Do you believe the seller's claims?

[papaof2]

Portable Car Inverter 150W Pure Sine Wave Inverter DC 12V to AC 110V Voltage Converter Transformer Power Bank Power Supply

www.aliexpress.us/item/3256804863938743.html

It's $15.99 instead of $33.31, has one AC outlet and two USB charge ports and free shipping but:

1) 150 watts is pushing the vehicular "12 volt outlet" (more commonly referred to by us seniors as "cigarette lighter") and the typical fusing is 10 amps. Fully charged lead-acid battery would be about 14 volts so 14V * 10A = 140 watts. The inverter is likely no more than 80% efficient so it might deliver 80% of that 140 watts or 140 * 0.8 = 112 watts. An actual 150 watts out would require 150 / 0.8 = 187.5 watts in. 187.5 / 14 = 13.39 amps - don't think that 10 amp fuse will last long...

2) Pure sine wave inverters at this price are RARE - about the rarity of geese that lay golden eggs :-( In January of 2020, eastwood.com was selling a 300 watt (continuous) pure sine wave inverter for $39.98 + $10.01 shipping or $49.99 delivered. Nice little inverter that delivers a very clean pure sine wave output and the price was very good for an inverter with true sine wave output. Sadly, Eastwood no longer lists this inverter - the smallest one they have listed is 1000 watts.

3) The most likely truth is that it's just another modified sine wave inverter that someone is trying to move regardless of truth.

However, I'll know tomorrow. The USPS tracking says the package will be here then and that's usually by noon. Shouldn't take more than 5 minutes to unbox the inverter, take it to the basement, hook it to 12 volt power and put the 'scope on its output to verify the waveform with a 100 watt load (incandescent bulb). I can also do efficiency testing (power input vs power output). That's about another 10 minutes for accurate testing or less than a minute to use the clamp-on DC ammeter which is probably close enough. Ordered on 12 Sep, delivered on 23 Sep - that's 11 days so it must have been shipped from their CA warehouse. I should set up one of the small DC 0-100 volts, 0-20 amps meters with some XT60 connectors - or maybe even binding posts to allow for quick tests of things like this. Probably could have AH, WH and so forth as well.

I could use another small inverter in the other vehicle occasionally, especially one that appears to be not much bigger than my two fists (3.62 x 2.44 x 1.41 inch). If it's actually pure sine wave, that's even better. Loaned out one about this power level that never came back (to power a heating pad for a family member on a 600 mile trip) - but that one was a BOGO from Woot so not many $$ involved).

Stay tuned for tomorrow's exciting sequel about cCc devices (cheap Chinese crap). Maybe that could be my new avatar or ID or website...

[feralferret]

"Stay tuned for tomorrow's exciting sequel about cCc devices (cheap Chinese crap). Maybe that could be my new avatar or ID or website..."

Sounds like an opportunity for your own YouTube channel doing reviews. 

[papaof2]

That name would probably violate some YT rule about "discriminatory terminology" or something - or maybe just insulting their liberal sensitivities...

I'd have to make a bunch on YT to be able to test/review all the crap I see advertised with obvious "No way in hell" claims.

[papaof2]

And the rest of the story ---

As I expected, the "150 watt Pure Sine Wave Inverter" for $15.99 isn't pure sine wave or even modified sine wave (multi-step approximation of a sine wave) - it's just a very basic square wave inverter.

However, it does provide at least 140 watts of output and it has a small amount of reserve for peaks - as seen on the 'scope with the 140 watt load.

The idle power is 0.4 amp at 13.14 volts (all testing was done "real world" using a 12 volt battery - in this case, the 4s3p LiFePO4 battery pack that has been tested to deliver more than 40 amps).

Using a triple tap adapter (because the inverter only has ONE AC outlet), the inverter was OK with a 100 watt incandescent bulb plus a 40 watt incandescent bulb (140 watts). The power input was 12.4 amps at 12.76 volts or 158.2 watts (remember, it's running from that LiFePO4 battery pack and the battery voltage will change with load). The efficiency was 140 / 158.2 = 88%. However, I don't think the 10 amp fuse powering your vehicle's "12 volt outlet" would last long at 125% of its rating.

The inverter has a fan (about 1 1/4") that runs continuously when the inverter is powered and 10 minutes delivering 140 watts left the metal case warm but not too hot to hold.

So what good is a square wave 120 volt AC inverter?

