Installing a DC-DC Converter (aka alternator charger or DC-DC Charger)

[Area 51]

Since the AC is rectified into DC I am not worried about the LiFePo4 batteries, rather the electronics that convert the AC to DC. Every power station manufacturer will tell you not to plug it into a modified sine wave inverter because the modified sine wave may damage the electronics. I've got a similar Fniri unit arriving Sunday and will be checking out the inverter waveform and noise. I'd rather spend a little money on a DC to DC charger than risk destroying expensive portable power stations.

Can't take a sine wave vs square wave at the same voltage and frequency = low end cheap component min design.
Same for same a square wave is more wattage or power vs a sinusoidal wave. The square wave is al harder on power components, on and off more abruptly. Steep wave front.

 

[KurtW]

Are we over thinking this issue? The latest portable power banks are designed to be plugged into standard AC wall outlets in pass through mode or to act as a UPS. How many of those outlets have pure sine wave output?

An alternator charger is certainly nice to have as another and possibly simultaneous power input. However, unless you are permanently charging the power bank through the LC, I wonder if the alternator charger is worth the expense and effort? Is it wise to add another tap off the hybrid system if not absolutely necessary? Also, keep in mind the Ecoflow alternator charger is max 800 watts which is roughly 1/3 the max charging rate of the LC inverter.

Overall, I really like the alternator chargers in general. Just raising questions.

US grid power provides a pure sine wave, unless there are distortions from equipment or other issues.

Are we overthinking it - perhaps. However when it comes to expensive equipment that isn't designed for abuse I'd rather overthink, overplan and overtest.

 

[Area 51]

US grid power provides a pure sine wave, unless there are distortions from equipment or other issues.

Are we overthinking it - perhaps. However when it comes to expensive equipment that isn't designed for abuse I'd rather overthink, overplan and overtest.

The loads create the problems not inherent to the grid sourced power.

 

[Markarian421]

There are some glitches after it crosses zero but the rest of the curve is pretty smooth.

 

[KurtW]

There are some glitches after it crosses zero but the rest of the curve is pretty smooth.

View attachment 24556View attachment 24557View attachment 24558

is this the waveform from the Landcruiser inverter?

 

[Markarian421]

The loads create the problems not inherent to the grid sourced power.

Yeah, to this point, the total voltage swing on the Land Cruiser's outlet with no load was just a little higher than at a wall outlet. It would be interesting to see what it looks like with a load on it. Hmm maybe I'll have to go boil some water.

 

[Markarian421]

is this the waveform from the Landcruiser inverter?

From the outlet in the back, yes.

 

[KurtW]

From the outlet in the back, yes.

View attachment 24562

You have just saved me a lot of time and money!!!! That's close enough to a pure sine wave for my comfort. Now on to spend money on a roof shelf for the LC

 

[Area 51]

There are some glitches after it crosses zero but the rest of the curve is pretty smooth.

View attachment 24556View attachment 24557View attachment 24558

I can't guesstimate if its simple switching or a PWM type sine wave.
If you open up the sweep rate a bit and look at the top of the wave form maybe focus on opening up to see the ripple better?
Looks like filter notches.

An Overview of Inverter Waveforms and Comparative Analysis - Solar PV Power Station Research

An inverter is a device that converts DC (direct current) power into AC (alternating current) power. Its output current's size and direction are regulated by the input AC power's voltage and phase. When fed with DC power, the inverter processes it to create an output current displaying various...

www.aimspowerinverters.com

 

[MSINAL]

From the outlet in the back, yes.

View attachment 24562

Thank you for taking time to do this. Remarkable result.

 

[Markarian421]

I can't guesstimate if its simple switching or a PWM type sine wave.
If you open up the sweep rate a bit and look at the top of the wave form maybe focus on opening up to see the ripple better?
Looks like filter notches.

An Overview of Inverter Waveforms and Comparative Analysis - Solar PV Power Station Research

An inverter is a device that converts DC (direct current) power into AC (alternating current) power. Its output current's size and direction are regulated by the input AC power's voltage and phase. When fed with DC power, the inverter processes it to create an output current displaying various...

www.aimspowerinverters.com

Well here's a real horror show of UPS waveforms:

Database of UPS inverter output waveforms (updated)

The LC's form looks a lot like this Eaton model: https://www.eaton.com/gb/en-gb/skuPage.5P1550I.html

And now the question is will I actually get anything done on my Land Cruiser today or will I just go around measuring waveforms from all the UPSs and batteries in the house . . . (we have PG&E for power -- our power goes out a lot while PG&E burns down lots of stuff).

 

[KurtW]

Well here's a real horror show of UPS waveforms:

Database of UPS inverter output waveforms (updated)

The LC's form looks a lot like this Eaton model: https://www.eaton.com/gb/en-gb/skuPage.5P1550I.html

And now the question is will I actually get anything done on my Land Cruiser today or will I just go around measuring waveforms from all the UPSs and batteries in the house . . . (we have PG&E for power -- our power goes out a lot while PG&E burns down lots of stuff).

The answer is no, you've dived deep into the rabbit hole, my friend! It will take at least 24 hours to claw your way out.

 

[KurtW]

From the outlet in the back, yes.

View attachment 24562

My cheap scope arrived yesterday and this morning I checked out the waveform. My scope is not close to capability or precision as your however I had almost identical results. I consider that definitive - the inverter will be fine for charging portable power stations and power other electronics.

Thank you for your answers!

 

[Markarian421]

My cheap scope arrived yesterday and this morning I checked out the waveform. My scope is not close to capability or precision as your however I had almost identical results. I consider that definitive - the inverter will be fine for charging portable power stations and power other electronics.

Thank you for your answers!

I'm curious about that scope! It looks way more portable than mine!

 

[KurtW]

I'm curious about that scope! It looks way more portable than mine!

It is pocket sized but with pretty decent features: Amazon.com

You can get it cheaper on AliExpress however I didn't want to wait 10 to 14 days for it.

 

[Markarian421]

It is pocket sized but with pretty decent features: Amazon.com

You can get it cheaper on AliExpress however I didn't want to wait 10 to 14 days for it.

Debugging stuff at home, 90% of the time I just hit the "autoset" button on mine and that's good enough, so something like this would probably do the job most of the time. I have a way fancier one at work for looking at imaging sensor timing signals and such, plus lots of more typical ones. But I got tired of having to drag some power supply or whatever to work to figure out what was going wrong.

 

[KurtW]

Debugging stuff at home, 90% of the time I just hit the "autoset" button on mine and that's good enough, so something like this would probably do the job most of the time. I have a way fancier one at work for looking at imaging sensor timing signals and such, plus lots of more typical ones. But I got tired of having to drag some power supply or whatever to work to figure out what was going wrong.

It has been decades since I used a scope at all; I need to relearn the basics of how to make the most use of it. Yay, another project (sigh).

 

[Markarian421]

It has been decades since I used a scope at all; I need to relearn the basics of how to make the most use of it. Yay, another project (sigh).

It's been nearly a decade since I used one a lot at work. We really built up our EE department, why have a physicist bumbling around on that stuff when you've got electrical engineers!