David Carter <dcar...@entertain-me.com> writes: > 1. Is it normal for a battery to fail after being fully and completely > discharged, or do I have a bad battery?
With the batteries we provide, most definitely yes. Usually, a lithium polymer cell is protected from overdischarge by the equipment it is installed in, but our batteries do not have this protection. That's both because we need to get all of the current they can provide to fire igniters, but also because it's powering a tracking system and flight computer, and about the last thing I think you would want that to do is shut down the flight computer while the rocket is still in flight or lost somewhere on the ground. So, we sacrifice the battery to keep the board running as long as possible. That does mean you need to be careful to turn things off when you're not using them, which is surprising in these days of smart electronics which work hard to prevent you from hurting the battery. Of course, even the best protection board won't prevent a battery from discharging while it's sitting in your range box. Lithium polymer batteries typically self-discharge about 5% per month. Leave them sitting long enough, and they'll be destroyed just as surely as leaving them plugged into something left on. > 2. Is the swelling of the battery normal? If not, what would cause this? An overdischarged battery can have all kinds of 'bad things' happen; this is one of them. > 3. What are some good ‘Best Practices’ for the care and handling of the > battery? Unplug when not in use, and keep them fully charged. It is best to leave them not quite full, but that's hard to manage, and the cost in lifetime for leaving them fully charged doesn't seem worth the hassle to me. And, of course, check the battery voltage before you launch. Take a look at typical lithium polymer discharge curves on the net to get a sense of how the voltage relates to remaining capacity. Short answer -- it doesn't drop very fast until the battery is nearly dead. -- -keith
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