smallest USB battery, or LiPo alternative?

[1rafayal]

Hi all,

am new to the forum and newish to electronics, so please let me know if I am making a fool of myself here

Right now I am building a proof of concept device for a remote control plane design I am working on. It is intended to be an instrumentation package to record altitude, pressure etc and runs off a small IoT board.

It needs to fit in to a small enclosure, which I have and run off a USB power supply. However I have been unable to find anything small enough to fit in the enclosure I have.

The dimensions of the case are

width = 10.8 cm
length = 7 cm
depth = 1.7 cm

If no such USB battery exists, which I doubt does, would it be possible to use a LiPo battery for this? Would there be any small enough that outputs 5 volts?

Thanks in advance

[paulca]

You have a number of options.

Split and regulate your main supply.  Also known in RC world as a uBEC - Micro battery elimination circuit.
Install another small LiPo and regulate it to 5V with a BEC.

There are pros and cons of each.  The split and regulate will experience noise from the high power motor control switching which may or may not interfere with your device.  Capacitors on the power leads of the regulator (though it should have some internally) and ferrite rings on any signal leads you have can help.

I used to run a plane with a 300W 12V main supply, a 12V video transmitter and a 7V RC receiver and servo rig.

I found using the BEC alone I got quite a lot of interference lines on the transmitted video and the RC reception was prone to drop outs and glitches.

I decied to run it off 2 LiPos instead.

A 5000mAh 3S for the main power.
A 1600mAh 3S for the 12V video transmitter and via the uBEC to the 7V Rx.

Some ideas:
uBEC: https://hobbyking.com/en_us/kingkong-5v-3a-ubec.html
(Note some are switchable between a few selections 4.5 - 9V - you might find a smaller one too if you search for "Small uBEC" make sure it's rated for what you need or it will get hot and cut out).

Small LiPo (there are dozens of examples, these will run a uBEC to provide 5V)  You will need to work out your flight time and current requirements to work out if it will last long enough):
https://hobbyking.com/en_us/turnigy-nano-tech-300mah-2s-45-90c-lipo-pack.html

You might find the FPV community over at an RC forum very helpful regards the telemetry.  There are off the shelf units already available for logging, video overlay or even transmission.

[Nusa]

Nearly all USB batteries are based on the 18650 Lithium Ion cell. That cell by itself measures 18mm x 65mm, which is too fat for your case. Which explains your difficulty in finding them.

[Ian.M]

Also an 'IoT board' in a model plane may get you in trouble with OFCOM.  A WiFi or GSM transceiver that flies is very different from a licensing point of view from a fixed or mobile terrestrial transceiver using the same hardware.   

You will probably be better off using a non-'IoT' board or MCU that can directly accept the typical LiPO voltage range of 4.2V fully charged to 3.0V fully discharged, and is designed for minimum power applications where no mains supply is available.  You'll need a telemetry solution that doesn't fall foul of OFCOM - if there is already a video link, consider telemetry over Audio - many MCUs have suitable peripheral modules built in to implement 1200 baud FSK modulation.

[1rafayal]

thanks for the replies guys.

I should probably give a little more explanation about the project, as this isnt really a traditional RC plane build.

The idea here is to have a weather balloon loft the plane up to a certain altitude, at which point the plane will be released and it will glide back down to earth, taking measurements as it goes. So, the package I am trying to design right now will be responsible for that, however I want it to be separate from the main battery that will be powering the control surfaces of the plane.

So perhaps its not really an RC plane, but more of a glider drone that is trying to return the instrument package to a certain location?

[Ian.M]

To stay within the UK drone laws, you'll need full remote control capability, so you can override the autopilot at any time, and unless you obtain special permission from the CAA, you will be limited to max 400 feet altitude and 500m horizontal distance, to comply with the 'line of sight' operation rules.

It is *POSSIBLE* to get CAA approval for a semi-autonomous UAV glider - see http://bura.brunel.ac.uk/handle/2438/10610 for the report of one such project.  I suspect that it would be rather difficult for a private individual to first get approval and then to meet the CAA operational and technical requirements.

Also you need CAA permission for weather balloon launches, which require the use of a standard meteorological balloon and for the payload to descend by parachute.   

