Power Inverter Install

[aawolf]

I'm planning a purchase and install of a PowerBright 600W inverter in the back seat of my 4Runner. From my research:

1) the inverter draws 100A.
2) the one-way run length from my car's battery will be 6.5'

My question is: do I need to run a second 6.5 foot cable back to the battery to hook up the negative connector on the inverter back to the negative post of the car battery? Or could I simply run the negative connector of the inverter 1 foot to a solid engine chassis ground position.

My understanding is running it 1 foot to chassis ground will be sufficient but now I'm having doubts because I see the inverter has a separate ground cable hookup that would ostensibly be the same exact run that I'm proposing to do with the negative inverter post -> chassis ground.

If I'm able to skip the return 6.5’ cable then I can use 1AWG cable vs 0AWG and it greatly simplifies punching through the firewall. I'd also plan to use the same "neg to chassis" technique when I install a 12V fridge.

Am I smoking the drapes here?

 

[aawolf]

Wanted to add...

I'll be doing the "Big 3" battery wire upgrade, so my battery's negative->chassis connection will be solid. I'm sensing this might be relevant.

 

[jeremyc74]

A solid chassis (or engine) ground is your best bet, assuming all the factory connection to the battery and alternator are in good shape. With that kind of current draw you want to keep the wire runs as short as possible.

You know a battery isn't going to last long if you're using that thing's full potential...right?


Edit: Can you post a photo of the wiring instructions for the inverter? The second ground is most likely intended to be an earth ground.

 

[calimobber]

do I need to run a second 6.5 foot cable back to the battery to hook up the negative connector

no, the body is a great ground and will work fine. I used the seat bolt for mine.

The other smaller ground is for the inverter case since the main ground is only grounding the internal circuits. Just connect it to the main grounding on the inverter.

1AWG cable vs 0AWG

really depends on what you running I run 2 awg for my 1000w and I just have to start the car for higher draws to keep the volts up.


Im a fan of Xantrex and would recommend the 1000w model so You can run some higher loads if needed. ive run my little coffee machine(600w) a handful of times.

http://www.amazon.com/Xantrex-806-1...e=UTF8&qid=1426557092&sr=1-1&keywords=xantrex

or the 600w model

http://www.amazon.com/Xantrex-806-1...e=UTF8&qid=1426557092&sr=1-4&keywords=xantrex


Look at my build for some idea's with the inverter

 

[jeremyc74]

Im a fan of Xantrex and would recommend the 1000w model so You can run some higher loads if needed. ive run my little coffee machine(600w) a handful of times.

Xantrex is good stuff. I have a 1750W version in my RV, and I run the microwave with it all the time. I have to start the truck to cook a hot pocket, but it gets the job done! :roll:

 

[IBallEngineer]

I'm planning a purchase and install of a PowerBright 600W inverter in the back seat of my 4Runner. From my research:

1) the inverter draws 100A.
2) the one-way run length from my car's battery will be 6.5'

My question is: do I need to run a second 6.5 foot cable back to the battery to hook up the negative connector on the inverter back to the negative post of the car battery? Or could I simply run the negative connector of the inverter 1 foot to a solid engine chassis ground position.

My understanding is running it 1 foot to chassis ground will be sufficient but now I'm having doubts because I see the inverter has a separate ground cable hookup that would ostensibly be the same exact run that I'm proposing to do with the negative inverter post -> chassis ground.

If I'm able to skip the return 6.5’ cable then I can use 1AWG cable vs 0AWG and it greatly simplifies punching through the firewall. I'd also plan to use the same "neg to chassis" technique when I install a 12V fridge.

Am I smoking the drapes here?

First off, like so many things, you are going to get a lot of opinions. And I will offer you one too. But don't mistake facts for opinions.

Fact#1 600W at 12V is 50 Amps, not 100.

So you can cool the jets a little on the wire size. If you think you'll upgrade later, go ahead and run as big as you can. I run 0 on a 1200W Inverter and have never had any issues. If you look at typical wire gauge charts 4 or 6 will work fine for your application. See the chart below

https://www.bluesea.com/resources/1437


Fact #2 Absolute ground is absolute ground. Until some connection messes it up.

What I'm saying is, grounding right to the chassis will work just fine, until something in the loop causes you grief. I run both cables all the way to the battery, only one connection on either end, never any doubt. So, in essence, it's up to you.

Have fun with it! :yo:

 

[calimobber]

Fact #2 Absolute ground is absolute ground. Until some connection messes it up.

What I'm saying is, grounding right to the chassis will work just fine, until something in the loop causes you grief. I run both cables all the way to the battery, only one connection on either end, never any doubt. So, in essence, it's up to you.

Just to throw this out there. I did the big 3 mod for grounding but I also got crazy and ran a 2 gauge the whole length of my car and bolted it to the frame a few times along the way so my frame is super grounded

 

[TheDurk]

Fact #2 Absolute ground is absolute ground. Until some connection messes it up.

