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diy solar

Off grid setup, phase 1 (DC side)

griftin

New Member
Joined
Dec 5, 2021
Messages
11
Hi, I'm working through my first complete off grid system, and would like some eyes on it, in case I missed an item. This is step 1 (waiting on parts)
Installed:
  • 2 12v 200ah liFePo4 batteries
  • 2 awg cabling
  • 1 manual power disconnect switch
  • 2 bus bars
  • 1 200 Amp DC breaker
  • 1 24v to 12v step down regulator
  • 1 DC fuse block
  • 1 tank heater (cold weather)
Missing:
  • 1 shunt/battery monitor
If you see any questionable choices, let me know what it is and how you'd remedy it.

Thanks!
 

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What is the inverter size in that Growatt? And what is your expected max usage?

What is the max continuous discharge rating for one of those batteries?

What is the amp rating on those bus bars? And the switch?

You need a Class T fuse at the battery.
You need a fuse for the 24V-12V DC-DC converter.
 
What is the inverter size in that Growatt? And what is your expected max usage?

What is the max continuous discharge rating for one of those batteries?

What is the amp rating on those bus bars? And the switch?

You need a Class T fuse at the battery.
You need a fuse for the 24V-12V DC-DC converter.
3000w inverter. I don't plan to push anywhere near the 3000. Just lights and a low energy refrigerator.

Discharge rate for one 12v : 100a

Bus bars: 250a @ 12v

Switch: 275a continuous

I have a breaker for the battery, and the converter I have a fuse after it, do I need one before?
 
I have a breaker for the battery, and the converter I have a fuse after it, do I need one before?
Your picture does not show any battery breaker, just the breaker before the Growatt. And I don't see a fuse in the picture or your item list.

With your two batteries in series you still only get 100A max continuous discharge. That's enough for up to about 2400W. Given inverter inefficiencies that would let you use about 2000W at the inverter. It sounds like that will meet your needs.

The 2AWG wire is good for up to about 120A so that works. You should have a 125A-150A Class T fuse as close to the battery as possible. The 200A breaker that you have between the positive bus bar and the Growatt is there to protect just that wire. That breaker is not protecting the battery wire at all. The 200A breaker might actually be a little too big given your batteries and it's the largest you would ever want to use with 2AWG wire and that assumes you are using high grade stranded copper wire with 105ºC rated insulation. I think it would be better if you used a 125A or 150A breaker for the Growatt instead of 200A.
 
Your picture does not show any battery breaker, just the breaker before the Growatt. And I don't see a fuse in the picture or your item list.

With your two batteries in series you still only get 100A max continuous discharge. That's enough for up to about 2400W. Given inverter inefficiencies that would let you use about 2000W at the inverter. It sounds like that will meet your needs.

The 2AWG wire is good for up to about 120A so that works. You should have a 125A-150A Class T fuse as close to the battery as possible. The 200A breaker that you have between the positive bus bar and the Growatt is there to protect just that wire. That breaker is not protecting the battery wire at all. The 200A breaker might actually be a little too big given your batteries and it's the largest you would ever want to use with 2AWG wire and that assumes you are using high grade stranded copper wire with 105ºC rated insulation. I think it would be better if you used a 125A or 150A breaker for the Growatt instead of 200A.
Ok, I have a 100 amp breaker, but that might be too small. I can get 2 150 amp breakers, one off the battery, and one after the bus bar. Unless a class t fuse is superior for some reason? I'm not familiar. As far as the step down converter, it's a 10 amp max converter. If I put a standard inline 10 amp fuse in front of it, will that do?
 
A Class T fuse is much better than any breaker you can get. LiFePO4 batteries can throw out a tremendous amount of current during a short circuit. If you search this forum about Class T fuses you can find a lot of good info.

For the DC converter, is the 10A max for the 12V output side? If so then a 10A inline fuse on the 24V input side should be fine.
 
3000w inverter. I don't plan to push anywhere near the 3000. Just lights and a low energy refrigerator.

Discharge rate for one 12v : 100a

Bus bars: 250a @ 12v

Switch: 275a continuous

I have a breaker for the battery, and the converter I have a fuse after it, do I need one before?
If that is a 48v Growatt I believe you need 2 more batteries in series to give you 48v and 200A. 9600 watts of storage.
 
If that is a 48v Growatt I believe you need 2 more batteries in series to give you 48v and 200A. 9600 watts of storage.
It is not. It's the 24v. I don't think I'll need the extra watt hours (or at least I hope) but if I change my mind later, yes, I'll definitely double up the batteries
 
Hi, I'm working through my first complete off grid system, and would like some eyes on it, in case I missed an item. This is step 1 (waiting on parts)
Installed:
  • 2 12v 200ah liFePo4 batteries
  • 2 awg cabling
  • 1 manual power disconnect switch
  • 2 bus bars
  • 1 200 Amp DC breaker
  • 1 24v to 12v step down regulator
  • 1 DC fuse block
  • 1 tank heater (cold weather)
Missing:
  • 1 shunt/battery monitor
If you see any questionable choices, let me know what it is and how you'd remedy it.

Thanks!
maybe fuses or breakers for the solar panels.. just a thought
 
Hi, I'm working through my first complete off grid system, and would like some eyes on it, in case I missed an item. This is step 1 (waiting on parts)
Installed:
  • 2 12v 200ah liFePo4 batteries
  • 2 awg cabling
  • 1 manual power disconnect switch
  • 2 bus bars
  • 1 200 Amp DC breaker
  • 1 24v to 12v step down regulator
  • 1 DC fuse block
  • 1 tank heater (cold weather)
Missing:
  • 1 shunt/battery monitor
If you see any questionable choices, let me know what it is and how you'd remedy it.

Thanks!
also ac breakers coming in and ac breakers going out. protect that equipment .some one here said fuses protect the wires going to and from so they do not get hot and set on fire. ect. some of that is my words. so much info here.
 
also ac breakers coming in and ac breakers going out. protect that equipment .some one here said fuses protect the wires going to and from so they do not get hot and set on fire. ect. some of that is my words. so much info here.
Since this thread is all about the DC side of the electrical system there should be no use of AC breakers on the DC side. The DC side should only have DC fuses and/or DC breakers.
 
Hi, I'm working through my first complete off grid system, and would like some eyes on it, in case I missed an item. This is step 1 (waiting on parts)
Installed:
  • 2 12v 200ah liFePo4 batteries
  • 2 awg cabling
  • 1 manual power disconnect switch
  • 2 bus bars
  • 1 200 Amp DC breaker
  • 1 24v to 12v step down regulator
  • 1 DC fuse block
  • 1 tank heater (cold weather)
Missing:
  • 1 shunt/battery monitor
If you see any questionable choices, let me know what it is and how you'd remedy it.

Thanks!
So, how did your system work?

I'm curious how the Lossigy batteries are performing, I have 4 just like yours, 12 Volt, 200 Ah, 100 Amp BMS.
 
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