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Discussion Starter #1 (Edited)
I didn't see too much detailed information on installing a large inverter in one of these trucks, so I rolled the dice and just went about it the best way I could determine. I think it turned out reasonably well. It's not the cleanest install imaginable, but it's easily removed for vehicle trade-in or sale purposes. Note that I did this install late last year, and have since driven over 5,000 miles with absolutely zero electrical issues, so I think it's a sound installation.

I chose the AIMS 3kw inverter-charger because AIMS is a well-reputed manufacturer of this sort of equipment, and I wanted the charging capability because I am considering building a large power pack for my camper, and I wanted to get familiar with how these things function. Better to spend an additional $300 now then blow it on a $3,000 inverter later. However, for most vehicle inverter applications, the charging isn't really necessary unless you want to be able to run your vehicle's accessories off AC.

I also wanted auxiliary outlets in the truck bed, so I made sure I chose an inverter with hardwire terminals. In retrospect, I should have put the outlets and inlet closer to the tailgate so they could be accessed easily without climbing into the bed. I could move them, but I'd have to either run new wire to the inverter or install a junction box somewhere to make the connection because the existing wire isn't long enough.

The bed outlets are a standard 20A GFCI outlet and a NEMA L5-30R. I chose the latter to make this installation mirror what you'd find on a 3kw generator. For my RV I have an L5-30 > TT-30 adapter, and a TT-30 > 14-50 adapter, so I can connect my 50-amp plug to the inverter via the bed outlet and utilize the full 3kw (the draw on the 20A outlets should not exceed 2.4 kw). You could just as easily use a TT-30 outlet, though, if your only application is an RV.

Now, for the numbers. My truck has dual alternators, 220A and 150A, for a combined maximum output of 370A. I also had the high-idle software added to my truck by the dealer so I can raise the idle speed to about 1200RPM via the cruise control button, which would be a good idea if a large continuous load is to be placed on the charging system at idle. 370A * 12V = 4.4kw, so 3kw should be well within the system's capabilities, although I admit to being unfamiliar with the magnitude of thermal losses due to the DC/AC conversion. 3kw / 12V = 250A, so I needed cable/terminals/fuses that could handle this huge current. The 4/0 welding cable is actually right around its limit at that amperage, but it's readily available (as are terminals, fuses, etc.) so I decided it was the best solution. 3kw/120V = 25A, so I went with 10-gauge SOOW (flexible) cable for the AC connection to the auxiliary outlets and inlet. This cable can handle about 30 amps for non-continuous loads or 24 amps for a continuous load (80% of intermittent load capacity), which is close enough to the theoretical maximum 25A that I can draw from the inverter continuously. More cautious types could go with 8-gauge.

I thought long and hard about where to locate the inverter. Putting it in the bed would totally eliminate the issue of routing cables into the cab, but the inverter would then be exposed to the elements without constructing some elaborate (and space-consuming) enclosure. I decided to play it safe and located it under the rear passenger-side seat. The particular inverter I chose is very tall, and I was just barely able to install it such that it does not interfere with the seat or the foot room in front of it. It is not the most aesthetically pleasing location but hey, it's a truck. Also, this inverter's ventilation holes are on its sides, so I don't think the fact that the top of it is covered is a problem. I knew I would have to drill a hole somewhere, and I wanted it to be easily concealable, so I did it in the back of the cab below the rear seat. I used a hole saw and installed a 2-1/4" clamp connector to protect the cables; note that the one I linked to above is only 2" (can't seem to find the 2-1/4" on Home Depot's website). It was extremely difficult routing the cables through the connector; if I were to do it again, I would go with two smaller holes and clamps. I was able to screw the clamp down on the cables enough that I didn't feel like I had to use any sealant, but I guess you could use silicone or something to totally eliminate the air gap.

Some of you may be wondering about the dedicated neutral wire. For the amount of current that this system needs to be able to handle, I did not want to roll the dice on the resistance across all the body/frame/engine/alternator connections, especially since many of these connections are exposed to the elements and may be subject to increasing resistance through time due to corrosion, dirt, rock salt, etc. The other thing that may be odd-looking is the bond I installed between the two alternators' positive terminals. I did a continuity test from one alternator to the other with the truck in its original configuration and found that there's no resistance between the two (it's one continuous system), but I realized that the current path from one alternator to the other routes through small (relatively speaking) 2-gauge cables to each battery and then to the starter. So if I made the connection to only one alternator, the current path from the other alternator to the inverter connection would be alternator 2 > battery > starter > battery > alternator 1, all through those smaller cables which have no overcurrent protection and could become very hot if I were drawing a full 3kw from the inverter. Plus, the voltage drop could make the system unable to provide the full 3kw at all. Therefore, I bonded them together with a small length of the welding cable.

