5kw inverter drives speakers, USB ports, and oscilloscope-meter nuts

[chess-equality]

So here goes

Only affects my 12v basic inverter. My 24v AIO doesn't have this issue.

The setup:
- 5kw 12v pure sine wave basic inverter, non-AIO, no built-in shore charger
- 4 x 200Ah parallel bank
- Monitored by Victron SmartShunt; batteries are good
- Used only as backup; powered off most of the time; batteries lightly cycled regularly.
- Load will mainly be an inverter-type air-conditioning unit 500w - 700w draw, and other electronics.
- Oscilloscope-meter shows waveform is sine wave, but the frequency is a different story (more below).

Works well with the aircon. But when I plug in my PC, static / RF noise are being picked up by the speakers, even with the power strip still turned off. The noise becomes all the louder when I turn the power strip on. And when this happens, the USB ports of the PC all stop functioning. It seems power has been cut off from the USB ports.

My PC is connected to an APC UPS, which I then connect to the power strip, which is connected to the inverter.

I did some tests; my ordinary meter says output freq. is a stable 60Hz, but in my oscilloscope-meter, freq. touches 60-70Hz for a few moments, then fluctuates from low to highs of up to 1-2 kHz (!). And the oscilloscope-meter also picks noise all around the inverter just by being near it, even if the leads are not connected (!).

I also tried using a 20-meter extension cord that is still coiled in its drum; the speaker noise gets reduced but doesn't go away, and still wrecks the USB ports.

Any ideas?

 

[Goboatingnow]

So here goes

Only affects my 12v basic inverter. My 24v AIO doesn't have this issue.

The setup:
- 5kw 12v pure sine wave basic inverter, non-AIO, no built-in shore charger
- 4 x 200Ah parallel bank
- Monitored by Victron SmartShunt; batteries are good
- Used only as backup; powered off most of the time; batteries lightly cycled regularly.
- Load will mainly be an inverter-type air-conditioning unit 500w - 700w draw, and other electronics.
- Oscilloscope-meter shows waveform is sine wave, but the frequency is a different story (more below).

Works well with the aircon. But when I plug in my PC, static / RF noise are being picked up by the speakers, even with the power strip still turned off. The noise beomes all the louder when I turn the power strip on. And when this happens, the USB ports of the PC all stop functioning. It seems power has been cut off from the USB ports.

My PC is connected to an APC UPS, which I then connect to the power strip, which is connected to the inverter.

I did some tests; my ordinary meter says output freq. is a stable 60Hz, but in my oscilloscope-meter, freq. touches 60-70Hz for a few moments, then fluctuates from low to highs of up to 1-2 kHz (!). And the oscilloscope-meter also picks noise all around the inverter just by being near it, even if the leads are not connected (!).

I also tried using a 20-meter extension cord that is still coiled in its drum; the speaker noise gets reduced but doesn't go away, and still wrecks the USB ports.

Any ideas?

Sounds like a poor quality invertor , what make is it. What are its grounding arrangements

 

[timselectric]

Sounds like a grounding issue. Especially since it's happening with the power strip off.(Only ground connected)

 

[chess-equality]

Sounds like a poor quality invertor , what make is it. What are its grounding arrangements

 

[chess-equality]

Sounds like a grounding issue. Especially since it's happening with the power strip off.(Only ground connected)

 

[chess-equality]

5000 Watt Inverter Pure Sine Wave with LCD Display Manufacturer

5000 Watt Inverter Pure Sine Wave DC to AC | Warranty: 2 Years | Brand: OEM | LCD Display | Peak Power: 10000W | Universal Socket

meindchina.com

It has an AC receptable and 3 terminals. I've strapped it in a mobile cart so that I could easily move it over; the batteries are in a trolley. How could the ground be done in this case?

 

[timselectric]

5000 Watt Inverter Pure Sine Wave with LCD Display Manufacturer

5000 Watt Inverter Pure Sine Wave DC to AC | Warranty: 2 Years | Brand: OEM | LCD Display | Peak Power: 10000W | Universal Socket

meindchina.com

It has an AC receptable and 3 terminals. I've strapped it in a mobile cart so that I could easily move it over; the batteries are in a trolley. How could the ground be done in this case?

You can try connecting a wire from the ground terminal to a known ground. (Metal case of existing equipment)

 

[chess-equality]

You can try connecting a wire from the ground terminal to a known ground. (Metal case of existing equipment)

Ok...I'm thinking of just laying a long wire to the ground rod outside, is this a good and safe idea?

 

[chrisski]

Recommend ditching the inverter and starting over.

I see so many things wrong with a 5000 watt constant 10000 watt peak inverter on a 12 volts system. There’s a couple of red flags with this inverter that I would not trust the rest of the design. These are some red flags I see:

-DC wiring too thin. I used 4/0 wiring on a 2000 watt constant inverter. The specs on this are extremely hard to read and call for a 25 mm2 DC wiring X 2, which is 2 pieces of 4 AWG, no where close to 4/0
-Too high an amp draw. A 5000 watt, 12 volt invert with a 9 volt cutoff has the potential to pull around 600 amps from the battery. The terminals in the back are not pictured very well and specifications are not published, but don’t look like they can handle that.

