12v system for off grid cabin for review

Jeff_W

New Member
Hi All,

Attached is the design I'm looking to install this summer in our off grid cabin. The cabin appliances will remain LP so I'm looking to introduce power for items I've listed in the design. I've sized for what we need and it should cover our requirements. Its essentially Will's classic 400W with shore power. Appreciate if you could review and provide any feed back, especially any safety concerns. Anything I missed or any recommendations.

The cabin will be used for summer vacations and weekends so I want to be able to turn it off and know there no issues when we're not there.. As for the winter, I will bring the battery home to store.

The grounding requirements I haven't figure out yet. But FilterGuy has posted some great info in the Resource center I'm currently going through.

Also I haven't purchased anything yet so I can change components. The inverter model is not finalized although I like the Samlex 1500W just not he price. For the batteries LiFePo4 seems to be the overwhelming consensus. I most likely will go with the Battle Born 100Ah but haven't ruled out the SOK.

Thanks!
 

Attachments

  • 425W Solar System for DIY Forum.pdf
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Rocketman

Solar Addict
Nice basic design.
Here are a few things I would consider changing:

Fuses look good.
Wires - from the mppt to the bus bar I would use 10ga wire - it can deliver 30amps - 14 is too small. And since you already have 2ga from batteries to buss bar - I would continue to use that wire to the inverter (no use buying more wire and more lugs - the 2 ga would be better anyway). Verify with the inverter you buy what wire it wants - if it has a surge option it may want thicker wire and fuses.

These items below are all options.
System - go with 24v instead of 12v - see if the 12v stuff can easily be 24v or add a 24 to 12v transformer. (Actually 48v is typically recommended for homes and cabins - but that would increase the cost of your system).

Battery monitor- I would go with the Smartshunt or BMV712 instead of the BMV702. Getting the battery info on my phone is easier and they will connect with the SmartSolar to pass the exact battery voltage and temperature back to the mppt. If you don’t need the display go with the Smartshunt.

Inverter - since you already have a couple of Victron items look at the Multiplus 2000 (or 3000). The Multiplus is an inverter/charger - so you can eliminate the charger.

Solar - that panel you choose will work fine for both 12 or 24v. However look at see if you can find used panels locally (see Santan solar for used panels for sale). The big 425w panel might be a bit unwieldy to work with. It may be easier to work with two 200watt panels. Also if you decide to go with 24v - you could get two of those panels (now or in future).

If you choose to go with the Victron inverter- look at the Victron GX devices (Cerbo or CCGX). They are expensive, but bring all the info on the system into one place.


Batteries- look on this site about getting the Eve or Lishen 280ah cells and making your own battery. They end up being much cheaper and are a fun project if you like DIY.

Good luck with your project
 

Jeff_W

New Member
Thank you for the detailed response! I’ll make the changes to the wire and you have given me lots to contemplate.

The panel is a bit of a beast at 82” x 40” so like you say it could be unwielding to work. It’s just the price is good.
 

Rocketman

Solar Addict
Oh, I just thought of one more thing...
Make sure the batteries you get (really the BMS) will support the discharge needed for the inverter. Many 12v batteries only have a 100amp max discharge (some say 100amp - but it can be lower). This is one of the ways going to 24v is twice as good.
 
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