weighs around 350 grams, the drone has no problem of payload weight with this cable.

 

[rjenkinsgb]

Did you read the details of my previous answer??

2 AWG would weigh about 25lb
00 AWG would weigh around 45lb

A 3m section would weigh 1/5 of that, so 5lb with the smallest practical cable.

 

[Pommie]

What are: the weight of the drone; the capacity of the battery and the time it can stay in the air?
This will give an average consumption from which to work.
I calculated (roughly) that it takes ~200W to keep 1kg in the air.

Mike.

 

[roineust]

The drone including batteries weighs in the order of 5kg.

 

[Pommie]

OK, that's one (of three) questions answered.

Mike.

 

[roineust]

Thanks for the knowledgeable replies, i read each and every reply, if there were questions that i was asked to answer and did not please forgive me, i plunged head first into the market-place in an attempt to find a good deal for the power supply and therefore my attention was loose.

 

[roineust]

The batteries of the drone are 4 parallel 5200mAh 4S LiPo.

It can stay in the air around 6 minutes with this battery configuration.

 

[Pommie]

So is that 16.8V 20800 mAh or 5200mAh? Assuming the later then that is ~80Wh so in 6 minutes (1/10th of an hour) it's using an average of 800W. That's 160W per kilogram = reasonable. That might be doable. Replace the onboard battery with one ¼ the size (to handle power surges) and continually charge it via the tether at 50A. That will still require a hefty cable of around 10AWG which will weigh about 1.5kg and you'll still drop ~1.7V (~0.1Ω) along the cable. How much extra weight can the drone handle?

Note, the above calculations don't take the weight of the tether into account.

Mike.
Edit, a 6AWG aluminium cable will only weigh ~1kG and have a resistance of ~60mΩ.

 

[roineust]

My mistake, with 20800 mAh the drone can hover closer to 8-9 minutes rather than 6 minutes, this means the cable AWG can be even higher than 10?

 

[rjenkinsgb]

Pommie was calculating based on 5200mAH = 6 minutes..

20800mAH in 9 minutes = 139A average current.

That makes the absolute minimum wire size 3 AWG.

(And if it is just 8 minutes, then you need 2 AWG, for 156A).

 

[Pommie]

That puts it back in the "very difficult" basket. A 30M (2x15) 3AWG copper cable will weigh just over 7kg. A 2AWG aluminium cable will weigh just over 3kg.

 

[roineust]

For the next several months if not more than that, I'll be using only a 3 meters length cable.

 

[Pancho144]

Might CK the Military Grade Drone Used inventory.

 

[roineust]

What do you think of the Meanwell SE-1500-15?

SE-1500-15 MEAN WELL | Jameco Electronics
MEAN WELL SE-1500-15 Switching Power Supply, Enclosed. Products in stock and ready to ship. Quotes, samples and datasheets at Jameco Electronics.
www.jameco.com www.jameco.com

Mean Well RSP-1500-15
Mean Well RSP-1500-15 AC-DC Single Output Enclosed power supply; Output 15VDC Single Output at 100A; PFC; forced air cooling
www.meanwell-web.com www.meanwell-web.com

Someone told me that there might be a problem where if i lower the throttle of the drone motors, a lot of current will go back into the power supply and ruin it, does the meanwell SE-1500-15 have protection against such problems?

I see that the difference between the meanwell SE series and the more expensive RSP series is a function called PFC, what does this function do?

Are these model differences of quality and functions (SE vs RSP) important for my application or is the SE good enough for me?