Inverter and Cable/Wire Size Question

[Brian_HR]

I've been reworking the electrical system on my 2021 Redhawk 24B in preparation for adding an inverter (and later solar panels and a solar charge controller). I've included a schematic of the electrical system as I've been able to reconstruct it. I moved the 3 cables (Generator, Leveling Jacks, RV Main 12 V panel) that were originally connected to the stock battery terminals to a bus bar and added a battery monitor so I can see the state of the batteries. I also added 2 Lion Energy UT1300 batteries providing 205 Ah.

Now, I'd like to add a Renogy 2,000W inverter and looking at the manual it states fuse and AWG minimums of 200A fuse and 2 AWG cable. The Renogy inverter states max continuous draw of 2,000W and peak of 4,000W. At 12V that is 166A current for 2,000W and 333A for the 4,000W peak.

My question is the wire size between the battery and inverter. The manual states 2 AWG minimum and in searching online I've seen tables state 2 AWG can carry a max of 115 to 181 amps. But other tables that recommend wire size for 150-200 A and runs of 7-10 ft (which is the distance for my cable run) have recommended wire sizes of 4 AWG. I'm a little confused and hoping the community can help provide some guidance. I don't want to melt wires by undersizing them but also don't want to oversize the wires as that just complicates the install.

I'd like to go with the 2,000 W inverter as it would power all the appliances in the rig except the the AC but would be OK going down to the 1,000W inverter if it means being safer with the existing wiring. All I'd lose is the microwave which we don't plan to use much (if at all).

Appreciate the help,

-Brian

P.S. I know the 4/0 AWG cables connecting the batteries are probably overkill but they were what I had on hand with the right length to connect the batteries.

[craigav]

There are a lot of charts that don't explain a lot, as there is a big difference in the max amps for inside a wiring cabinet, vs in open air, vs a lot of other conditions. In any case, I would go with 2/0 (or if you have a lot of 4/0 left I would use that). You could go with the 2awg as the recommended minimum, however I would only do that if I never planned to use more than 1000 watts continuous at a time other than the possible surge current. As mentioned, there are a lot of charts. Take a look at this chart and at the bottom of the page is a calculator where you can enter the length of the circuit to get an idea of the voltage drop. You should pay most attention to the column listed as "Maximum amps for power transmission vs "chassis wiring".

https://www.powerstream.com/Wire_Size.htm

~CA

[Vicr]

What size wire will your incoming DC lugs accept on your inverter?

[Brian_HR]

Originally Posted by Vicr

What size wire will your incoming DC lugs accept on your inverter?

According to the manual they are M8.

[Brian_HR]

Originally Posted by craigav

There are a lot of charts that don't explain a lot, as there is a big difference in the max amps for inside a wiring cabinet, vs in open air, vs a lot of other conditions. In any case, I would go with 2/0 (or if you have a lot of 4/0 left I would use that). You could go with the 2awg as the recommended minimum, however I would only do that if I never planned to use more than 1000 watts continuous at a time other than the possible surge current. As mentioned, there are a lot of charts. Take a look at this chart and at the bottom of the page is a calculator where you can enter the length of the circuit to get an idea of the voltage drop. You should pay most attention to the column listed as "Maximum amps for power transmission vs "chassis wiring".

https://www.powerstream.com/Wire_Size.htm

~CA

Thanks @CA. I had seen this chart and don't fully understand Chassis Wiring vs Power Transmission although in the notes it says that both are conservative. Maybe that's why other charts are showing the ability to carry 150-200 amps over ~10 ft with 4 AWG wire?

I'm leaning towards the 1,000W inverter as it will meet 95+% of our needs and I feel the 2AWG wiring we have leading up to the bus bar will be able to handle any load the inverter can provide.

