3000 watt inverter moditied sine wave any recommendations

aldinga · Member

3000 watt inverter moditied sine wave any recommendations

Mike Harding · Guru

3000W / 12V = 250A

www.prysmiancable.com.au/wp-content/uploads/2014/12/TechCG_2015-AU-v4_LOWRES.pdf

So 70mm csa cable is called for. This has 0.68mV/m/A voltage drop 0r 170mV for 1m length (x 2) plus the drop across connectors.

So keep the inverter *very* close to the batteries and check it has the facility to correctly terminate 70mm cable (I doubt it) before you buy.

My 100Ah Powersonic AGM battery shows a discharge time of 19m at a rate of 99A so you'll about 300Ah fully charged to get even a few minutes use.

Currents this high are impracticable in domestic environments. I'd find another way to do it.

T1 Terry · Guru

About the only thing a modified sine wave inverter is good for is resistive loads like a kettle or electric heater etc, can't run electronic appliances off it or electric motors unless they are brush type without causing serious damage to the equipment and/or serious heating of an induction motor.
That is why they are cheap, no one wants them, Pure Sine Wave or PSW is what you need to run stuff like you do at home and you need lithium batteries if you want to drag that much current for more than a few mins, you just couldn't carry that many AGM batteries in the average RV and even a big converted tour coach would be struggling.

T1 Terry

Jaahn · Guru

Hi aldinga smile

Not very positive replies are they furious Well not going to get better from me but I will explain a few things to think about.

Modified square wave inverters were what we had when we did not have anything else better !! Now we can get FULL SINE WAVE types for not a lot more money so that is now recommended. You can run anything from them without a problem ! The old square wave types had limitations and some things do not run well on them, and may be damaged or the inverter itself may be damaged. How do you know what will happen, try them and see what fails !!! disbelief

To answer some general questions about either type of inverters.

As far as the quality of the 3000W units for sale, I would say the first is the connecting wiring supplied and the connections. I have never seen a cheap one with wires that remotely look big enough. Indeed I have never used the supplied wires with any of mine for the inverter wiring. You will need big wires and short too. They are usually self protected for overload and will cut out if too hot. The main problem with 3000W units is the voltage drop cutout protection. The combined voltage drop of the wires and the connectors added to the sagging battery voltage under that extreme load usually means they cut out from low voltage repeatedly and at a quickening rate. Your choice if you want to use one that big. You will need lots of batteries. hmm

The other thing to look at with cheap inverters is the standby current. If it is high then you must turn it off when not in use. And also using small loads may not be very efficient and use a larger current that it should. Not easy to know what the part load efficiency is as it is not usually shown. Better ones go to sleep when not used, with a very small standby current. Even better ones are auto start.

On safety note, you should know that inverters produce 240V AC and it will kill you just the same as the mains power. BUT the inverter has no earth so that is another added level of danger. You should not wire them in to the van system and should only plug one appliance in to their socket at a time.

Jaahn

-- Edited by Jaahn on Wednesday 15th of August 2018 07:01:02 PM