New Off Grid solar, battery setup - advice please

JD Solar and EV

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Dec 2, 2020
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Hi All,



My first post is after advice on setting up a solar panel, inverter and battery setup for my off grid property on the Sunshine Coast.


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In April, my wife and I purchased a block of land with a 12mx6m shed but without town services and I am in the process of setting up power, water harvesting, and toilet/ showers so when we occasionally visit we can move away from running a generator for all power requirements.



So far I have purchased 42x Nissan Leaf cells and 11x 190W solar panels. I was planning on buying an MPP Solar 5048 inverter but haven't got that far yet.

The batteries will be ~12kWh although not capacity tested yet, in 7S6P to have 53ish volts to run a 48V system.



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The panels are used but seem in decent condition and on a quick test of one today the output was high 30's open circuit voltage and over 5Amps so somewhere near 190W seems likely.


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I'm after your advice of solar panel configuration to supply the inverter.

Thoughts on whether it is necessary to run a BMS or is this inverter capable of handling that?

Setup for safely using the 240V out of the inverter for approximately 4 powerpoints.




Any advice welcome, regards JD
 

daromer

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Yes you need BMS. ALways a BMS On Lithium batteries. The inverter have none built in.
Those batteries are 14s to reach that voltage. Each cell is 2s.

The inverter says max 450V. That means you can max have 9 cells in series. to be honest that might be to stretch it if you ever have cold days... During clouding you will reach above the open voltage and have the inverter go off alarming. No matter what people says this will happen one day or another!
So you can either use 9 max of the solar panels or have 5s2p of them. Neither less you cant use all panels. I dont know what the minimum voltage of that inverter is though.
 

JD Solar and EV

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daromer said:
Yes you need BMS. ALways a BMS On Lithium batteries. The inverter have none built in.
Those batteries are 14s to reach that voltage. Each cell is 2s.

The inverter says max 450V. That means you can max have 9 cells in series. to be honest that might be to stretch it if you ever have cold days... During clouding you will reach above the open voltage and have the inverter go off alarming. No matter what people says this will happen one day or another!
So you can either use 9 max of the solar panels or have 5s2p of them. Neither less you cant use all panels. I dont know what the minimum voltage of that inverter is though.

Yes 14S, 7x2S6P.

I was thinking either 5S2P or 3S3P. Waiting for recommendations on Volts and Amps input.

I dont know what the minimum voltage of that inverter is though.

Low DC Cut Off Voltage? The minimum setting for that is 40.0V

Here is the user manual:

http://www.mppsolar.com/manual/PIP-MG (PF1.0)/PIP-MG 5KVA manual-20190717.pdf
 

not2bme

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Oct 16, 2017
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479
The PIP you chose is a high voltage version. That means it typically has a starting voltage of 150V and a max of 450V.

Your panels have an open Voc of 44.80V, which means a theoretical max of 44.8*10panels in series = 448.0V. But in theory you'd want to be safe, so you run 9 panels 44.8V*9=403V, and daromer says that's iffy. Plus the fact that you have 11 panels not 9 panels, so you lose out on 2 panels.
But since you have 11 panels, it's a prime number so there's no way to divide it, therefore you will be stuck with 10 panels as the best option. 5 panels in series and two of them you join together in parallel. 5 in series * 44.8 = 224V and the Vmp of 36.92V*5= 184.6V That's probably on the low end of the MPPT, so in the mornings it might not be strong enough to get that voltage to start the MPPT.

Other option is to get the low voltage PV version, where the max Voc is 150V. Then you can put strings of 3 in series, but that will max out again at 9 panels, since you only have 11panels. You can possibly do strings of 2 in series, but that's just a lot of wiring. Doable, just lot of wiring.

So if you can, buy a few more panels. And figure out if you want high voltage wiring or low voltage wiring for PV. There's no wrong way just what you prefer.
 

JD Solar and EV

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Dec 2, 2020
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not2bme said:
The PIP you chose is a high voltage version. That means it typically has a starting voltage of 150V and a max of 450V.

Your panels have an open Voc of 44.80V, which means a theoretical max of 44.8*10panels in series = 448.0V. But in theory you'd want to be safe, so you run 9 panels 44.8V*9=403V, and daromer says that's iffy. Plus the fact that you have 11 panels not 9 panels, so you lose out on 2 panels.
But since you have 11 panels, it's a prime number so there's no way to divide it, therefore you will be stuck with 10 panels as the best option. 5 panels in series and two of them you join together in parallel. 5 in series * 44.8 = 224V and the Vmp of 36.92V*5= 184.6V That's probably on the low end of the MPPT, so in the mornings it might not be strong enough to get that voltage to start the MPPT.

Other option is to get the low voltage PV version, where the max Voc is 150V. Then you can put strings of 3 in series, but that will max out again at 9 panels, since you only have 11panels. You can possibly do strings of 2 in series, but that's just a lot of wiring. Doable, just lot of wiring.

So if you can, buy a few more panels. And figure out if you want high voltage wiring or low voltage wiring for PV. There's no wrong way just what you prefer.


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This is from the manual.

Seems like 120V is the minimum.
 

JD Solar and EV

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Hmm, thought this forum might be a bit more active. Am I asking for advice that is out of the scope of this forum?
 

daromer

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You have gotten answer or is it something missing ?
 

daromer

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You need 4 outlets and in between the inverter and the outlets fuses/breakers and even better also an rcd. This of course depends a little bit of where you live how this should be done. Where i live all my outputs have main breaker, rcd and then breakers for each outlet
 

OffGridInTheCity

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I'm in the US. My inverter output goes to standard US 240/120v Distribution Panels. Exactly as you have for the power coming into your house from the Grid. From the Distribution Panels I run standard wiring to outlets and ATS(s) - all the same wire size, circuit breakers as one would do from a main panel to circuits in your house to meet code.

Is this what you're thinking about?

Happy to discuss further...
 

daromer

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Sounds like you already have it set up then ?
 

JD Solar and EV

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You need 4 outlets and in between the inverter and the outlets fuses/breakers and even better also an rcd. This of course depends a little bit of where you live how this should be done. Where i live all my outputs have main breaker, rcd and then breakers for each outlet
My off grid place is close to Maleny on the Sunshine Coast.

If I run lighting on one circuit and appliances on another circuit with four 3 pin outlets, does it sound right to have the inverter wired to the distribution box, a circuit breaker and an RCD safety switch on each lot of cabling?

Are you running another breaker near the outlet or just a main breaker in the distribution box that splits into smaller breakers for each outlet?
 

daromer

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JD i dont want to be this but you might want to consult with a local electrician for that job?

Inverter -> box with main switch, rcd and breakers for each outlet -> outlets.

Thats how its done in most places but this vary alot between who you ask and area. Where i live thats how you do it. You can have multiple outlets on same breaker but if plan higher loads or dont want one to trip another then you use multiple breakers. For instance in a house here you can for each room have like 3 breakers or more.
One for the outlets. One for half of the lights. One misc extras. This is just an example though.
 
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