Aside from the hole I had to drill in the cab, the only really annoying part of the installation was routing the huge cables out of the engine bay. I had to remove the passenger-side battery to install the fuse block anyway, so while I was in there I pushed the cables through a small gap between the sheet metal that constitutes the fender. I then removed the wheel well shroud from outside (it's held in by little Torx screws) and was able to route the cables on the inside of this shroud down to the back of the passenger side front wheel well and have them pop out right next to the frame rail. From there I routed them over the running board anchors and secured them with zip-ties. I covered the exposed positive cable with wire loom as an extra added protection against the possibility of the insulation being compromised from road debris or some unforeseeable catastrophe. To secure the inverter to the floor I just used two 2-1/2" self-tapping hex-head screws from Home Depot and drilled right through the carpet and into the metal floor below (after checking under the cab about a dozen times to make sure I wasn't going to hit anything).

The install works about as well as I could have hoped. I am able to run a pair of 1500-watt space heaters off it simultaneously. I don't even have to use the high idle; as soon as the truck's electrical system detects the voltage drop (at that load, the alternators can't supply the needed current at idle so the batteries begin to deplete) it increases the RPM on its own. One thing I have not yet tested is starting my 15k BTU/hr air conditioner, which is an important test because the space heaters are resistive (as opposed to inductive, like the AC's compressor) loads and, as such, their starting current is no higher than their running current. Update: the inverter has no problem starting and running my 15k BTU/hr air conditioner, even while simultaneously powering my 1200-watt water heater, DC power converter, and refrigerator.

I may have forgotten some details, so if you have any questions feel free to ask. Rather than answer in a reply, however, I'll probably just add the relevant information to this initial post so that anyone reading this in the future will be able to find all of the info in one place.

Edit 1: A note on circuit breakers and fuses. I tried a 300A circuit breaker and it tripped under a load that I estimate to be about 230A. At that point I decided to go the simpler route of a fuse and block, and just deal with replacing the fuse in the (extremely unlikely) event that I ever blow one. Breakers can degrade over time, and my understanding is that they're designed to "fail safe," so they'll trip at lower, rather than higher currents than their rated capacity. I don't have detailed or technical knowledge of circuit breakers, so it would be interesting to hear others' experiences in this area.

Edit 2: For reference, the length of my cables (neutral and hot) is about 20 feet, for a total length of 40 feet from the hot side of the alternator to the inverter and back to the neutral side. Less is always better, as wire has finite resistance. Remember, P = (I^2)*R (where P=power [watts], I=current [amps], and R=resistance [ohms]). This means that your power loss due to a given resistance is going to be much greater if that resistance is on the 12 VDC side as opposed to the 120 VAC side. How much greater? Well, for a given value of P and R, the current on the 12 VDC side (upstream of the inverter) will be 10 times greater than the current on the 120 VAC side (downstream of the inverter). 10^2 == 100, therefore the heat (or power) dissipated across the same value of R (assuming a corresponding impedance on the 120 VAC side) will be one hundred times greater. Coupling this with the understanding that the cable or wire used to transmit the power has its own resistivity (resistance per unit length), it's easy to see why you're always better off locating the inverter as close to the DC voltage source as possible in order to minimize the length of cable that the low-voltage DC current has to flow through. You can always just use extension cords or hardwire some auxiliary outlets on the 120 VAC side. This is a much better solution than locating the inverter far away from the alternator(s).

Edit 3: If you are going to install something like this, I recommend doing a "bench test," in which you wire up your inverter with the correct-length cables, fuse block and/or breaker and anything else and load it under your worst-case scenario conditions, but before actually drilling any holes or routing cables. A poster below proposed the use of bulkhead connections instead of drilling a large hole in the cab; if you do this, make sure those bulkhead connections are used in your bench test, as those connections have finite resistance. Also, do not use bulkhead connections for any 120 VAC circuits! Doing so poses a major electrocution hazard.

Edit 3A: There is a discussion about the safety of using bulkhead conductors for 120 VAC somewhere between posts 10 and 20 of this thread. I maintain my recommendation -- in the strongest possible terms -- against doing this, but if you have a strong fundamental understanding of electromagnetism you may be capable of doing the requisite analysis to safely deviate from standard practices and implement this design.

Edit 3B: I've done some more thinking about the use of bulkhead conductors for 120 VAC circuits. I still think it's a bad idea, but it's not necessarily suicidal/homicidal provided that you are using GFCI for all your circuits and the inverter's ground terminal on the AC side is bonded to the vehicle chassis. This gets a lot more complicated if you are using an inverter-charger that may be connected to shore power, because you need to make sure that your inverter has an internal relay that breaks the chassis-neutral bonding when shore power is supplied. If it doesn't, then an open neutral connection on the shore power side could result in the vehicle chassis being energized at line voltage. In that scenario, if the inverter circuit is not GFCI-protected, you're basically asking for someone to be electrocuted. If what you just read doesn't make perfect sense, just drill the damn holes for your 120 VAC cables and insulation. ;)

Edit 4: A note on AC cable/wire selection. You could use Romex for the auxiliary connections, but solid-core cabling like Romex needs to be secured such that it's never really subjected to any kind of physical movement. The one advantage (aside from cost) to using Romex is that it's easy to connect to hardwire terminals. What I wound up doing was using outdoor-rated flexible SOOW cable, and then inside the auxiliary outlet and power inlet gangboxes I connected the SOOW to the outlets/inlets using a very short (three inches or so) length of 10/2 Romex and wire nuts. I did this because the stranded SOOW cable is difficult to insert into the hardwire terminals on the outlets/inlets. The gangboxes got pretty crowded, though. You could skip this and tie the SOOW in directly, but you need to be extremely careful about individual strands of the wire not seating fully and remaining exposed, as this nearly guarantees a ground fault (electrocution hazard!) or short circuit.

