Feedback on new solar system

[TonyJ]

Hi all,

We are installing 16 extra solar panels on our roof and adding battery storage.

The battery is a 1.2KW Lithium Iron Phosphate with 10 years warranty made by Enphase.

The installed cost of the panels and battery is $8888. Does that sound reasonable? 

They have suggested that we might need an extra battery in the future - another $2500. They have recommended to monitor use for a few months and then consider adding another. 

I would appreciate any feedback on whether we are doing the right thing.

Thanks,

Tony

[EricL]

Hello @Takatapui 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your solar setup.

What a clever and resourceful setup you’ve created! By building your own LiFePO4 batteries, you’ve significantly reduced costs while creating a robust energy storage solution. Your system is impressive, providing power for appliances like fridges, freezers, and induction elements while maximizing solar energy by running high-demand tasks during surplus sunlight. With 10kWh storage and 2345W of solar panels, your balance of investment and functionality is excellent. The LiFePO4 batteries offer high discharge capacity and low maintenance, and your use of a 3000W inverter with UPS adds reliability.

This project shows how sustainable living can be cost-effective and fun. It’s a great example of achieving energy independence with a bit of research and creativity.

Just a friendly reminder to all members: any electrical wiring must be carried out by a licensed electrician to ensure safety and compliance with local regulations.

Again, thank you for sharing such a fantastic project.

Eric

[Kev]

That looks like a good setup @Takatapui 

I don't want to sound negative with the following - your construction is awesome and probably works extremely well for you and would be awesome if you are off grid.

I think you may want to revisit some of your calcs. Most inverters are only about 92% efficient.

The batteries look like they are wired parallel, so it's a 12v 824Ah system supplying your 3kW inverter. The current draw from each individual battery should not exceed it's ability (most LiFePo have max current similar to their Ah rating - ie, 200Ah usually supply 200A of current - but it's best to check the specifications of the batteries, along with the recharge rate)

Therefore, (12 x 824 x 0.92) = ~9100Wh of available energy.

Most plug in appliances use 2400W while they are working so you'll get about 3.8hrs of continuous use. Most appliances do not run continuously.

I don't understand that your first pair of batteries cost NZD3400, but the next pair cost you NZD2000 - that's a great discount.

How much were the 4 BMS'? I'm curious about the entire build price. I've looked into this myself and came to the realisation that with the price of electricity (for me) at the moment of 25c/kWh, if I were to achieve a full cycle each day (let's say 10kWh to make the maths easier) then I would save $2.50 per day.

Currently, a 200Ah (quality) battery costs around AUD1500 (or $6k for 4 of them) and the BMS' I guess are around AUD250 (or $1k for 4 of them) and I'd advise people to not just get one off ebay for this - they are critical to the battery system.

So I'd be looking at over $7k (plus breakers, high current switches, heavy wiring, meeting regulations etc)

I already have a hybrid inverter on the solar PV array - so that isn't a cost for me.

Now, the ROI would be $7500/$2.50 = 3000days or 8.2yrs (not allowing for the increase in electricity prices)

For me, it isn't viable yet - I would like to see the ROI closer to 5yrs.

Your setup is great and works for you - it wouldn't for me yet.

I hope this view assists others that are following this conversation.

Cheers,

Kev

[Kev]

Hi EricL,

Firstly, you are correct that people need to ensure it is wired properly and meets specifications. The DC side is dealing with a huge amount of power (read current) and it can go south fairly fast if things aren't to spec - like wire size, breakers, shunts, BMS needs to be suited to the battery, etc. And always handy to have a fire extinguisher mounted close by.

I would like to clarify a couple of points you have made.

On the DC side, the wiring doesn't need to be done by a licenced electrician - this can be done by a knowledgeable person (to avoid catastrophes)

It is the connection from inverter to the mains power that needs to be done by a licenced electrician. ( I assume it's the same rules in NZ)

People will also need to consider the grid requirements. 'Anti islanding' is a main feature to protect workers on the grid - but your electrician will know about this.

Cheers,

Kev