Powering 120 volt LED bulbs. Although powering 12 volt LED lighting is more efficient, you probably have extension cords and lighting fixtures that would allow you to provide convenient lighting for a large area. A "40 watt equivalent" LED draws about 6 watts. Six of those bulbs would be 36 watts. 36 / .88 efficiency = 40.5 watts from battery to inverter = 40.5 / 12 = 3.4 amps. Your vehicle's battery probably does NOT have an AH (ampere hour) rating but it will have an RC (Reserve Capacity) rating. There is no ACCURATE RC to AH conversion but dividing the RC by 1.9 is a useful estimate. Go check the label on that battery. Assume the RC is 140. 140 / 1.9 = 73AH. Unless your vehicle has a lithium battery, it's some version of lead-acid (flooded, AGM, Gel) and you don't want to use more than 50% of that capacity because you probably want to be able to start the vehicle at some point in the future. If you run the battery dead, you could get 73 / 3.4 = 21 hours of light. Half that would be 11.5 hours. Would having overnight power for six 40 watt equivalent LED bulbs be useful? If you limit that to 3 bulbs, you would get 20 hours. See the possibilities?

Maybe an older heating pad - not sure how one with the newer electronic controls will respond to a square wave. Possibly something to test?

Definitely an older laptop - I used a series of different brands on a similar square wave inverter for years (Compaq, ThinkPad and some semi-current Dells).

A 100-150 watt soldering gun or soldering iron that doesn't have electronic controls.

An older corded electric drill (no speed control) if you don't push it hard - nothing bigger than 3/32" or so in wood (OK for starting screws - from experience with a "140 watt" inverter that used a 60 cycle vibrator to generate AC power from the 12 volt lead-acid battery that fit in the case and the inverter could also charge the battery, a product from about 1957 - I may have the "Museum of Ancient Power Conversion" in the basement ;-) I could fit a modern 300 watt pure sine wave inverter and a high capacity LiFePO4 battery into that case.

Definitely NOT a charger for the higher voltage (20 volts and up) battery-powered tools - the Ryobi charger for their 40 volt batteries specifically says to NOT use it on modified sine power so the square wave is definitely out.

Of course, the advertiser doesn't care how you use it or whether you can use it - they just want your $$.

[feralferret]

I'm sure you could come up with a suitable channel name.

[feralferret]

Yesterday I saw an indoor amplified TV antenna that claimed to have a 400 mile range. Forty miles I might believe. TV signals are line of sight. The curvature of the earth makes a 400 mile claim a complete joke.

Some people will say anything to try to sell you something. Some of those people have the last name "Biden", but that's another story.

[papaof2]

There's a "to the horizon" calculator for determining distance to the horizon based on your altitude at www.ringbell.co.uk/info/hdist.htm

I've used it for computing distance covered by an EMP from a nuke, depending on the height at which the nuke is detonated (also affected by the "How big?" and "How EMP efficient?" statistics of the nuke).

It also works for line-of-sight antenna distances. An antenna 30 feet above ground would see the horizon at 6.7 miles. If you add the transmitting antenna's height to the receiving antenna's height you get their combined "horizon" distance. With the transmitting antenna at 750 feet and the receiving antenna at 30 feet, the total "height" is 780 feet and the distance to the horizon is 34.2 miles. A TV transmitting antenna at 1000 feet sees the horizon at 38.7 miles. With the transmitting antenna at 1000 feet and the receiving antenna at 30 feet, it's 39.3 miles so your "40 miles" is actually a ballpark figure ;-)

[feralferret]

Having worked in radio and TV, I knew that.  

Back in Amarillo, Texas where I did most of my broadcast work, most of the TV broadcast antennas were between 1,400 and 1,600 feet AGL.  For many years, one of the TV stations was broadcasting from what at the time was Texas Tallest Tower.  FM from anywhere up to around 1,000 feet AGL.  Most were Class C or C1 with an ERP of 100 KW or slightly less.

One FM station where I had he engineering contract was putting 32 KW transmitter output into a six bay circular polarized antenna at just above 900 feet on one of the older TV towers for 100 KW ERP.  That was a real pain when the antenna was damaged by lightning.

The land was very flat, so very little terrain blocking.  When I had a really good FM only Radio Shack receiver in my car (which had an AM only factory receiver) I was able to listen to a couple of the stronger stations at 95-100 miles away.  None of the factory AM/FM car receivers I had in later vehicles could receive the same stations past about 75 miles, some less.  Talk about outstanding sensitivity!  I was heartbroken when that receiver was stolen from my car while living in Houston.

I used to regularly listen to an FM station located in Plainview, TX on a home stereo with a set of rabbit ears for the antenna while sitting in my house in Amarillo.  Antenna positioning was fairly critical with one side vertical and the other side horizontal.  A distance of 77 miles between towns.  The actual distance to the FM tower was a little more as it was located south of Plainview in order to increase their signal into Lubbock.  A yagi antenna located 30 feet up would have been way too easy.  At the time, none of the radio stations in Amarillo had any decent rock programming. The station in Plainview was AOR (Album Oriented Rock) and was catering to the student audience at Texas Tech University in Lubbock.  I was in my early twenties at the time.