Re: Using cordless tool batteries to power a drone

wrote in news:prvact$87v$ snipped-for-privacy@gioia.aioe.org:

6

The 18650s are all made by maybee three major battery makers and Panasonic is the best and was the originally contracted maker. The units being dubbed any higher than 1200 mA/h are bogus.

If it were true, all cars would be electric by now. And powered by little 4X original spec 18650s.

. 9000 mah is one. They check out at around 1000 mah. Good ones are actually 3000 mah or so, get the unprotected ones so you can draw current without it cutting out. I have a 20 volt pack I put together for a Black and Decker leaf blower. It will now blow off my whole lawn from one charge. I use a balance charger to keep it happy.

(...)

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Yeah: (search for battery tests) etc...

However, you're wasting your time trying to fly with 18650 cells. There's a reason that most drones use LiPo cells. It's called specific energy and energy density: LiPo is about 1.8MJ/kg while Lithium Ion is about 0.5MJ/kg. In other words, you need about 3 times the weight in batteries to power your drone with 18650 cells as you would with LiPo. Actually, more if you include the weight of the steel outer casing on the 18650.

More later, after I'm done with todays plumbing project.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

You gotta watch out for "fake" webasites like

I think you under-estimate innertia.

--
  When I tried casting out nines I made a hash of it.

Why do plumbing projects alway come up in November?

Cheers

Yep. Here's the discharge curves for two of eBay's cheapest junk

18650 cells, rated at 5800 and 5000 ma-hr, which is science fiction. Note that I tested at 1.5A so that I don't have to wait forever for the test to complete: I would give them 1000 ma-hr and 900 ma-hr respectively. I've seen worse. I use a West Mountain Radio CBA-II for generating the curves:

I routinely test cells that I pull out of laptop batteries that measure around 2000 ma-hr. Unfortunately, I can't seem to find where I buried that data or graphs.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

Actually, the timing was fairly good for me. The story on this one is rather interesting.

I help maintain computers, phones, internet, and plumbing in a small office building owned by a customer/friend[1]. There are four bathrooms, each with a very expensive metered faucet on the sink: Three years after installation, all four metered faucets failed to automatically turn off the water. When I tore one apart, I discovered that there was a Schrader bicycle tire valve screwed into the center of the "metering valve cartridge" (item #7) that had failed because the valve spring had rusted away. Since bicycle valves are normally not used in this manner and normally not immersed in water, I was worried that the proper spring might be made from stainless steel or something equally rust resistant. A call to tech support informed me that the valve was not user replaceable and that the assembly would cost me only $36 on Amazon. No thanks. I went to my car, dug though my box of bicycle parts, found a new tire valve, and had it working in a few minutes. I'll fix the other faucets tomorrow and determine the spring material over the next week or so.

[1] Customers pay me. Friends do not. Otherwise, they're the same.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

John Doe wrote in news:ps2p37$dp2$1@dont- email.me:

Fuck You, mindless child.

Go play with your drill motor.

John Doe wrote

Yes, just measured a 40C one at 190 g inclusive huge terminal blocks, see picture below.

Those lipos are cool, 40C, you can start a car with one. I used one to replace the sealed lead acid in my tire pump compressor. Smaller, lighter, no leaking, I have several lipo chargers, those charge at low current, Small ones I charge on the lab supply.

And all that lipo stuff is ebay, just read the reviews and recommendation in the RC groups to find the right model / seller.

These are from ebay and work for me:

wrote in news:ps3nc8$1d1q$1 @gioia.aioe.org:

The new stuff is called LiFePo.

John Doe wroye

How is your flight time compared to the lipos? What drone do you use?

...

Right, I had some larger balls planned for landing on water. If too big those steal air flow from the propelloers (in my case).

Just looked it up, bit cheaper than my Hubsan, size is about the same I think.

I see. The hubsan uses 2 cell lipos 2700 mAh 7.4V 10C

I used batteries with welded connection strips, they do that on order here.

An other experiment I did was power the drone via a coax cable:

Couple of hundred volts at 100 kHz over a thin coax, stepdown transformer and rectifier at the drone side:

The diodes are in the air stream, and the transformer too on the other side for balance, battery is in the drone too as backup against power failure.

Unlimited flight time, was intended to put an antenna up there,

John Doe wrote

Yes, quite similar what I had, lipos are better.

To what voltage level did you charge?

Yes, I use 4.2 V too, use the lab supply with current limit.

My drone takes a little over 10 A full throttle at 7.4 V (2 cells). Switches for that much current are heavy.

Switches for that much current are heavy. And you want to be able to quickly change batteries, I have several lipos so I can fly longer, so you need the connectors anyways, and there is for the lipos the charge balancing connector. for charging, use a special charger for that. The liion I charge one at the time.

A couple of FETs shouldn't be too heavy. OTOH, good ones (milliohm RDS(on)), to minimize the heatsink, may be a little heavy on the pocketbook.

On a sunny day (Fri, 14 Dec 2018 22:20:06 -0000 (UTC)) it happened John Doe wrote in :

Important is the voltage under load where the system cuts off. This is very different from the no load voltage you measure after flight. In my case with the H501S I can read battery voltage from the remote, it is displayed there, else you need ground testing with a voltmeter:

that is with amp meter, but adding - or only using a voltmeter should be easy. Did you try flying with 2 lipos in parallel? Oh, and do not connect a full and an empty lipo together in parallel, things may go up in flames as a huge current can flow, charge both to full first.

I have never done any mods to the battery sensors, not even sure such a mod exists for the Hubsan.

No I meant lipos, could give you 25 minutes flying time.

About metering: BTW I use a MASTECH MS2108 Digital True RMS Clamp Multimeter AC DC Voltage Frequency Tester was about 31 $ IIRC ebay auction, now these cost 65 $ it seems. So far it works OK. Not all clamp on meters are DC capable, the AC ones are just transformers, so beware. But a normal 10 A meter should perhaps work too, you will lose some voltage,