Edit 5: You will need serious cable cutters to cut 4/0 effectively and without creating a mess. The cutters I link to below will work, but something larger would probably be better. For stripping insulation I just used a sharp box cutter and was very careful not to cut any of the strands.

Edit 6: Here is a handy voltage drop calculator. My parameters are:

Wire Material: Copper
Wire Size: 4/0 AWG
Voltage: 14 (approximate alternator voltage)
Phase: DC
Number of conductors: single set of conductors
Distance: 20 feet (it specifies one-way distance, not round-trip)
Load Current: 250A

I get a voltage drop of 0.49V, which sounds about right as compared to my practical measurements. You can measure voltage drop at a specific inverter load by measuring V_alternator - V_inverter. V_alternator is the voltage measured across the alternator's positive terminal and its metal housing. V_inverter is the voltage measured across the inverter's positive and negative terminals. Both measurements need to be taken while the inverter is under load; i.e., the values will be different for different loads. Do this during your bench test. If your voltage drop is significantly greater than what the calculator predicts, take a look at your connections and any other resistive devices in the current path (fuse/block, bulkhead conductors, etc.) and see how bypassing them affects the drop. Of course, you can't bypass the fuse/block for the full install, but if you find that it's adding significant resistance you will realize ahead of time that there's some debris or other issue that needs to be addressed before you go any further; these issues are much easier to diagnose with all the wiring and other hardware exposed than post-install. Remember, if V_inverter drops below some specified cutoff voltage (probably 10.5 V), the inverter will shut itself off. And don't forget that resistance under load means heat dissipation, at a rate of I^2*R.

Below are links to some of the hardware I used for the install:

AIMS 3kw inverter-charger: https://www.amazon.com/gp/product/B00NZCRFRQ/ref=oh_aui_detailpage_o02_s01?ie=UTF8&psc=1
16-ton hydraulic crimper (the 10-ton is not large enough for the terminals I used): https://www.amazon.com/gp/product/B00GXQ2E5E/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
ANL fuse block: https://www.amazon.com/gp/product/B000K2K7TW/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
300A ANL fuses: https://www.ebay.com/itm/300A-AMP-ANL-Type-Fuse-Platinum-Plated-High-Quality-Fuses-6-Pack-Car-Audio-Blade-/173191129908?hash=item2852feeb34
4/0 terminals: https://www.amazon.com/gp/product/B00030CYU6/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
4/0 flexible welding cable (black): https://www.amazon.com/gp/product/B00KD27670/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
4/0 flexible welding cable (red): https://www.amazon.com/Gauge-Premium-Extra-Flexible-Welding/dp/B00KD27C9M/ref=pd_bxgy_469_2?_encoding=UTF8&pd_rd_i=B00KD27C9M&pd_rd_r=EBQAF3T2BK5B12QHTF0Z&pd_rd_w=CI1XU&pd_rd_wg=igc4s&psc=1&refRID=EBQAF3T2BK5B12QHTF0Z
Heat shrink (red): https://www.amazon.com/gp/product/B01F2LG3JS/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
Heat shrink (black): https://www.amazon.com/gp/product/B01F2LGF5U/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
3/4" wire loom (red): https://www.amazon.com/gp/product/B00TE1SCQU/ref=oh_aui_detailpage_o06_s01?ie=UTF8&psc=1
10/3 SOOW cord: https://www.homedepot.com/p/Southwire-By-the-Foot-10-3-600-Volt-CU-Black-Flexible-Portable-Power-SOOW-Cord-55809799/204632922
15-amp power inlet (outdoor rated): https://www.gordonelectricsupply.com/index~text~5653456~path~product~part~5653456~ds~dept~process~search?gclid=CjwKCAjw-bLVBRBMEiwAmKSB8yYhMgcbfabQHNAQbLEU_3qj2oGwrS3G3vLhgB7sYfZ0Zmsd5hn4CRoCJMkQAvD_BwE
2-inch clamp connector (EXAMPLE -- see discussion above): https://www.homedepot.com/p/Halex-2-in-Non-Metallic-NM-Sheathed-Cable-Clamp-Connectors-05120/100127021
Cable cutters: https://www.homedepot.com/p/Pro-sKit-10-in-Cable-Cutter-200-069/206369452?cm_mmc=Shopping|VF|G|0|G-VF-PLA|&gclid=Cj0KCQjwqM3VBRCwARIsAKcekb1uAvdlBn8XipEJwd2tUdetj85Y1zKRneqqgkiAhkz4-2oOwdZrQNAaAgrvEALw_wcB&dclid=CIHVwZW8gNoCFYS9swodiUcOgQ







































Update: The install looks a lot cleaner with these Maxliner floor mats covering the cables routed under the back seat.





