BESTEK Pure Sine Wave Power Inverter, 300W DC 12-17V to 110V AC Car Adapter | Vehicle Plug in Cigarette Lighter Outlet Solar Inverter, 4.8A Dual USB Fast Charging Ports for Phone, Laptop, CPAP(Black)

I'm an experienced EE by profession and education, a mixed-signal RF/analog/digital guy, and I tested this unit six ways to Sunday (i.e. extensively, see images). It does everything the brochure says it will do, and fully loaded (okay, almost fully, 253 watts of incandescent load), it runs quietly and stays cool as a cucumber. Make that a fresh refrigerated cucumber from where? Whole Foods, of course. Output voltage regulation is excellent; I tested it from 10 VDC in to 14.4 VDC, and it sags only a little, from 114 VAC RMS down to 110 VAC RMS. Your attached appliances will never know the difference. Mine clocked in at 59.99 Hz from 14V in, 60.02 Hz at 10V in; again, your appliances will never know the frequency difference, as frequency regulation is excellent. I ran FFT on the sinusoidal output to check harmonics; the highest was the 4th at 40 dB down. The sinusoidal output is very pure, very clean. Ever the curious one, I took a look inside. Four TO-220 nicely heat-sinked switching FETs (presumably) operating in tandem to drive a series toroidal inductor/capacitor low-pass (shaping) filter. The switching frequency is right at 25 kHz, and pulses range from 760 nS up to whatever width is required to maintain the waveform, depending on load and phase angle. I measured this on the driven side of the L/C output filter, see pics. This unit does generate some hash in the AM radio band, no surprise. It might generate RF noise at higher frequencies including the HF bands (I didn’t test that; hey, this is a free product review), but if you’re a ham radio operator, you’re probably running off of batteries if you need low noise. It’s probably within FCC Part 15 unintentional radiator limits; I didn’t test conducted or radiated emissions either. I bought this unit because my DJI drone battery chargers (3 different drones, 3 different chargers) refused to recognize my older “modified” sine inverters as providing useful AC power. I don’t blame them; whoever named it “modified sine wave” definitely worked in marketing, not engineering. And they’re rude. All of my DJI chargers work fine with this Bestek Sine unit, and why wouldn’t they? They’re being fed a swell, 60-Hz sine wave, just like at home. I highly recommend this unit. It’s internally fused, so you’ll have to do some soldering if you pop the fuse. You need to remember that 300 watts at 120 VAC is only 2.5 amps, but at your 12V input, it’s 25 amps assuming 100% conversion efficiency. Assuming a realistic conversion efficiency north of 80%, that’s 30 amps. Many automotive cigar lighters are fused at 10A. Never replace a 10A fuse with a 30A fuse to keep it from popping. There’s a reason auto manufacturers made that a 10A fuse, and it’s the wiring between your battery/charging system and the cigar outlet. Don’t turn your car into a crispy critter by upping any fuse, certainly not this one. If you need 300W, either make sure your car or truck cigar lighter fuse can handle the 30A, or buy some healthy alligator clips and attach this unit, via dual inline 30A fuses, directly to your battery. It’s also worth noting that most automotive alternators will produce about 50 amps at idle. I plugged three 100W incandescent bulbs to my Bestek 300 W Sine Wave inverter and read 253 watts on my handy Kill A Watt P3 test instrument. I attached it to my 36 AH fishing-motor battery and ran it for several minutes with no discernible heating of the inverter casing or the air at its vents. I also attached my iPhone to the USB output, and the USB outputs on this unit are indeed wired to charge iPhones (proper resistor-divider values on the USB data pins). It measured 1.56A into my iPhone, probably current limited by the phone, for a nice fast charge. The fan seems to have two speeds: modest and off. When operating, it’s fairly quiet. As you might expect, whether the fan runs or not is not so much affected by load; most of the power dissipated in switch FETS is related to moving charge and intermediate resistance value during transitions, not to Rdson losses. Assuming these are FETs (highly likely). I tested low-voltage and overvoltage cutoff points, and found that the unit had hysteresis at both ends, as any good design would. The unit I examined would cut off at 9.77 volts and would stay off until voltage rose to 10.994 volts. For overvoltage, the unit would trip off at 15.57 volts and start back up when voltage dropped below 15.000. Unlike another reviewer, I did not note any beeping sound from the unit when input voltage dropped too low. Note that common wisdom for lead-acid batteries and gel cells says not to take them below 11.6 volts/no load. I’m not sure how that translates to loaded voltage, but exercise caution if running this thing at full load for an extended time repeatedly from a battery that is not being charged. I’m going to give this unit an A+, and I’m a hard grader. And $45.99? At that price point, you may not expect much: you’ll be pleasantly surprised with this Bestek unit. Worth every penny. And no, I’m not on the company’s payroll; just pleasantly surprised and impressed with this unit’s design excellence and manufacturing quality. That and I was a little bored today, thought I would take some measurements and share my insights. Can you tell? :)

