Power Inverters

Most inverters deliver a "modified" sine wave which can be quite a mess electrically speaking. What you get out of a standard 115VAC wall socket is a sine wave with noise on it. That's usually good enough for most things.

It's quite possible that you have some electrical issues with both the microwave and printer. I used to get HP printers and use them, until one decide that it just wasn't going to work with my inverter. Plug it in the wall socket, and hey presto! - it's working. Inverter? Nothing. No problem at all with Lexmark and Cannon branded printers.

 

So if would have some electrical issues with microwave and printer why with the old inverter(that I still use right now) I dont have any issue whatsoever and never ever had no matter what appliances I plug into. Just a thought !

 

It's a wierd electrical compatibility thing that I used to run into. Generally it involves what we call "impedance mismatches." It means that one side or the other is loading down the circuit just enough to make it inoperable. Another problem could be part of the input circuit to the applicances has been damaged that results in the same sort of behavior. Best bet might be to go back to ThermoKing and ask them for a different inverter.

 

Looking for a good 2000 watt inverter. I have now been through 2 Whistler Pro 2000w inverters in one year. I think they overheat. It may be poor fans but I am not sure. First one worked great for almost exactly a year, second one failed after about 2 months. Cannot find anyone to fix them so back to square one. Only reason I need 2000w is my Kurieg Coffee maker that I am not willing to give up, (ever) Any suggestions? Do I really need to spend a boatload to get a good inverter? Paid about $180 for these on Amazon

 

Maybe a larger inverter would work? Might seem like overkill but it would put less stress on it and make it last longer. Like I said before, it won't ever hurt them to replace the fans with better ones when you get them. The electronics can be fine in these things but for some reason they go with the cheapest crappiest fans they can possibly find.

 

I've noticed a recurring issue while looking through this tread: the advertised wattage VS the actual wattage of an inverter.
It was often suggested that an inverter should be rated about twice what you need for it to work. For example, a 1000W heater should run fine off a 2000W inverter.

I'll explain why this issue keeps coming up: the sine wave.

A modified sine wave inverter won't give out power like a household-power outlet; it will turn the DC power into something similar to AC power. Your appliance will recognise the power as AC but will only "understand" it to a certain degree. The quality of the power, how close it gets to 100% AC, depends on the brand. We call that the "AC output efficiency".

Now, most devices you would need in a truck will work on a modified sine wave. Unless it is something very sophisticated, like medical equipment, it will work. High-tech gadgets actually use the pure wave to synchronise their functions, like using a ticking clock. If you are not driving an ambulance, a pure sine wave is, more often than not, not worth it.

On average, a modified sine wave inverter will deliver usable power at an efficiency of around 60% that of household AC. Again, that depends on brand. (Pure sine is near pure AC, so this doesn’t apply)

So, for a modified sine wave inverter the AC output efficiency will tell you just how good the inverter is and just how much you can trust it to deliver the power you need. If the power delivered is only 60% as efficient as household power, then you need twice as much. It will also have a tendency to heat up (a lot).

I suggest checking for the average efficiency. Most brands will advertise a “Peak” AC output efficiency, which is measured while running something of low wattage. This is, as you might expect, an inflated number. What is important is the average output efficiency with a large load, near the maximum of the inverter. Some truck ready (or truck approved) inverters will be able to provide around 90% AC output efficiency. Unfortunately, there really is very little chance of finding that out unless you try it or rely on trust.

If you have any questions, feel free to ask!

P.S.: On another matter, I would advise against settling for lower gage cables or cheap connectors, if you are going to plug something up on your batteries, specially an inverter. They tend to draw a lot of power and your cables might not be able to stand it for a long time. It is downright dangerous.

 

The "advertised" power output on a UL listed unit is the actual power output whether the output waveform is a pure sine wave or a modified sine wave. If the units performance doesn't match the advertised spec, UL won't list the device. PERIOD. The usual rule of thumb when specifying a DC-AC converter is to double the available power output compared to the average demand load to make up for power surges at appliance start-up, load surges, etc. If you match a load to the inverter at a 1:1 match, you're liable to encounter output circuit protection shutdown events, especially as the electronics age.

 

I read few times what Alex-Tundra and ironpony psted and it was like I was trying to read something written in chinese. I envy u gentlemen for ur knowledge.
My question is : should I put in the garbage my Thermoking inverter or the thing can be tricked to work ?

 

The laser printer probably needs a Pure-Sine wave inverter to work. It is one of the devices that is often listed as an exemple of a machine that would not work off a modified sine wave inverter. There is no way to make a modified sine inverter produce pure sine, so tricking is into doing that is not possible.

The microwave and the boiler combination...that's very strange. Both items should work with modified sine wave, though maybe not at the same time, with the power your unit is supposed to provide. I can make a few guesses:

- Either: the inverter doesn't recognise the microwave as a charge, essentially, the "brain" of the inverter doesn't understand your microwave needs power. It understand the needs of the boiler, however, and then understands the microwave while it's running.

- Or: the inverter doesn't provide a sine-wave good enough to run the microwave. However, when you increase the charge on it, by using your boiler, it provides a slightly different sine wave and ends up making the microwave work as well.

In both cases, I'd say your inverter is the problem. But then again, these are only guesses...

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As for the AC output efficiency, I'm not talking about the "peak watts" and "continuous watts", for which you are entirely correct. I'm talking about efficiency.
AC output efficiency is not how many watts, but how good those watts are (well, not exactly, but it's the simple way of saying it) for your machine, how well they will interact with the AC circuits of your equipment.

For exemple, imagine trying to cut down a tree with an axe. You will be putting just as much power into your swings whether or not it is sharp. But you will do a much better, and much faster, job if it is.

I hope this clears things up!

 

Thank u very much sir for making me understand the things. I will try another Thermoking inverter.
Now another question: in order to make my laser printer work I will need a pure sine wave inverter ....am I right ? If the answer is yes can u name a brand that u vouch for as a pure sine wave inverter(no bull) ?
Thanx again.