Most inverters output "modified sine wave", which is essentially a stepped square wave approximation of a sine wave. This is perfectly satisfactory for many purposes, like lighting, electronics that use switching power supplies (laptops, phone chargers, etc.), but may cause problems for devices that are quite sensitive to the quality of power they get such as motors, some medical devices, etc. Such devices need a "pure sine wave" inverter, which delivers a smoothly-varying sine wave much like that provided by the electric utility.
This inverter is just such a "pure sine wave" model, and outputs a rather nice sine wave (see attached photos). It's a pretty typical sinusoidal wave with a frequency of 59.5 Hz (utility power in North America is 60 Hz, and 59.5 Hz is perfectly acceptable). The peak-to-peak voltage of my unit was 158 V, which corresponds to an RMS voltage of 111 V. This is within the nominal range of 110-120V found in North America, and should be universally compatible with any device.
If one zooms in on the waveform, one can see the 24.3 kHz switching steps of about 10 V that the device produces. This is an unavoidable consequence of converting DC to AC, and it's at such a high frequency that it should have no effect whatsoever on any device connected to it. Ideally, I'd like to see some sort of low-pass filter applied to the output of the inverter to filter that 24.3 kHz noise, but then I remembered that this is a $40 item and that such noise isn't going to affect anything.
The 12V cord is thick and looks to be the 11 AWG (4mm^2) cable Bestek uses for their battery clamps-to-lighter-socket set. This is perfectly fine for this power level. The 12V plug is spring-loaded and fits snugly into the receptacle.
A small fan comes on as needed and isn't terribly loud. Still, it comes on periodically when the unit is idle with no load attached, for which I'm deducting one star from "noise level".
The quality of the circuit board on my unit looked fine, with no assembly problems, bad solder joints, etc.
There's two small downsides that I've noticed:
1. The fuses are inside the unit, require its disassembly (pop off the rubber feet, unscrew the four screws there, then unscrew the circuit board inside from the supporting posts), and the fuses (two 25A automotive "Mini" size fuses wired in parallel) are soldered to the board. Again, I realized it's built to a price point, but having the fuses soldered to the board rather than being in sockets and preferably accessible from the outside of the unit is incredibly inconvenient. Having an in-line fuse in the cord or 12V lighter plug would be fine as well, but having them be internal and soldered down is annoying.
2. The cord is not detachable. While Bestek offers a nice battery clamps-to-lighter-socket set, it sure would be handy to simply be able to unplug the lighter cord and replace it with a cord with battery clamps that's connected directly to the unit. It'd also make the unit more compact for storage.
In short, my initial impression is that the inverter is a perfectly serviceable pure sine wave inverter that is far superior to modified sine wave inverters at only a slight price premium. While it's bulkier than some other inverters for its power level, it's not excessively large. The power it outputs is quite acceptable and makes my home UPSs (which are normally very sensitive to power quality) happy. The lack of easily-replaceable fuses is annoying enough to warrant the deduction of a star; it wouldn't be hard for them to have a higher-rated internal fuse that's there to prevent fires in the event of a major fault and a fuse for the rated current in-line with the cable or in the plug to prevent overheating in the event of a normal overload. Other than the fuse issue, I'm perfectly happy with the unit so far.
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BESTEK 300Watt Pure Sine Wave Power Inverter Car Adapter DC 12V to AC 110V with 4.2A Dual Smart USB Ports
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BESTEK 300Watt Pure Sine Wave Power Inverter with 150W Modified Power Inverter Car 12V to 110V Adapter with Dual 4.2A USB Ports55.99 64.94This bundle contains 2 items -
BESTEK 300Watt Pure Sine Wave Power Inverter Dual 4.2A USB Ports with 12.1ft / 3.7m 12AWG 12V 24V Cigarette Lighter Extension Cord59.38 64.98This bundle contains 2 items
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Product Description
Designed for your devices that require careful protection
BESTEK Advantage
America's leading power inverter brand. Provides 300 watts continuous DC to AC power and 700 watts of peak power.
- Pure Sine Wave Power Inverter
- 2 AC Outlets
- 2 Smart USB Charging Ports
- Smart Cooling Fan
- Built-in 40 Amps Fuse
- Aluminum Alloy Housing
BESTEK 300W Pure Sine Wave Power Inverter
[Pure Sine Wave] BESTEK Power Inverter with 2 USB ports and 2 AC outlet.For charging your iPad, please use the 2.1A USB port and keep the other USB port free. It's normal for the inverter to become warm to the touch while you are using it, avoid placing the inverter in direct sunlight or next to heat-sensitive materials. Do not use to power high power electric devices such as hair dryers, electric heaters, which might blow a fuse.
- Designed for your devices that require careful protection
- Detects your devices automatically
- Top Speed Charging
- Built-in fuse, Full protection
- Easier to dissipate heat
- Isolation Voltage Protection
- Durable Cigarette Lighter
- Ultra Compact
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Pure Sine WaveDesigned for your devices that require careful protection.Provides sine wave output which is more stable and can be applied to the curling iron,hair straightener and the electric toothbrush within 300W designed for your devices. |
2 AC Outlets And 2 USB Charging PortsEquipped with 2 Smart USB charging ports, which detects your devices automatically to deliver its fastest charge speed up to 2.4 amps per port/4.8 amps max, and you can charge most phones and tablets simultaneously. |
Smart Cooling FanSmart cooling fan system makes the car power inverter very silent when operating,and the fan runs faster when the device gets warmer or output power exceeds 70W. |
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Durable Cigarette LighterDouble durable springs each side for tight mount stable and electrical safety.The lighter socket is resistant to up to 5000 times of insertion and extraction, can plug into almost all vehicles. |
Isolation Voltage ProtectionSafe charging design provides protection against, overheating, under and over voltage charging, short circuiting, overloads, and overcharging. |
Car Becomes RVWith our car power inverter, you can use most of home appliances in your car in the open air, such a watching TV, playing games, give you the experience like being in an RV. |
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| BESTEK 300W power inverter(red) | BESTEK 200W power inverter(white) | BESTEK 200W power inverter(black) | BESTEK power strip(white and gray) | BESTEK 75W power inverter(black and silver) | |
| Color | Red | White | Black | White and Gray | Black and silver |
| Power | 300W | 200W | 200W | --- | 75W |
| Feature | Smart cooling fan | ETC and Smart cooling fan | ETC and Smart cooling fan | FCC | Silent Cooling Fan |
| isolation voltage protection | ✓ | ✓ | ✓ | ✓ | ✓ |
| USB Port | 4.2A Dual USB | 4.2A 4 USB | 4.2A 4 USB | 2.4A 3 USB | 3.1A Dual USB |
| Dimension | 4.8 x 3.1 x 1.9 inches | 6.2 x 3.3 x 1.4 inches | 6.2 x 3.3 x 1.4 inches | 3.4 x 3.1 x 3.4 inches | 5.5 x 2.4 x 1.6 inches |
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Reviewed in the United States on May 16, 2019
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Top reviews from other countries
I-Cycle Electric Bike Company
Keep an eye on these for a few days in case they fail
Reviewed in Canada on August 23, 2019Verified Purchase
Lynn G
BESTEK 300W Pure Sine Wave Power Inverter
Reviewed in Canada on June 15, 2020Verified Purchase
Systems Engineer
Nice and compact
Reviewed in Canada on February 11, 2020Verified Purchase
Larry
Good product
Reviewed in Canada on November 23, 2019Verified Purchase
Denis
super
Reviewed in Canada on November 14, 2019Verified Purchase
