I need a new inverter, should I invest little more and upgrade to All-In-One unit with it?

[teemust]

So I need to upgrade my inverter, it has been working fine but is a chinese 1500w/3000w, only take 1kw constant and definitely not more than 1500w even as surge.

I use normal 220v dorm fridge which pulls around 1kw when cycling. So if I use my computer at the same time, its a risk that when it filps out on me.

I am a student who lives in a RV build. So money is of issue right now..

So should I put under 400€ for a new inverter (giandel 24v 3000w is now around 355€+shipping) or should I look for around the same money for "hybrid/off-grid" inverter.. or buy a 24v fridge but in here where I live (Finland) they are +600€ for a size I can live with...

I have been looking for the chinese markets but the quality is again the issue.

Isolar SPH or Vevor hybrid or Powmr is what I have been found.

 

[time2roll]

Since the inverter is working are you sure the battery cables are large enough that the shut down is not from voltage drop?
Same for the battery is adequately sized to provide the needed power without a low voltage error shut down? Especially when low on charge.
Could be a combination of both.

If you have some extra wire, consider doubling up the cable and see what happens.

Consider getting the larger wire for the larger inverter first and connect to the existing. Worst case the wire is in place ready for the new inverter.

 

[fafrd]

So I need to upgrade my inverter, it has been working fine but is a chinese 1500w/3000w, only take 1kw constant and definitely not more than 1500w even as surge.

I use normal 220v dorm fridge which pulls around 1kw when cycling. So if I use my computer at the same time, its a risk that when it filps out on me.

I am a student who lives in a RV build. So money is of issue right now..

So should I put under 400€ for a new inverter (giandel 24v 3000w is now around 355€+shipping) or should I look for around the same money for "hybrid/off-grid" inverter.. or buy a 24v fridge but in here where I live (Finland) they are +600€ for a size I can live with...

I have been looking for the chinese markets but the quality is again the issue.

Isolar SPH or Vevor hybrid or Powmr is what I have been found.

What battery voltage are you using, what gauge wire for the battery cables, and how long are they?

 

[Tomthumb62]

I use normal 220v dorm fridge which pulls around 1kw when cycling.

So should I put under 400€ for a new inverter (giandel 24v 3000w is now around 355€+shipping)

So keep in mind that a larger inverter will have a bigger idle draw. Roughly speaking, can vary quite a bit by model:

1000W inverter = 10-12w idle draw
2000W = 20-24w idle draw
3000W = 30-34w idle draw

This means that when the inverter is turned on and is ready to provide power any given moment a connected device asks for it, this is what the inverter uses from your battery just to power itself. Might not seem like a lot, but IF you have a device that cannot afford to be powered off at night (like a fridge), then your idle draw is a 24/7 draw, which can add up and eat into your battery bank very quickly. With our previous 2000W inverter, it used 24W, or 576Wh per day. If you're running off a single 12v 100Ah battery, that would be a bit less than half of your total battery capacity...just to have a 2000W inverter powered on!!

If I were you, I would consider not replacing your inverter, but buying a second one. Find out how much juice you need to run your computer (use a kill-a-watt device to measure it) and then buy an inverter a tad bigger than you need. For example, if you measure that your computer (I assume you're referring to a desktop PC and not a laptop) uses 500W, then look for a 700W inverter.

Then hook up the second inverter and power your fridge from one inverter (which will remain on 24/7) and your PC from the second inverter (which you will turn off when you're finished with your computer). This would save you money and reduce your idle draw by not going up to a larger inverter, which would need to remain on 24/7. You might even find that the fridge can run just fine from the 700W inverter and you'd reduce your idle draw even more since then it would be the 1500W inverter that would get powered down when you finish using your PC.

If however, you're running a laptop (not a super high-end mega desktop-replacement or gaming machine), then your current inverter will be just fine.

 

[SilverbackMP]

What about finding something used? Like a low frequency Outback 3000 watt unit (assuming this is 12v)? Not sure how common these are in the UK/Europe though.

 

[Daddy Tanuki]

What about finding something used? Like a low frequency Outback 3000 watt unit (assuming this is 12v)? Not sure how common these are in the UK/Europe though.

good idea about looking for used, but if in the EU, i would look at victron or if chineesium then the signeer power, it does have following at being a half way reliable unit and if memory serves me correctly, its the company that makes aims inverters for aims. I have one i bought as a test mule but do not have enough hours on it to comment as too quality, though others seem to like it for the price point. it seems to me that a used one could be had in his price range.

 

[teemust]

Thanks for the good ideas. My parents have a party this weekend so I am busy helping out. But will try the thicker cables on sunday.
I also somehow missed the options of second inverter, maybe just modified sine wave...

Some answers for the questions: Its a 24v system, 130Ah lifepo4 and the cables are 6mm/10awg.

