diy solar

diy solar

Help needed for my first mini system!

L

ladycage

New Member
Joined
Dec 31, 2022
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ATL
Hello,

I am completely new to solar energy systems but I have watched YouTube videos and have been inspired to build my first solar system. It is going to be a small system for now until I feel more confident in my ability and knowledge to upgrade to a 48V system to supplement my electric bill. For now I have a 12v 100ah Btr LIfePO4 battery with 100A BMS, 3000W 12V 120VAC Pure Sine Wave HF inverter, HQST 12/24V 40A MPPT SCC negative grounded max solar input 100v 600W:12v or 1200W:24v. I have 4 Rich 100W solar panels VOC 22.8V ISC 5.46A IMP 5.15A. I have 60 feet 10 awg solar wire for the MC4 connections, 2 sets of 2 awg battery cables. I will be mounting the system on a steel utility cart with wheels so that I can move it when I build a bigger system. I am not sure about the circuit breaker sizes and/or fuses I need to put in place to protect my items. Would any of you knowledgeable and experienced solar system DIYers suggest or assist me with what else I need to purchase and sizes for the breakers.

Thank you so much for reading and your assistance if you are able to help.
 
ladycage said:
Hello,

I am completely new to solar energy systems but I have watched YouTube videos and have been inspired to build my first solar system. It is going to be a small system for now until I feel more confident in my ability and knowledge to upgrade to a 48V system to supplement my electric bill. For now I have a 12v 100ah Btr LIfePO4 battery with 100A BMS, 3000W 12V 120VAC Pure Sine Wave HF inverter, HQST 12/24V 40A MPPT SCC negative grounded max solar input 100v 600W:12v or 1200W:24v. I have 4 Rich 100W solar panels VOC 22.8V ISC 5.46A IMP 5.15A. I have 60 feet 10 awg solar wire for the MC4 connections, 2 sets of 2 awg battery cables. I will be mounting the system on a steel utility cart with wheels so that I can move it when I build a bigger system. I am not sure about the circuit breaker sizes and/or fuses I need to put in place to protect my items. Would any of you knowledgeable and experienced solar system DIYers suggest or assist me with what else I need to purchase and sizes for the breakers.

Thank you so much for reading and your assistance if you are able to help.
Click to expand...
2 awg wire is way to small for a 12 volt 3000 watt inverter. 2 awg is only rated for 115 amps. A 3000 watt inverter will probably draw 250 amps when fully loaded.
 
Bobert said:
2 awg wire is way to small for a 12 volt 3000 watt inverter. 2 awg is only rated for 115 amps. A 3000 watt inverter will probably draw 250 amps when fully loaded.
Click to expand...
Worse than that.
3000 ac watts / .85 conversion factor / 10 volts low cutoff = 352.941176471 inverter amps
352.941176471 inverter amps /.8 fuse headroom = 441.176470588 fuse amps

A 3000 watt inverter is not really practical at 12 volts nominal.
 
John Frum said:
Worse than that.
3000 ac watts / .85 conversion factor / 10 volts low cutoff = 352.941176471 inverter amps
352.941176471 inverter amps /.8 fuse headroom = 441.176470588 fuse amps

A 3000 watt inverter is not really practical at 12 volts nominal.
Click to expand...
Ok, I may just buy a 24v Hybrid SCC. I was just using this system to get familiar with connecting wires and seeing how solar power would work at my location. I would only use the 12v system to power a fan, 32" TV and 12w light all of which would on my patio under me gazebo for the summer. I was starting out with 12v just to make sure that I don't hurt myself and get shocked while getting use to working with the wires and electronic equipment. As a newbie I thought that was the best route but maybe I was mistaken, maybe I should just take the plunge and good big right away, IDK
 