UPDATE: I've since relocated the in-bed inlet/outlet to make room for my auxiliary fuel tank. This has the added benefit of making the inlet/outlet accessible while standing behind the tailgate. I definitely should have done it this way from the outset.







 

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thank you for the install details.

I had a large inverter installed in my last truck - planing to do this same install latter this year
 

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Now I'm wondering if your RV AC will start and run.I have a 13,500 btu and was told a Micro Air Easy Start wired to AC unit will start and run off 1 Honda 2000 gen.You said AC is important so if you never heard of this maybe something to look into to start your AC unit.But I'd like to know if it's needed with your setup.Nice write up!
 

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Now I'm wondering if your RV AC will start and run.I have a 13,500 btu and was told a Micro Air Easy Start wired to AC unit will start and run off 1 Honda 2000 gen.You said AC is important so if you never heard of this maybe something to look into to start your AC unit.But I'd like to know if it's needed with your setup.Nice write up!
Thanks. I think what you're describing is a start capacitor that can be charged up at the continuous rate of the power supply and then discharge at a much faster rate to start inductive loads like compressors (or motors, more generally). My 15k BTU/hr AC will start and run on a 3kw generator even when connected with a crappy 16-gauge 100-foot extension cord, so I am pretty sure my inverter can handle the load, especially since it's rated for 6kw instantaneous (20-second, I believe) draw. The only question is whether my truck's batteries and alternators can supply that instantaneous juice without the voltage dropping below the inverter's cut-off voltage. Once the weather warms up I will try it and update the writeup accordingly.
 

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Thanks Nate for bringing this to my attention. I haven't been over here on DF for a while.

I am installing a 1500w inverter in a semi truck to run a fridge and microwave. I would like a bigger one but I already have this one. I am using the same size welding cable you are but I have solder on ends instead of the crimp on. I was just going to come off the batteries and go straight into the sleeper. I see you went to the alternator.

Why didn't you just go off one of the batteries?
 

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Thanks Nate for bringing this to my attention. I haven't been over here on DF for a while.

I am installing a 1500w inverter in a semi truck to run a fridge and microwave. I would like a bigger one but I already have this one. I am using the same size welding cable you are but I have solder on ends instead of the crimp on. I was just going to come off the batteries and go straight into the sleeper. I see you went to the alternator.

Why didn't you just go off one of the batteries?
Two words: voltage drop.

I'm not planning on drawing any significant power unless the truck is running (and I don't suggest you do either, unless you have a separate battery pack and an isolator, a much more complicated system), so if I were to connect to the battery instead, the current would have to flow through the alternators' connections to the battery. As I pointed out in the OP, that connection is made using small 2-gauge cables; not nearly large enough to supply 250A continuously in a safe manner.

1500w/12V=125A, and at that huge current, even if you don't exceed the safe capacity of the 2-gauge cables, the voltage drop across them will probably be such that your inverter's low-voltage safety shutoff will be tripped. You can completely eliminate that problem by tying your inverter directly into the alternator(s).
 

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Discussion Starter #9
Nice install.

I am quite anal about how stuff enters the cab and would probably have gone with something like https://ceautoelectricsupply.com/product/500-amp-weatherproof-bulkhead-connectors/ for my power from the battery?
I saw these too and considered going this route, but I wanted to minimize voltage drop. The bulkhead interface (especially the exterior one which is exposed to debris, moisture, corrosion, salt, etc.) will have some finite resistance associated with it. Now, I didn't try them so it may be so small as to be negligible, but I was comfortable drilling the hole so I went that route and totally avoided that issue. Note that if you want auxiliary outlets in your bed, I discourage you in the strongest possible terms from using bulkhead connectors to get 120VAC out of your cab. That would be a major electrocution hazard.
 

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Two words: voltage drop.

I'm not planning on drawing any significant power unless the truck is running (and I don't suggest you do either, unless you have a separate battery pack and an isolator, a much more complicated system), so if I were to connect to the battery instead, the current would have to flow through the alternators' connections to the battery. As I pointed out in the OP, that connection is made using small 2-gauge cables; not nearly large enough to supply 250A continuously in a safe manner.

1500w/12V=125A, and at that huge current, even if you don't exceed the safe capacity of the 2-gauge cables, the voltage drop across them will probably be such that your inverter's low-voltage safety shutoff will be tripped. You can completely eliminate that problem by tying your inverter directly into the alternator(s).

Ok I understand now. For some reason that part must have gone over my head. I wont be using power when the truck is shut off. I'm using the truck to pull a camper. I will have separate shore power outlets that I can run off the generator or plug into the pole at the campground. For simplicity when I pull in I want to be able to open the side box on the truck shut the inverter off then plug the fridge into a separate outlet powered by the generator or shore power.

If I am only using a 1500 watt inverter do you think I should use the same fuse you did or should I go smaller?

Here is a picture just so you can kind of see what I have going on here. I hope to be wiring it all up here in the next few weeks.
 

