What wire size for Solar and Victron MPPT?

[Superduty]

Victron Smart Solar MPPT 100/30

What size wiring should I use for solar panel to MPPT and then from MPPT to battery?

Wire length from panel to MPPT is about 15 feet.

Wire length from MPPT to battery is about 1 foot.

Battery is 12v 100AH LiFePo4.

Solar panel is as shown in the photo below.

 

[Peter_n_Margaret]

Follow the instructions.
Cheers,
Peter
OKA196 motorhome

 

[Superduty]

Follow the instructions.
Cheers,
Peter
OKA196 motorhome

Super helpful. One of the most informative responses on EP.

Thanks

 

[Peter_n_Margaret]

The wiring size instructions are written on the panel spec that you posted.
Perhaps it is the view that Panasonic don't know anything about the subject?
Cheers,
Peter
OKA196 motorhome

 

[dstock]

I always go 10 gauge from the panel to the MPPT controller and to the battery. I prefer a little bit of overkill when it comes to solar wiring based on my experiences with thinner gauge wire.

 

[Pacific Northwest yetti]

10 awg, dont forget to fuse/ breaker. Victron makes a good product.

 

[dstefan]

PV cable is *usually* 10 awg. While any good wire will work, PV is also UV resistant and is your best bet.

 

[sancap]

There is a reason that most Victron products will accept 6 gauge wire. Go as big as you can whenever you can.

 

[NatersXJ6]

I’ve found that low voltage landscape wire at the big box is a good option for vehicle solar panels. Really
Good UV protected and thick insulation, paired cable with marking to sort positive and negative, and available in 12 AWG. A huge plus…’sold by the foot!

 

[jonyjoe101]

From the panel to the mppt controller 10 gauge is good especially if its pure copper wire. You might even get away with 12 gauge pure copper. From the panel your pushing high voltage 30 plus volts from a 330 watt panel, the more volts your pushing the lower the gauge is required even at the 15 feet distance. When I started solar installation I used 10 gauge speaker wire (copper clad wire) because I didn't know any better, its still on the roof of my van for the past 10 years and has worked good but I wish it was pure copper instead.
From the mppt to the battery is where you need at the minimum 10 gauge pure copper since you will only be pushing low voltage (14 volts) which has severe voltage drop issues at longer distances.

Either way once you got the system up and running verify the voltage at the battery terminals against what the mppt controller is reading to see if you have voltage drop. Every controller I ever had, had at least a .5 volt difference, which results in low performance from the panel.

With 330 watts you should be able to at least get about 15 amps of charge power when the sun is overhead. I get about 15 amps on my lifepo4 from my 365 watt panel. I was getting about 12 amps from a 240 watt panel. My lifepo4 is usually 80 percent charge every time. The more empty (lower voltage) the battery is will result in more amps going into the battery. If your not getting at least 15 amps, you probably have voltage drop issues on the controller. Raising the bulk setting will fix that.

 

[Superduty]

There is a reason that most Victron products will accept 6 gauge wire. Go as big as you can whenever you can.

So most of the advice above is for 10awg and 12awg. You are recommending 6awg. That is a big difference. When I see such a difference in advice, I have to assume someone is right and someone is wrong.

Bigger wire = less voltage drop. But in reality is 6awg needed for this? How much better will this system be with 6awg vs 10awg.

 

[NatersXJ6]

It will be expensive and difficult to work with 6 AWG. Use any available online DC voltage wire size calculator. I ran 2 different sites and both said 19 AWG, so literally, using the 12 or 14 that is commonly available and easy to run into MC4 connectors is all you reasonably need. Personally,
I would probably just run it all from 12, as it is easy to buy and work with all one size.

 

[calicamper]

Just for reference my Siemens/ Enphase House system has a max of 16, 250watt panels per harness run which consists of 12 gauge heavily insulated loom bundle. From the panel to mppt. 12 is definitely ok. ?

 

[Peter_n_Margaret]

It is amps that cause voltage drop.
The OP's panel is only going to deliver around 6A in ideal conditions. Besides, PV panels are effectively a constant power source, so they will compensate for some voltage drop with higher amps to maintain the same power, so a little undersize between the panel and the controller is of little consequence to the effective output.
On the other hand, it is important to avoid significant voltage drop between the controller and the battery otherwise the set charge parameters will be compromised. But the OP's situation only has a very short distance involved.

The Panasonic advise on the panel is totally adequate, in my view.

Here is a voltage drop calculator...
VOTLAGE DROP =[cable length (in metres) X current (in amps) X 0.0164] divided by cable cross-section in mm.sq.
All metric, because the whole world (except 3 countries) is metric.
Note that "cable length" must include BOTH +ve and -ve cables added together.
Cheers,
Peter
OKA196 motorhome

 

[Peter_n_Margaret]

"Nominal" 25C.
Cheers,
Peter
OKA196 motorhome.