Assuming you manage to clear everything with the CAA, do you plan on transmitting live telemetry, or just data-logging, requiring recovery of the payload?

[Habropoda]

The number of batteries that will fit in that enclosure is nearly infinite.  The same goes for 5V converters.  Some specifications on the power requirements of your device are needed to narrow down the choices.

As noted, RC hobby sites are a good resource.  An examples of other choices is Adafruit's easy-to-use selection of lipo batteries and matching Powerboost converter/chargers:
https://www.adafruit.com/category/138

Your project sounds interesting.  It would solve the recovery problem inherent in balloon exploration.

[paulca]

[jonovid]

had this idea of putting a mic and its electronics in to a ballpoint pen. but the battery cost more then I was prepared to pay for.
inside pen case diameter is just 5 mm . Inductive charging is how  u do it.  - the idea is a ballpoint pen spy mic .
everything fit into the pen case except a battery.  two ultra small batteries  are too expensive for a one off hobby project.

[1rafayal]

Hi Ian.M,

thanks for that, I had no idea the CAA would be picky about this sort of thing.

I can put in a manual override that would allow me to take control of the vehicle at any point in time, that shouldnt be a big problem for me. But from what you are saying the biggest issue would just be getting the permission to launch the thing in the first place

I wasnt planning to broadcast anything live, I wanted to simply record data, video and images for future projects that I have in mind. One thing I would like to try out is launching a rocket or space plane from a balloon platform, I was hoping the data I record from this experiment could help me with the design for that build.

[1rafayal]

Thanks for the link Habropoda! I can see a couple of components on there that might work out for what I am trying to do at the moment. So once I get paid I will order some and start experimenting!

If nothing else, I will simply scale the build up a little, physically and give myself a little more room to work with.

[1rafayal]

paulca, this is almost exactly what I am trying to do!

I just wanted the glider to be smart enough to try and get back to a certain location all by itself if possible.

[Ian.M]

I just wanted the glider to be smart enough to try and get back to a certain location all by itself if possible.

It *may* be possible to get CAA authorisation if the payload parachute is actually a RC paraglider 'chute.  http://www.hooked-on-rc-airplanes.com/rc-paraglider.html may give you some ideas.

However I suspect that given typical British weather patterns, return to origin will be a forlorn hope as your best glide speed will almost certainly be less than high altitude wind speeds, so the most you can hope for is for the autopilot to steer towards one of a number of predetermined 'down range' ditch sites.

https://ukhas.org.uk/ is probably your best resource for legal high altitude ballooning in the UK.
 

[paulca]

RC paraglider will not be an option.  Dropping a paraglider from a non-inflated state to getting it flying normally is a highly skilled endeavour.  Without rapid and correct input it's likely to cravat, twist and spin to it's doom.

Check this out:
(This is the guy who taught me to fly)  Actions starts around 2:45.



For the OP I think the only way you could get permission is if you were part of a club, organisation such as a university which will give it some credibility.  The CAA will require detailed plans which show you have thought everything out.

Don't be expecting to "Return to launch".  Due to high altitude winds being very high speed at times and the long time it takes a balloon to ascend you could be looking at travelling 50-100 miles before release point.  Jet stream winds over the UK get to well over 100mph routinely.  Don't be tempted to think you can glide from 80,000ft either.  The glider will most likely fall, tumble and spin for the first 50,000ft of that.  You might be able to glide 50 miles from 30,000ft, but you will be gliding into a headwind which might well be faster than the gliders speed (so going backwards).

[1rafayal]

I have had to give up on the overall project

Thanks to everyone who chipped in on this with their advice, however I need to come up with a new idea.

Basically, the CAA wont agree to such a complex device being launched. I tried to team up with a school to see if the academic approach would work, but the CAA would have none of it.

So, I need to come up with a new project. I live near Edinburgh, apparently one of the reservoirs up in the Pentlads is man made and may have the remains of a village that was there prior to being filled.

Perhaps I can make a submarine?

[soubitos]

and THIS is how people are not allowed to advance....
If you worked for a multinational corporation, you'd have no problems
Or the military
Or the enemy!