Replacing Factory Inverter with Pure Sine Wave Inverter

[Mattlikesbikes]

Touching base on this again. I've been mulling this over while Shadowfax has been in the shop and I couldn't do anything anyways and I've figured out my plan.

I'm going to cut off the factory connectors and, on the bare wires from the rest of the truck, attach my own connectors. Then I'll make two new harnesses to plug into those new connectors.

First harness will be the factory connectors. To switch back to the factory inverter, I just attach this harness and plug in the factory inverter.

Second harness will be setup for the replacement inverter in whatever way I choose.

While this doesn't let me return to completely stock (the new connectors will be present), it does greatly simplify the connector situation as I can use connectors that I know are rated for the amperage I'll be encountering. It also avoids the mess of trying to use the factory ones from a parts standpoint.

My inverter either shat the bed already (6wks, 3000 miles) or just cannot power anything I own. So Paying very close attention here.

One question - on some of these connectors you can release each wire and pin by pushing in tabs. If you could strip the plug off, you could use the pins with different plugs

 

[ccw]

My inverter either shat the bed already (6wks, 3000 miles) or just cannot power anything I own. So Paying very close attention here.

One question - on some of these connectors you can release each wire and pin by pushing in tabs. If you could strip the plug off, you could use the pins with different plugs

Try it with a phone charger that you would use in a wall outlet. Those are some of the most forgiving devices when it comes to power quality, so if one of those doesn’t work I would suspect the inverter is dead.

That’s a very good point! And would be completely non-destructive. Would need to see if there’s another plug I can use that uses the same pins, but absolutely worth looking into. Thanks for bringing it up!

 

[Mattlikesbikes]

Try it with a phone charger that you would use in a wall outlet. Those are some of the most forgiving devices when it comes to power quality, so if one of those doesn’t work I would suspect the inverter is dead.

That’s a very good point! And would be completely non-destructive. Would need to see if there’s another plug I can use that uses the same pins, but absolutely worth looking into. Thanks for bringing it up!

So far a USB phone charger is all it will power. For the laptop, wondering if a stand alone inverter with a cig plug will be the easy option. So much for charging Makita batteries.

I'm putting a battery and inverter in the camper shell bed setup, so may stick with just that. But if you work out a good solution here I'll likely copy that too. With the 6.7 and almost 400amp of alternators, there is no reason not to have obscene electric capabilities.

 

[Modman]

With the 6.7 and almost 400amp of alternators, there is no reason not to have obscene electric capabilities.

Or the 7.3L w/dual alts for that matter!!

 

[ccw]

So far a USB phone charger is all it will power. For the laptop, wondering if a stand alone inverter with a cig plug will be the easy option. So much for charging Makita batteries.

I'm putting a battery and inverter in the camper shell bed setup, so may stick with just that. But if you work out a good solution here I'll likely copy that too. With the 6.7 and almost 400amp of alternators, there is no reason not to have obscene electric capabilities.

I’m guessing it’s the power signal, then, and not that the inverter is broken. As frustrating as that is.

Agreed on the fact we have tons of power on tap! Will definitely keep this thread updated, though FYI (both for you and anyone else following this thread) this won’t be happening until the new year.

It’s also implicitly intertwined with the broader electrical system I’m making for the truck. The broader electrical planning started after I made this thread, and you can follow that process here:

Shadowfax Electrical Planning

Ok, I'm wanting to start planning out the electrical system for Shadowfax, and I'm realizing this may be more complicated than I was originally thinking. Would love advice and suggestions from those of you with more experience in this than me. Also understandable if this is something I should...

www.fordtremor.com

This thread went quiet as I put my time and energy into the broader planning.

 

[Frazior]

Hey, @ccw , where did you ever get with this? I am looking forward to doing this type of mod when I get my truck and would be in for a couple of the OEM style plugs/connectors if you have come up with something.

 

[ccw]

Hey! I’ve been side tracked with broader electrical and radio planning that this intertwines with.

From earlier in this thread this is still my plan:

Touching base on this again. I've been mulling this over while Shadowfax has been in the shop and I couldn't do anything anyways and I've figured out my plan.

