I am writing this morning about a different topic than my build because I am mad at the post office. My RVJET should have arrived two days ago and I am still without a plane. It is in the teens outside today so I thought it would be a perfect assembly day. Instead, I am going to talk about a safety system I have been thinking about for our drones.
Have you ever had a lipo suddenly dump its charge in the air? Maybe, you have had a particularly good day cloud surfing and lost track of time or distance? I would like to come up with an emergency battery switching system for such occasions. This post will be more of a brainstorm and ideas of what capabilities would be needed. I can get into hardware/firmware specifics as it is developed.
I think the first thing people are going to ask about is weight. People are pushing X-8's to 3.5kg, I think the RVJET can push it close to 3-3.5 with batteries and cameras for long flights. The Skyhunter claims 20-25,000 mah worth of battery capacity. So I would think that you would want at least 20% of main pack capacity in your reserve pack. The test plane that I will use for this is an old 8ft Telemaster. These are docile craft with very predictable flight characteristics. I have modified this with motors in wing pods that will have 10000 mah capacity each (two 6s 5000) I would have to add a 2000 mah battery to each wing to give me the reserve battery power. In a plane that can easily go all up at 7kg we have some room to add some batteries and hardware for a switcher. I think the last time I had it all up with mapping cameras it was around 5kg. With two 2450mah packs at 400g each I should be able to keep the necessary items well below the two kilogram cushion I have.
We have an air frame and an idea. I have not thought of all the parameters or what all needs to be measured to indicate a possible failure. The first and easiest is when you have discharged to 20% of main power that batteries could switch to auxiliary power. Severe voltage fluctuations, amperage flow drops, internal resistance spikes, overheating are few of the possible indicators of a faulty cell or power system. This will be an open project and I welcome any and all collaborators. If you have other ideas of what is needed in the firmware or the hardware, please comment. I think this would be a system independent of autopilots and osd's for cross platform integration. I think that you would be able to see when it switches to auxiliary power by a spike or drop in the battery level indicator on osd's. Another use would be a battery cutoff. If you are running multiple parallel packs. If a single pack is faulty it can cut it off from the system so it doesn't draw down the good pack. These are all initial thoughts. Thank you for reading and I hope that you have happy and safe flying.