- Oct 30, 2003
- West Valley City, Utah, USA
- Sport Copter Vortex 582
- Total Flight Time
- FW: 200 Gyro: 51
...says the guy planning to fly with a two-stroke! But seriously, Brian, old-school lead-acid batteries can fail catastrophically, too. From what I've seen of your level of care, you'll not likely have an issue with either type. I don't think the alternator on a 503 can exceed the max charge-rate rating of any battery designed to start the engine, although it could exceed the battery's max voltage on a long flight....anything above a 0% chance of failure would make me nervous to fly with.
I did have a catastrophic battery failure once - the lead-acid Sears Diehard battery in my '69 Torino. The charging regulator failed and overcharged the battery, which exploded under the hood, scattering plastic and acid all over the engine compartment. From inside the car, it sounded like a backfire, so I continued driving to work. When I came out to drive home, the car started normally, but the throttle linkage was sticking due to rapid corrosion. When I pulled into a gas station to check under the hood, all that was left of the battery was the plates, sitting in about an inch of acid in what was left of the bottom of the battery case. The car was pretty much ruined by acid damage. Obviously, a failure like this in flight could be unpleasant in a number of ways.
If the rectifier/regulator in a typical Rotax setup failed, or if it even lost its ground connection, the same thing could happen to any battery. If it's an issue of confidence, enclose the battery in an ammo case, vented out one side away from fuel system components, and monitor battery voltage in your panel, preferably independent of the aircraft's main power bus and frame ground.
I just retired from a job in which I managed a pool of lithium-ion batteries used in computerized prosthetics. In tens of thousands of repair and maintenance jobs, I never saw one fail that wasn't abused, electrically or physically. In another previous job, we subjected hundreds of smart phones to vacuum deposition of a polymer coating. Some of the lithium-ion batteries puffed up like a pillow and broke the cases of the phones, but none failed catastrophically.
I'm not sure what happened with the lithium batteries which failed during testing of the Boeing 787 a few years ago. I suspect their containers may have constrained their expansion as cabin pressure dropped, causing uneven pressure on their cases, or charge/discharge rates got out of hand.
Most of the videos on YouTube, with the exception of early laptop computers and some Samsung phones, have had their internal protective circuitry intentionally disabled to create a dramatic video. I'd consider any starting battery certified for aircraft use to be as reasonable a risk as any other, provided you don't exceed their ratings or try to charge them at temps below freezing.
The exception, of course, is Ebay/Amazon batteries of unknown origin.