What I'm saying is, grounding right to the chassis will work just fine, until something in the loop causes you grief. I run both cables all the way to the battery, only one connection on either end, never any doubt. So, in essence, it's up to you.

Have fun with it! :yo:

"Grounding to the chassis will work just fine".... assuming the battery-post to chassis side is also up to it. Toyota's stock negative wiring is pretty anemic, so your end-to-end is better. A loop is only as good as its weakest link.

 

[pluton]

Careful about those inverters; Xantrex is a good name, but I have the 600 watt model shown and these are the weak, cheeseball units in the Xantrex lineup.
It may work fine for your use, but don't be surprised if it can't handle the load. Buy with a return option if possible, and test with your intended load. If you are just running small electronics and battery chargers, it'll be fine.
This is the "real" heavy-duty unit, at considerably higher cost, of course:
Power Inverter, Pure Sine Wave Inverter, Marine Inverter, PROsine

Personally, I just have small 160 watt units that I can stuff in the seat back when not being used.

 

[aawolf]

Thanks for all of the great input guys. My takeaway: It seems like I should be OK running 1 AWG 6.5'f one way to the positive connector on the Inverter, connecting the Inverter's "chassis ground" port via 1 AWG directly to the negative connection on the Inverter, and connecting the Inverter's negative connection on the inverter via 1 AWG directly to chassis ground. No ground return run to battery.

I'll respond to the highlights below.

You know a battery isn't going to last long if you're using that thing's full potential...right?
...
The second ground is most likely intended to be an earth ground.

Yup! I've completed a secondary battery install (Optima Yellow Top) in the engine bay. It will be isolated with a National Luna Intelligent Solenoid. Also, I'll only mostly ever be using it for laptops and phones, so about 50% of that capacity.

What's an "earth ground"? I'm having a hard time googling that to differentiate between the normal negative terminal ground flow we're talking about. This particular inverter's manual calls it the "chassis ground" cable and instructs me to run this cable to the chassis nearby. The negative connection is supposed to be run back to the battery (which is the instruction I'm hoping to ignore ).

Fact#1 600W at 12V is 50 Amps, not 100.

So you can cool the jets a little on the wire size. If you think you'll upgrade later, go ahead and run as big as you can. I run 0 on a 1200W Inverter and have never had any issues. If you look at typical wire gauge charts 4 or 6 will work fine for your application. See the chart below

https://www.bluesea.com/resources/1437

Yup, true enough, science is science.. though this inverter has a "peak load" of 1000W, so theoretically higher current flow. I'm saying 100A based on their product manual (page 4) but you're likely right that they're padding this number to play it safe.

As far as cable size, there's wild variation in wire-gauge recommendations all over the internet. That chart you linked is one of the more lax ones I've seen. I'm a fan of the overly cautious ones. I like this one because it allows you to plug in precise numbers (note: meters not feet).

Just to throw this out there. I did the big 3 mod for grounding but I also got crazy and ran a 2 gauge the whole length of my car and bolted it to the frame a few times along the way so my frame is super grounded

Wow, I knew about the Big 3 upgrade (and plan on doing it), but I thought 3rd gens have a pretty hearty/solid chassis current flow. Is the 2 AWG down the length of the body something shown to give a measurable improvement?

"Grounding to the chassis will work just fine".... assuming the battery-post to chassis side is also up to it. Toyota's stock negative wiring is pretty anemic, so your end-to-end is better. A loop is only as good as its weakest link.

Yup I'll be upgrading the "Big 3" electrical connections (especially the negative-battery-post-to-chassis connection) with solid 4 AWG prior to working on the Inverter wiring.

 

[jeremyc74]

Fact#1 600W at 12V is 50 Amps, not 100.

Nope, not when we're talking about a 600W inverter.

600W at 12V is 50amps, but the inverter is rated to deliver 600W continuous at 120V, which isn't the same thing. Typical small inverters like this are only about 80-85% efficient (until you start spending a lot more money), so that will be added to the draw on the 12V side. With a 600W load on the A/C side you're going to be looking at closer 60amps with a constant load. This particular inverter is rated to deliver 1000W peak, so that's probably why they're recommending it be wired for a 100Amp draw.

 

[jeremyc74]

Yup! I've completed a secondary battery install (Optima Yellow Top) in the engine bay. It will be isolated with a National Luna Intelligent Solenoid. Also, I'll only mostly ever be using it for laptops and phones, so about 50% of that capacity.

What's an "earth ground"? I'm having a hard time googling that to differentiate between the normal negative terminal ground flow we're talking about. This particular inverter's manual calls it the "chassis ground" cable and instructs me to run this cable to the chassis nearby. The negative connection is supposed to be run back to the battery (which is the instruction I'm hoping to ignore ).

.

