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What is going on in a mini inverter?
#1
It seems to me that one of those little “boxes” that sit on the 110v power cord to invert the voltage to 12v does very little …..   1) inverts the power 2) moderates the amp output to a spec, and 3) sometimes protect from reverse polarity.     What else could be going on in there?

I am asking because I purchased a device that runs on 12v 3amp.  BUT…the seller (who seems to know only what his sellers blurb says) is claiming I will damage the device if I hook it up straight from my 12v system using an anderson connect to a fuse panel with 5amp fuse.     

What else might be provided by that little inverter box on the 110v power cord?
1989 Honeywell motorhome
Ford E350 chassis.  460 engine
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#2
The 120vac to 12vdc power switching power supplies are pretty simple.

I have one 3 amp rated one which came with my 13.3 inch led tv which must be a decade old at this point.

Last year i opened it added a finned heatsink to the non finned heatsink within and cut and filed plastic casing to accommodate it.

Of course i lopped off the original dc output connector and anderson powerpoled.it.

The only weirdness is the dc output ground wire is not sheathed. Is is open strand and surrounds the inner + wire. They do this for electrical noise suppression, same goes the little.ferrite barrel which might be molded.over the dc output wire on all power supplies which come with devices. Zome are just snap on. Worthy of pilfering from old unused powersupplies.

I was hoping adding the heatsink would allow the supply to output over 3 amps.continuous safely, but it really heaTs up quickly above 3 amps output, so my ministrations will just extend its useful life powering a 3 amp load.

Its output DCVoltage is in the 12.08 to 11.88 range. ive been using it since i moved out of van to power fans usually powered by van dc system.
I could use my 40 amp meanwell adjustable vtage powersupply, or my 100 amp.powermax adjustable voltage power supply, or my 18 or 22am agm baTteries, but my papst clamp fan can only draw 3 amps at max speed amd this little inline powersupply/brick is basically perfect.for the task at hand.

They are cheap.

The seller is not.going to say yes modify it without concern, Whomever reaponds is aN electrical idiot following a legalese script placed before them.
If they ask an engineer the engineer dumbs down the speak 2x, first for the idiot behind the output computdr and the expected drooling litigeous idiot on the receiver computer.

Modify the dc output cord with amderson, without concern.

Confirm polarity first, and if you really want, add a 3 amp inline fuse on the +.

Now my dell 120v to 19.5dc powersupply has 3 dc outout wires in cord.. The third wire is super thin and.is for a.pin inside the standard barrell connector When thin wire is compromised, laptop will power up fine, but wont charge internal baTtery and laptop tells me tonuse authentic 90 watt poweraupply.
Same message if barrell.connector is not fully seated.
[-] The following 3 users say Thank You to sternwake for this post:
  • RoamingKat (01-02-2023), rvpopeye (01-02-2023), frater secessus (01-02-2023)
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#3
Thanks!

I find it difficult to ask straight questions from one of these guy selling stuff. Maybe I should find out their job title first? As in… “don’t ask the shipping clerk tough questions”.

Thank you for your time!
1989 Honeywell motorhome
Ford E350 chassis.  460 engine
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#4
So not too long after my last post in this thread, the '3 amp' 120vac to 12vdc converter for my 12vdc tv, which i was using to power some fans, and also separatwly   powering my dc to dc boost converter to hokd my small ub12180 battery at 14.7v, released the magic smoke.
I was careful to not ask more.than 3 amps.from it, but returned to that distinctive smell of electronics failure, so i cut off the APP and 18 gauge from CB and salvaged the finned heatsink and the plastic casing, and tossed the rest.  Sorry landfill.

Saw this netgear 120vac to 12vdc converter for a failed router, rated 2.5 amps max, in the closet.
   
  I opened it up, for curiosity sake, then attached  quick connectors to use with some 12awg Powerpoles which already had quick connects attached.
Holds 12.23v pretty steadily.



Its plastic casing get hot.powering 1 amp of fans
It gets Merely warm powering 0.62 amps.of.fans.

I zip tied 4 92 antec 92mm 3 speed fans together side by side.
They fill out a household return hvac vent nearly perfectly, and with my room's door closed, when hvac runs, the negative pressure pulls about 3x the amount.of cold air into the hottest bedroom in house, compared to without.

My meanwell rsp-500-15 has been running non stop since the failure.of.other supply., rarely delivering more than 1/40 th of its capacity, powering mostly fans.
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#5
Nice.
I have had no issues with this little thing on a 5amp fuse wired to the 12v system.
Sometimes I find a inverter on a 110v power cable which says it’s output is 9 volts

It there a small inverter ( 300watts or less) that lets me pick the output voltage? 110 in and sort of a “dial a voltage out?
1989 Honeywell motorhome
Ford E350 chassis.  460 engine
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#6
Calling a AC to DC Power Supply, an inverter, might not sit right with some in the RV world.

