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Customer Review

96 of 158 people found the following review helpful
2.0 out of 5 stars OK for some purposes, November 17, 2011
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This review is from: BESTEK 150W Power Inverter with 3.1A Dual USB Charging Ports (Electronics)
This inverter produces a square wave AC output, which is unsuitable for inductive loads such as fluorescent lights or computer notebook power supplies or for motors, instead of the nice sinusoidal AC output of normal mains power. It should work for resistive loads like incandescent lights, although those are higher power and are being phased out now.

Even if at this price point one has to expect it, the user should be aware of this significant limitation. When connected to even low power fluorescent lights or computer notebook power supplies, the inverter does not power the device and its indicator LED switches from green to blinking red. The USB DC output was sufficient to power devices such as USB lights however.

The plastic face on one side of the inverter was cracked inside or otherwise not firmly attached to the body so that side pulls out a few millimeters when an AC plug is removed. One therefore has to hold the face in place to avoid separating or breaking it further.

The end that plugs into the car power port is short enough and the face/body large enough that it may not fit in some cars without a wired extender because the large body may be physically blocked by the plastics in the car console.
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Showing 1-3 of 3 posts in this discussion
Initial post: Mar 6, 2012 7:59:44 PM PST
R. Fealing says:
This contradicts many many of the other reviews - most of them talk about powering a laptop, this one says you can't. Anyone with any feedback?

In reply to an earlier post on Nov 10, 2012 7:51:07 PM PST
Last edited by the author on Nov 10, 2012 8:08:40 PM PST
J. B. Lantz says:
A modified sine wave is a crude, blocky substitute for a pure sine wave, but its not a square wave. I've used a 120V-input switching-supply camera charger with my modified-sine wave inverter [not this particular product] with no problems. Don't recall if I used it with my laptop.

Virtually all laptops and most AC-to-DC power adapters today in general use SWITCHING power supplies. Switching power supplies maintain a constant voltage across an output capacitor essentially by rapidly switching on and off the input power, as necessary, to compensate for the current being drawn. A bit like maintaining a constant water level in leaky tank by automatically turning on and off an input faucet to compensate for the leak. Though I'm not an EE and can't say for sure, I think that most switching power supplies are probably not very fussy about the sinusoidal purity of the input waveform that they turn on and off. (If one of you out there IS an EE, please correct me if I'm mistaken about this!)

PS Read also Ted Pavlik's review, "The THD must be terrible...." Like I said, a modified sinusoid is crude and blocky; if I understand THD correctly, it probably is terrible. Apparently unacceptable for some purposes.

Posted on Mar 27, 2013 8:20:46 AM PDT
Shinobi says:
[Customers don't think this post adds to the discussion. Show post anyway. Show all unhelpful posts.]
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