Connecting solar panels

[Markw]

Below is what I am wanting to end up with. My goal is to increase the watt output while keeping the voltage the same.



I know I will need at least 2 mp4 extension cables (one for pos an one for neg) to go from this to the electrical setup. Where I am unsure is what I need to use for the green connections. Do I use branch connectors or is there something else I should use?

 

[abnorm]

''Do I use branch connectors ''...................YES

 

[Markw]

Cool. To make sure I have it correct...I would connect the Y ends to the solar panels and the single end to the cable that gets plugged into the electrical setup?

 

[abnorm]

Yes that's correct

 

[Markw]

Thanks

 

[AmargosaWayne]

The watt output doesn't change. Watts = Amps * Volts.

Two 100 watt panels will always give (ideally) 200 watts,

Serial increases voltage.

Parallel increases amps.

Hooking up two panels in parallel as per your diagram increases Amps x 2 keeping the voltage the same.

 

[Markw]

OK, I know I'm missing something (or possibly more than one) but I can't seem to think of it. Any advice would be appreciated (please keep in mind that the panels and controller have already been purchased). I also have a 1000 continuous watt generator for the days when there isn't enough sun. I just noticed I left out that the panels are 12v ones.

My load needs consist basically of a gaming laptop (brick says 150W), a 30Q compressor fridge, 2 phones and some LED lights. I also have a 570WH solar charger I would like to keep charged.



Other questions:

Would series be preferable over the parallel connection for the panels?
Is the bolt on fuse too large or small for the application?
Would adding a continuous duty solenoid Be a good idea or should I skip that?

 

[Camper]

I say if it works..... leave it alone.

 

[Markw]

I say if it works..... leave it alone.

Actually, it isn't built yet, still acquiring pieces.

 

[AmargosaWayne]

The single 150A fuse could be a problem. That's a lot of current that can flow downstream.
The fuse box could melt before that 150A fuse blows.
A 150A fuse may be too much for a 750W inverter.
Those items need to be protected with separate fuses with appropriate capacity for the different loads.

 

[Curtistalmage]

Looks good to me
I would use a Marine circuit breaker instead of the fuse .
Parallel on the panels that way if one shaded the other still works.
Skip the solenoid and add a DC to DC charger.
One last thing would be a battery monitor so you know exactly what’s going in and coming out . O and a breaker on the positive in from the panels . They will still energize the system with the main breaker tripped.

 

[abnorm]

FUSES are sized to protect wires...........WIRES are sized by the anticipated Load.......every + wire should be fused

The 750 w inverter probably needs a #4 fused @100 amp and the fuse box a #10 fused @30 amp (fridge/phone/Box) ............TWO separate fused wires

You're getting a bunch of wires on the Battery Posts?......maybe a buss bar is in order to organize

I'd install a ciggy plug or two and a USB for the phone.....I like the ones that glow the system voltage....NightLight!

 

[Markw]

The single 150A fuse could be a problem. That's a lot of current that can flow downstream.
The fuse box could melt before that 150A fuse blows.
A 150A fuse may be too much for a 750W inverter.
Those items need to be protected with separate fuses with appropriate capacity for the different loads.

This is why I am asking before I build it. I would rather get it right the first time than end up blowing components because I didn't ask.

 

[Burbanlife]

The solar panel wires need to go into a 2 pole dc breaker, not just a in line fuse that goes to the controller, it disconnects the neg. and pos. . but something like this NEC code. https://smile.amazon.com/dp/B09BRB38Y1?ref=ppx_yo2ov_dt_b_product_details&th=1

 

[abnorm]

NEC does not apply

 

[jonyjoe303]

since you have an mppt controller its better to connect your panels in series. Mppt requires high voltage panels to extract every amp available. 2x100 watt panels (12 volt panels are actually 21 volt panels) connected in series will equal 42 volts which is perfect for mppt. With the 200 watt panels in good sunlight you should max out at about 10 amps of charge power ( I usually maxed out at 12 amps with a 240 watt panel).
Here is a post that dealt with series versus parallel and it showed an actual improvement in output
https://vanlivingforum.com/threads/is-this-a-proper-amount-of-amps-for-200w-of-panels.41071/

Since you will be using lifepo4, you will need a coulombmeter, I recommend the tk15 (cost about 50 dollars), its what I use on my 220ah lifepo4. This will ensure you get your battery fully charge everytime. Since this reads the voltage from the battery terminals, you know right away if you have voltage drop problems from the controller to the battery. The reason for a coulombmeter is that lifepo4 voltage is about 13.1 volts from 20 to 90 percent,without counting amps you wouldnt know the actual SOC until its practically empty.

 

[Markw]

Made some changes to the layout. As always, constructive input is appreciated. Eventually I plan to add a 100-200 watt portable panel for a total of 300-400 watts but that will be at least a couple of months away. I will be adding a battery monitor and likely an MT-50 to the controller even though I haven't added it to the drawing.

Question: Will the 30A controller be able to handle the extra panels or would I need to replace it?

 

[abnorm]

You have no wire sizes listed and too many connections at the battery

Inverter & fuse box has 30 amp and a 100 amp circuit sharing a Negative wire.....how big is that?

Again the DCDC and the MPPT are sharing a positive wire (SIZE) and NO Negative for the DCDC ?

A shunt is usually placed on the Negative

Need a fuse after the DCDC

 

[tx2sturgis]

Minor changes I would make:

1) The 40A fuse near the controller needs to be closer to the battery. I like to use MRBF's on my Lithium (LiFePo4) batteries. Fuses are available in the range of 30 to 300 amps. These fuses protect the battery (and cables) from any and all shorts that might occur downstream in your cables and connections. It is acceptable to fuse the MRBF with a 'fail safe' fuse of say, 50 or 80 amps, then a smaller inline fuse of 25 or 40 amps (for example) closer to the load.

https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A
https://www.bluesea.com/products/5194/MRBF_Surface_Mount_Fuse_Block_-_Independent_Source
2) The inverter needs to have it's own heavy ground cable return to the battery or buss bar. It should not be sharing it's ground on a fuse panel that will be fused at 30 amps. This can cause a ground return current loss to other components on the fuse block when the inverter is producing maximum (or near maximum) power.

3) The lithium batteries should be wired with alternating POS and NEG supply lines. This is critical with lithium batteries to help balance the load and charging currents.

 

[Markw]

You have no wire sizes listed and too many connections at the battery

Inverter & fuse box has 30 amp and a 100 amp circuit sharing a Negative wire.....how big is that?

Again the DCDC and the MPPT are sharing a positive wire (SIZE) and NO Negative for the DCDC ?

A shunt is usually placed on the Negative

Need a fuse after the DCDC

I plan to have wire sizes appropriate for the need, still researching that (will likely follow suggestions by Will Prowse).

Will alter the shunt setup to the negative.

The dc-dc isn't actually going to be spliced into the cable from the controller, it will be connected to the battery.

As for there being too many connections to the battery, any constructive suggestion on a connection setup would be appreciated... I'm still learning all this so obviously mistakes will be made. This is why this post exist, to help lessen expensive mistakes.