Generally,
Converters are considered the 120Vac to 12vDC ( nominal) devices.
Inverters are 12vDC to 120vAC

My Meanwell RSP-500-15 adjustable Voltage Power supply, has an Output DC voltage range from 13.12v to 19.23v, and while rated for 500 watts, can do 600 watts all day long with the extra ventilation and heatsinking that I've added.
The original voltage adjustment potentiometer requires a jeweler's screwdriver and a fine touch to dial in the voltage desired. I've replaced it with a 10 turn fingertwist potentiometer for easy and precise voltage control

It's been coasting along, rarely ever having to power more than 50 watts of fans, as of late.

There are smaller versions. and some with different voltage ranges. the -15 on my meanwell signifies that its nominal voltage is 15 volts, but the range is 13.12 to 19.23, even though the spec sheet stats a much narrower range. there are -5 and -12, and -24 versions with adjustable ranges around those numbers.

There are laboratory power supplies that have a wide range of output DC voltages, and one can also limit maximum amperage as well. This one is rated for only 5 amps. some will go as high as 50.

https://www.amazon.com/LW-K3010D-Adjusta...2GZF4M9AUQ&keywords=benchtop+power+supply&qid=1678573019&s=industrial&sprefix=benchtop+power+supply%2Cindustrial%2C233&sr=1-6
This link below is along the lines of my Meanwell, 120 to 240VAC in, 0 to 48VDC out, rated for 480 watts and it comes with a fingertwist dial for voltage control. One needs to provide their own voltmeter and 120vac wiring to and DC out, from this unit..

https://www.amazon.com/Adjustable-Conver...KU377TY64K&keywords=AC+to+DC+adjustable+voltage+power+supply&qid=1678571495&sprefix=ac+to+dc+adjustable+voltage+power+supply%2Caps%2C380&sr=8-4.

There are tons of power supplies that look similar to this all over the net. The link above is just the first I saw on Amazon using the search words one sees up top. These and similar, are also often called LED Power Supplies, and there will be hundreds of hits using that search term.

I had one back in 2013 or so, that was a 12vDC nominal supply, its range was about 10.5v to 15.4v, and rated for 30 amps. It would however, when hooked to a healthy depleted battery and voltage cranked towards the upper range, provide in excess of 36 amps, and would make strange noises. 35 amps and it was OK. I added better fans and heatsinking and potentiometer and worked the thing hard, but always had to adjust voltage to keep amps below, but up near 35 amps when bulk charging as fast as possible was desired.

Eventually i got sick of babysitting it, and cranked it to 14.7v, hooked it to a healthy depleted battery and let it go. 17 minutes later the magic smoke escaped and i ordered the meanwell rsp500-15.
The Meanwell has constant current limiting on overload, so will not smoke itself by outputting more than it can handle safely. but of course it would still get super hot if kept at its limit, without the extra heatsinking and ventilation. Its internal fan when it kicks on is super loud and annoying. My Noctua fans are much quieter and prevent super loud fan from coming on until it is outputting 27+ amps for many minutes in 65f+ ambient.

If one wants a higher quality supply like a Meanwell RSP series, the tiny adjustment potentiometer is a limiting factor, desoldering it and running wires to an external potentiometer is kind of involved and requires some soldering skills. The tiny pot provided is only rated for 25 cycles, and once one has adjusted it this many times it will act all weird and the power supply will audibly struggle trying to hold a voltage within that ' worn out' range.
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#7
Oops… yeah, thinking inverter when I mean converter.

I’d like to go from 12v to anything lower. I have seen in-line 110v to 9v, And 110v to 5v. I know I cannot hook them up without the little device…but it drives me crazy to run the inverter to get from my battery to the standard wall outlet only to plug in a device that then converts it to 5v.
1989 Honeywell motorhome
Ford E350 chassis.  460 engine
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#8
Blue Sea sells a 12VDC device with dual USB ports. Though it doesn't supply high amps USB. I installed one in my cargo van.

https://www.amazon.com/gp/product/B0082CXEI8

In my Class C, I use a USB dongle that plugs into a ciggy port, the dongle provides two ports with high amp USB. The current model says max 18W, the one I bought in 2022 says max 24W per USB port. It's part of a kit that can charge laptops using supplied adapters.

https://www.amazon.com/gp/product/B07RLBV18M
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#9
Getting from 12.x vDC to lesser DC voltages requires a buck converter, also called a step down converter.

I make extensive use of these, for speed controlling 12vdc fans, and for dimming 12vdc LED lights, and most recently, to charge a single 1.2v Nimh Eneloop battery within some beard clippers. I found setting it to 2.36v yields about 0.15 charge rate into the when new 1900 mah battery. A bit slow but I dont need to monitor it closely for fear of overcharge.