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Ok I understand now. For some reason that part must have gone over my head. I wont be using power when the truck is shut off. I'm using the truck to pull a camper. I will have separate shore power outlets that I can run off the generator or plug into the pole at the campground. For simplicity when I pull in I want to be able to open the side box on the truck shut the inverter off then plug the fridge into a separate outlet powered by the generator or shore power.

If I am only using a 1500 watt inverter do you think I should use the same fuse you did or should I go smaller?

Here is a picture just so you can kind of see what I have going on here. I hope to be wiring it all up here in the next few weeks.
I see what you're getting at. I would definitely wire it directly to the alternator like I did. There's literally zero advantage to wiring it into the battery for our (very similar) applications; it's worse in every respect.

For wiring, the bigger the better. Even if you don't need 4/0 you'll have less voltage drop with those big cables than with smaller cables, even if the smaller ones can safely handle 125A.

As for the fuse, I'd size the fuse for the biggest load you can conceive of placing on the system, but no bigger. I would not go over 150A for your system; any continuous draw over 150A in your situation indicates something seriously wrong. I added a note in the OP about using a circuit breaker in lieu of a fuse; my experience wasn't so great.

By the way, I would strongly recommend setting this up on a "bench" and ensuring it does what you expect it to do before going through the pain of wiring everything. By that, I mean make your cables and just hook up the inverter to the truck with it sitting on a table or something, and with the engine running, load test the inverter. Push the thing to its limit and make sure it does what you want. Hell, I'd push it beyond its limit and see at what point it cuts out. For this test, you should make sure that you wire it up using the actual cables you'll use for the full install (same length), and also connect anything else that will add resistance (such as the fuse and block). This way, you can be confident that once you install everything it will work as expected. The last thing you want to do is spend a day (or days) routing huge cables all over the place, only to find out that you need to mount the inverter somewhere else because the voltage drop is too great.

Keep us posted on your project. I'm interested to hear how it goes. Let me know if I can be of any further help.
 

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There are two main considerations when selecting the wire gauge for a particular application. The first is safety related and has to do with how much current the conductor can carry before heating excessively. When I was putting my home wiring together I was required to use a much larger gauge wire than the power company used on the overhead service. The power company installer said they were allowed to use smaller wire because it is air cooled and so not as likely to overheat. I suspect the fact that it doesn't touch anything either means it can run hotter without concern. In any event, the heating effect is related to the square of the cross section of the wire so heating drops pretty quickly with larger wire.

The second consideration is power loss or as some put it, voltage loss, along a length of wire. The calculation for this is relative to the diameter of the wire, the length of the wire and the current carried. More current or more length mean more voltage drop for a given diameter. This is related to heating but is a separate issue.

I don't mean to step on any toes here and you should do what ever makes you comfortable but the ideas expressed here are pretty conservative. You certainly will not go wrong with big fat wires but the same rules that apply to homes don't apply to trucks. It is the same thing about air cooling. If you have your wiring running under carpets or in enclosed spaces then home rules may be most applicable but if your wiring runs in the open then you can back off a bit on the gauge sizes from a safety standpoint.

I like breakers. Properly chosen electromagnetic breakers in a well designed box are what run most homes in this country. I've had to replace a breaker or two because they failed but they are pretty reliable overall. Fuses are reliable too but when they fail it is much more complicated to replace a fuse than to reset a breaker. It always seem that when it is time to replace a fuse there isn't one at hand.

I don't see the electrocution hazard associated with bulkhead connectors. With all of the kids sticking paperclips in sockets you would expect to see reports of massive deaths every night but it just doesn't happen. It is unpleasant to get zapped but the fact is that 120V is pretty safe. In Europe they use 240V and even they aren't dying in droves. There might be a small hazard to the vehicle due to the potential for a short but again it doesn't happen in houses very often so I don't see it as suicide in a truck.

If I did this, and I might, I would put the inverter under the hood, keep the high amp cables very short and run the 120V from there.
 

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There are two main considerations when selecting the wire gauge for a particular application. The first is safety related and has to do with how much current the conductor can carry before heating excessively. When I was putting my home wiring together I was required to use a much larger gauge wire than the power company used on the overhead service. The power company installer said they were allowed to use smaller wire because it is air cooled and so not as likely to overheat. I suspect the fact that it doesn't touch anything either means it can run hotter without concern. In any event, the heating effect is related to the square of the cross section of the wire so heating drops pretty quickly with larger wire.

The second consideration is power loss or as some put it, voltage loss, along a length of wire. The calculation for this is relative to the diameter of the wire, the length of the wire and the current carried. More current or more length mean more voltage drop for a given diameter. This is related to heating but is a separate issue.

I don't mean to step on any toes here and you should do what ever makes you comfortable but the ideas expressed here are pretty conservative. You certainly will not go wrong with big fat wires but the same rules that apply to homes don't apply to trucks. It is the same thing about air cooling. If you have your wiring running under carpets or in enclosed spaces then home rules may be most applicable but if your wiring runs in the open then you can back off a bit on the gauge sizes from a safety standpoint.

