Quote Originally Posted by jape View Post
Milton, many USA devices have a switch, sometimes under a plate on the back, for going from 110 to 220 volts! Not saying you are stupid but many folk do not even know of this and these threads get read by many. If you checked for that and it doesn't have this switch you can often get some devices rewired easily.

You can just use a simple step-down 220 to 110 converter as you have bought, that should be fine as long as you looked at the wattage the tender uses and got one in that range. In layman's terms, Watts = Volts x Amps P = V I

You should also look at the 'herz' in these cases as some are 50, some are 60 and they do not always match up or work just by changing voltage. You can get more expensive devices will transform/convert and match frequencies. Always get electrical advice for two reasons: wrong wattage can cause a fire, easily, wrong frequency can f**k up sensitive equipment including some types of battery (which can even have circuitry built into them)!
I have looked at the back of the Tender, which is clearly marked for input as 110V and without a switch for different voltage settings. I don't remember what the frequency spec is. Need to go home and check. Just looked up the Wikipedia and found that China is 50hz versus the States at 60hz. The converter is marked for frequency range 50hz to 60hz. Now I am wondering what that "frequency range" means. Does it mean that it doesn't care what the input frequency is as long as it is in the range, in which case the voltage will be stepped down as advertised? But does it also convert the frequency from 60 to 50 (unlikely)? Would the tender (actually a Battery Tender Junior, rated output 12V 750mA) survive the 60hz? Argh, headache.
The converter is rated at 100W, which should give it plenty of head room.