For 5 amps or less of fans/leds, I like the XL4005 based buck converters.

https://www.amazon.com/XL4005-Adjustable...rd_w=HpoVZ&content-id=amzn1.sym.68174014-ed7a-4e35-badd-6d3576b85c0b&pf_rd_p=68174014-ed7a-4e35-badd-6d3576b85c0b&pf_rd_r=19WC22EPYJCQ8ZX6BSVV&pd_rd_wg=zWaMB&pd_rd_r=d15bebb7-1cb0-4646-8508-153d25f53b4f&pd_rd_i=B09SWLFH3J&psc=1

Here is a 300 watt version. it has two adjustment potentiometers, the second one controls maximum amperage allowed.

https://www.amazon.com/Anmbest-Converter...1LQXQZPP42&keywords=dc+to+dc+buck+converter&qid=1678586835&sprefix=dc+to+dc+buck+converter%2Caps%2C135&sr=8-13

I have a 150 watt version I've yet to employ full time.
Note that to maintain these max output wattage ratings these should have 50 or 60mm fans attached to their heatsinks.

i also have 150 watt step up boost converter. input 12.0v dc, output anything higher upto about 33vdc. got one of these slow boat from China at least 8 years ago. I use it fairly regularly. I gutted an old ventilated inline power brick from I cant remember what, installed it inside with a 60mm fan, and have modified it with a external potentiometer, and a 2 decimal voltmeter capable of handling 100 volts. I use it for battery to battery charging, but also to charge some power tool batteries that are 18 or 24v. Anderson Powerpoles for input and output, but also a 4 pin computer fan connector too. It has greatly exceeded 150 watts unintentionally.

In my weaker moments i wish I had a 300 watt buck boost converter inside the casing with fans and voltmeters and ammeters and dual fingertwist dials for voltage and amperage adjustments, but I really don't have an immediate need for such.

I have several 24vDC fans. For these, I speed control them with a 10 amp combo buck/boost converter. My papst fan as a range of 7.44 to 30 volts and I use the amperage potentiometer to limit voltage to about 30 and retasked a small blue pot to keep minimum voltage above 7.33 for the one fan and ~9v for the other. The fans can handle more but they dont really spin faster, just consume more significantly more amperage . There are not a lot of these combo buck boost converters available. I've had no luck with the smaller ones rated for 5 amps. Smoked them all. no issues with the unit shown here:

https://www.amazon.com/XINGYHENG-High-po...rd_w=Dfhdn&content-id=amzn1.sym.c283371f-7974-465c-b809-831433e1ef42&pf_rd_p=c283371f-7974-465c-b809-831433e1ef42&pf_rd_r=H0Z27X27XFMF7RD311NE&pd_rd_wg=ZbgcT&pd_rd_r=4bcaf56f-f4dc-454f-8148-a939232f5fad&pd_rd_i=B08LZ2RWC1&psc=1

I've got one of these^ powering two 24v fans, and one powering my clamp papst fan, and one backup waiting to be employed.

Here is the other 8/10 amp buck boost converter I own. It works and has been reliable, but is bulkier and.

https://www.amazon.com/Converter-1-25-30...rd_w=ifIFy&content-id=amzn1.sym.6953b182-f957-43e6-9fe3-866e180e1e05&pf_rd_p=6953b182-f957-43e6-9fe3-866e180e1e05&pf_rd_r=JGGR4ZVA45TR347FSRQ6&pd_rd_wg=cYG1V&pd_rd_r=65a1fae5-041c-4669-aec5-81711b5990a3&pd_rd_i=B08HS76XG1&psc=1

I've not found any higher amperage/wattage buck boost converters. many product descriptions say they do both buck and noost, but then they are either just buck or boost, not both. I've even been sent one which was buck only and the seller said keep it then sent me the combo unit with an apology, they look the same but the buck only had just one potentiometer..

Removing the little blue potentiometer to solder in wires to circuit board for finger twist voltage adjustment, takes some practice and soldering skills but is not really difficult. I think I elaborated on this process somewhere here, a few tricks to make it go simpler.

I avoid inverter use, whenever possible.

This seems to be a new offering, 20 amp buck boost step up step down converter. I suspect is buck or boost but not both, despite the description.
https://www.amazon.com/Dc-Dc-Converter-A...D3T2P9JX38&keywords=buck+boost+step+up+step+down+converter&qid=1678589443&s=industrial&sprefix=buck+boost+step+up+step+down+converter%2Cindustrial%2C113&sr=1-20
[-] The following 1 user says Thank You to sternwake for this post:
  • rvpopeye (03-12-2023)
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