The quest to use my truck as a generator continues | chapter 2 | more power

Guda

Superstrut Strut
Okay so I have been playing with electric math!

20 amp charging is the goal.

20 amps outta the inverter 120v side is 2400w. 2400w at 12v on the DC side is 200 amps. My alternator puts out 250amps, maybe. Looks like they ran 4awg to a 175amp Anderson. Maybe the cold will enable the 25 amp fudge...

10a charging might be reality.

Here is where I cant find the answer.

How long does it take to make 4000w at 120v 10amps?

I am looking at my SCC and seeing it made about 4000w on a day that it just filled the battery. I'm assuming I use about 4000w a day currently.
 

Dzl

Unofficial Forum Librarian
Staff member
Moderator
Okay so I have been playing with electric math!

20 amp charging is the goal.

20 amps outta the inverter 120v side is 2400w. 2400w at 12v on the DC side is 200 amps. My alternator puts out 250amps, maybe. Looks like they ran 4awg to a 175amp Anderson.
To output 2400W your inverter will need an input of 2400W + Inefficiency. If that is 85% for sake of example 2400W / 0.85 = 2825W input, or 236A @ 12V.

Voltage drop might also need to be factored in.

Maybe the cold will enable the 25 amp fudge...
Not a good idea

4 AWG is already too small for 175A, let alone over 200A
There is a temperature correction factor that can be used for cold temperatures, but do you actually live somewhere that never gets into the 70's, in either case the correction would not be enough. With wiring you always want to oversize, my conservative calculations, plan for worst case, not the opposite.


How long does it take to make 4000w at 120v 10amps?
Watts Watt-Hours.

The raw math:
120V x 10A = 1200W
4000Wh / 1200W = 3.33 Hrs

(this math assumes the entirety of the charge would be at the full 1200W which in practice it likely would not due to charge profile--I can't remember your situation)
 

chrisski

Photon Sorcerer
I’m really curious as to whether this 250 amp alternator will easily put out the 100 amp or 200 amps you’re talking about. Alternators do not put out a lot of energy at idle, but once driving they start to put out extra amps. So, this engine would need to be rigged at higher RPMs than normal.

My truck, a 6.0 Powerstroke, has something called a high idle mod where my normal idle of about 600 RPM can get boosted to 1200 or 2400 RPM. At those RPMs, the alternator would put out enough power.

All alternators are different, and this is one companies chart, https://balmar.net/balmar-technology/alternator-output-curves/, and it shows how some lower power alternators outperform higher power alternators at certain RPMs, but all put out more amps cold than hot.

CFB837E9-27EA-459D-BA66-F78590E3DF16.png
Not done correctly, this project has a risk of causing a second fire. Although a typical US home might be 100 amp or 200 amp connection, pushing that many amps DC though a 12 volt connection is different.

If you push that many amps through your wires for that amount of time, they will get hot, so that is another reason to size up.

For wire size, how long the run is will make a huge difference. I decided on 4/0 wire for 135 amps of output, but that is for a 10’ run. THe actual calculation was for a surge of up to 200 amps, which I have it fussed for. I calculated conservatively with a voltage loss calculator, wire amapacity, and finally looked at the temperature rating of the wire. I decided on a 60 degree Celsius rating, the coolest I could find published. THinner wires could handle the amps, but those were rated at 90 degrees Celsius, which is hot enough to burn, or 105 degrees degreed celcius, which is hot enough to boil water.

For 200 amps of output, I had calculated 600 MCM (may be KCM, but six hundred of whatever the gauge is above 4/0). I calculated for 350 surge amps for that one. I was scolded for even thinking of pushing that many amps and was told I’d need wire 1500 MCM, which would be as thick as my wrist. One other thing I was told to get is good insurance for when my project burns down.
 
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Guda

Superstrut Strut
To output 2400W your inverter will need an input of 2400W + Inefficiency. If that is 85% for sake of example 2400W / 0.85 = 2825W input, or 236A @ 12V.
Ah, 0.85. Ug

Not a good idea

4 AWG is already too small for 175A, let alone over 200A
There is a temperature correction factor that can be used for cold temperatures, but do you actually live somewhere that never gets into the 70's, in either case the correction would not be enough. With wiring you always want to oversize, my conservative calculations, plan for worst case, not the opposite.
Double ug. Tbh the chart is kinda hard to understand,

Watts Watt-Hours.