Ok, so what's going on is that the inverter is designed for installations in vehicles where they might not have a solid enough connection to pass electrical code for A/C systems. The "chassis ground" is the equivalent of the third prong on a power cord. Without getting into the whole big mess of earth grounding, basically what it will do is prevent you from getting shocked to death if a live A/C wire from the inverter came into contact with your vehicle chassis. By grounding the chassis the inverter will see a short and the protection circuits will kick in and kill it, or it will blow a fuse.

So the short answer (pun intended) is that you're fine to connect both of those to the vehicle chassis.

 

[NHRunner]

Nope, not when we're talking about a 600W inverter.

600W at 12V is 50amps, but the inverter is rated to deliver 600W continuous at 120V, which isn't the same thing. Typical small inverters like this are only about 80-85% efficient (until you start spending a lot more money), so that will be added to the draw on the 12V side. With a 600W load on the A/C side you're going to be looking at closer 60amps with a constant load.

You don't have to account for the efficiency of the inverter. That's already accounted for in the figures that they present to the customer.

 

[aawolf]

You don't have to account for the efficiency of the inverter. That's already accounted for in the figures that they present to the customer.

I think Jeremey was just explaining why you can't just look at the Inverter's output wattage a derive the input current draw with the standard

watts = voltage x current

forumla (as an IBallEngineer suggested earlier in the thread). You're correct though, my Inverter's 1000W peak + 85% efficiency comes out to be right around the 100A input current draw that the manufacturer presents to the customer. That's what I'll be going by.

 

[NHRunner]

ohhhh

That explains where that 100W figure came from. Makes sense.

You're right about the variety of wire gauge selections. Seems to be anywhere between 6 and 2 gauge in most charts. Personally, I'd go 4 gauge. I guess it won't hurt to go oversize so that you have the ability to tap into and draw a little more power in the future for other goodies.

 

[IBallEngineer]

Nope, not when we're talking about a 600W inverter.

600W at 12V is 50amps, but the inverter is rated to deliver 600W continuous at 120V, which isn't the same thing. Typical small inverters like this are only about 80-85% efficient (until you start spending a lot more money), so that will be added to the draw on the 12V side. With a 600W load on the A/C side you're going to be looking at closer 60amps with a constant load. This particular inverter is rated to deliver 1000W peak, so that's probably why they're recommending it be wired for a 100Amp draw.

I don't follow your math. Higher voltage lowers the amp draw, but that doesn't change at the DC side of the inverter. 600W at 120V is 5 amps and even this calculator calls that a 55.2 Amp draw on the DC side accounting for efficiency(heat) loss.

BatteryStuff Tools | AC to DC Amperage Calclator Through An Inverter

So if we go back to my earlier post and see the chart, or look at this one. 0 or 2/0 is overkill. I doubt the lugs on a 600W inverter could accommodate bigger than 2G.

Wire gauge - amp ratings chart help! - Expedition Portal!

 

[IBallEngineer]

As far as cable size, there's wild variation in wire-gauge recommendations all over the internet. That chart you linked is one of the more lax ones I've seen. I'm a fan of the overly cautious ones. I like this one because it allows you to plug in precise numbers (note: meters not feet).



.

You are right, the variations are many, and the 2nd chart I sent was even more liberal than the first. The site you sent me recommended Triple OTT for 110Amps at 2 meters. That, my friend is WAY over kill. I've run 1200W inverters on 0 with runs close to that length at least 5 different times. I've run 2000W inverters on 2/0 with 12' runs.
And if your 600W Inverter draws 100Amps, throw it away, it's junk.

You'll be fine with the decisions you've made. But I like science!

lane:

 

[jeremyc74]

I don't follow your math.l]!

You're wiring for input current draw, not output current. The inverter is rated for 600W at 120V A/V. NOT 600w at 12VDC. I'm not really sure what's so hard to grasp there.

 

[aawolf]

The site you sent me recommended Triple OTT for 110Amps at 2 meters. That, my friend is WAY over kill.

Eh.. you left the calculator on 1% voltage drop which is extremely stringent. At 3% (the usual recommendation for optimal functioning of electronics) it says 3AWG for 110A over 2 meters. Seems reasonable, no?

The inverter is 1000W peak output, so I'm guessing that's 100 amp peak input current draw. Given it's a pure sine wave inverter with 4.6 out of 5 stars in 52 reviews on Amazon, I'm inclined to believe it's not junk.

 

[IBallEngineer]

You're wiring for input current draw, not output current. The inverter is rated for 600W at 120V A/V. NOT 600w at 12VDC. I'm not really sure what's so hard to grasp there.

First of all, we aren't discussing the A/C wiring. Do the math is all I'm saying.

So again, 120V AC draws 5amps at 600W. 600W at 12V is 50 amps. Here is the Inverter example again.

BatteryStuff Tools | AC to DC Amperage Calclator Through An Inverter