Wiring Charge Controller and Inverter-Charger

[Danjo]

I’m getting closer to finalizing the location of my charge controller and inverter-charger (ugh!). I’m planning on mounting it in the cabinet above the driver.

Since the controller and inverter are next to each other, can I run just one pair of cables to the batteries to a junction near the controller and inverter?

Thanks

[Native]

Originally Posted by Danjo

I’m getting closer to finalizing the location of my charge controller and inverter-charger (ugh!). I’m planning on mounting it in the cabinet above the driver.

Since the controller and inverter are next to each other, can I run just one pair of cables to the batteries to a junction near the controller and inverter?

Thanks

Yes you can. Make sure your highest consumer or producer of current has the same thickness of cabling as the run to the battery. Use proper crimp-on cable lugs and insulate the points at which all cable are connected together. You would not want your power to short-circuit


If it were my project, I would terminate the run from the battery at the inverter/charger, then run cables to the charge controller. I would also install the appropriate size of cut-off master switches and fuzing to both protect the cabling and the components and to allow you to remove any component for service.

[Danjo]

Originally Posted by Native

Yes you can. Make sure your highest consumer or producer of current has the same thickness of cabling as the run to the battery. Use proper crimp-on cable lugs and insulate the points at which all cable are connected together. You would not want your power to short-circuit


If it were my project, I would terminate the run from the battery at the inverter/charger, then run cables to the charge controller. I would also install the appropriate size of cut-off master switches and fuzing to both protect the cabling and the components and to allow you to remove any component for service.

Thanks. What about sizing the conductors? If I have a 60 amp controller, and a 30 amp inverter, do I calculate for 90 amps?

[Native]

Originally Posted by Danjo

Thanks. What about sizing the conductors? If I have a 60 amp controller, and a 30 amp inverter, do I calculate for 90 amps?

If there is a chance of both the charge controller and the converter/inverter charging the batteries at the same time, then figure for 90 amps.


Bear in mind that the run length for the total current will be the total path of the cables from the battery to the first connection point *AND BACK*. So, if you have 10 feet between the batteries and the first connection, you would run the calculators for 20 feet.

[dzl_]

Is this basically what you are envisioning (negative wiring excluded for simplicity)?







If so, I believe this will work just fine. In fact it will be ideal in some situations (shorter path between the solar charge controller and the inverter/charger means when the inverter is inverting and the PV array is producing current will have a shorter path to flow between the two (as opposed to flowing to the battery and back out to the inverter)). It also means you only have to run the one pair or large gauge wires back to the battery.


But as Native said, always use total (round trip) wire length to calculate voltage drop, and always account for the maximum current that could flow through the circuit. And anywhere you drop down in wire size needs its own fuse, so either you can do as Native said and use the same wire size for all the legs, or you can use smaller wires for the SCC and inverter but they should be fused individually at or near the place you drop down in wire size (i.e. the junction box or busbar).


The rule of thumb for fuses is they should be roughly 1.25x the max current of the device or circuit, and trip before the max amperage of the wire is exceeded. But, its always best to first check to see if the manufacturer has recommended fuse sizes and types, usually they do.

[Danjo]

Originally Posted by dzl_

Is this basically what you are envisioning (negative wiring excluded for simplicity)?







If so, I believe this will work just fine. In fact it will be ideal in some situations (shorter path between the solar charge controller and the inverter/charger means when the inverter is inverting and the PV array is producing current will have a shorter path to flow between the two (as opposed to flowing to the battery and back out to the inverter)). It also means you only have to run the one pair or large gauge wires back to the battery.


But as Native said, always use total (round trip) wire length to calculate voltage drop, and always account for the maximum current that could flow through the circuit. And anywhere you drop down in wire size needs its own fuse, so either you can do as Native said and use the same wire size for all the legs, or you can use smaller wires for the SCC and inverter but they should be fused individually at or near the place you drop down in wire size (i.e. the junction box or busbar).


The rule of thumb for fuses is they should be roughly 1.25x the max current of the device or circuit, and trip before the max amperage of the wire is exceeded. But, its always best to first check to see if the manufacturer has recommended fuse sizes and types, usually they do.

Thanks, yes that is what I was thinking. I was thinking that

The positive and negative cables come into the cabinet with the negative going to a busbar and the positive going through a fuse or fused switch, then to a busbar.

I’d attach the inverter, the charge controller and the appliance fuse block to the bus bar using appropriately-sized, fused conductors,

It’s all starting to come together in my head. The line and load being on the same conductor is new to me.

Edit: I just saw that the “main” from the battery is fused at the battery. That makes more sense.

[dzl_]

Originally Posted by Danjo

I’d attach the inverter, the charge controller and the appliance fuse block to the bus bar using appropriately-sized, fused conductors,

I was going to ask about the DC distribution. This arrangement might make even more sense with DC distro coming off the same busbar. Definitely a bit more efficient when your chargers are supplying power. When on battery power, it'll depend on wire length, gauge, etc, and calculating line loss/voltage drop, to figure out what would be more efficient. What is your system voltage?

