120V Bed Outlet waveform/etc.

A good laptop switching power supply like those provided by Dell, HP, Sony etc.; or quality cordless tool charger; should run fine from a cheap inverter, as will most newer TVs and other consumer electronics. If the connected device buzzes loudly or smells/runs hot there is a problem.

FWIW most inexpensive back-up power supplies for computers/etc.--often called a UPS (Uninterruptible Power Supply, but they aren't really¹)--also use this so-called "modified sine wave" output, that is really a stepped square wave poor approximation of a sine wave.

This is a typical SOHO "UPS" switching from AC to backup power:


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¹ - The output of a true UPS is the inverter's output with the AC input converted to DC and used to operate the inverter and keep the battery(s) charged. They do not "switch over" to the battery when power fails as they are always running from the converted DC or battery--hence their output is truly "uninterrupted". True UPSs also almost always have pure or near pure sine wave outputs. If you can find one being surplussed it can be a less expensive way to get a sine wave inverter by cannibalizing its components.

 

Where is the inverter and has anybody replaced it? I won't use modified square wave ever, for anything so it's useless for me unless I find another use for that connection or swap the inverter.

 

It's underneath the rear box of the center console:

 

Ahhhh so that's what the vents are for back there. I'm going to see about replacing that with a slightly larger PSW inverter, thanks for the info!

 

Someone has looked into it, and it's not very practical. I believe it had to do with the size of the wire necessary to handle that long of a run, and it's just more cost effective to buy a standalone inverter that clips to the battery. If you try it though, that'd be neat!

 

It's the first thing I used to look for in UPS's, Our's were monsters. They would run whole racks on a true sine wave. I have a cheapo inverter that I use to charge small items like batteries. It's old and makes a lot of noise.

 

In the last server room we set up the all AC power and the UPS units was in separate room kept at 85° F, two firewalls away from the actual server room--nothing but 48 VDC in the server room--servers, routers, switches, lighting, everything--kept at 76° F. Climate control costs were cut nearly in half as compared to having the backups and AC powered servers in the same room...

 

Thats an excellent idea. Too many server rooms I have worked in used so much power to keep everything cool.
I however don't care much anymore, retired.

 

Me too, since April of 2016. That was literally the last IT project I managed...

 

Yay.

 

New guy here raising an oldish thread sorry but you all seem to know a lot about the inverters after my searching. My question... I have an unplanned trip coming up next weekend and want to take my new to me 2012 TRD Sport with me to show it off. I have an Edgestar 12 Volt DC / 110 Volt AC refrigerator. I use this in my camper trailer. This trip I will not take trailer so... The bed of the truck has the 110V inverter outlet but don't see a 12VDC outlet. My question is does the inverter powering the Refrige with AC use a lot more Battery power than if I run a straight 12volt socket? I use the refrige in my Jeep on just 12v and it is fine overnight as long as I drive daily. I have replaced my stock battery with a group 31 Odyssey in Tacoma. Only going to be out 2 nights.
Does anyone have experience running a refrige and should I run a 12v or is the 110v OK? ( I always carry a jump starter)

 

If your fridge was designed to run on 12 volt (I suspect it was), then yes it will use more power if run through the inverter. Inverters are not terribly efficient, meaning that there is power loss in conversion to 12v DC.

Edit: found this on a quick search: "High quality sine wave inverters are rated at 90-95% efficiency. Lower quality modified sine wave inverters are less efficient - 75-85%."

The high quality inverters they are talking about are "pure sine wave" inverters

 

I agree powering the fridge from a 12 V source is the way to go.

However my experience with cheap low power inverters, like the one in our trucks, has been that achieving 75-85% efficiency from any "not a sine wave at all" inverter would be a best case scenario;, at higher loads 50-60% efficiency is not unusual...

 

Another consideration, most likely the refrigerator actually runs on 12 VDC and the 120 VAC is run through either an external AC-->DC power supply--which if running from AC just adds another layer of inefficiency...

 

On another site a member reminded me ( I did not know) the 110V inverter does not run at all when engine is off. So I guess I will run a 12VDC adapter to the bed even if for only this trip!!! These sites are a life saver

 

A couple things that were actually missed here and I want to touch on them for future reference. Our inverters are modified square (or sine if you prefer though less accurate) wave, they're kinda nasty or as I like to call it dirty power, I avoid them at all cost for many reasons from my own personal health to the longevity of the product it's powering. So in short, I would use it last resort only and not if you have another option.

Also, an inverter can be far more efficient than a 12v option in many situations. If you're running power over any distance you're better off switching that power to AC first. Also, there is no energy star rating for DC applications so in many cases the items are inefficient. In these cases the power savings of an energy star rated item far make up for any conversion losses. In my case, I converted a 5cuft energy star chest freezer to a fridge and ran it from a 24v inverter (far better than a 12v system) and this unit only pulled 12w per hour which is incredibly low.

So there are some cases where you do yourself well to explore options.

 

I had thought the "modified sine wave" issue was pretty much covered in my initial post here, and followup here. What did I miss?

The low voltage DC v. AC transmission distance issue is real however it would take a lot more than the 15 to 20 feet I would expect people here would be carrying the power for it to be a practical concern.

I do agree that many newer appliances are quite efficient--I just replaced a 28 year old "50-pint/day"dehumidifier that ate up 860 W running with a new unit the consumes just 320 W...

 

Sorry I should have qualified that comment to be specific to the new string of replies not the OP as you mention them being MSW versus PSW though you didn't mention how dirty MSW is if I recall.

Also, in terms of DC power a 20 foot run is HUGE!! If you're talking 14awg wire which would be common at 15 amps that would be a 10% plus voltage drop which would take a 12V system down to basically dead. Not many people are doing 2awg wire which is really what you would need in a run that long.

Wow, not sure how much that thing runs per day but that's a HUGE power savings! At 10 hours a day that's roughly a $20 a month savings!

 

It's in my electronics lab in the barn (about 8 x 16 feet) and runs quite a bit here--probably 6 to 8 hours a day actual runtime in the more humid seasons.

I often tend to forget things like that "normal" people would try to pull 15A DC, 20 feet (which is really 40 ft.) through a 14 AWG cable--it would never occur to me to try...

 

Not to hijack thread, but I too am retired IT, December 1st, 2015!

To add just a bit to the thread, I had a portable genset that was so "dirty" it made a ceiling fan buzz. I have switched over to Honda inverter gensets and the power is clean enough that I have had no problems. I no longer have access to a scope so I'm not sure how "clean" they are.

I have done so very little with the outlet in my truck that it doesn't really affect me one way or another.