The raw math:
120V x 10A = 1200W
4000Wh / 1200W = 3.33 Hrs

(this math assumes the entirety of the charge would be at the full 1200W which in practice it likely would not due to charge profile--I can't remember your situation)
Oh well then I am all good at 10a. Thats good news.

I’m really curious as to whether this 250 amp alternator will easily put out the 100 amp or 200 amps you’re talking about. Alternators do not put out a lot of energy at idle, but once driving they start to put out extra amps. So, this engine would need to be rigged at higher RPMs than normal.
It has a 2000w inverter now. When the load increases the trucks rpms go up. Not sure how all that works

My truck, a 6.0 Powerstroke, has something called a high idle mod where my normal idle of about 600 RPM can get boosted to 1200 or 2400 RPM. At those RPMs, the alternator would put out enough power.
I've got a Powerstroke also. Not sure which one. 2005 6.L , I think maybe. Yup thats what I does when the inverter is under load.
All alternators are different, and this is one companies chart, https://balmar.net/balmar-technology/alternator-output-curves/, and it shows how some lower power alternators outperform higher power alternators at certain RPMs, but all put out more amps cold than hot.
The one I have was cheap off ebay. If I burn it, https://www.mechman.com/alternators...series-alternator-to-replace-ford-t-mount-6g/
Thats the bees knees alternator. I also can add a 2nd one also.
Not done correctly, this project has a risk of causing a second fire. Although a typical US home might be 100 amp or 200 amp connection, pushing that many amps DC though a 12 volt connection is different.

If you push that many amps through your wires for that amount of time, they will get hot, so that is another reason to size up.
I am shooing for 20a. But I seam to be okay for 10a. I might just get one of those heat reader gun things.

For wire size, how long the run is will make a huge difference. I decided on 4/0 wire for 135 amps of output, but that is for a 10’ run. THe actual calculation was for a surge of up to 200 amps, which I have it fussed for. I calculated conservatively with a voltage loss calculator, wire amapacity, and finally looked at the temperature rating of the wire. I decided on a 60 degree Celsius rating, the coolest I could find published. THinner wires could handle the amps, but those were rated at 90 degrees Celsius, which is hot enough to burn, or 105 degrees degreed celcius, which is hot enough to boil water.
If I have to run 4/0 from the hood to the bed thats going to be major. There is all this stuff in the box that I have no idea if it will handle 200 amps. Then I'd be adding a whole new run & by passing all the boxes connections. The box connects & disconnects automatically. Most likely I'll never really need it when its warm.
For 200 amps of output, I had calculated 600 MCM (may be KCM, but six hundred of whatever the gauge is above 4/0). I calculated for 350 surge amps for that one. I was scolded for even thinking of pushing that many amps and was told I’d need wire 1500 MCM, which would be as thick as my wrist. One other thing I was told to get is good insurance for when my project burns down.
2 fire references... I do have full coverage on my truck & the box is insured also. But if I never have another fire it will be too soon.

I might just be happy with 10a. 3.5 hours on the worst days is not bad. Thats about how much sun I need if I only get sun in the morning or evening.

Guda, any chance your truck has the PTO option installed?
Not sure. I think I know where you are going. I talked to that company that makes the PTO generator. $12.500... And they only do install in house. Mid west or east coast area. They are close to the place that makes F350 & most all their installs for people on the west coast are in brand new trucks straight from the factory. Too rich for my blood.

As of now

Just waiting on the lugs & have to find a few more parts. Finding all the parts to do all the stuff I want is a challenge. When I was looking at where I want to run the cord to run the block heater I found where the installer ran the boxes power cables.

When they installed it they gave me this rubber grommet & said "if you ever remove the box here is the plug for the hole". Glad I didn't throw it away.... They should have cut a hole in it to run the wires through..... You guessed it, wire chaffing on the metal edge... Lucky I caught it & as soon as I have all the parts I am going to fix that.

Cant thank you guys enough!
 

