12v Series-parrallel system with future upgradability

[Offgridummy]

I'm building a camper system. Currently the plan will be 4x100w panels run 2 banks in series parrallel. Initially I will only be running 200ah of Lifepo4 batteries. Ultimately I suspect I will need to upgrade to 600w of panels and 400ah of battery. I have purchased a victron 60a smart mppt controller with the future upgrade in mind.

My question is, if/when I upgrade how shall I wire my 6x100w of panels? 2 banks of 3 panels each? Is this an effcient way? I ask because I am currently figuring the wire size I need to run. Thanks for any help, I am a newb.

 

[Rednecktek]

My question is, if/when I upgrade how shall I wire my 6x100w of panels? 2 banks of 3 panels each? Is this an effcient way?

That decision will be based on the VoC of the panels and how you want to deal with shading. Most 100w panels are around 20VoC so if you did a 3s/2p setup that would still give you overhead to add more panels later. Shading issues will be benefitted by doing more in Parallel, clean sun will be happier with Series connections. For 6 panels doing a 3s/2p is probably going to be the sweet spot.

I ask because I am currently figuring the wire size I need to run. Thanks for any help, I am a newb.

We were all n00bs once. Most MC4 connectors are designed to take up to 10AWG wire, which is rated for up to 30a of current. Most 100w panels will amp out at about 5a and that only adds up when in parallel so you'll have lots of overhead later if you just run 10AWG right out the gate. It's also kind of a sweet spot in wire costs because it's so common.

So, in the future if you did a 3s/2p setup, your array would be sending about 60v @ 10a to the charge controller in optimum conditions. That's a really happy range for that controller to work with. That also pretty much maxes out what you could put to the battery (12v @ 60a = 720w) without running a complete parallel charging circuit.

 

[sunshine_eggo]

I'm building a camper system. Currently the plan will be 4x100w panels run 2 banks in series parrallel.

2S2P

Initially I will only be running 200ah of Lifepo4 batteries. Ultimately I suspect I will need to upgrade to 600w of panels and 400ah of battery. I have purchased a victron 60a smart mppt controller with the future upgrade in mind.

60A * 12V = 720W

My question is, if/when I upgrade how shall I wire my 6x100w of panels? 2 banks of 3 panels each? Is this an effcient way? I ask because I am currently figuring the wire size I need to run. Thanks for any help, I am a newb.

In order of increasing wiring efficiency:
6P
2S3P
3S2P
6S (might be possible if you get a 150V controller)

If you have other roof protrusions, more parallel is better for shading/partial shading tolerance.

You can determine your own config with a voltage drop calculator:

https://www.calculator.net/voltage-drop-calculator.html (use the estimated resistance tab).

Use Vmp and Isc of the panels. You'll need two calcs - panels to combiner and combiner to MPPT.

Anything less than 2-3% voltage drop is good. That equates directly to lost power, i.e., 2-3% power loss from a 2-3% voltage drop.

 

[HRTKD]

Use the online Victron MPPT calculator to know how to configure your panels - and which panels - for your Victron controller.

MPPT Calculator - Victron Energy

MPPT Calculator - Victron Energy

www.victronenergy.com

 

[John Frum]

In order of wiring efficiency:
6P
2S3P
3S2P
6S (might be possible if you get a 150V controller

Ascending order.

 

[sunshine_eggo]

Ascending order.

WHEW! FIXED! THANKS!

 

[Offgridummy]

Thanks for the replies guys. I have ordered my supplies.