According to manufacturers, you should never remove the battery when the computer is plugged in. Removing the battery does not extend battery life because all batteries have "shelf" life and are no good after a certain time. Today's batteries actually will last longer if you keep it in the laptop.
The battery goes dead. should not hurt the plane, unless the batteries leak. battery may not charge if plugged into an automatic charger.
A fully charged 12 volt automotive battery should have 12.68 volts.
Keep plugged into charger whenever not in use, until fully charged.
As long as you keep them charged you do not have to remove them. A fully charged battery will not freeze, but a dead battery will.
12 volt batteries if fully charged should show 14.2 volts
Fully charged battery should have 12.6 volts. 75% charged 12.4 volts, 50% charged 12.2 volts, & 25% charged 12.0 volts.
If you're using processor intensive applications such as pro audio and video workstations software, you should definitely have your computer plugged in. That also applies to when you're updating your computer's software. Ideally, you'll want neither to leave your computer plugged in all the time nor run it on batteries until it dies. To optimise battery life, you should always disconnect your charger once your batteries are fully charged, and charge your batteries all the way when they get low without disconnecting the power during the charge cycle.
Rechargeable batteries normally have to be charged fully before first use.
Computers don't have batteries so I'm assuming you're talking about a laptop. Laptops with their battery SHOULD work when its plugged in. Some laptops can even work WITHOUT the battery but still plugged in. However, if your battery has a critical flaw (dead short) then even with it plugged in, it won't work. I suggest you try the laptop with the battery removed. If it works, that is the problem, otherwise, your laptop has other problems.
This is a loaded question. The new battery should be charged, but it should not require charging, it should be charged between 80 and 100% when sold with out any extra attention. Most motorcycle batteries operate in thwe 80% to 90% charged range depending on how they are used.
Yes the electric motor should run when plugged in even if the battery won't hold a charge.
If they are good batteries fully charged when installed and connected in parellel, yes it should handle them.