HRTKD

Boondocker
Not sure. I think I know where you are going. I talked to that company that makes the PTO generator. $12.500... And they only do install in house. Mid west or east coast area. They are close to the place that makes F350 & most all their installs for people on the west coast are in brand new trucks straight from the factory. Too rich for my blood.

Too rich for my blood also. I didn't order the PTO option on my F-350, so it's never been a consideration. There are far less expensive solutions. I for one, would not want to run my diesel, with all it's emissions equipment, just to generate power. Maybe if I was doing field maintenance, in remote locations, it would make sense, but not when my truck is sitting next to my house.
 

Dzl

Unofficial Forum Librarian
Staff member
Moderator
Ah, 0.85. Ug
You can look it up for your specific inverter, but that is a decent ballpark, most middle of the road or budget inverters are in the ballpark of low to mid 80's. Higher end inverters can reach low to mid 90's.
Double ug. Tbh the chart is kinda hard to understand,
I know it can be. I struggled to understand wiring charts for a long time. The issue is that there are a lot of variables (believe it or not that chart is the simplified version) I can help you with specifics if you need help as I've put a decent amount of effort into trying to understand the details. The simplest way to not stress over the details and to avoid the math is to do the opposite of what you are currently doing: substantially oversize your wire, (and buy high quality, high temperature wire).

The Blue Sea Circuit Wizard can do a lot of this for you, you just have to check the right boxes and input the right values (always erring on the conservative side). You would need to check "inside engine compartment" box, correctly select the temperature rating of your wire and a few other parameters like distance. The link is in my signature.

The full current path should be properly rated too, or you need to have a way to limit current or at the least a fuse sized slightly smaller than your lowest rated component in the current path.
 

Dzl

Unofficial Forum Librarian
Staff member
Moderator
Assuming 15ft round trip, in engine compartment, 250A variable current, 90*C or higher rated wire (check this), and a duration of 4hrs, with a target of <3% voltage drop, 4/0 is the smallest size that could be used according to the Blue Sea Calculator.
 

Guda

Superstrut Strut
There are far less expensive solutions. I for one, would not want to run my diesel, with all it's emissions equipment, just to generate power. Maybe if I was doing field maintenance, in remote locations, it would make sense, but not when my truck is sitting next to my house.
Why would I want to have a noisy, oil change needing whole another engine when I have one? Drive it to the oil change place & they change the oil. Generators are junk & waste of $. I hate generators

You can look it up for your specific inverter, but that is a decent ballpark, most middle of the road or budget inverters are in the ballpark of low to mid 80's. Higher end inverters can reach low to mid 90's.
Oh thats the conversation rate. I see
The simplest way to not stress over the details and to avoid the math is to do the opposite of what you are currently doing: substantially oversize your wire, (and buy high quality, high temperature wire).
I'm not going to rewire the whole system. There is a deference between charging wire vs inverter wire that seams to be over looked. I am running 4/0 to the inverter. There is 4awg running to the battery. My old 12v SCC used be 10 awg & the inverter was 1/0. No problem. I didn;t need 1/0 from the SCC to the battery. So I should not need 4/0 to the alternator. You need to remember there is a whole crap $5000 system in place. If the $5000 turd burns down my truck thats parked away from my house. Oh well, its all crap. So crap the 2000w inverter cant even do 1200w.... LET IT BURN! I'll use the insurance $ to buy a sailboat. Be like Jimmy Buffet

Tbh I am a little suspicious of USA standards. China seams to run just fine on 2 8awg instead of 1 4/0. A little extra heat is good in the winter. Like I am wasting $ buying all this huge wire. USA standards are written by people trying to sell stuff. Never can trust someone selling stuff.
 
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Dzl

Unofficial Forum Librarian
Staff member
Moderator
I'm not going to rewire the whole system.
One more reason @HRTKD's suggestion of a generator might be worth considering. It may be the path of least resistance.

There is a difference between charging wire vs inverter wire that seams to be over looked.
Not to the wire there is not. The wire experiences electrons flowing through it, the byproduct of this is heat, the smaller the wire or the more current the more heat, enough heat and you get fire. Doesn't matter whether it is charging or discharging.

