[waldo22]

1/0 is serious!

 

[MJSullivan56]

1/0 is seriousl.

Ya think?

 

[MJSullivan56]

Whoever here suggested 1/0 cable for a 1500w inverter is an idiot. Here’s a detail of a binding post from a 2000w inverter as compared to 1/0 copper cable. Total overkill. At most 1 gauge would be more than enough to handle such use cases. Lesson? Don’t listen to idiots on the web. YMMV.

 

[MJSullivan56]

Ok. A me culpa is appropriate here. I suggested previously that only idiots would recommend 1/0 gauge cable (or greater) for use with a 1500W 12V DC inverter. It turns out that I am indeed the idiot. Not surprisingly, there are two things at play here: the idiocy of assuming that Amazon/Alibaba products for sale on the internet had a modicum of truth to their claims. The other is the idiocy of believing in the fallacy that those with knowledge of "best practices" would understand the previous point and be able to quantify their knowledge in such a way that us mere-mortals might fully grok.

Anyway, the well-recommended Giantel 2000W 12v - 120v Inverter (that I recently purchased from Amazon) specs imply that the item can deliver 2000W continuously (as do pretty much all other similar Chinese products). The issue appears to be how one defines the term "continuously". Additionally, on YouTube there are plenty of reviews of such inexpensive Chinese inverters that convincingly show these items do in fact deliver in the real-world.

That being said, people who are subject-matter experts on the matter clearly understand that such a claim should mean, to anyone with a brain of course, that it means 24/7 CONTINUOUSLY. Duh. What else could it mean? Whereas the Chinese manufacturers of such inverters likely assume that continuously means "in the context of typical household usage of energy over the course of a day".

How do I come to this conclusion?

Well, I opened up said 2000W inverter (see attached photo) and discovered that the cabling from the exterior mounting lugs to the (obviously interior) circuit board -- where I could see with my little eye -- get this: two 10 AWG cables per circuit! (or put another way, the internal pair are only equal to a single 5 AWG cable). So we have a discrepancy here. If we assume that 5 AWG is promoted to satisfy the energy requirements of a 2000W load and if we also assume 1/0 AWG is the officially published sizing to satisfy the energy requirements of a theoretical 2000W load, then we have a discrepancy of approximately 55/20, or 2.75)

Now if we then take 24 hrs / 2.75 we end up with approximately 9 hrs. Ergo my hypothesis: the Chinese manufacturers have decided that "continuously" should mean something like: "this thing can run continuously for X hours at full load, beyond which we ain't responsible in the real world". To further simplify things, I would round that to 8hrs or 1/3 of a day (or more accurately, 1/3 of forever, or more to the point 1/3 of continuously). Which means what? That likely that the generally-assumed idea of what it means to be a "2000W 12v to 120v inverter" is a device that will work in-the-real-world "continuously connected to" most normal, ordinary, real-world, modern household loads. A mouthful, but not necessarily a lie either. A begrudging duh is somewhat in order I guess. Anyway, I believe this is the core of the discrepancy. However I'm open to further enlightenment.

Dang, after that diatribe (which felt good btw), I'm still not sure if I should keep this puppy or not? Given my use case of course...

 

[SunWizard]

Not all the chinese inverters are bad, I bought this WZRELB one, I used it daily for over a year at 1700-1800w continuous charging my car. It got better reviews than other made in china brands.

Pardon Our Interruption...

 

[MJSullivan56]

Not all the chinese inverters are bad, I bought this WZRELB one, I used it daily for over a year at 1700-1800w continuous charging my car. It got better reviews than other made in china brands.

Pardon Our Interruption...

So here’s the question: how does one know that the item you purchased a year (or two?) ago will today be any better than what I just ordered?

 

[MJSullivan56]

FWIW, here is an internal photo showing four 10AWG wires per lug going to four transformers. That is the equivalent of a single 4AWG cable which can handle approximately 200A or 2400W at 0-4ft, so I think I will keep the unit. One thing for sure: unless you are running long lengths of 12v cable, 2AWG is more than enough for a typical 2000W inverter. 1/0AWG is indeed overkill for this application. YMMV.

 

[Moe]

From wire ampacity charts:

120V x 15A (12A) = 1,800W (1,440W) 14 AWG copper 60°C residential
at 90% inverter efficiency:
12V x 167A (133A) = 2,000W (1,600W) 1/0 AWG copper 90°C minimum
fused at 170A wire rating

(80% continuous)
.

 

[MJSullivan56]

From wire ampacity charts:

120V x 15A (12A) = 1,800W (1,440W) 14 AWG copper 60°C residential
at 90% inverter efficiency:
12V x 167A (133A) = 2,000W (1,600W) 1/0 AWG copper 90°C minimum
fused at 170A wire rating

(80% continuous)
.

yeah, but the reasonably-priced "2000W" inverters generally available online clearly cannot do 80% load. That is my point.

 

[MJSullivan56]

Anyway, here’s a photo of my “2000W” inverter with 1/0AWG cables to a 175A Anderson connector.

 

[SunWizard]

yeah, but the reasonably-priced "2000W" inverters generally available online clearly cannot do 80% load. That is my point.

The inverter I linked above is one of the cheapest at around $190 and it clearly does 80% load (1600w) every day for a year for me. And its commonly available since the same one is still on ebay here after 3 years:
2000w inverter on ebay here
As I said way back on this thread don't trust most of the inverter listings, especially the ones who don't list 2 figures: continuous and surge watts. And even then you have to check independent reviews who used it at high load for at least a month. Even the WZRELB brand has different 2000w models, and maybe this one is better since it has 2 cooling fans.

