I am an electrical professional. Electricity is my business.
The subject of power supplies is a re-occurring subject on most forums which talk about battery operated equipment.
There is one golden rule in the electrical/electronic servicing business.
POWER SUPPLIES AIN'T POWER SUPPLIES.
Most people outside of the electrical/electronic servicing business have no idea about the way electricity functions and the safety aspects of main power supplies.
FIRST RULE: If the mains power supply you are purchasing DOES NOT carry a mains safety compliance certificate from the electrical certification authority in your country of residence then it is a safety hazard. The power supply has not been destructive tested in a certified testing laboratory. The chances are that the insulating materials are constructed from sub-standard non-flame retardant materials. The electronic components are sub-standard counterfeit components.
SECOND RULE: A true professional knows about the first rule and only purchases genuine manufacturer branded products.
There are three ways manufacturer's rate power supplies; peak to peak, peak and RMS. For a power supply to be effective it should be capable of delivering twice the required intermittent power drawn by the appliance. Fully charged 2650ma NiMH batteries are capable of delivering up to ten times their rated current for a few milliseconds and maybe up to half a second.
The only way to rate a DC power supply is maximum continuous user current. If that is not stated AC RMS will give you a good indicator. If either is not stated then the chances are that the rating is peak or peak to peak AC sine wave.
Switched mode power supplies are cheap to manufacture. Most switched mode power supplies on the market operate at 60% efficiency. To operate on the safe side you need to reduce the stated wattage rating of a switched mode power supply by 50% of the stated rating.
Good quality, standard transformer power supplies are bulky and contain heavy duty rectifier, capacitors, regulators and heat sinks. They are expensive and designed for continuous maximum output DC current without thermal overload or protection shut down. If you want power supply reliability then you will have to purchase a power supply with a current rating of double what your battery powered appliance will draw. Yes it will cost you more. In the long run that expensive power supply will have outlived the cheap power supplies on the market by a factor of three or four times. It will also will survive user abuse because of the inbuilt short circuit protection. If the power supply does fail it is usually cheap to repair with off the shelf components from your local electronics store.
I have had a regulated power supply drawing maximum current, the heat sink almost blistering the finger on touch, the fuse lighting up like a light bulb. The fuse eventually failed because of metal fatigue. I replaced the fuse and the power supply performed reliably for years of constant use until I retired it.
Electrocution from mains supplies and death by toxic smoke inhalation from a house fire is a painful way to die. If an individual wants to consider themselves as a prospective candidate for a Darwin Award
http://www.darwinawards.com/ that is their prerogative. If you want to live a long productive life then do you homework before purchasing a cheap power supply being sold on the internet. You would not install substandard brakes on your motor vehicle; the same with electricity. If you do not know anything about electricity then spend the money, go genuine and purchase the recommended power supply for your appliance from the manufacturer.