Its possible that your charge rate will never get close to 250A, I don't know, and I don't think you know either.

I am running 4/0 to the inverter. There is 4awg running to the battery. My old 12v SCC used be 10 awg & the inverter was 1/0. No problem. I didn;t need 1/0 from the SCC to the battey. So I should not need 4/0 to the battery.
I'm not saying you do, I'm only saying the wire needs to handle the current that will flow through it. I don't know what that is because I don't understand your system fully. But your alternator is rated to 250A and your load is roughly ~250A. If your charge rate is less than 250A you could use smaller wire sized to the max charge rate. I don't know what your max charge rate is, but you seem set on using as much of your alternators rated output as you can.

The reason you could use smaller wire with your SCC is not because it was for charging, it is because the charge current was much lower. But in this case you are trying to use a 250A alternator with no current limiting device (I believe) so this is a totally different context than your SCC. There will be much more current flowing through the wire.

If you do use smaller wire, make sure to use a smaller fuse on the charge circuit (100A would be in the right ballpark for 4AWG in engine bay probably, but you would want to double check that and calculate based on your specific conditions).
 

Hedges

I See Electromagnetic Fields!
The other reason you might use smaller wire for charging is if you don't care about voltage drop.
For an inverter or motor, we want to deliver full voltage.
If your inverter is cranking out 200A at 14.5V while your battery is getting 200A at 12.5V, what's the big deal?
So long as wire temperature doesn't exceed insulation rating, the watts dissipated in wire is just power and heat. As battery comes up in voltage the current will taper off.
(May not be able to get 2V drop in that short a wire without exceeding ampacity, but my point is that limiting to 3% voltage loss isn't all that important.)
 
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Dzl

Unofficial Forum Librarian
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The other reason you might use smaller wire for charging is if you don't care about voltage drop.
In this situation I think that ampacity would be the limiting factor. Even setting allowable voltage drop to 50% 😀 the blue sea calculator recommends 4/0 for max continuous current of 250A, in engine bay (or 3/0 for 200A). I am not sure how well the assumptions I made match OP's situation (see attached).

I am also not sure how to accurately or safely calculate what the max current between alternator and battery bank would be. If it will never get close to 200A 4/0 may well be overkill.
 

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Guda

Superstrut Strut
One more reason @HRTKD's suggestion of a generator might be worth considering. It may be the path of least resistance.
The project is all but done. Waiting on lugs. Need a drill bit for my hole saw. Then its all about putting it together

This cost less than $500... Good luck getting anything but short lived junk generator for that $. I had 3 generators because one was always in the shop. One burned down my place. I rented a high end 2000w over a month ago & hated it.

I don't need a generator. With the correct battery, a wind turbine & the rest of my PV deployed , I'll never need a generator.

Now, being able to have mobile power is a real handy option. I'm adding a MC 250 SCC once I get the correct battery for my home. Then I can build out a PV trailer. Do that with a generator....

Not to the wire there is not. The wire experiences electrons flowing through it, the byproduct of this is heat, the smaller the wire or the more current the more heat, enough heat and you get fire. Doesn't matter whether it is charging or discharging
The 4awg works fine at 10a tho.

Its possible that your charge rate will never get close to 250A, I don't know, and I don't think you know either.
Totally. I watched a video about a fancy system. They drained their trucks battery while running to the point it stopped. Then they added that 370 amp alternator. They where getting like 50 amps at their trailer. Ya so no idea how much power actually gets to the back. Its more since I installed the 250amp alternator

I'm not saying you do, I'm only saying the wire needs to handle the current that will flow through it. I don't know what that is because I don't understand your system fully. But your alternator is rated to 250A and your load is roughly ~250A. If your charge rate is less than 250A you could use smaller wire sized to the max charge rate. I don't know what your max charge rate is, but you seem set on using as much of your alternators rated output as you can.
Me either! LOL! I used to have a super nice multi meter that clamped to read amps. Maybe I'll get another one someday
Remember, I want 20amps but will be totally okay with 10amps. We can have goals. If I want to get more amps than what I have I'll have to upgrade wire size on the run to the alternator.