I'm going to cut off the factory connectors and, on the bare wires from the rest of the truck, attach my own connectors. Then I'll make two new harnesses to plug into those new connectors.

First harness will be the factory connectors. To switch back to the factory inverter, I just attach this harness and plug in the factory inverter.

Second harness will be setup for the replacement inverter in whatever way I choose.

While this doesn't let me return to completely stock (the new connectors will be present), it does greatly simplify the connector situation as I can use connectors that I know are rated for the amperage I'll be encountering. It also avoids the mess of trying to use the factory ones from a parts standpoint.

The only difference with the broader electrical planning is I won’t touch the factory power feed to the inverter. Instead I’ll be running my own power to the back seat for all of my accessories and having that behind low voltage protection.

Implementation still to come.

 

[Raspy]

A 400 watt inverter needs #8 wires feeding 12 volts to it, as it will draw nearly 40 amps at peak, depending on its efficiency and assuming the efficiency is 90%.

 

[CADUCKHUNTER]

A 400 watt inverter needs #8 wires feeding 12 volts to it, as it will draw nearly 40 amps at peak, depending on its efficiency and assuming the efficiency is 90%.

I would like to do this upgrade also

 

[shermanator2]

A 400 watt inverter needs #8 wires feeding 12 volts to it, as it will draw nearly 40 amps at peak, depending on its efficiency and assuming the efficiency is 90%.

I do not know if CCW completed this mod, but I have the same concern. A pure sine inverter will tend to be less efficient than the "modified sine" factory type inverter and therefore require more input current. I looked up the WaganTech inverter that CCW showed. As silly as it is, they do not specify a maximum input current. They spec a maximum efficiency of 90%, which is also useless because what needs to be known is the minimum efficiency, particularly at max output load. They supply it with #11 wire on the input side, which seems too small for the what I agree can be something like 40A on the input. If you were pulling 400W and were not paying attention and let your battery run down to 10.1V where this shuts off, you would be pulling at least 44A on the 12V side. I notice that the fuse they recommend is 100A.

 

[ccw]

A 400 watt inverter needs #8 wires feeding 12 volts to it, as it will draw nearly 40 amps at peak, depending on its efficiency and assuming the efficiency is 90%.

I do not know if CCW completed this mod, but I have the same concern. A pure sine inverter will tend to be less efficient than the "modified sine" factory type inverter and therefore require more input current. I looked up the WaganTech inverter that CCW showed. As silly as it is, they do not specify a maximum input current. They spec a maximum efficiency of 90%, which is also useless because what needs to be known is the minimum efficiency, particularly at max output load. They supply it with #11 wire on the input side, which seems too small for the what I agree can be something like 40A on the input. If you were pulling 400W and were not paying attention and let your battery run down to 10.1V where this shuts off, you would be pulling at least 44A on the 12V side. I notice that the fuse they recommend is 100A.

Haven't completed it yet (new blocker is figuring out where to put everything for the broader install) but my plan is to run 6 AWG wire to the inverter, so I should be all good.

 

[Raspy]

I do not know if CCW completed this mod, but I have the same concern. A pure sine inverter will tend to be less efficient than the "modified sine" factory type inverter and therefore require more input current. I looked up the WaganTech inverter that CCW showed. As silly as it is, they do not specify a maximum input current. They spec a maximum efficiency of 90%, which is also useless because what needs to be known is the minimum efficiency, particularly at max output load. They supply it with #11 wire on the input side, which seems too small for the what I agree can be something like 40A on the input. If you were pulling 400W and were not paying attention and let your battery run down to 10.1V where this shuts off, you would be pulling at least 44A on the 12V side. I notice that the fuse they recommend is 100A.