I like breakers. Properly chosen electromagnetic breakers in a well designed box are what run most homes in this country. I've had to replace a breaker or two because they failed but they are pretty reliable overall. Fuses are reliable too but when they fail it is much more complicated to replace a fuse than to reset a breaker. It always seem that when it is time to replace a fuse there isn't one at hand.

I don't see the electrocution hazard associated with bulkhead connectors. With all of the kids sticking paperclips in sockets you would expect to see reports of massive deaths every night but it just doesn't happen. It is unpleasant to get zapped but the fact is that 120V is pretty safe. In Europe they use 240V and even they aren't dying in droves. There might be a small hazard to the vehicle due to the potential for a short but again it doesn't happen in houses very often so I don't see it as suicide in a truck.

If I did this, and I might, I would put the inverter under the hood, keep the high amp cables very short and run the 120V from there.
The voltage drop issue, aside from the (arguably negligible, as you pointed out) dangers due to resistive heating, is that most inverters are set up to cut off if the voltage across them drops below 10.5 VDC. So over-sizing the DC wiring -- again, not with regard to safety from a resistive heating standpoint -- can help with this. Precise measurements of resistivity (and hence resistance) for specific wire gauges might not be a bad idea, but are beyond the scope of my writeup.

As for breakers vs. fuses, I like the breaker idea, but I would definitely measure the resistance across the breaker and compare it to a fuse before making a decision. The impedance in a breaker may be negligible at 120 VAC but the corresponding resistance at 12 VDC means an order-of-magnitude higher voltage drop, or a two-orders-of-magnitude higher power loss due to resistive heating.

Regarding bulkheads for 120 VAC, having the (bare) 120 VAC conductor within a few millimeters of the vehicle chassis in an environment prone to moisture (especially since a water-salt solution -- with its reduced resistivity -- is not an uncommon finding in winter) or full submersion just does not seem like a good idea. I don't know exactly what the result would be of having a 120 VAC energized bulkhead conductor submerged in such close proximity to ground, and I won't speculate (this brings up the matter of whether to bond the inverter's ground to the vehicle chassis, which I did not address). But unless you've actually implemented this design and verified its safety I don't think you should endorse it. On the other hand, if there's a way to completely insulate the 120 VAC conductor in a watertight fashion, I will retract my skepticism.

Finally, I can't speak for other vehicles, but I challenge anyone to find a suitable place to mount a 3 kilowatt inverter in the engine bay of an L5P Silverado or Sierra. Mounting the fuse block was hard enough!
 

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The voltage drop issue, aside from the (arguably negligible, as you pointed out) dangers due to resistive heating, is that most inverters are set up to cut off if the voltage across them drops below 10.5 VDC. So over-sizing the DC wiring -- again, not with regard to safety from a resistive heating standpoint -- can help with this. Precise measurements of resistivity (and hence resistance) for specific wire gauges might not be a bad idea, but are beyond the scope of my writeup.

As for breakers vs. fuses, I like the breaker idea, but I would definitely measure the resistance across the breaker and compare it to a fuse before making a decision. The impedance in a breaker may be negligible at 120 VAC but the corresponding resistance at 12 VDC means an order-of-magnitude higher voltage drop, or a two-orders-of-magnitude higher power loss due to resistive heating.

Regarding bulkheads for 120 VAC, having the (bare) 120 VAC conductor within a few millimeters of the vehicle chassis in an environment prone to moisture (especially since a water-salt solution -- with its reduced resistivity -- is not an uncommon finding in winter) or full submersion just does not seem like a good idea. I don't know exactly what the result would be of having a 120 VAC energized bulkhead conductor submerged in such close proximity to ground, and I won't speculate (this brings up the matter of whether to bond the inverter's ground to the vehicle chassis, which I did not address). But unless you've actually implemented this design and verified its safety I don't think you should endorse it. On the other hand, if there's a way to completely insulate the 120 VAC conductor in a watertight fashion, I will retract my skepticism.

Finally, I can't speak for other vehicles, but I challenge anyone to find a suitable place to mount a 3 kilowatt inverter in the engine bay of an L5P Silverado or Sierra. Mounting the fuse block was hard enough!
There is a real danger of getting into an argument here and I don't want to do that. I'll just say a couple of things.

The listed bulkhead connector had covers to protect the terminals from the elements. 120 volts doesn't flow much through clean water because water itself is a pretty good insulator. It is the contaminants in the water that make it a good conductor. Salt spray is another matter. That has all of the ions necessary to make a pretty good conductor. It would be necessary to guard against that but I don't see a real problem. Even lacking protective covers, it should be possible to shield it pretty well with silicone or bed liner. I think a search among marine suppliers would surely provide a perfect solution to the problem.

I don't think anyone would expect to find a place for the inverter you have pictured under the hood of a Duramax truck. I was thinking of a more flat style and mounting it in front of the cooling stack. Not having done it yet I can't say it would work but that is where I would look.

I don't know why a big inverter isn't a factory option but considering how long it took them to decide to integrate a brake controller I guess it isn't surprising. I bet if they put it on the options list as a trailer towing 2.0 option it would sell nicely. In the mean time I'm glad to see what others have done to solve the problem.
 

