Utility transformers can then "step-up" or increase this backfeed to thousands of volts—enough to kill a utility lineman making outage repairs a long way from your house. You could also cause expensive damage to utility equipment and your generator.

The only safe way to connect a portable electric generator to your existing wiring is to have a licensed electrical contractor install a transfer switch. The transfer switch transfers power from the utility power lines to the power coming from your generator.

Never plug a portable electric generator into a regular household outlet.
Plugging a generator into a regular household outlet can energize "dead" power lines and injure neighbors or utility workers. Connect individual appliances that have their outdoor-rated power cords directly to the receptacle outlet of the generator, or connect these cord-connected appliances to the generator with the appropriate outdoor-rated power cord having a sufficient wire gauge to handle the electrical load.

Don't overload the generator.
Do not operate more appliances and equipment than the output rating of the generator. Overloading your generator can seriously damage your valuable appliances and electronics. Prioritize your needs. A portable electric generator should be used only when necessary, and only to power essential equipment.

Never use a generator indoors or in an attached garage.
Just like your automobile, a portable generator uses an internal combustion engine that emits deadly carbon monoxide. Be sure to place the generator where exhaust fumes will not enter the house. Only operate it outdoors in a well-ventilated, dry area, away from air intakes to the home, and protected from direct exposure to rain and snow, preferably under a canopy, open shed or carport.

Use the proper power cords.
Plug individual appliances into the generator using heavy-duty, outdoor-rated cords with a wire gauge adequate for the appliance load. Overloaded cords can cause fires or equipment damage. Don't use extension cords with exposed wires or worn shielding. Make sure the cords from the generator don't present a tripping hazard. Don't run cords under rugs where heat might build up or cord damage may go unnoticed.

Read and adhere to the manufacturer's instructions for safe operation.
Don't cut corners when it comes to safety. Carefully read and observe all instructions in your portable electric generator's owner manual. 

To prevent electrical shock, make sure your generator is properly grounded.
Consult your manufacturer's manual for correct grounding procedures. 

Do not store fuel indoors or try to refuel a generator while it's running.
Gasoline (and other flammable liquids) should be stored outside of living areas in properly labeled, non-glass safety containers. They should not be stored in a garage if a fuel-burning appliance is in the garage. The vapor from gasoline can travel invisibly along the ground and be ignited by pilot lights or electric arcs caused by turning on the lights. Avoid spilling fuel on hot components. Put out all flames or cigarettes when handling gasoline. Always have a fully charged, approved fire extinguisher located near the generator. Never attempt to refuel a portable generator while it's running.

Turn off all equipment powered by the generator before shutting down your generator. 

Avoid getting burned.
Many generator parts are hot enough to burn you during operation.

Keep children away from portable electric generators at all times.

You should not plan to use a regular automotive starting battery, especially for high power transmitters. Starter batteries are designed to put out a huge current flow for the few seconds it takes to start your vehicle’s engine. Their overall capacity is quite low and they do not withstand repeated deep charge/discharge cycles. 

To use your simple backup system, you’ll need a battery charger that is designed to charge marine/RV batteries. Most automotive battery chargers available today are switch selectable between charging starter batteries and deep cycle batteries. Some hams successfully leave their battery on the automatic charger all the time. If you do this, be sure that the battery charger is an automatic model that will stop charging the battery when fully charged. In many instances, you can also leave your radios connected directly to the battery simultaneously with the charger. This will provide you with an inexpensive, reliable and ample power source during power outages. 

If you must keep your battery inside, buy a gel cell-type battery. This type of battery uses a gelled electrolyte, and is sealed so that it will not vent hydrogen gas nor spill acid inside your house. If you can, put your conventional lead acid deep cycle battery in the garage or in a secure, covered and dry area outside your house (keep it above freezing, or warmer if possible).  If you need to run power cables for very far, be sure to use #4, #6 or #8 gauge wire. Connections between multiple batteries should be made with #0 gauge wire or thicker. 

If you power a typical 25 amp drawing HF transmitter along a 20 foot run of #8 gauge wire, you will be amazed to measure up to 1.5 volt voltage drops. Low voltage to your transmitter results in other hams telling you that your frequency is unstable and and your transmitter sounds chirpy! 

Tutorial from BatteryUniversity.com 

Sharing battery knowledge (BU1)

It is my pleasure bringing to you Battery University, the institution for Learning the basics about batteries. In each of the short commentaries you will read about the best battery choices, new battery technologies and ways to make your batteries last longer. Practical, down-to-earth battery information is sometimes hard to find. Battery manufacturers are often too optimistic with their promises and only emphasize positive features.  Read tutorial here..

Wind turbines used to generate electricity come in a wide variety of sizes. Large wind turbines, which are usually installed in clusters called windfarms, can generate large amounts of electricity. Large wind turbines may even produce hundreds of megawatts (MW) of electricity - enough to power hundreds of homes. Small wind turbines, which are generally defined as producing no more than 100 kW of electricity, are designed to be installed at homes, farms and small businesses either as a source of backup electricity, or to offset use of utility power and reduce electricity bills. Very small wind turbines (20-500 watt units) are used to charge batteries for sailboats and other recreational uses. Read..