48v fully off-grid advice from experts on my idea

Q&A and troubleshooting
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Hi brains trust, I’m hoping I can get some help from the people who know these products inside out as I’m ready to purchase but worry I’ll buy and then be told later I could have made better choices.

My background is im a qualified auto electrician and have wired up many 12v vehicle and marine off-grid setups with a typical battery, solar panel, 100/50 solar controller and inverter and love the off-grid life.

I’m now building a large workshop shed and want to go fully off-grid and have an idea in mind but wanted to share it for ideas and potential change if needed to a better setup

For battery’s I’m In Australia and for budget can’t beat the Kings 300ah 12v lithium, people stay clear of kings products being cheap but I’ve used these in many vehicles and perform fantastic, im open to ideas for others but at $600aud per battery I’m hoping to buy 8 battery’s and run them in 48v .

Now my idea is to have a lot of panels, buy the multi RS unit 48/6000 and from what I can understand this will give me 2x3000w solar mppt chargers, run 48v, give me around 5000w of inverter power depending on inverter temperature and can be expanded with a screen for info.

My main questions are would this setup be ideal for off-grid and budget, is there a smarter choice while still being affordable and if I wanted to double my capacity and output, would I run two systems side by side but not linked or can you connect the 240v outputs together and sync the rs unit so you have around 10000w of available inverter power in stead of 2x5000w and how many panels would be correct for either option.

My idea was to run as many panels as I can and slightly over panel as long as I don’t exceed the max voltage of 450v I’ll post below my notes which hopefully make sense with prices I was trying to work out the most cost effective way

16x 475w panels - 7600w / $1920

32x 475w panels - 15,200 / $3840

Multi RS Solar - $2500

Multi RS Solar X2 - $5000

Victron screen $299

Lithium battery 14.4kwh $2400

Lithium battery 28.8 kwh $4800

7600w / 5000w charger 14.4kwh $7120

7600w / 5000w charger 28.8kwh $9520

15,200w / 10,000w charger 14.4kwh $11,539

15,200w / 10,000w charger 28.8kwh $13,939

Lastly I wondered how battery monitoring works as all the 12v setups I’ve build have a standalone shunt / screen, does the multi RS calculate everything internally and only needs the victron screen to display or do I still need a suitable 48v shunt to read battery drain / charge.

Hope this all makes sense, super excited to build the kit and appreciate everyone’s input.

Josh.

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While you can use 12V batteries in series to get 48V, its not the preferred way. While i dont know Kings, not many “dropin” LiFePo have wired communication, also no balancing between the batteries, only internally. Current 48V packs feature a full 16s balancer with wired communication, and more or less accurate SOC tracking.

I recommend looking at 48V packs, a good starting point is the compatibility list. Does not mean that batteries not listed are incompatible though.

As for the multi RS, i have no personal experience. But, be aware of a quirk of the MPPT RS 450 which also applies to the MPPT inside the multi RS: PV voltage can max be a factor of eight of the battery float voltage. This comes into play when you want to use a 15S battery instead of a 16S. Your PV voltage could be a max 408V when using pylontechs for example.

I assume you plan on using eight panels in series. This could be on the limit of PV input voltage of the MPPT. Use the MPPT calculator to make sure youre not shooting over with voltage.

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Hi @Josh94

you should go with 48V-batteries with included compatible BMS. The BMS tells the GX device the charge and discharge limits.

Checkout Andi’s off-grid garage one YouTube.

You are talking about a workshop.
Do you have 3 phase machinery?
If you plan to use heavy machinery like welding, go with a combination of RS4500/MPPT and MP2. This can be combined with AC-PV like Fronius.

The MP2 shall support higher burst currents.
Whereas the Multi RS has higher efficiency.

If you need a display, go for Ekrano.
, else use Cerbo GX MK2.

Don’t underestimate DC-distribution with 2-3 Lynx.

Have you checked MPPT Calculator - Victron Energy

I have not find reference to Victron battery size recommendation but I would plan to charge with 0.25C which leads to 60kWh for 15kWp.
Especially on an offgrid system.

Did you consider a backup generator?