-Brian

[craigav]

Just as a thought of what I would suggest (simply my opinion) I would still go with the 2000 watt inverter as I would prefer to have an inverter loaded to 50% of its rating instead of 100%. (Assuming the price wasn't too much more). Also, you could consider keeping your 2awg and later on (if ever) run another 2awg (having two inputs) which is not really recommended by me, however renogy mentions using two input cables and I think the 2000w renogy inverter has two + and two - inputs for that purpose. Keep in mind (and part of my reasoning) that many (not all of course and some more and some less) kitchen appliances run right at 1200 watts such as coffee makers, electric skillets, fryers, and many more, so I would plan to be able to run 1200w max and get the 2000 watt inverter and I would also add inline with the cabling a ~120 amp resettable breaker between the batteries and your smart shunt (as close to the batteries as feasible).

[Vicr]

Looking at the practical side of things the incoming lugs are an M8 which is .323". The largest size wire that will fit in the lug is #1 AWG .2893 which is good for 150 amps.

[craigav]

Originally Posted by Vicr

Looking at the practical side of things the incoming lugs are an M8 which is .323". The largest size wire that will fit in the lug is #1 AWG .2893 which is good for 150 amps.

Hi Vicr, I am not sure we are on the same page, these would work just fine if one chose to go with 2/0 cable and attach it to the back of the inverter with the M8 bolt terminal connections on the inverter. I think I have seen 4/0 lugs with an M8 ring. Not that it matters in this case going with 2wg. Thanks, CA

As I gave it some thought, I suspect the reason for the difference here is because it is not a lug connection on the inverter, it is a M8 terminal bolt connection instead. ~CA

[Rustynuts]

Originally Posted by Vicr

Looking at the practical side of things the incoming lugs are an M8 which is .323". The largest size wire that will fit in the lug is #1 AWG .2893 which is good for 150 amps.

Why not just use 4/0 with a 3/8 crimped on lug and bolt on to the inverter lug?

[Brian_HR]

Originally Posted by craigav

Just as a thought of what I would suggest (simply my opinion) I would still go with the 2000 watt inverter as I would prefer to have an inverter loaded to 50% of its rating instead of 100%. (Assuming the price wasn't too much more). Also, you could consider keeping your 2awg and later on (if ever) run another 2awg (having two inputs) which is not really recommended by me, however renogy mentions using two input cables and I think the 2000w renogy inverter has two + and two - inputs for that purpose. Keep in mind (and part of my reasoning) that many (not all of course and some more and some less) kitchen appliances run right at 1200 watts such as coffee makers, electric skillets, fryers, and many more, so I would plan to be able to run 1200w max and get the 2000 watt inverter and I would also add inline with the cabling a ~120 amp resettable breaker between the batteries and your smart shunt (as close to the batteries as feasible).

@CA, the % utilization is something I hadn't considered. Thinking about it some more, I can think of 3 use cases:

1. Making coffee with Mixpresso Single Cup Coffee Maker: 800 Watts
2. Watching TV with Synology Media Server: ~100 Watts
3. Using Computers + iPads (3 people): 195 watts (conservative estimate)

Obviously we wouldn't be able to do all of these at the same time but individually I think they'd all fit within the capabilities of the 1000W inverter. Does that make sense or am I thinking about it wrong?

Some other considerations in favor of the 1000W inverter is it will be easier to fit within the space under the kitchen counter that I'm preferring. Finally, I'm thinking about the size of the hole I'll have to drill into the rig to run the wires and 2AWG is a smaller hole and easier to crimp, route, etc than 2/0 or 4/0.

The 2000W would definitely provide more flexibility and we wouldn't need to think about what equipment is being used at the same time. It would also allow the use of the microwave if we need it.

Hmm.... tough choice.

-Brian

[Vicr]

When I asked the OP for the lug size he said M8. In most electrical equipment a lug has a female opening, M8 is a diameter, hence my post about cable size. The OP didn't tell me the inverter didn't have lugs. The inverter has posts which is not a lug, huge difference.