This is a good buy for a pure sine wave inverter. I needed something to power my electric blanket in a semi and the one I had kept faulting. This worked with my unit. I recommend

For what I plan on doing with this, it will work just fine. It is nice and compact and the fan is quiet. It will not work with my 4000 peak amp jump starters when I plug into the 12 volt 10 amp connector. Evidently, the internal electronics of the jump starters think the inrush current is an overload and shuts down. I ordered a couple of Milwaukee type 12 volt tool batteries with an adapter to connect to and wired it to the cigarettes connector and now it works fine. It would be nice if they could add circuitry to reduce the inrush current. The sine wave is very good. The frequency is right at 60 hertz and very clean and the voltage is at 111 VAC. Turn on the unit before plugging in anything to it. It take a second or two to stabilize.

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.

This is the best inverter ive ever owned. Small, incredibly quiet. My cellphone and Ipad are always topped up now and it charges all my tools with no problem (drills, headlamps, etc)

This is a great little sinewave inverter. I purchased it mainly to power a tv with Travelfi when in the rv, and if I needed to work I didnt have a way to power my laptop without running the big generator on my rig. It’s simple to use, but needs to be monitored with a timer as you want battery voltage around 12v with engine off. Very happy with this…

The USB plugs in our Honda do not provide for Turbo charging my new phone. As we have a DC outlet in the center console in the back, I plug this in there and have a USB charging cord in the port. If I need to charge it, I just flip the convenient on switch. This leaves the regular USB car charger free for my spouse's phone. The Inverter is also good for when I travel with my laptop.

I had great success powering my Dell laptop and working while my family drove me to vacation! Nothing like working that remotely! Later however, I must admit I had a malfunction with my inverter, and when I reached out for troubleshooting help I received quick replies, compassionate and professional attitude and a quick resolution. I ended up receiving a full replacement just to make sure I would not have the same issue again. I haven't had that kind of a positive experience from other companies in a long while. WAY TO GO BESTEK, and especially the rep, "Lan" -- Thank you!

Great Quality Product Just as Advertised and Looks/Works Perfect!

Works great, small form factor, the only thing I would change is to add a bit more space between the outlets

After using 6 months I am writing the review. This is a decent product for its price. I have tested it with different equipment and it worked. The max load I used is 250 Watts. A few good things are (1) It is not too heavy and too big so you can carry it easily even inside a laptop bag. (2) Pure sine will protect your sensitive and expensive devices such as laptops. (3) Cigarette plug is very firm and will hold in place, unlike other cigarette plugs. (4) It has two regular plugs and two USB plugs which is sufficient. There are a few drawbacks for people who are buying to use with a car or SUV. (1) Most cars come with a 10 to 15 amps fuse for cigarette lighter plug. So you can only get 120 Watts if your fuse is rated 10 AMPS and 180 Watts if your fuse is rated at 15 AMPS. Make sure you don't plug anything which uses more than this wattage otherwise car fuse will be blown. (2) There is no external fuse on the wire. If you end up blowing up the fuse of this inverter then you can't replace it by yourself unless you are a technician since the fuse is soldered on the board inside. (3)You can't clamp on the battery directly since there is no extension for clamps which means you have to buy an extension that can cost around $20. (4) Since it is plastic this can get hot in summer but In Canada, we should be fine. (5) The supplied voltage is around 108V to 110V, which means it can take a little bit more time to charge your laptop than a regular wall outlet. Note: If your car supplies power to cigarette lighter plug while the engine is off then make sure to unplug it. Because on power off it also consumes little power to supply those USB extensions. If you worry about blowing up the fuse inside your car there are cigarette lighter extensions with a build-in fuse which will cost around $20. Make sure you test it when it arrives sometime they don't work. Another one I bought did not work but it was in the return window so I was able to return it. If the manufacturer is reading my review. Please fix the issue of the fuse to make it really good inverter. Conclusion If you get it for a decent price then go for it.

Now that I have had a chance to use it for a full week under load, I can say it worked well. I used it just under 80% of full load rating without any issues. The fan does get a little loud at night. The cooling fan modulates it's rate to keep things working. The physical size Vs. power output is spot on at 300W. The sign wave on my oscilloscope looked clean without spikes or steps of a conventional inverter. This is now my GoTo inverter, converting 12v DC to 115 AC. The USB charging ports are a good bonus. This inverter does use some power when plugged in and turned on weather there is load on it or not, so turn it off after use.

Not good! 1. Failed to be Pure Sign wave. 2. Low AC voltage output 107. 3. With no load still draw .850 ma. 4. Fan runs all the time, at least it's quiet. Within one minute of powering a 120 volt led house light I could see it flickering and it was dimmer then standard hydro power. After using test equipment I came to the first 3 comments in this review. Gary W