Sunday 31 March 2013

Best Battery!!!

I love maths ... some calculations have just more than halved the battery cost for the same performance, enjoy the post :)

I ask myself, which battery has best capacity to weight ratio?  Out comes the spreadsheet!


I went through all the 3 Cell batteries on the Hobbyking website, found the lightest for each mAmp and divided by the weight to give mAmps per gram.

The Comparison 

There a big difference between the best and worst batteries!  The best battery when compared to worst battery is 34% better, like for like that gives an extra two minutes of hovering flight.

FYI, interesting the best overall battery is in the model speed boat section.

Ultimately I'm looking at time in the air.  So what about the 6100mAh battery? It's has a worse mAh/g however it holds a third more power.

According to the eCalc website site, it estimates the best 4500 mAh battery 17.4 mins in the air where the 6100mAh battery gives 19.4 mins in the air!!!

Do we have a winner?  I thought so except a school boy error ... I forgot the cost!!!

The Cost of Power

6100mAh battery is $100 USD and the 4500mAh battery is $58 USD.  Both are a lot for a battery!

Perhaps one day I'll buy these batteries however I want to constrain the costs.  The 5500 mAh battery $96 however the 5000 mAh battery is $27 USD.  Much more like it!

My Winner

I think we have a winner!!!  It gives me more air time at 17.6 mins and half the cost of the "best" specification battery.



More interestingly this battery is light enough to parallel which that gives 24 mins of hover time with thrust left over for maneuverability.

Friday 29 March 2013

Battery Investigation

What an amazing website this one is: eCalc

It is fantastic, all the aeronautic calculations for you!!!  It's been a big help and homed my design ... I'll write a bit more about it on another post :)

Batteries!  What to choose from?  I know I need a 3 cell battery for the right voltage yet with hundreds of 3S battery it's difficult to decide.

Lots of people on their quadcopters are using 2100 or 2500mAh.  Yes why not use that! :)

Oh dear, on the calculation website only 10 mins of hover time and about 6 mins of high powered flight :(

I need time in the air, therefore a big battery.  What's the largest 3 Cell battery on Hobbyking?  How's about a nice big 8400 mAh?


It's a beast of a battery at 640 grams yet that gives me about 21 mins of both fancy high powered flight and hovering.

One thing that was bothering me was the heavier the battery the more power needed to make the drone hover.  The more power need to keep it in the air the less we have for accelerating forward and maneuverability

Ummm, we could have a drone with a long hovering time yet not able to keep up with me.  Ummmm.

I was thinking, is this the best battery?  

The above battery is the lightest 8400mAh for that capacity and is the best (on Hobbyking) battery in terms of mAh per gram.  Are there batteries with less capacity with a better mAh per gram?  

Then I starting thinking, if I optimise the mAh per gram then this reduces the weight and we have more flying time :)  Yea!!!

Then I remembered my basic physics, I find the best mAh per gram battery and then put them in parallel !!  could then have the correct voltage and lots of power!!!  Why not 10000mAh?  Yes, this could be excellent!!!  

Time to create a spreadsheet to find out :)

Tuesday 26 March 2013

I've Been Framed

I've been doing some basic calculations on power, weight, etc. and I released that it is time pin my flag to the mask to choose an airframe :)

Weight is critical on a hovering aircraft so let's go for a light one ... to be exact, the lightest and strongest my pocket will afford!

I've seen some airframes ... some amazing carbon fiber ones at a lovely high price, some very good looking ones however out of fiber glass or worse.  With the amount of crashing that's bound to happen, I think I'll need something stronger than fiber glass and ply wood.


So what have I chosen?  A while back I was really taken with Warthox videos ... this is amazing Quadcopter video.

It's just fantastic!  There is the option of carbon fiber however, as I'm starting out, aluminium is best.

So I've placed my order! I'm going via Flyduino and those guys are great, I placed the order yesterday evening and shipping today!

I'm so looking forward to starting to see something more physical in addition to the electronics.

Time to chose the motors, batteries and ECS :)

Saturday 16 March 2013

Power to the People

I've been getting a bit side tracked with all the sensor issues.  Time to learn about batteries :)

Lithium Polymer, LiPo, is where it's at ... better than Nickel Metal Hydride yet cheaper than Lithium Ion.

There's a huge range of batteries from Hobbyist websites, so let's investigate what I need:

  • Light weight ... postman will love me however it's for the drone's benefit
  • Large energy capacity ... fly forever!
  • Small size
  • Cheap ... not cost me a fortune :)
I want everything!  I can't have everything :)

Something I've learned is the important of the battery "C Rating".  It stands for also how quickly you can safely drain the battery without damaging it.  Great little guide here!

What does that mean for me?

Four motors for me and lets say 20 Amps motors each = 80 Amps Continuous Discharge.  So I need a battery that will have a large capacity multiplied by"C Rating" = 80A continuous discharge.

Let's say the batteries I'm looking at have 2000mAh capacity, I therefore need it to have 80A / 2000mAh =  40 C Rating.

Voltage and Power

How much voltage do I need?  This relates to the type of motor I'm going to use!

Interesting, first to decide which are the right motors and then you'll know how much voltage you'll need.  Once you know that then you'll know which are the right batteries for you :)

So which motors?  Haha, that depends on how much power I need and that depends on the weight of the drone!

To add extra dimension, the more dynamic responsiveness I want the drone then the more instant power it'll need.  how dynamic I want the drone to move?  Plus also the money factor :)

Time to make an estimate of the drone weight!

Monday 11 March 2013

Mainboard with chips?

Crazy weekend!  I was sweating at one point.

My lovely copy of Visual Studio Express hung during the deployment to the ArgonR1 mainboard.  Not to worry, reboot the computer and ArgonR1 and then deploy again.  Wrong.

The laptop wouldn't talk to the ArgonR1.  Was it fried?  Oh no!

I read on the forums it was best to re-flash the ArgonR1's firmware.  Great, downloaded the firmware and was ready to reset using Microsoft's MFDeploy.


Oh no, MFDeploy could not talk to the mainboard!  How then to recover?

All drivers deleted and re-installed, computer rebooted and still no joy!

Saturday blown, Sunday I was super worried.  Was the board dead?

I inspected the board just to see if there was something physically wrong with it ... that was the trick!!!

TOP TIP:  If your Gadgeteer Mainboard won't accept the deployment then do:

  1. Disconnect your Mainboard from it's power source
  2. Disconnect all modules ... except the computer power & communication module of course :)
  3. Power up the board and all will be good
Then board was the talking to MFDeploy, yea!  It was alive, I was very happy!  

With MFDeploy you can delete the current deployment, haha top idea!  Given there was some weird half deployment on the board that seemed a top idea :)

Then Visual Studio was as happy as me and was uploading programs to the ArgonR1 again :)

Excellent, I didn't have to re-flash the firmware or any other of those "risky" style operations, how fantastic.  

I love this little ArgonR1 board :)

Saturday 9 March 2013

I2C Scratching my head

Back in the swing of the development after a time away and now scratching my head!

To recap, where am I ... sensors!!!!  Sensors are everything so the lovely drone knows what is happening.

The problem is that I need loads of sensors and not enough ports on my Gadgeteer board to connect them all.  The cunning plan is to network them together with the I2C protocol.


I'm having a big problem though :(

I just cannot get the a single sensor to talk to the Gadgeteer board!  


Not sure what to do next.

I've double checked the soldering, all good.  I've ensured the wiring is correct, all good.  Resistors on the I2C and Clock lines are good.  The C# code module code is super simple and no joy.

I think I'll have to buy an I2C Gadgeteer component just to check the module code is correct.