Usually it has been seen that people who use laptops actually plug the laptop to the power supply. However this was ist kobalt is the wrong way of charging the battery. You should charge a battery once or twice a month. The battery should be charge fully at least 30 minutes before you start using it. In case you are going to use direct power supply, then it is best to remove the battery. This will ensure two things -- first, the battery since it is charged already will not discharge uselessly and second, it will ensure that the battery life is extended.
Power cords - Again, in my opinion, they are poor quality and might damage your electronics. Duct tape sand paper painter's tape lithium facts and bungee cords are good though.
This can be a problem for where the battery is not used that often but is can be important when it is needed for emergencies such as power outages. As the battery does not store well over extended amounts of time, it is possible that when they are needed they will not be usable. But for things that are used and recharged on a regular basis such as for portable electrical equipment, they are very good. But there is not always a slowing amount of capacity when they are getting old and it is possible for them to just not work without any reason being obvious.
The mating lithium bettery stock process between the two engines can be in series or in parallel. When the two powertrains are mated in series, only one of the motors controls the cars movement. The other one simply assists the first, dominant engine. This occurs most often in mild or assist hybrids. The Saturn Vue Green Line Belt Alternator System (BAS) is a good example. The concept vehicle named the Volt from GM is another good example of a series (but not a mild) hybrid.
As mentioned earlier, there are different types of batteries. You can choose a lithium ion battery if your primary source is electric power supply, but you do switch from fixed power to a battery on a regular basis. A Nickel based battery is preferable if you use a battery as your primary source.
Battery chargers for mobile phones are notable in that they come in a wide variety of connector-styles and voltages, most of which are not compatible with other manufactures' phones or even different models of phones from a single manufacturer.