Newbie Help - Putting together a small system

[OzSteve]

Hi all,

I'm really new to this, I have a Bluetti AC180 but want to build a small system to run a full sized fridge/TV/Lights at home. Not mobile
My issue is, wiring and what level of product (like MPPT and so on)
Here is what I am thinking:

2x 200Ah Lifepo4 batteries (I can run 2 in series, or 4 in parallel, what's better? or would I need 2x 300Ah?)
Renogy 2000w Pure Sine Wave Inverter Charger
upto 1kW of solar panels (and again, need to know what panels I can use)
Looking at a Victron MPPT (just unsure on size)
Is there anything else I'll need? I'd like a screen to monitor (or something I can use on a PC/Pi)

Then comes the wiring types/thickness and fuses and so on that I'll need. All this will be mounted in a 22u rack.

Oh, I am in Australia so some other recommendations might not be available here. I'd like to stick to Victron or Renogy


Thanks in advance

 

[Dagoth Ur Does Solar]

Here's some higher-level stuff to think about:

1. There's a huge gap in quality of equipment (and price) between Victron and Renogy. If those were my two options, I would try to spring for Victron if possible. If I were building a second system right now, and didn't want to go with an all-in-one unit, I'd buy Victron personally.
2. I personally would avoid putting batteries in series if at all possible. It's mostly unneeded complexity, IMO, when you could just buy individual batteries at the voltage you want your system to be at. There are cheap 12V, 24V and 48V LFP batteries nowadays.
3. Going to 48V rather than 12V or 24V can be more expensive up front for the hardware, but the cost can be offset by being able to go with smaller diameter (thus less expensive) cables, and they can as a result of the higher voltage, scale much higher in terms of input PV and output wattage. For example, going with a 3000W output inverter on a 12V system requires almost comically thick cables.
4. Panels are mostly agnostic- almost everything uses MC4 connectors now, so you really need to learn about how the specs of panels interact to make sure you don't go over the voltage your MPPT can support. Basic MPPTs tend to expect you to have strings of panels in series and get to a higher voltage with lower amperage- so with 1000W of panels, it's likely you'll have a string of between a 3 and 10 panels in a string. However, going over the voltage limit of your SCC will likely damage it (or start a fire), so it's imperative you keep your voltage in the specified range for your particular SCC.
5. If you want to monitor your solar system remotely, two big options are Victron's proprietary system (you'll need at the bare minimum a Pi and some Victron cables to get everything set up) - or SolarAssistant, which is a paid piece of software that runs on a Pi and can connect to a variety of AIO units and other equipment to pull in data and let you manage it via the cloud (or locally with MQTT).

I'm relatively new to this myself, but this is some of what I had learned building my first system.

 

[mikefitz]

Don't use batteries in series, at 24 volts use 24v batteries at 48 volts use 48 volt batteries. Don't buy Renogy batteries.
1000 watts of panels needs a 40 amp MPPT controller at 24 volts and a 20 amp controller at 48 volts.
If possible use Victron products , they integrate together, Renogy , whilst attractive is price, can have reliability and support issues. Problems with Renogy products are common on this forum.
Suggest Victron Smart 150/45, for a 24 volt system

SmartSolar MPPT 150/35 & 150/45 - Victron Energy

Maximize the energy-harvest, driving it intelligently to achieve full charge in the shortest possible time using the SmartSolar MPPT. Learn more now.

www.victronenergy.com

Panels can be whatever is easily available, even Renogy panels are good!
Go for so called 1/2 cell panels if you have a partial shading situation, also, are good all round panels.
Generally the larger domestic sized panels, around 400 watts are the best value.
It's OK to have slightly higher panel power into the controller provided you don't exceed the input voltage of the controller
You need to do the sums using Voc for the panels to calculate the string voltage.

Example, ( talen at random of the internet, there will be many more suppliers)

333W WINAICO WST-MG Mono Half Cell Solar Module

When you buy from WINAICO, you are buying products from a manufacturer specialising in premium-quality solar panels. As a Taiwanese module manufacturer with German and other subsidiary companies around the world, WINAICO is positioned amongst top brand manufacturers with a high-quality product...

www.solaronline.com.au

3 panels in series with Voc at 36.7 gives a string volts of 110 volts, well within the controller limit of 150 volts

190W SOLMAX Shingled Monocrystalline Solar Panel

Solmax New Energy manufacture high-quality and cost-effective solar panels suitable for grid feed and off-grid commercial, industrial, institutional, residential and commercial Applications. Features include: 5 Year Product Warranty High conversion efficiency High quality cells with...

www.solaronline.com.au

4 panels in series with Voc at 30.55 gives a string volts of 122 volts

Victron smart shunt is ideal for battery monitoring.