I think the 100 amp fuse is mainly to prevent overloads during a high surge of output current, but not as a regular continuous load. I, as a rule of thumb for quick calculations, take the rated output (400 watts at 120 volts = 3.33 amps), multiply that times 11 to get to the approximate 12 volt amp load, which allows for the 90% efficiency rating, as 10% of the 12 volt current is lost to heat, to get the total amp draw on the 12 volt side at full rated output assuming 90% efficiency. Answer: 36.67 amps at 12 volts. #8 THHN can carry 55 amps, so it is a good choice. #8 tinned marine romex is even a better choice. #6 is possibly better, but not really needed as the truck will be running with a long term load of this nature and heat loss will be minimal from the wires. The charging voltage from the truck will be above 14 volts. Variables are the length of the 12 volt wires and the actual efficiency of the inverter. 400 watts is still pretty low and it would be nice to get to a bigger unit. Especially if the 12 volt wiring is all going to be upgraded anyway. I'm not sure how important it is to have a true sine wave inverter vs the modified sine wave type. Especially considering what type of equipment will be used around the truck. I've never had a problem running things with modified sine wave inverters, but they can produce a audible hum in some equipment.

 

[shermanator2]

This is a great discussion on some interesting and probably important details. I look at it this way; At 90% efficiency (best case according to the specs) to get 400W out you need 400/0.9 = 444 W in. At 12V, that means 444/12=37A which agrees with Raspy. If however, if you leave this running without the truck engine running, you will discharge the batteries until the inverter shuts down at 10V, Just before it shuts down it will be drawing 444/10=44.4A.

#8 wire can certainly safely carry this, but lets look at how that effects the efficiency. I do not know where the inverter is located or how much wire length will be needed to get to the battery. Lets say 10 ft of wire to get to the battery. If I run both positive in negative to the battery (maybe I would tie the negative to body ground) it would be a total of 20ft. 20ft of #8 wire has a resistance of 0.013 ohms. At 37A this leads to a drop of 0.47V and a power loss of 17.6W. The net efficiency is now only 86.5% but we probably don't care a lot. The only real effect is that we will run the battery down a little faster and the inverter will shut down at a battery voltage of 10.5V instead of 10V.

For fun let's do the same calculation with CCW's #6 wire. 20ft of #6 wire has a resistance of 0.0081 ohms leading to a voltage drop of 0.3V, power loss of 11W, and an efficiency of 87.8%. hmmm... Probably not significant so #8 is probably fine. If it was me, I wold still run #6 because that is just the way I am.

 

[ccw]

This is a great discussion on some interesting and probably important details. I look at it this way; At 90% efficiency (best case according to the specs) to get 400W out you need 400/0.9 = 444 W in. At 12V, that means 444/12=37A which agrees with Raspy. If however, if you leave this running without the truck engine running, you will discharge the batteries until the inverter shuts down at 10V, Just before it shuts down it will be drawing 444/10=44.4A.

#8 wire can certainly safely carry this, but lets look at how that effects the efficiency. I do not know where the inverter is located or how much wire length will be needed to get to the battery. Lets say 10 ft of wire to get to the battery. If I run both positive in negative to the battery (maybe I would tie the negative to body ground) it would be a total of 20ft. 20ft of #8 wire has a resistance of 0.013 ohms. At 37A this leads to a drop of 0.47V and a power loss of 17.6W. The net efficiency is now only 86.5% but we probably don't care a lot. The only real effect is that we will run the battery down a little faster and the inverter will shut down at a battery voltage of 10.5V instead of 10V.

For fun let's do the same calculation with CCW's #6 wire. 20ft of #6 wire has a resistance of 0.0081 ohms leading to a voltage drop of 0.3V, power loss of 11W, and an efficiency of 87.8%. hmmm... Probably not significant so #8 is probably fine. If it was me, I wold still run #6 because that is just the way I am.

Great write-up! For even more fun with my setup I’m running 00 gauge from the battery to the back seat, then a short (couple of feet?) length of 6 gauge from the fuse block to the inverter.

 

[BroncOh]

Come to the dark side of the 3/0 cable club.

 

[ccw]

Come to the dark side of the 3/0 cable club.

I need to put that $300 towards other things lol. Going to keep my $200 of 2/0.

 

[Canyon Trekker]

Great discussion! Inverter efficiency is calculated as loss of power of input to output. Since DC is converted to AC, (DC to RMS) the constant is power in watts. (P = I x E) In the discussion above, the efficiency is generally referring to the system efficiency, which takes into consideration loss through the distribution. These are two different efficiency discussions. A pure sine wave inverter is more efficient than a modified inverter, simply because you get more power out through the conversion. (Typically, 90% vs. as low as 70% on a modified sine wave.) The modified inverter has less power out for the same current in, as described above.