I used 1/0 cables as all the experts advise, and has worked on the >100 inverters I have installed in off grid solar systems.

 

[MJSullivan56]

I used 1/0 cables as all the experts advise, and has worked on the >100 inverters I have installed in off grid solar systems.

Sadly, anecdotal at best. What would be actually helpful would be if you opened up said inverter and summed up the cross-sections of all the undersized wires coming from the lug to the transformers. Bet you anything it isn’t anywhere close to 1/0. But happy to be proven wrong.

 

[SunWizard]

Code is very clear on wire sizing and has not changed on the >40 years I have been doing this. It is also based on the distance. There are different rules that allow smaller wires on short 3" runs inside equipment.

 

[MJSullivan56]

Code is very clear on wire sizing and has not changed on the >40 years I have been doing this. It is also based on the distance. There are different rules that allow smaller wires on short 3" runs inside equipment.

Again, it would be actually helpful if people would make the effort to look inside their devices and confirm what these manufacturers are using. It’s safe bet that in most cases they are almost certainly using four 6” to 10” lengths of 10AWG for those “2000w” inverters. AFAIK, most pro electric guides don’t distinguish any significant differences between 6” versus 36” in the sizes we are talking about.

 

[SunWizard]

AFAIK, most pro electric guides don’t distinguish any significant differences between 6” versus 36” in the sizes we are talking about.

Here is a good chart, showing that for "chassis wiring" the amp rating is almost doubled and #4 is enough where 1/0 is needed to the inverter (as in above code link):

https://theinverterstore.com/faq-items/what-size-of-cable-should-i-use-with-my-inverter-and-battery/?srsltid=AfmBOopyWSKYzKIa2l6256sINqdd-cFJgFsY_-iFm7V4gAyK-EN3ZWbs

and here is a good chart showing wire size versus distance (add both cables length):

https://cdn.shopify.com/s/files/1/0062/6052/3111/files/12V_Inverter_Cable_Chart-02.22.2019-logo.png?v=1604534080

showing that if you keep the total cable roundtrip distance to only 2' (not practical for most) you could use a #6.

 

[Moe]

Sadly, anecdotal at best.

IMO >100 anecdotes are statistically significant.

@SunWizard beat me to it, but you can’t compare ratings for chassis wiring to those for power transmission.

You did the wiring right for your desired 120V output. From your description (can’t maintain 80%) your choice of inverter may be inadequate for your desired output. It appears at least to me you regret not making the wiring equally inadequate to match it?

 

[MJSullivan56]

IMO >100 anecdotes are statistically significant.

@SunWizard beat me to it, but you can’t compare ratings for chassis wiring to those for power transmission.

You did the wiring right for your desired 120V output. From your description (can’t maintain 80%) your choice of inverter may be inadequate for your desired output. It appears at least to me you regret not making the wiring equally inadequate to match it?

36” of cable hardly qualifies as “power transmission”. In fact the data provided kinda proves my point: for in-car inverters such as what I’m building in the frunk for my ID.4 there is no need for 1/0AWG cable for a 2000w inverter — UNLESS you are running many feet of cable such as what typically happens in an RV. Clearly you understand that is not my use case, right?

 

[Moe]

36” of cable hardly qualifies as “power transmission”. In fact the data provided kinda proves my point: for in-car inverters such as what I’m building in the frunk for my ID.4 there is no need for 1/0AWG cable for a 2000w inverter — UNLESS you are running many feet of cable such as what typically happens in an RV. Clearly you understand that is not my use case, right?

I’m referring to the ampacity for nearly 170A, not the voltage drop. Even in an RV, an inverter is as close to the batteries as possible because tenths of a volt matter. Given the Powerpoles and emergency in the subject, I understood this to be something only plugged in during a residential blackout, not permanently mounted. I guess I missed that.

edit: Either way, I’d want to not just unplug but remove everything you’ve added before taking it into the shop, especially for an electrical problem. YMMV

 

[SunWizard]

36” of cable hardly qualifies as “power transmission”. In fact the data provided kinda proves my point: for in-car inverters such as what I’m building in the frunk for my ID.4 there is no need for 1/0AWG cable for a 2000w inverter — UNLESS you are running many feet of cable such as what typically happens in an RV.

From your proposed layout, it looks like your total cable length is 6'? That is the where you need 1/0 and is typical if you put the inverter 3' away from the battery and no bends. Have you measured?

 

[MJSullivan56]

From your proposed layout, it looks like your total cable length is 6'? That is the where you need 1/0 and is typical if you put the inverter 3' away from the battery and no bends. Have you measured?

Currently just 48” believe it or not. Which could easily be reduced to 36” if I were sporting thinner gauge cable. That being said, IMHO, anyone else attempting such an enhancement I would recommend 1AWG for the following reasons:

1.) the largest OEM cable connected to the ID.4 12v battery is also just 1AWG. And…
2.) the cables supplied with the inverter are equivalent to 3AWG. And…
3.) the summation of the internal cabling inside the unit is 4AWG.

As hinted at elsewhere, my use case is to run our refrigerator during emergencies. So yes it would run “constantly” but of course, the load would have wide fluctuations over the course of any hour.