Edit: I just saw that the “main” from the battery is fused at the battery. That makes more sense.

Yeah, definitely makes sense to keep the fuse as close to the source as possible, with the main fuse that means as close to the positive battery terminal as possible, the standard for the marine world is within 7", ideally right on the battery terminal (these MRBF fuses are great for that).

One more question, 30A seems pretty low for an inverter/charger, and its fairly rare to see a system with a larger charge controller than inverter (not that there is any problem with it), are you sure you've calculated the inverter/charger amperage right?

[Danjo]

Originally Posted by dzl_

I was going to ask about the DC distribution. This arrangement might make even more sense with DC distro coming off the same busbar. Definitely a bit more efficient when your chargers are supplying power. When on battery power, it'll depend on wire length, gauge, etc, and calculating line loss/voltage drop, to figure out what would be more efficient. What is your system voltage?


Yeah, definitely makes sense to keep the fuse as close to the source as possible, with the main fuse that means as close to the positive battery terminal as possible, the standard for the marine world is within 7", ideally right on the battery terminal (these MRBF fuses are great for that).

One more question, 30A seems pretty low for an inverter/charger, and its fairly rare to see a system with a larger charge controller than inverter (not that there is any problem with it), are you sure you've calculated the inverter/charger amperage right?

I guess I need to check my numbers. I took the Max Current Input number and actually typed it wrong. Max current input is 35A.

The system is 12V

It’s a 1000W inverter, so should I be sizing for that? 83A? Or 100A?

So about that conductor size to include the output of the charge controller:

I have 6x100 Watt panels @ 12v that’s 50A

83A + 50A = 133A

133A x 1.2 = 160A

The Blue Sea table for a 30’ run @ 3% loss says I need a 4/0 conductor. The Blue Sea Wizard, using the 133A value says I need 3/0

Thoughts?

Thanks!

[Native]

Your compartment is 15 feet from the batteries ... wow, it adds up quickly.


4/0 cables are thick. I would suggest running parallel 2/0 cables. Parallel 2/0 cables provide the equivalent of a single 5/0 cable in capacity. You might be able to get away with parallel 1/0 cables as they are equivalent to a single 3/0 cable and *almost* a single 4/0 cable.

[Danjo]

Originally Posted by Native

Your compartment is 15 feet from the batteries ... wow, it adds up quickly.


4/0 cables are thick. I would suggest running parallel 2/0 cables. Parallel 2/0 cables provide the equivalent of a single 5/0 cable in capacity. You might be able to get away with parallel 1/0 cables as they are equivalent to a single 3/0 cable and *almost* a single 4/0 cable.

That’s a thought.

I’m eventually going to shorten the distance by making a bolt on battery box under the secondary battery door. Just need to make sure it’s strong enough. Not ideal but the best I can come up with. And hard to steal so there’s that

[dzl_]

Originally Posted by Danjo

I guess I need to check my numbers. I took the Max Current Input number and actually typed it wrong. Max current input is 35A.

The system is 12V

It’s a 1000W inverter, so should I be sizing for that? 83A? Or 100A?

So about that conductor size to include the output of the charge controller:

I have 6x100 Watt panels @ 12v that’s 50A

83A + 50A = 133A

133A x 1.2 = 160A

The Blue Sea table for a 30’ run @ 3% loss says I need a 4/0 conductor. The Blue Sea Wizard, using the 133A value says I need 3/0

Thoughts?

Thanks!

So as I understand it, you will need to account for the max current flowing in one direction at one time. In other words greater of (1) the total output of all charge sources OR (2) the total simultaneous draw of all AC & DC consumers.


So in your situation, for the main conductor between your battery bank and busbar, that would be the greater of:

1. The rated output of your Solar Charge Controller + rated output of the AC charger.
2. Maximum load of all AC (inverter) & DC loads combined

But to the best of my understanding, you don't need to add charge and discharge current together, just take the larger of the two,


Do you have a link to the inverter/charger and charge controller?

[dzl_]

Based on what I think I understand so far, this is what I'm now picturing your design looking like:



Does this look right? Do you have any idea what your max DC loads current will be?




edit: clarification on the 100A figure for the 1000W inverter. If the 1000W rating is output and we assume the inverter is about 80% efficient (conservative but too conservative) input power would be about 1200W and 100A would be pretty accurate @ 12v.

[Native]

I'd say that is a fair assessment, _DSL.

[Danjo]

Originally Posted by dzl_

I was going to ask about the DC distribution. This arrangement might make even more sense with DC distro coming off the same busbar. Definitely a bit more efficient when your chargers are supplying power. When on battery power, it'll depend on wire length, gauge, etc, and calculating line loss/voltage drop, to figure out what would be more efficient. What is your system voltage?


Yeah, definitely makes sense to keep the fuse as close to the source as possible, with the main fuse that means as close to the positive battery terminal as possible, the standard for the marine world is within 7", ideally right on the battery terminal (these MRBF fuses are great for that).