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Discussion Starter #15
There is a real danger of getting into an argument here and I don't want to do that. I'll just say a couple of things.

The listed bulkhead connector had covers to protect the terminals from the elements. 120 volts doesn't flow much through clean water because water itself is a pretty good insulator. It is the contaminants in the water that make it a good conductor. Salt spray is another matter. That has all of the ions necessary to make a pretty good conductor. It would be necessary to guard against that but I don't see a real problem. Even lacking protective covers, it should be possible to shield it pretty well with silicone or bed liner. I think a search among marine suppliers would surely provide a perfect solution to the problem.

I don't think anyone would expect to find a place for the inverter you have pictured under the hood of a Duramax truck. I was thinking of a more flat style and mounting it in front of the cooling stack. Not having done it yet I can't say it would work but that is where I would look.

I don't know why a big inverter isn't a factory option but considering how long it took them to decide to integrate a brake controller I guess it isn't surprising. I bet if they put it on the options list as a trailer towing 2.0 option it would sell nicely. In the mean time I'm glad to see what others have done to solve the problem.
You and I are apparently both reasonably intelligent, articulate, and capable human beings, so I don't think one of us proposing an alternative to the other's opinion or recommendation is going to start an argument. The only reason I came out guns-up against the bulkhead connector idea you re-endorsed was that those connectors are designed for (and are safe with) 12 VDC, and using them for 120 VAC, while technically possible, is going to require significant efforts to fully insulate the conductor. I have absolutely no doubt that you are capable of doing this (since you obviously understand the effect on resistivity of dissolving an ionic compound in water) safely, but it is not even close to a standard practice in any kind of automotive or residential wiring, at least as far as I've seen. Generally, walls/bulkheads are drilled for holes large enough to pass the conductor and its insulation through. I think if you're going to recommend that people deviate substantially from common practices that you should also offer at least some warning about the potential hazards and ways of mitigating them. There are a lot of folks on this message board who, no doubt, consider themselves "handy" dudes but are just frighteningly lost in the sauce, such as the guy who posted this thread about a 2 kw inverter wired with 12-gauge wire. While you and I are sitting here discussing the precise nature of voltage drop in terms of Maxwell's equations, this guy is pushing 200 amps through red-hot Romex (without a breaker or fuse) and burning down his truck and house. If you are an electrical engineer you can probably figure out a way to safely pass 120 VAC across bulkhead connectors in an outdoor environment. But if you don't really have any serious understanding of electromagnetism you'll probably be better off just following my initial advice.

Anyway. As for the marine supply stuff for insulating bulkhead connectors, I'm sure there's something available. However, most products and practices in that realm will still be geared toward 12 VDC, so anyone going this route will need to do some real analysis prior to implementation. As stated, my view is that anyone who does not have an understanding of the fundamentals of electromagnetism -- as distinct from practical knowledge/experience -- will not be capable of performing that analysis, and thus should not do this. Just one guy's opinion.

I'll edit the part of the OP referring to bulkhead connectors to reference our discussion here, so that readers can make a decision based on their individual judgment.

</SOAPBOX>

I wholeheartedly agree about installing the inverter in the engine bay if space is available; this design coupled with auxiliary cab/bed outlets and a remote power switch for the inverter would be the cleanest and best installation possible. The only caveat is moisture; the other day I was rolling through some pretty deep mud holes and water briefly came up over the hood. As long as this hazard is mitigated I think under the hood would be the best, but given how crowded modern engine bays are, this may not be practical.

I, too, have wondered why this isn't an option from the factory. If nothing else, they could do something about the almost-worthless 150w dashboard inverter. If you've never scoped the waveform coming out of that thing, take it from me that it is not pretty. It does okay charging my laptop and my Dewalt batteries; that's all I use it for. But they should spend a couple more bucks and offer at least a 500w inverter with a waveform that looks vaguely reminiscent of a sine wave.
 

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Question for the OP.

Wondering what type of "camper" you are using this with? Is it cab over, travel trailer or 5th wheel? Also why not just use a 3K generator? If you were running it strictly off a bank of batteries and didn't the noise I get that, but the truck makes noise any way, although probably less than a generator, and possibly less fuel.

Not criticizing your choice, at all, just wondering why you did it the way you did.

Also on pushing stranded wire into terminals, twist them together and solder the 3/8" or so you need to make it solid.

Nice job and nice write up, and I agree with you on isolating the 120v. It's not voltage that kills it's amperage, and 5ma across the heart will stop it.

If someone doubts, grab the + and - terminals of a 12v truck battery with one hand on each. Then report back, if able.

As for kids not dying when sticking a paper clip in an outlet? First off it's a 50-50 chance of hitting the hot wire vs neutral or possibly the ground depending on the clip. Second of all they may not have a good path to ground, which is what kills, it's the current path through the heart to ground.

In EITHER case it's not worth the risk, period, to not know you have a short to chassis, and find out when the wife or kid steps out, holding onto the truck, into a puddle of water.

