First design. In over my head.

[annafromarizona]

Hi

Trying to live off grid in southern Arizona.


Now, just have to put all the pieces together of my solar system. Oh, boy.

I have:

Victron multiplus 24V/3000 Watt Inverter
Victron MPPT 150/85 charge controller
6 - 305 Watt solar panels
8 - 200ah 3.2V lithium iron phosphate battery cells (w/BMS)
Battery monitor
Battery on/off switches
300a and 400a fuses
MC4 connectors/ solar panel wiring
A wooden shed

Still have to source:
Whatever the heck wiring to go between the charge controller/Battery/inverter
circuit breakers (PV-charge controller)
Battery protection device
grounding rod/copper wiring


Hope you all are having a nice warm winter!

Anna

 

[chrisski]

In my signature block, I have a link to what I bought (my RV build part 2). I am in central AZ so all that was delivered there.

Looking at the diagram, the shunt probably wants to be the first thing after the battery so you measure current to and from the battery. Looks like you chose to measure it from the SCC, and my smaller Victron SCCs I use all show the same data as My Victron shunt.

 

[Smokin]

Sell everything and move to VA and get a Sailboat Yacht and outfit it and Cruise the ICW. Da Heck the the Desert. Don't waste you youth living out there.

 

[100 Proof]

I'm not seeing a BMS in your sketch.

 

[WYtreasure]

Welcome to the party Anna. Now get off the pot and get to work ?

 

[GLC]

I'm not seeing a BMS in your sketch.

8 - 200ah 3.2V lithium iron phosphate battery cells (w/BMS)

 

[sunshine_eggo]

Hi

Trying to live off grid in southern Arizona.


Now, just have to put all the pieces together of my solar system. Oh, boy.

I have:

Victron multiplus 24V/3000 Watt Inverter
Victron MPPT 150/85 charge controller
6 - 305 Watt solar panels
8 - 200ah 3.2V lithium iron phosphate battery cells (w/BMS)
Battery monitor
Battery on/off switches
300a and 400a fuses
MC4 connectors/ solar panel wiring
A wooden shed

Welcome.

Mesa resident with off-grid property out past Show Low.

I essentially have a larger version of what you have. 40' shipping container is my "shed".

I assume you plan to run your A/C when it's miserable during the summer. Your system is not properly sized for that unless you're okay with running A/C from about 8a-4p only with very little other power use.

If you have an absorption fridge (propane or AC power), don't even think about running it on AC power. It will take about 1/3rd of your total solar production. Run on propane or replace with compressor fridge.

For winter heating, use propane to run the furnace as needed. Stay comfy in bed with a good old fashioned electric blanket between you and your comforter. Do not use electric resistance heating. Disappointment will ensue.

Still have to source:
Whatever the heck wiring to go between the charge controller/Battery/inverter

MPPT to battery: 85A, 2awg wire.
Battery to inverter: 3000W/24V/.85 = 147A, 2/0awg wire

circuit breakers (PV-charge controller)

Depending on how you wire your panels, which I suspect is 2S3P, you'll need a fuse/breaker in each string. It will need to be the size listed on the back of the panel

Battery protection device

200A class T fuse with fuse holder. Blue Sea systems or comparable product.

grounding rod/copper wiring

Grounding rod at Home Depot.

If you're referring to AC wiring, 3000W/120VAC = 25A, 10awg will do it.


Diagram:




Shunt is in the wrong place. It should be between the battery and bus bar. Battery on one side, everything else on the other side of the shunt.

While the MP provides two DC terminals, you do not have to use both. If you use both, you'll need a fuse breaker on each.

Recommend a Cerbo GX for remote monitoring/logging.

 

[Koldsimer]

Looks like you have a solid plan. Quality gear goes a long way in saving money and frustration down the road. Definitely have plenty of sun and space for an array! If you can, consult with a professional company to get a legit wiring diagram. That helped me so much with installing my system.

My wife and I lived in a travel trailer completely off grid for 5 months while building our house and all i can say is prepare yourself for the challenges!

