Seeking Advice: Wire Size for simple 12v solar system (and breakers)

[RidingWithStymie]

Hello friends,

I have been reading this forum for a few years, but this is my first post. I would be grateful for advice on what wire size to use for the following simple 12v solar system in my van. I will gladly provide more detail or even photographs if requested.

I’m about to add a second Lithium battery in parallel. I will follow best practices for wire layout, but I’m confused as to wire size. I have consulted two different charts/calculators online and they give different results.

My setup:
Wires: All of my wires are currently 10AWG

Solar Panel: 1 x 200 watt 12v monocrystalline panel on roof

Charge Controller: Renogy Wanderer 30A PWM

Batteries: 2 x 100Ah SOK 12V LiFePO4 (Parallel)

NO inverter.

Everything I run is 12-volt via either USB or cigarette lighter connector. I run the following:

12v Alpicool fridge
Laptop computer via 12v cig lighter cord (no inverter required)
WeBoost cell signal booster
Charging USB items, such as phone, etc.
(Soon I will add a Starlink dish (12v))

What size wires do you recommend to connect the batteries to each other and out to the charge controller and out to the downstream? I assume they should all be the same size?

Also, I have 30A breakers both to and from charge controller. Should I also add 30A breakers inline from batteries to downstream?

I appreciate anyone’s advice/suggestions. Please feel free to ask questions.

Thank you,

Greg

 

[Rocketman]

As long as you decide to maintain no inverter.

With everything on - including the new Starlink you may be getting close to or be over the 30amps. If you are close you may want to go up a wire size to 8awg - 40amps.

If you ever need just a little more power from your solar panel - by changing out the pwm charge controller with a high quality mppt charge controller- you will get a little more power out of your current panel.

Yes you want breakers on both sides of the solar charge controller- the panel side is to “turn the sun off” to reset it or do maintenance- the other side is to protect the wire.

Fuses and breakers are to protect the wire - not the load. If the load dies and shorts out - it’s dead… but you want to protect the wire so the wire does not cause a fire.

 

[Tomthumb62]

Like what @Rocketman said, it all depends upon if you ever think you might want an inverter some day. It’s not that expensive to upgrade the parallel battery cables to something that can handle 200+ amps, like these:

2 Gauge (2 AWG) Extreme Battery Cable with Ends - Copper Extra Flexible Stranded

www.batterycablesusa.com

They sell it by the foot, but you can order by the inch, so you can select the perfect length for your batteries. Measure from terminal to terminal then add 2-3” for some wiggle room. They have the best options, price and quality I’ve come across to date.

 

[RidingWithStymie]

Rocketman, I really appreciate your response. I'm going to take your advice and go with 8awg wire.

I had done some calculations (which I didn't save and lost the file when my laptop crashed). I think it may be literally impossible for me to exceed 30 amps currently, since the multi-socket outlet that I plug everything into has a 10 amp fuse.

I'm going to use 8awg wire and install 30 amp breakers in the wires from battery to the outlet. I already have breakers installed to/from the charge controller.

Thanks again,

Greg

PS - Tomthumb62, Thanks for your advice as well.

 

[RidingWithStymie]

Like what @Rocketman said, it all depends upon if you ever think you might want an inverter some day. It’s not that expensive to upgrade the parallel battery cables to something that can handle 200+ amps, like these:

2 Gauge (2 AWG) Extreme Battery Cable with Ends - Copper Extra Flexible Stranded

www.batterycablesusa.com

They sell it by the foot, but you can order by the inch, so you can select the perfect length for your batteries. Measure from terminal to terminal then add 2-3” for some wiggle room. They have the best options, price and quality I’ve come across to date.

I like the fact that these cables are measured "hole to hole." And the price is right. I'm gonna jump on these. Thanks for the tip General Thumb!

 

[Tomthumb62]

I like the fact that these cables are measured "hole to hole." And the price is right. I'm gonna jump on these. Thanks for the tip General Thumb!

I spent a lot of money buying other battery cables before someone on this forum recommended this company. They don’t sell on Amazon or eBay so I think their overhead is lower hence the good price. The ability to customize the terminal ends is great, they’ll even do 90 degree lugs if you leave them a note in the note box on the order form. Shipping has usually been 4-5 days to my rural location on the west coast.

They have regular flexible, marine tinned and “extreme” cables to choose from. I’ve only ordered the extreme version and I think the only difference is the thicker insulation. Regardless, all versions are temperature rated for 105C (typically the highest rating found for non industrial applications.)