Truck has 2 batteries like normal. Then in the powerbox there is a 200ah 12v battery. 4awg is how everything is wired currently. I am replacing the wire from the powerbox battery to 4/0. Then running that to a 3000w 120v inverter then hooking all that to distribution blocks to run the 2000w 115v inverter thats already in the powerbox.

The reason you could use smaller wire with your SCC is not because it was for charging, it is because the charge current was much lower. But in this case you are trying to use a 250A alternator with no current limiting device (I believe) so this is a totally different context than your SCC. There will be much more current flowing through the wire.
I wish I had better info. I have been running like this for months without any heat issues. Even when it was hot before I got my solar up.

If you do use smaller wire, make sure to use a smaller fuse on the charge circuit (100A would be in the right ballpark for 4AWG in engine bay probably, but you would want to double check that and calculate based on your specific conditions).
I'm only using 1200w at 120v out of the 3000w inverter. Like if the inverter in the box currently just did 120v I would not have to do any of this.

The other reason you might use smaller wire for charging is if you don't care about voltage drop.
For an inverter or motor, we want to deliver full voltage.
If your inverter is cranking out 200A at 14.5V while your battery is getting 200A at 12.5V, what's the big deal?
So long as wire temperature doesn't exceed insulation rating, the watts dissipated in wire is just power and heat. As battery comes up in voltage the current will taper off.
(May not be able to get 2V drop in that short a wire without exceeding ampacity, but my point is that limiting to 3% voltage loss isn't all that important.)
Once I start the build I will poke around with the multi meter to see if I can find this out

In this situation I think that ampacity would be the limiting factor. Even setting allowable voltage drop to 50% 😀 the blue sea calculator recommends 4/0 for max continuous current of 250A, in engine bay (or 3/0 for 200A). I am not sure how well the assumptions I made match OP's situation (see attached).

I am also not sure how to accurately or safely calculate what the max current between alternator and battery bank would be. If it will never get close to 200A 4/0 may well be overkill.
2 ends to the equation. Alternator to battery, battery to inverter. 3000w 12v inverter needs 4/0 from battery. The trucks off & I can pull what ever from the battery. Trucks on, I need to be careful of how much I draw.
 

Guda

Superstrut Strut

@snoobler @Dzl & the rest of the great folks here for bring up the wire size. My old RV 12v system had huge inverter wire but small wire from the SCC. So I just thought that was the deal. Now I've got it & have wire size chart open all the time.​


So now I'm working on the build & looked at the wire from the alternator to the battery. Its to small. I need to upgrade that wire & the wire the connects the trucks 2 batteries. I wonder if there is a upgrade set or if I am going to have to make all those wires. That wire is so small its probably limiting how much power can get to the box. Seams weird to put big wires back to the box without making that alternator wire bigger.
 

nwillitts

Solar Addict

@snoobler @Dzl & the rest of the great folks here for bring up the wire size. My old RV 12v system had huge inverter wire but small wire from the SCC. So I just thought that was the deal. Now I've got it & have wire size chart open all the time.​


So now I'm working on the build & looked at the wire from the alternator to the battery. Its to small. I need to upgrade that wire & the wire the connects the trucks 2 batteries. I wonder if there is a upgrade set or if I am going to have to make all those wires. That wire is so small its probably limiting how much power can get to the box. Seams weird to put big wires back to the box without making that alternator wire bigger.
make your own,i did.
 

Guda

Superstrut Strut
Weeks of acquiring parts, components & planing. Now I am 5+ days into the build & everything is going great. I did find this https://www.ficmrepair.com/index.cfm/page/ptype=results/category_id=40/mode=cat/cat40.htm
I'll be making my own 4/0 harness after I am done with this build.

I have a day of wiring in the box & its done. I have about another day of wiring the house side of all this. I had to cut off shipping container doors & drill through over 1.5 inches of steel to get a place to mount the outdoor NEMA 18x18x6 box. It took about a hour to drill 1/2" out to a 3/4" hole.

I can not wait to be done with this. I have been so lucky with the weather I haven't needed any auxiliary power. Also lucky for this forum. Never thought I needed bigger wire but holy cow I need HUGE wire ever since I put that 250amp alternator in, in like June....

Much thanks!
 

Guda

Superstrut Strut
 
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