If you have been reading my posts on the Comment Wall you are aware that I am building a fairly large R/C racing boat for autonomous offshore competition.
The R/C boat I have selected is the Zippkit VBox 2013 edition that is 46" long and 17" in beam. The boat is normally powered by a 26cc gas engine of around 5 - 7 hp, however I plan to use a brushless electric motor in place of the gas engine.
Since I do not need speeds of 50 - 60 mph for the kind of competition that I envision, I feel that a brushless electric motor of around 3 hp will be sufficient to drive the boat at around 25 - 30 mph. Therefore I have identified a Leopard 5692 1000kva 3000 watt 56 mm dia brushless motor as being a suitable candidate for my purposes.
I have decided on using twin 6S 10,000mahr LiPo batteries in parallel to power the motor. So now I am researching high current, water cooled ESCs with 180 - 220 amp capacity to control the motor.
After the propulsion and steering hardware have been installed in the hull, I plan to integrate a Pixhawk navigation controller and associated components into the hull to provide autonomous navigation.
I will begin the Project Discussion with the installation of the propulsion and steering hardware and then move on to the integration of the navigation controller platform.
Thanks for the kudos, much appreciated.
The navigation controller board will be powered by its own 3S 2200 mahr battery.
Since the Hifei ESC is presently powered by two 6S 5000mahr they will be supplying approximately 60 amps each at full throttle. My main concern will be the run time before the ESC goes into hard cutoff at 3.0 vdc/cell. The ESC will actually cutoff at more than 3.3vdc to protect the batteries. Hard cutoffs are set at 3.0vdc while soft cutoffs are set at 3.3vdc.
The ESC has a data logging feature that I plan to use to see what the current consumption and battery voltage looks like over a typical course at different speeds. This will allow me to determine how long I can run before having to recharge the batteries before making another run. I could also put in LiPo battery monitor that would be visible on the deck to allow me to quickly see how much battery life is left prior to each circuit of the course.
What would be most helpful would be to provide a way to use either the Pixhawk ADC 3.3vdc or 6.6vdc converters to monitor a battery scaled voltage monitoring circuit whose output could be sent back in the MavLink telemetry.
Tom C AVD
Hi Tom. You can do exactly what your after re the ADC 3.3 or ADC 6.6 for voltage monitoring. If you have a look at the BATT_2_ parameters on
they are slightly incorrect (I'll fix them up soon). You can use ANY analogue pin to measure input voltage. So for instance if you hooked your voltage up the 6.6v ADC which is pin 15 on the pixhawk then you would set BATT_2_VOLT_PIN = 15 and this data would automatically get sent back to the ground station and displayed (assuming the ground station supports the second battery data). You would need to set some of the other BATT_2 parameters as well.
Now you will need a voltage divider to ensure the correct voltage range is supplied to the ADC. So 6.6v would be a full battery and then dropping down from there. I'm not the expert in this area however this page is very helpful
Thanks for the great information, much appreciated.
I will give it a look and setup what is necessary to measure my battery voltage.
Tom C AVD
I have added an external USB port to the front of the navigation controller water resistant cover so that I do not have to take the cover off to communicate with the Pixhawk.
I have finished painting the navigation controller deck cover plate and will be attaching the navigation controller plate to the deck cover plate this coming week. I will then attach the rudder servo and ESC cables to the Pixhawk and route them through a deck plate penetration so that they will be accessible below the deck plate. I will also wire up a XT60 connector that will mate with the input connector on the Power Module. I will run the power wires from the XT60 connector through a deck plate penetration so I can attach a 3S 2200mahr LiPo on the underside of the deck plate to power the Pixhawk and associated components.
Tom C AVD
I am doing the same thing but for business I would love to hear how this is working out for you!
I am about ready to ballast/trim the hull and then try some testing in the Manual Mode to make sure that it performs correctly before proceeding further.
Tom C AVD
Since RMRC is no longer stocking 6S 10,000mahr LiPos at a reasonable price ($159 plus shippint), I was kind of up a creek so to speak until I made the acquaintance of a member who had two RMRC 6S 10,000mahr LiPos that he no longer needed.
I took the batteries out in trade for some consulting and aircraft assembly work and I am now in the process of build battery mounts out of 1/4" thick HDPC to mount the batteries above the floor of the hull.
I will put small HDPC blocks in the corners of the bottom of the mounts to raise the mounts off the hull floor and provide clearance for Velcro tie down straps.
Once I have the boat trimmed out with the batteries, I will epoxy the mounts to the floor of the hull and I will be ready to test out the hull with the navigation controller.
Tom C AVD
Tom, Have you had her out on the water yet? Early in the day before the storms set in.
David R. Boulanger
Lovely project. I'm dying to seeing how it works.
Do you have any idea, what should be the average range of this wit?
Probably get it out on the water some time next week.
I just got the Velcro straps for hold the batteries down to the battery mounting plates today.
We have had lake shoreline restoration going on for the last two weeks so next week the lake will finally be available for testing.
Tom C AVD
With the two 6S 10,000mahr batteries, I can probably get from 20- 30 minutes of run time at 20 - 30 mph.
Only actual testing will accurately answer that question:-)
Tom C AVD
Is there an update? I'm dying to see how this thing ran? Impressed with the craftsmanship on the build!