You fuse to protect your cables so with 2awg you'd be looking at something like a 150A fuse. I'd probably put a 125A DC breaker on it. You'll be limiting your inverter output to 1500W (at 12V) before your breaker flips but your battery can't supply more than 100A anyway so it'll be limited to 1200W anyway. For your 10awg cables you again need a fuse or breaker rated to the cable.
 
ladycage said:
Ok, I may just buy a 24v Hybrid SCC.
Click to expand...
I think you are referring to an all in one.
An all in one is an inverter, ac2dc charger, automatic transfer switch and MPPT solar charge controller in one unit.
24 volts is pretty safe.
 
ladycage said:
Ok, I may just buy a 24v Hybrid SCC. I was just using this system to get familiar with connecting wires and seeing how solar power would work at my location. I would only use the 12v system to power a fan, 32" TV and 12w light all of which would on my patio under me gazebo for the summer. I was starting out with 12v just to make sure that I don't hurt myself and get shocked while getting use to working with the wires and electronic equipment. As a newbie I thought that was the best route but maybe I was mistaken, maybe I should just take the plunge and good big right away, IDK
Click to expand...
1200W will be plenty for that load, just fuse/breaker for your cables that way even if the inverter tries to pull more the breaker will flip but in reality the BMS should throttle the output anyway.
 
ShaneC said:
You fuse to protect your cables so with 2awg you'd be looking at something like a 150A fuse. I'd probably put a 125A DC breaker on it. You'll be limiting your inverter output to 1500W (at 12V) before your breaker flips but your battery can't supply more than 100A anyway so it'll be limited to 1200W anyway. For your 10awg cables you again need a fuse or breaker rated to the cable.
Click to expand...
This is what I was thinking about, using a fuse to limit the inverter to my 12v capacity. 1000-1200W should be more than enough for my first system. I have an Ecoflow Delta mini for emergency outages and it was able to power my needs for the gazebo so I figured I would try to build my own similar capacity system. Thanks for the suggestion of using a 125A breaker for my inverter and 100A for my battery.
 
John Frum said:
I think you are referring to an all in one.
An all in one is an inverter, ac2dc charger, automatic transfer switch and MPPT solar charge controller in one unit.
24 volts is pretty safe.
Click to expand...
Yes I was referring to an all-in-one. I was thinking about a PowMr 3000k/2400W 24V system and also a EG4 6500 for 48V system once I learn more.
 
ShaneC said:
1200W will be plenty for that load, just fuse/breaker for your cables that way even if the inverter tries to pull more the breaker will flip but in reality the BMS should throttle the output anyway.
Click to expand...
Is it better to use fuses or breakers?
 
ladycage said:
This is what I was thinking about, using a fuse to limit the inverter to my 12v capacity. 1000-1200W should be more than enough for my first system. I have an Ecoflow Delta mini for emergency outages and it was able to power my needs for the gazebo so I figured I would try to build my own similar capacity system. Thanks for the suggestion of using a 125A breaker for my inverter and 100A for my battery.
Click to expand...
With a 125 amp breaker or fuse your BMS is very likely to trip first.
 
Have a look at the trip curve at this link.

187-Series Circuit Breaker - Surface Mount 120A - Blue Sea Systems

Thermal circuit breakers provide heavy duty circuit protection for 25 to 200 Amp loads when switching and circuit protection are both required.
www.bluesea.com www.bluesea.com
The breaker will pass current at 100% rating indefinitely.
The BMS usually trips at its over-current rating in ~30 seconds.
 
Last edited:
ladycage said:
Thanks so much this is really helpful. Looks like I need a 100-110A breaker.
Click to expand...
Even a 100 amp breaker is not likely to open before the BMS.

187-Series Circuit Breaker - Surface Mount 100A - Blue Sea Systems

Thermal circuit breakers provide heavy duty circuit protection for 25 to 200 Amp loads when switching and circuit protection are both required.
www.bluesea.com www.bluesea.com
The trip curve shows that the breaker will trip somewhere between ~30 and ~500 seconds at 125 amps.
 
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