So, to understand system efficiency, wire size comes into play here. The more power loss you have through the wires, the less power you have at the inverter input. The efficiency of the inverter is the same in any case. But with lesser gauge wire, you now have less power at the input, and the inverter will work harder with lower voltage to attain the desired output. Heat is the result of all this extra work. (And generally buzzing) Heat is loss. It just goes downhill from there.

A pure sinewave inverter may require more power at the input to maintain its output and efficiency, therefore, the wire size has to be big enough to overcome any loss that would be the case with smaller wire. Bigger is better.

@BroncoHooves has an ideal system that if you look at his avatar, shows the drop at the inverter, is minimal. This allows the inverter to operate at its full potential without much loss in the system delivery. This may be overkill for a 400-watt inverter conversion but drives the point.

So, what's the problem with modified inverters? Simple. Many devices with transformer inputs (typically any device that plugs into a wall) require a constant change (RMS sinewave) to meet the maximum efficiency of the conversion for input to output for the load. (Device conversion, not the vehicle inverter) Transformers need constant change to pass constant output. A modified inverter is stepped, and depending on how many steps are in the design, the "change" is only realized at the moment of the step. The more steps, the better the conversion. This is a very inefficient transfer of power. This is why many devices will work in the home, but not in the vehicle with the modified inverter. Some devices based on design, will work "OK", but not to full efficiency.

Hope this helps.

Here is a link describing inverter efficiency.

What is Inverter Efficiency?

www.inverter.com

 

[shermanator2]

A pure sine wave inverter is more efficient than a modified inverter, simply because you get more power out through the conversion. (Typically, 90% vs. as low as 70% on a modified sine wave.) The modified inverter has less power out for the same current in, as described above.

This is interesting and I am not sure that I am convinced that it is true in general. Just thinking about making a stepped wave verses a continuous sine wave it seems that I could make the former with less loss. I am not saying it is wrong, I just need to learn more about the actual design, and even better see some real test data. It is unfortunate that the data sheet for the inverter that CCW bought only gives a maximum (peak) efficiency and not a curve or at least an efficiency at max load.

(P = I x E)

Also interesting that you use E for your voltage variable. Maybe that is a navy thing or you are even older than I am. I was taught that way by my dad when I was a kid, but by 1980 when I was inn college, we were taught that the convention was to use v.

 

[Canyon Trekker]

This is interesting and I am not sure that I am convinced that it is true in general. Just thinking about making a stepped wave verses a continuous sine wave it seems that I could make the former with less loss. I am not saying it is wrong, I just need to learn more about the actual design, and even better see some real test data. It is unfortunate that the data sheet for the inverter that CCW bought only gives a maximum (peak) efficiency and not a curve or at least an efficiency at max load.


Also interesting that you use E for your voltage variable. Maybe that is a navy thing or you are even older than I am. I was taught that way by my dad when I was a kid, but by 1980 when I was inn college, we were taught that the convention was to use v.

I'm older than dirt! (At least the dirt in my compost pile.) I worked in electronics for over 50 years. (Then retired recently) There are definitely different schemes on this formula, European always use "V", but I still refer to the old "PIE" chart. Even some of those use V as the variable now. It really depends on the instructor for terms.

 

[Modman]

I'm older than dirt! (At least the dirt in my compost pile.) I worked in electronics for over 50 years. (Then retired recently) There are definitely different schemes on this formula, European always use "V", but I still refer to the old "PIE" chart. Even some of those use V as the variable now. It really depends on the instructor for terms.

They are related. We used "E" in school at times which stands for electromotive force. EMF = electromotive force = E. Voltage is sometimes referred to analogous to pressure, current to flow. E is the forcing function creating the voltage "pressure" since pressure is force/area. Mostly, as @Canyon Trekker provided they are used interchangeably, though, except for in academia where nomenclature gets scrutinized... That's my recollection at least...