The entire advertisement seems as if it was run through translation software and proofread, which I’m-giving the benefit of the doubt and thinking perhaps the specs in the original language are correct but got mistranslated. It happens a lot on sites like E-Bay and alaibaba. An example would be an extra 0 being put in a solar panel claiming 300 watts of production instead of the actual 30 watts.

 

[mrzed001]

Ok...I'm thinking of just laying a long wire to the ground rod outside, is this a good and safe idea?

It is not safe ....

You have a NON ISOLATED inverter. (the All-in-one's are usually isolated to battery)

Your inverter produces floating ground power.
So if you connect one of the inverter's output to ground then on ALL battery terminals there will be AC voltage and ampere.

Sorry, I have only a Hungarian video to demonstrate it, but a picture worth a thousand words ... and so a video is worth thousand pictures.
(1 ground rod left, one rod on the right representing you ... and a non isolated inverter's one port connected to ground)

If he would touch the battery terminal ... that could mean lethal shock.

 

[timselectric]

Ok...I'm thinking of just laying a long wire to the ground rod outside, is this a good and safe idea?

Yes

 

[timselectric]

It is not safe ....

You have a NON ISOLATED inverter. (the All-in-one's are usually isolated to battery)

Your inverter produces floating ground power.
So if you connect one of the inverter's output to ground then on ALL battery terminals there will be AC voltage and ampere.

Sorry, I have only a Hungarian video to demonstrate it, but a picture worth a thousand words ... and so a video is worth thousand pictures.
(1 ground rod left, one rod on the right representing you ... and a non isolated inverter's one port connected to ground)

If he would touch the battery terminal ... that could mean lethal shock.

Connect ground terminal to ground. Not one of the current carrying conductors.

 

[mrzed001]

Connect ground terminal to ground. Not one of the current carrying conductors.

This is a 240V European inverter. Where 1 wire should be Line, the other Neutral.
Except in floating ground BOTH cables have 120V on them (compared to ground).

To solve it you need to ground one of the terminals. That will be the neutral.

 

[Goboatingnow]

There’s is no specific reason to ground the invertor other then it may help with noise. Floating output AC in itself is quite acceptable. There is no particular reason to ground the neutral if the invertor is being used as a extension lead inverter . Where yOu are feeding a full house of something that’s different. The

These cheap inverters are notoriously noisy , both locally near field RF noise and switching noise which can be coupled out into the AC or the DC or both , grounding the case may make little difference in many cases , the outputs could need additional RF filtering and so forth

 

[chess-equality]

Recommend ditching the inverter and starting over.

I see so many things wrong with a 5000 watt constant 10000 watt peak inverter on a 12 volts system. There’s a couple of red flags with this inverter that I would not trust the rest of the design. These are some red flags I see:

-DC wiring too thin. I used 4/0 wiring on a 2000 watt constant inverter. The specs on this are extremely hard to read and call for a 25 mm2 DC wiring X 2, which is 2 pieces of 4 AWG, no where close to 4/0
-Too high an amp draw. A 5000 watt, 12 volt invert with a 9 volt cutoff has the potential to pull around 600 amps from the battery. The terminals in the back are not pictured very well and specifications are not published, but don’t look like they can handle that.

The entire advertisement seems as if it was run through translation software and proofread, which I’m-giving the benefit of the doubt and thinking perhaps the specs in the original language are correct but got mistranslated. It happens a lot on sites like E-Bay and alaibaba. An example would be an extra 0 being put in a solar panel claiming 300 watts of production instead of the actual 30 watts.

I don't really intend to use more than 1kw. I just oversized it thinking that it will not be stressed too much. I have already sized the loads, but I will still monitor the draw from the Victron BT and the PDU-style power strip with a digital watt-meter.

But yes something like a Victron would be nice. It's just that, being in the Philippines, there's only one Victron dealer (and I don't think he has ready stock, and his prices are quite padded), so commissioning one (= importing) for a DIY backup seems to be overkill, and the purely Chinese brands are more accessible locally. My 24v AIO, I think it's one of those Voltronic clones.

But the Victron is tempting...

 

[timselectric]

There’s is no specific reason to ground the invertor other then it may help with noise

That's the purpose of this thread.

 

[Goboatingnow]

That's the purpose of this thread.

Yes but grounding may not change either radiated noise or AC or DC coupled noise

 

[chess-equality]

It is not safe ....

You have a NON ISOLATED inverter. (the All-in-one's are usually isolated to battery)

Your inverter produces floating ground power.
So if you connect one of the inverter's output to ground then on ALL battery terminals there will be AC voltage and ampere.

Sorry, I have only a Hungarian video to demonstrate it, but a picture worth a thousand words ... and so a video is worth thousand pictures.
(1 ground rod left, one rod on the right representing you ... and a non isolated inverter's one port connected to ground)

If he would touch the battery terminal ... that could mean lethal shock.

Interesting, will have to research more on this.

 

[timselectric]

Yes but grounding may not change either radiated noise or AC or DC coupled noise

May not, but worth a shot.
That's why I said it was something to try.

 

[mrzed001]

Interesting, will have to research more on this.

Off-grid Garage Andy had similar problems with his non isolated inverter.
He simply solved the problem and bought an isolated inverter ... did no follow up or investigation.