I would like to see the rig set up and in use though. I have a 2K inverter setup on my 5th wheel but it is battery supplied (4-6v 232ah batteries) and cannot draw near the power you can, but I can use mine in after and before generator hrs and total silence.
 

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Discussion Starter #17
Question for the OP.

Wondering what type of "camper" you are using this with? Is it cab over, travel trailer or 5th wheel? Also why not just use a 3K generator? If you were running it strictly off a bank of batteries and didn't the noise I get that, but the truck makes noise any way, although probably less than a generator, and possibly less fuel.

Not criticizing your choice, at all, just wondering why you did it the way you did.

Also on pushing stranded wire into terminals, twist them together and solder the 3/8" or so you need to make it solid.

Nice job and nice write up, and I agree with you on isolating the 120v. It's not voltage that kills it's amperage, and 5ma across the heart will stop it.

If someone doubts, grab the + and - terminals of a 12v truck battery with one hand on each. Then report back, if able.

As for kids not dying when sticking a paper clip in an outlet? First off it's a 50-50 chance of hitting the hot wire vs neutral or possibly the ground depending on the clip. Second of all they may not have a good path to ground, which is what kills, it's the current path through the heart to ground.

In EITHER case it's not worth the risk, period, to not know you have a short to chassis, and find out when the wife or kid steps out, holding onto the truck, into a puddle of water.

I would like to see the rig set up and in use though. I have a 2K inverter setup on my 5th wheel but it is battery supplied (4-6v 232ah batteries) and cannot draw near the power you can, but I can use mine in after and before generator hrs and total silence.
I kind of just wanted to see if I could do it and get the full 3kw, and in that sense it was a success. I don't think I'll use the functionality enough to justify a 150 pound space-consuming generator, plus I'd like to be able to run my 1200 watt air compressor for inflating high pressure tires and high volume rafts. Both of those applications are short bursts of high current draw, so I figured the inverter would be useful.

As for the 12 VDC battery: I've grabbed both terminals of car and truck batteries many times to illustrate exactly the opposite of what you stated. ;) 12 VDC is not nearly enough voltage to induce current through both of your arms and torso; at that voltage the resistance of your tissue is effectively infinite. At higher voltages, electrical breakdown can occur, and this often results in electrocution. But it's not like voltage and current are separate and independent parameters of a system; current flows as the result of applying voltage. V=IR, but it turns out that R itself is actually a function of V, so it can get pretty complicated. But 12 VDC does not pose an electrocution hazard, although it can still burn you via resistive heating (it can even be used to weld, in a pinch).

Oh, and it's a travel trailer. And another cool capability would be running the AC in the camper while we are on the road, so our animals can ride in there while us humans occupy the truck.
 

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Discussion Starter #19 (Edited)
Ok thanks for the correction and info. Lol big job for a "I wonder" :)
Haha, no kidding. But I'm also planning on "eventually" doing something like this on a much larger scale for the next camper (which will be a large fifth wheel) involving a 12 kw 48 VDC inverter-charger (split-phase 120/240 VAC output) and a bank of AGM batteries. This power pack will require the same amount of DC current, so now that I've worked with the 4/0 cables and terminals I'll be a lot more confident going into that $5k+ project.

One application of the truck inverter I'm really looking forward to, though, is running my Porter-Cable air compressor for inflating rafts for river trips. Inflating two five-person rafts with a shitty little DC pump is painful and extremely time consuming. I suspect that my 2-CFM @90 PSI compressor will do it much more rapidly. The compressor is also great for inflating truck and trailer tires (100 ft extension cord gets it to the trailer axles with room to spare).
 

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This is what I installed in my truck. https://www.ebay.com/itm/Puma-12-Volt-1-5-Gallon-Oil-Less-Air-Compressor-Free-Shipping-Oiless-12V/252693385387?epid=2254404946&hash=item3ad5b310ab:g:LgkAAOSwA3dYXKjJ
Mine is a 1hp, they no longer sell. Rated 1.5cfm at 90 psi. 12v DC and is on a 40 amp circuit, powered from the battery through a relay, controlled by a lighted witch on the dash.

This is the second time I have done this with the same model compressor. The first was in 2002 on an '01 Jeep Wrangler we had. The motor has a 100% duty cycle and will air up an 80 PSI tire (265/75R16) from flat to 80 in about 2 min.

Just flat out pump and last a long time. Have not worn one out yet. Mine is mounted under rear drivers side door, tucked inside inner frame rail, tank and all, but separated from each other. Mine fills the 1.5 gal tank in a little over a min at 125 psi, where I have it set to cut off.

My batteries in my 5th wheel inverter setup are (4) US2200's in series parallel to 12v, for a total of 464ah. or 232ah usable going by the 50% rule. If I ever upgrade these it will be to lithium's. One single 200ah lithium will do what 4 lead acid batteries will do, safely, and last a lot longer. And for the RV it will weigh about half or less of the lead batteries.

After getting used to my Tesla Powerwall at 13.2KW powered by our 4.5KW solar panels, on our home, I am spoiled for lithium and their usable ah.
 
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