For the inverter consider Victrom Multiplus ( inverter charger) if you want safe and simple integration into the domestic AC system.
Use of inverters in a dwelling powering distributed appliances needs a separate discussion , perhaps a need to comply with local codes.
Cables,

Part 1: Choosing the Correct Wire Size for a DC Circuit - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

Fuses,

Part 1: Choosing the Correct Wire Size for a DC Circuit - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

Mike

 

[OzSteve]

Thanks for the replies.

My system will only be used for power outages and I'll run extension cords to various items.

So, keep it 12v with a 2K inverter? 24/48v batteries are a lot more expensive here. All I need is runtime for any outages.

Also, the run of cables from the solar panels to the box will be 60 foot odd. Solar will only really be needed to keep the batteries charged.

I'm happy to stick with Victron, what would be comparable to the Renogy 2000w Pure Sine Wave Inverter Charger?

Thanks again

Here is how the Bluetti and my Brass Monkey fridge/freezer looks when charging. Need longer cables

 

[Dagoth Ur Does Solar]

So, keep it 12v with a 2K inverter? 24/48v batteries are a lot more expensive here.

Just to verify, you're comparing 12v and 24v batteries of the correct amp hour numbers, right?

As in, a 12v 100Ah battery has the same amount of energy as a 24v 50Ah battery.

I only ask because in the US, if you're ordering Chinese batteries, the prices are very similar.

 

[OzSteve]

24v batteries here are a lot more expensive than 12v. I can get a 12v 200aH for $700 and a 24v 100Ah for $1600 (or a 300Ah 12v for $1200)
Or a SOK 48v 100Ah $3K

So I'd like to run this on the 12v side of things as it's only for emergencies.

 

[Danke]

24v batteries here are a lot more expensive than 12v. I can get a 12v 200aH for $700 and a 24v 100Ah for $1600 (or a 300Ah 12v for $1200)
Or a SOK 48v 100Ah $3K

So I'd like to run this on the 12v side of things as it's only for emergencies.

That must be local pricing. You could order a rack battery from China for a lot less.

 

[Dagoth Ur Does Solar]

24v batteries here are a lot more expensive than 12v. I can get a 12v 200aH for $700 and a 24v 100Ah for $1600 (or a 300Ah 12v for $1200)
Or a SOK 48v 100Ah $3K

So I'd like to run this on the 12v side of things as it's only for emergencies.

If that's really the case, that's crazy (and sucks!). I'm in the US, so obviously the market must be quite different here. You can get decent 12v 100Ah LFP batteries for like, $250 USD or less.

That said, I could understand why 12v would be what you'd lean towards. I have a 12v system with a 3000W inverter, but I am limiting its max draw with a breaker so that I don't get close to 3000W continuous. My math said a single 4/0 AWG wire wouldn't be enough to handle that much amperage, and they're already comically huge for a little 12v system. If I was doing it again, I'd stick to a 2000W inverter max to keep the wiring more reasonable- but even with a 2000W inverter depending on what else you have there you might end up with 4/0 AWG wire.

I don't own any Victron (yet), so I wouldn't want to make you a recommendation on what inverter to buy, specifically.

That must be local pricing. You could order a rack battery from China for a lot less.

That's what I thought- I figured the usual suspects for cheap Chinese batteries would have some stock in an Australian warehouse.

 

[OzSteve]

Yeah I want to get a 2000w inverter max. I never thought of chinese batteries as I thought shipping would be a lot and then warranty and so on.
120Ah LFP's are $400 odd (so $268 USD)

So the plan, 2x 200Ah. 2000w inverter and then build up solar panels for it. The Victron vs Renogy is like double the price, but if it's a lot better quality then I'd go with it.

I'll check out aliexpress for batteries

Next questions, breakers/fuses and where? I'll do up a diagram and post what I am thinking

 

[OzSteve]

Okay, been researching a LOT. Looks like I am going with Victron/SOK combo in 48v

So, now I'm looking at the Victron 48V 3000VA MultiPlus-II 48/3000/35-32 Inverter/Charger 1x (to start) SOK 48V100Ah LiFePO4 Battery Pack
Now I need to know what would be the best MPPT for this and best solar panels to use to get 1kW would be ideal

 

[Orkeven]

Okay, been researching a LOT. Looks like I am going with Victron/SOK combo in 48v

So, now I'm looking at the Victron 48V 3000VA MultiPlus-II 48/3000/35-32 Inverter/Charger 1x (to start) SOK 48V100Ah LiFePO4 Battery Pack
Now I need to know what would be the best MPPT for this and best solar panels to use to get 1kW would be ideal

I'm also a beginner but from what I have gathered so far, 6 200W panel with 3 in series and 2 in parallel (3S2P) should work for you. Therefore, a 40A MPPT should ordinarily suffice.

Edit: I just learned that to get the correct rating for the intended MPPT, one should divide the number of total watts from the panels by the battery bank voltage. In your case, that will be 1200/48 = 25. So, maybe a 30A MPPT will suffice as well. However, you may be planning to boost your setup later, and may need a higher ampere rated MPPT.