 

[100 Proof]

8 - 200ah 3.2V lithium iron phosphate battery cells (w/BMS)

I saw it in the parts list, but not in the sketch/schematic. It should be there for clarity.

 

[rmaddy]

While the MP provides two DC terminals, you do not have to use both. If you use both, you'll need a fuse breaker on each.

Curious why your updated diagram suggests eliminating the fuse between the inverter switch and the inverter. I would have thought a 150A fuse would be appropriate there (3000W / 24V / .85 = 150A).

 

[GLC]

I saw it in the parts list, but not in the sketch/schematic. It should be there for clarity.

Understand, since I do not build my own batteries, I never see my BMS so I did not know if the BMS was hidden or not.

 

[sunshine_eggo]

Curious why your updated diagram suggests eliminating the fuse between the inverter switch and the inverter.

There's already a 200A fuse in that circuit. No need to double fuse.

I would have thought a 150A fuse would be appropriate there (3000W / 24V / .85 = 150A).

You fuse for 1.25X. I rounded up to 200A

 

[chrisski]

If you’re going to use 24 volts instead of the inverter low voltage cutoff, do you recommend putting in a 220 amp Victron Battery protect or something similar to shut the load down when the voltage gets too low?


When I designed for my three inverters I have used I calculated the low voltage cutoff, but putting a failsafe like this in would make me feel good about calculating with the higher volrate to get lesser amps for smaller fuses and wires. Otherwise for a 3000 watt inverter on a 20.5 volt low voltage cutoff, you end up with 4/0 wire and a 225 amp class T fuse. That is a big difference since the 20.5 volts only happens at the last 5% when the battery dies.

 

[rmaddy]

You fuse for 1.25X. I rounded up to 200A

Oops. I left out that step. Silly me.

If you’re going to use 24 volts instead of the inverter low voltage cutoff, do you recommend putting in a 220 amp Victron Battery protect or something similar to shut the load down when the voltage gets too low?

Never use a battery protect between the battery and inverter. Victron states this. A battery protect would be fine between the DC fuse box and the battery. In fact, it could replace the disconnect switch currently in that location since the battery protect can be turned on and off.

 

[rmaddy]

Never use a battery protect between the battery and inverter. Victron states this.

I should add that the battery protect does have a relay that could be used to control an inverter if the inverter supports a remote shutdown switch. That's a perfectly safe possibility. In the OP's case it's not needed since the MultiPlus can be programmed to shutdown at a user defined voltage or SOC.

 

[John Frum]

I should add that the battery protect does have a relay that could be used to control an inverter if the inverter supports a remote shutdown switch. That's a perfectly safe possibility. In the OP's case it's not needed since the MultiPlus can be programmed to shutdown at a user defined voltage or SOC.

If the inverter supports remote switching its easier than that.
This diagram shows how its done.

Flowchart Maker & Online Diagram Software

tinyurl.com

 

[chrisski]

I should add that the battery protect does have a relay that could be used to control an inverter if the inverter supports a remote shutdown switch. That's a perfectly safe possibility. In the OP's case it's not needed since the MultiPlus can be programmed to shutdown at a user defined voltage or SOC.

With the multiplus, that is nice.

For not using the inverter on the 220 amp batttery protect, there was only one document for the 12 / 24 volt version, which makes no mention of don’t use with an inverter.

I certainly believe you both and I remember Smooth Joey telling me about this a few days ago. I just wish it was shown in the one downloadable docement for the12/24 volt 220 amp version.

BatteryProtect - Victron Energy

Disconnect the battery from non essential loads before it is completely discharged with Victron Energy's BatteryProtect. Find a dealer near you.

www.victronenergy.com

 

[rmaddy]

I just wish it was shown in the one downloadable docement for the12/24 volt 220 amp version.

Pull up the user manual. Read step 4 under the Installation section:

4. The short circuit protection of the BP will be activated if you try to directly connect loads with capacitors on their input (eg inverters). For that use case, please use the BP to control the remote on/off switch on the inverter, instead of disconnecting the higher power DC line.

OP - sorry for the tangent