 

[fafrd]

Thanks for the good ideas. My parents have a party this weekend so I am busy helping out. But will try the thicker cables on sunday.
I also somehow missed the options of second inverter, maybe just modified sine wave...

Some answers for the questions: Its a 24v system, 130Ah lifepo4 and the cables are 6mm/10awg.

You didn’t provide the length of the cables.

If we assume 5 feet for each, 10 feet round-trip in 6AWG = 4mOhms.

Sounds as though you are looking for more than the 1500W surge you are getting.

If we target 3000W and assume your cheap Chinese inverter has 80% efficiency, 3000WAC out needs 3750WDC in which is 150A @ 25VDC.

150A through 4mOhms is an 0.6V drop.

Plus, with a LiFePO4 battery there will be some internal resistance which will droop voltage even more upon current surge.

Drawing 150A from a 130Ah battery is exceeding 1C which is almost certainly contributing to your issue.

So if it were me, I’d get ahold of a multimeter and characterize voltage drop as a function of output power, both through your cables and through your battery.

Between minimizing voltage drop through your battery cables and adding a second 24V LiFePO4 battery in parallel, your inverter could be fine…

What is the low voltage disconnect setting of your inverter and is the failure you are concerned about associated with the inverter cutting out or the BMS shutting down the battery?

 

[time2roll]

#10 wire is too small. Double would be minimum. Triple is better. I would have #6 with existing inverter if spending money.

I don't think you need a new inverter. The LFP battery should be fine with existing. Just need better wire.

 

[fafrd]

#10 wire is too small. Double would be minimum. Triple is better. I would have #6 with existing inverter if spending money.

Wow, thanks for the catch - I misread 6AWG instead of 6mm (10AWG).

To deliver 1500WAC, 1875WDC or 75A @ 25VDC is needed for an inverter with 80% efficiency.

75A means you need a breaker sized at 90A and wire gauge should be sized for at least 108A, meaning 6 AWG.

He’s talking about increasing peak output power to 3kW, and that would need a wire rated for 216A, meaning 1 AWG or even 1/0 AWG.

My advice to the OP would be to invest in proper battery cables for your maximum target output power first and then reevaluate whether you existing inverter is sufficient or not.

10AWG has resistance of 1 mOhm per foot, so 10 feet round-trip is 10mOhms which will drop 0.75V when carrying 75A (in addition to being unsafe).

1/0AWG has 0.1 mOhm per foot of resistance, so 10 feet round trip is only 1 mOhm which will drop only 75 millivolts carrying 75A.

 

[teemust]

So, I finally had sometime to fix the cables, now they are 25mm2/4awg and very short, around 0.5m/2feet. It helped, I can pull just shy of 1900w but as I hit more the inverter starts to peep and maybe around 15seconds it shuts off.

And if I pull more than 2300w it shuts off in a second.

But now I am happier with it. Now if the fridge cycles I am quite sure it will be fine.

 

[pollenface]

Glad to read of your success

 

[fafrd]

So, I finally had sometime to fix the cables, now they are 25mm2/4awg and very short, around 0.5m/2feet. It helped, I can pull just shy of 1900w but as I hit more the inverter starts to peep and maybe around 15seconds it shuts off.

And if I pull more than 2300w it shuts off in a second.

But now I am happier with it. Now if the fridge cycles I am quite sure it will be fine.

If you use a multimeter to check voltage at the inverter end of those battery cables, you’ll probably see that at 1900W you are getting close to Low Voltage Disconnect (Low Voltage Warning) and at 2300W you are under…

Sounds like you are already good with close to 1900W of peak but if you ever have a need for more, you’re 4 feet (round trip) of 4AWG cables has a resistance of 1.0mOhm so you are dropping 115mV in those wires when drawing 115A to deliver 2300W @ 80% efficiency.

The resistance of 1/0 wires is only 40% that of 4AWG, so outputting 2300W would only drop battery voltage by 45.5mV (69.5mV higher voltage at the inverter).

When you are outputting 1900W with your 4AWG cables, the cables are dropping 95mV, so cabling losses from 2300W w/ 1/0AWG are less than half that or cabling losses of 1900W w/ 4AWG…

Of course, this assumes the internal resistance of your battery or the contact resistance of your connections is not as large as the 1mOhm cabling resistance presented by your 4AWG cables.

If you measure the total voltage drop powered versus unpowered at both ends of the 4AWG battery cables, you can get an idea of how IR+CR compares to cabling resistance.

Best to do that at a few different power levels and graph the results as there are usually some ‘surface effects’ that can represent an unrealistically high resistance from 0A to any continuous amperage.

So data comparing the voltage drops at both ends at 1800W versus 1200W versus 600W, for example, is the best way to get a swag of how much you might gain from larger cables (or if you’d be better served by putting some effort into reducing contact resistance, example).