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Why Do DC Inverters Damage Items?

ryevick

Mar 7, 2017
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I'm new to all of this. I just want to find out why some products (particular, heating pads) will not work with a power inverter in a truck and in fact get damaged by them. Is there some type of adapter I could do to eliminate this problem?

I really need to find a solution. I had an older one that worked with an inverter for years and since it gave out I can't find a replacement.
 

bertus

Moderator
Nov 8, 2019
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Hello,

Do you have details on the used inverter?
It sound like the output voltage is varying with the change of input voltage.
The regulation of the output voltage seems not to work well.
What is the input voltage range of the new inverter?

Bertus
 

crutschow

May 7, 2021
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Does the heating pad have any electronics or is it a simple ON/OFF type.
The electronic type could be damaged if the inverter generates a quasi-sinewave and not a true sinewave.
 

ryevick

Mar 7, 2017
7
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Mar 7, 2017
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I don't have the model of the previous inverter. The one that I may be using in the near future is a Cobra Electronics CPI 1575 - 1,500 Watt Power Inverter. I'll list some specs below.

The heating pad was a Sunbeam XLarge King XpressHeat 6 with Heat Settings. Sunbeam said the heating pad was not to be used with a power inverter but I'm sure that must be because the problems caused by the inverters. It doesn't make sense that a proper power inverter would not work fine with it.

I need to make whatever changes that I need to make to have this functional on the road.

Inverter Specs (This is one I own and MAY NOT BE THE ONE THAT CAUSED THE DAMAGE)
Specifications •
Continuous output power (1 hour) . . . . . . . . . . . 1500W
Surge rating (0.1 second) . . . . . . . . . . . . . . . . . . 3000W
Peak efficiency (12V – 1⁄2 load) . . . . . . . . . . . . . . > 88%
Efficiency (full load, 12V) . . . . . . . . . . . . . . . . . . . > 83%
No load current draw . . . . . . . . . . . . . . . . < 0.6A (12.6V)
Output waveform (resistive load) . . . Modified sine wave
Output frequency . . . . . . . . . . . . . . . . . . . . 58HZ – 62HZ
Output voltage . . . . . . . . . . . . . . . . . . . . . . 109V – 120V
USB output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5V
Input voltage . . . . . . . . . . . . . . . . . . 10.4VDC – 14.4VDC
Alarm voltage (unload) . . . . . . . . . . . . . . .10.2V – 10.8V
Shutdown voltage (unload) . . . . . . . . . . . . . 9.2V – 9.8V
Operating temperature range . . . . . . . . . . . . 0°C – 40°C
(32°F – 104°F)
Storage temperature range . . . . . . . . . . . . -40°C – 85°C
(-40°F – 185°F)
Protection . . . . . . . . . .Overload, short-circuit, overtemp,
reverse polarity, under/over voltage
Notes
All protection is automatically recovered.
To protect the battery, if the unit needs to be restarted
after low voltage protection, the voltage of DC input
should be above 12V.
To extend the life of the fan, it will stop when there is no
load. The speed of the fan increases as the load increases.
The unit is completely insulated in input and output for
added safety.
 

Kiwi

Jan 28, 2013
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From your posted inverter specs..."Output waveform (resistive load) . . . Modified sine wave".
Manufacturer manual states... "not to be used with inverters".

Looks like the electronics in the controller require pure sine wave AC from mains, not the rounded off square wave produced by your inverter.
I would expect them to advise if a pure sign wave inverter is a suitable power supply, but they don't.
They also advise that generators are not to be used, so I suspect the electronics are rather fussy in regards to power supply.
 

ryevick

Mar 7, 2017
7
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Mar 7, 2017
Messages
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From your posted inverter specs..."Output waveform (resistive load) . . . Modified sine wave".
Manufacturer manual states... "not to be used with inverters".

Looks like the electronics in the controller require pure sine wave AC from mains, not the rounded off square wave produced by your inverter.
I would expect them to advise if a pure sign wave inverter is a suitable power supply, but they don't.
They also advise that generators are not to be used, so I suspect the electronics are rather fussy in regards to power supply.

I'm looking at some smaller 300 Watt Pure Sine Wave inverters to maybe use just for the heating pad. Like I said before I don't know a lot about this stuff but how could a Pure Sine Wave inverter not work? That's as good or better than a lot of home outlets isn't it?
 

kellys_eye

Jun 25, 2010
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I've been changing all my gensets to inverter-types, they now all have a 'pure' sine wave output. Although I haven't had any particular issues with waveform distortions (either via a modified sine wave or harmonics) I run a lot of compressors as well as electronics on-site and don't want to risk damage.

The cheaper the equipment the less well 'smoothed' (filtered) the output too so eliminate this as an issue by going for 'pure' sine wave right from the outset. It may cost a little more but the old adage "buy cheap, buy twice" still applies.
 

ryevick

Mar 7, 2017
7
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Mar 7, 2017
Messages
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I've been changing all my gensets to inverter-types, they now all have a 'pure' sine wave output. Although I haven't had any particular issues with waveform distortions (either via a modified sine wave or harmonics) I run a lot of compressors as well as electronics on-site and don't want to risk damage.

The cheaper the equipment the less well 'smoothed' (filtered) the output too so eliminate this as an issue by going for 'pure' sine wave right from the outset. It may cost a little more but the old adage "buy cheap, buy twice" still applies.

Since you mentioned it, I recently purchased a Champion 3650-Watt Dual Fuel Generator for simple home backup use and after reading a few things, purchased a Tripp Lite ISOBAR6Ultra Isobar 6 Outlet Surge Protector. What I read said to use something like this that is UL rated if you needed to power something like a computer via a generator. It says it is Certified to meet strict UL standards (UL 1449 4th Edition).
 

crutschow

May 7, 2021
448
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A surge protector won't improve the waveform from the inverter.

It might be cheaper to see if you can find a heating pad without any electronics (if they still make them).
 

roughshawd

Jul 13, 2020
190
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Jul 13, 2020
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Basically, an AC wave form is a sine wave, where the Positive and the Negative are primarily the same in each sweep. Problem is that DC is only the very top of the positive wave in an AC flow. When you take a device that is designed to work in a "modified sine wave" and you dump direct current into it, it is expecting each power flux to have a negative flux of the same current, and when there is it is supposed to dump the + current to ground, before the next power dump. I would assume that the circuit they designed is fairly simple, and requires this - dump to keep the components from burning up, or the returning - dump drives a set of meters that keep everything in working order. Personally, my teachers were always testing the devices to see if they worked or not, if you can afford another pad, then try it out, it might work. but don't trust it, because it might work a while, then burn up your entire fortune!!!
 

Audioguru

Sep 24, 2016
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The name Sunbeam and the logo are the same as the Chinese garbage batteries sold cheaply in "dollar" stores.
Poor quality does not last long. But Amazon replaces anything they sell.
I wonder how many people return the junk then it is replaced with more of the same junk?
 
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