One more question, 30A seems pretty low for an inverter/charger, and its fairly rare to see a system with a larger charge controller than inverter (not that there is any problem with it), are you sure you've calculated the inverter/charger amperage right?

You’re right! This totally needs to be included.

Car stereo ~ 40A
Lighting ~ 10A
Water Pump ~ 5A
Refrigerator ~ 5A
Water Heater Ignitor ~ 1A

Total ~ 60A

Note: I still haven’t purchased the stereo. I can only approximate. And looking at the numbers, I might just live with my Milwaukee charger/radio, though a nice sound system is still really desired.

Here’s the inverter/charger manual

https://www.renogy.com/content/RNG-I...T-C-Manual.pdf

[dzl_]

Okay, updated schematic:

From a safety / ampacity standpoint (NOT accounting for voltage drop and assuming 105C marine grade wire) I would think these values would be acceptable minimums (based on safety alone):
Leg 1 = Battery to busbar = 200A fuse and 2 AWG (210A) or greater
Leg 2 = Busbar to SCC = 60A fuse and 8 AWG (80A) or greater
Leg 3 = Busbar to Fuse Block = 75A fuse and 8 AWG or greater
Leg 4 = Busbar to Inverter = 125A fuse and 4 AWG or greater


BUT as I'm sure you have surmised, voltage drop will be the factor that dictates your wire size (at least for leg 1). And remember that voltage drop applies to the whole path current will take.



Using a dc appliance as an example that would be Leg 1 + Leg 3 + leg 3b (dc distro to appliance).


Based on the cost of large gauge copper wire, and voltage drop for high amp low voltage circuits, if I were in your shoes I would be doing whatever I could to minimize distances for the high amp legs of the system.



Regarding the inverter:
It looks like that is a rebranded Yiyen Inverter. Very similar to AIMS inverters (another brand that uses rebranded Yiyen inverters). Renogy documentation and tech support is sometimes lacking, so it may be helpful to know this in the future.


Looks like a pretty solid inverter, pure sine and low frequency

[Danjo]

Originally Posted by dzl_

Okay, updated schematic:

From a safety / ampacity standpoint (NOT accounting for voltage drop and assuming 105C marine grade wire) I would think these values would be acceptable minimums (based on safety alone):
Leg 1 = Battery to busbar = 200A fuse and 2 AWG (210A) or greater
Leg 2 = SCC to Busbar = 60A fuse and 8 AWG (80A) or greater
Leg 3 = DC distro to Busbar = 75A fuse and 8 AWG or greater
Leg 4 = Inverter to Busbar = 125A fuse and 4 AWG or greater


BUT as I'm sure you have surmised, voltage drop will be the factor that dictates your wire size (at least for leg 1). And remember that voltage drop applies to the whole path current will take.



Using a dc appliance as an example that would be Leg 1 + Leg 3 + leg 3b (dc distro to appliance).


Based on the cost of large gauge copper wire, and voltage drop for high amp low voltage circuits, if I were in your shoes I would be doing whatever I could to minimize distances for the high amp legs of the system.



Regarding the inverter:
It looks like that is a rebranded Yiyen Inverter. Very similar to AIMS inverters (another brand that uses rebranded Yiyen inverters). Renogy documentation and tech support is sometimes lacking, so it may be helpful to know this in the future.


Looks like a pretty solid inverter, pure sine and low frequency

Wow, well I was expecting larger wire sizes.

You’re right about the quality of Renogy tech support. They sure talk a good game up front but when you dig a little they come up short. But I’m invested now!


Thanks for your help!

[dzl_]

Wow, well I was expecting larger wire sizes

Well to be very clear, you will want larger wire sizes.

The calculations above are based on safety alone ("ampacity" and based on marine grade 105*C wire--when you use a calculator like the blue sea calculator you must use 105*C wire because its a marine calculator). They should be viewed as the absolute minimum safety floor you should not go below, but they don't account for voltage drop / power loss, which are more functional / efficiency considerations.

When you account for voltage drop (if your target is <3%) you'll probably want at least:

Leg 1: 4/0 AWG (< 2%)

Leg 2: 6 AWG (< 1%)

Leg 3: 4 AWG (< 1%)

Leg 4: 4 AWG (< 1%)

These are just estimates (legs 2, 3, 4, assume less than 4ft round trip), you'll want to calculate yourself.

[Danjo]

I got some of the 4/0 cable today. Windy Nation screwed up and only sent half.

I must say, that 4/0 is some big stuff!!!

[Danjo]

I also gotta thank you dzl_

I opened a tech support case with Renogy about the same time I started this thread. You should know your assistance was like 100x more helpful and thorough. They really pissed me off that after dropping nearly $3K they wouldnt take a little more time

[sproutroot]

Make sure that the charger in your inverter/charger won't overload the system. I'm pretty sure when I sized my cables I had to size based on the charger, not the inverter.