Can you plug in a small powerful electric generator device to a battery to make electric energy for forward backward usage?

Answer 1

The device described here goes under a few different names, and one is a motor-generator set. The motor-generator set (MG set) already exists, and one example might be the ones in submarines. Let's look at the setup.

The electrical bus in the modern submarine is AC, and the storage batteries are DC. This MG set has a DC end connected to the batteries, and an AC end connected to the electrical bus. By sticking that MG set between the batteries and the AC bus, the AC power, delivered normally by steam turbine generators, charges the batteries and keeps the lights and everything else powered up. If the turbine generator goes down, the MG set, which has been acting as an AC motor and a DC generator, will switch functions. In its new configuration, the MG set's DC end becomes a motor (taking battery power), and the AC end becomes a generator, which then powers up the ship's AC electrical bus.

There may be some small MG sets out there, and a bit of searching may reveal a source or sources. Certainly as this equipment already exists, it is just a matter of finding it in the right size. Note, however, that banks of storage batteries can be set up, an AC charging system can keep them up, and a big inverter can convert the stored DC to a usable AC voltage for delivering power to any AC device (with load limits, of course). The advantage here would be that you can buy all the batteries you need, a small emergency generator, a battery charger, and a handful of inverters right now. All of those things are common, readily available, and fairly inexpensive compared to what you'd have to shell out for a little MG set.