I'm using a voltage converter to go from 220V to 110V to charge a small appliance. The recommended charging time is 6-8 hours. However, this is specified for US AC voltage 110V@60Hz, whereas the converter provides 110V@50Hz.
Will providing 50Hz affect overall charging time compared to 60Hz, and if so, how much?

Note: the device in question is basic handheld Stun Gun, I bought it recently, but it designed specifically for US market 110V/60Hz, European version for 220V AC is not available for this model. Therefore I use low-power(45W) AC-AC voltage converter 220V/110V to charge its internal battery. I assume this should not damage the unit. :)

  • \$\begingroup\$ What do you mean by "charging"? \$\endgroup\$
    – EM Fields
    Jul 21, 2015 at 14:23
  • 1
    \$\begingroup\$ I mean to charge the built-in rechargeable battery. Is there any other meaning for this? \$\endgroup\$
    – minto
    Jul 21, 2015 at 17:12
  • \$\begingroup\$ To answer your question - not significantly if at all. \$\endgroup\$
    – Alec Teal
    Jul 21, 2015 at 20:18
  • \$\begingroup\$ Hey, maybe you have a Vandegraff (sp?) generator for a small appliance. :-D \$\endgroup\$
    – donjuedo
    Jul 21, 2015 at 20:57
  • \$\begingroup\$ No, it just Stun Gun, very handy :) \$\endgroup\$
    – minto
    Jul 21, 2015 at 21:22

2 Answers 2


No it won't have any effect.
The 220v or 110v AC at 50 or 60Hz is stepped down to a lower voltage and rectified to DC before it is used to charge anything.
So since the actual charging uses the rectified DC, the original AC frequency doesn't make any difference.

  • \$\begingroup\$ Not necessarily true. The circuits doing the stepdown may have different efficiencies on different frequencies. \$\endgroup\$
    – sharptooth
    Jul 21, 2015 at 13:43
  • \$\begingroup\$ @sharptooth Perhaps they will, which might lead to a different power consumption figure, but this is unlikely to have any significant effect on the charging performance - which is what the OP asked about. \$\endgroup\$
    – brhans
    Jul 21, 2015 at 14:12
  • \$\begingroup\$ I really missed point that lower voltage are rectified to DC before its used to charge anything. Another thing is when 110v 50Hz is used to power the appliances which use electric motors (like blenders), in this case, theoretically, the blender will provide less power at 50Hz. \$\endgroup\$
    – minto
    Jul 21, 2015 at 14:34
  • 1
    \$\begingroup\$ @minto Blender motors are universal (brushed) type- they should not produce less power at the same voltage (even DC). Some motors (induction type) will run 20% slower on 50Hz and at the same voltage the torque under load will be similar, so 20% less horsepower. \$\endgroup\$ Jul 21, 2015 at 14:39
  • 1
    \$\begingroup\$ @sharptooth: Why would mains power be "limited for some reason"? Please make sure your comments are relevant to this answer (or to the original question). \$\endgroup\$
    – Dave Tweed
    Jul 21, 2015 at 16:15

If your appliance's specified input frequency is 60Hz, then one would think that its internal charger is obviously frequency sensitive.

Consequently, if the appliance's internal charger circuitry is transformer-coupled to the mains and is rated for 60Hz service, the inductive reactance of its transformer's primary will cause the impedance presented to the mains to be lower than it would be with a 60Hz input.

As a consequence, the transformer's primary will draw about 20% more current than it would in the 60Hz case.

However, since the transformer's turns ratio won't change, its output voltage will be the same in either the 50 or 60Hz case.

Then, assuming some sort of brute force rectifier-capacitor supply in front of the charger proper, its reservoir capacitor's capacitance will have been chosen to yield an acceptable ripple in order to meet the charge time specification.

Since the cost of the reservoir capacitor will go with the product of voltage and capacitance, and since:

$$C = \frac{Idt}{dV}\text{ ,}$$

Where I is the average input current to the charger, dT is the period of the rectified waveform and dV is the acceptable ripple voltage out of the raw supply.

it's likely - if zillions of these products were produced - that C was minimized by making \$ dt\$ as small as possible.

If such was the case, then at 50Hz, \$dt \$ would be equal to 20 milliseconds and, for the same ripple amplitude, C would have to be increased by about 20%

  • \$\begingroup\$ you probably meant overall charging time would have to be increased by about 20%? (not the capacitance of capacitor) \$\endgroup\$
    – minto
    Jul 21, 2015 at 23:12

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