# Will the lower frequency of 50Hz AC affect overall charging time? [closed]

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. :)

## closed as off-topic by Adam Davis, Daniel Grillo, Ricardo, Nick Alexeev♦Jul 21 '15 at 21:05

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – Adam Davis, Daniel Grillo, Ricardo, Nick Alexeev
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• What do you mean by "charging"? – EM Fields Jul 21 '15 at 14:23
• I mean to charge the built-in rechargeable battery. Is there any other meaning for this? – minto Jul 21 '15 at 17:12
• To answer your question - not significantly if at all. – Alec Teal Jul 21 '15 at 20:18
• Hey, maybe you have a Vandegraff (sp?) generator for a small appliance. :-D – donjuedo Jul 21 '15 at 20:57
• No, it just Stun Gun, very handy :) – minto Jul 21 '15 at 21:22

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.

• Not necessarily true. The circuits doing the stepdown may have different efficiencies on different frequencies. – sharptooth Jul 21 '15 at 13:43
• @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. – brhans Jul 21 '15 at 14:12
• 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. – minto Jul 21 '15 at 14:34
• @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. – Spehro Pefhany Jul 21 '15 at 14:39
• A universal motor will provide more power for the same voltage at 50 Hz because the inductive impedance is less at 50 Hz. If the question about universal motors were to be asked separately, I would provide more detail. – Charles Cowie Jul 21 '15 at 15:10

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%

• you probably meant overall charging time would have to be increased by about 20%? (not the capacitance of capacitor) – minto Jul 21 '15 at 23:12