Please Check and Comment on My Wiring Diagram

[ManKzin]

Here is the 3rd Draft after some help from Rob, The only thing that i have a question about is the 12V Boat Panel with Fuses. The Boat Panel has about 9 devices that can attach to it none exceed 20A.
1) Can i use a Class T 25A fuse or should i use a Class T 100A?
2) Can I put the isolator switch after the fuse in order that i can use a small one (the same size as the boat panel switches) Or do i have to use a 100A Isolator Disconnect Switch before the Class T fuse?

 

[robbob2112]

I would suggest using pure copper bus bars instead of the brass LiTime ones. They will carry the 300amps, well from my measuring a set I have they carry 304amps. I dunno which brand 150amp bar you plan on, just realize there are a ton of brass bars that are plated and list way more current than they can actually carry without getting red hot.


Would be good if you posted a list with links to all the equipment you intend to buy

 

[ManKzin]

I would suggest using pure copper bus bars instead of the brass LiTime ones. They will carry the 300amps, well from my measuring a set I have they carry 304amps. I dunno which brand 150amp bar you plan on, just realize there are a ton of brass bars that are plated and list way more current than they can actually carry without getting red hot.


Would be good if you posted a list with links to all the equipment you intend to buy

Plan to provide a parts list with links and what I paid for them. Just a heads up, it will be a few months before I get everything as I am trying not to break the bank and looking for deals as I wait. I will also provide the final wiring diagram and the full plans the cart I am building. You will be impressed with the cart. As it combines a lot of what others have done and what I actually want. Thanks for the suggestion for the bus bars, but unfortunately I already brought those items and can't return without a restocking fee. Oh and the other bus bar that is 150A is for the negative return from the 20A boat panel that has 1 USB, 1 cig socket, and 6 switches. I know that's over kill but it the only one I could find.

 

[robbob2112]

Well, you broke rule number one..... buy nothing until your plan/design is complete. And if it has to be inspected and permitted buy nothing until the paperwork is approved.

Once you get a list we can give it a once over and make suggestions like different bus bars and the like.

The only suggestion I have at this point is a MRBF fuse on each positive battery post.

 

[ManKzin]

Well, you broke rule number one..... buy nothing until your plan/design is complete. And if it has to be inspected and permitted buy nothing until the paperwork is approved.

Once you get a list we can give it a once over and make suggestions like different bus bars and the like.

The only suggestion I have at this point is a MRBF fuse on each positive battery post.

 

[ManKzin]

I plan on doing 300A ANL fuses to protect the system from each battery. The one I have on the positive bus bar is for when I recharge all the batteries using the 40A Litime Charger, it doesn't make sense to put 40A MRBF on each battery either.

 

[robbob2112]

ANL fuses run to hot - they are from car audio - anything from car audio should be kept there. They also have a very low AIC compared to the class T or MRBF even.

The ANL has an AIC around 5000amps the MRBF is good to 10,000 amps. The class T is good to 20,000amps. Because of the extremely low internal impedance of the LFP batteries they can put out 7000amps in the event of a BMS failure in a dead short.

If your fuse AIC doesn't exceed the possible arc size when the fuse blows it will just arc across it and continue to pass current until the casing burns away and the cable ends come apart.

So you do need MRBF on each battery post and you do need a class T on the main line between the bus bar and the inverter.

The size of the MRBF on the battery post would depend on the max current output of the BMS. If it is a 100amp BMS you would put 125amp fuses. If it is 200 amps 250amp fuses... i.e. max BMS current * 1.25 = fuse size.

The line from your charger to the bus bar should be a 50 amp fuse - Fuses protect wires they don't protect equipment.

Here is why you fuse all the batteries - If one cell in a battery fails and shorts that battery will have lower voltage and the other batteries will dump max current into the shorted battery. That current is enough to blow the BMS into a short and get even more current. The time involved for all of this to happen is under a second. If you have fuses that means the one on the shorted battery will fail and current will cut off from it and the other two will keep working.

If your cable runs between battery and bus bar are more than 7 inches long I would think about fusing the bus bar end as well.... I say think because you need to make certain that where the cables are install nothing can ever drop on them or rub or have a chance to short them out.

I've done the math in the past, you can dig it up if you want. It was 4 parallel 12v batteries with 100amp BMS. But the deal is that if you have a 2ft cable run and something shorts from the middle of that cable to the negative it can flash from 24c to 200c in under a second. 300amps coming down the cable to the short point and 100 amps coming up the cable to the short point. Assuming the shorting item/wrench/etc survives the inital flash and is welded into place it takes under a minute for a box end wrench to melt and be molten steel flying all over.


Have a look at this thread (I know it is long, will summarize

J

Thread 'House burned down'

Apr 28, 2024

So, after 4 to 5 years of working flawless, the 100 kwh lifepo4 battery caught fire at night and burned our house down. Luckily our family just made in out on time.
Inspection of the fire expert revealed that a melt fuse melted, and created an arc between the 2 points wich ultimatly started the fire.
So i learned to not use melt fuse anymore, plus once the house is rebuild, i will put the new system in a seperate shed outdoor.

• Jejochen
• Replies: 1,152
• Forum: Up in smoke... learn from my mistake!

• 
• 
• 

The summary is the guy had 1 cell short in one of 7 parallel battery banks. All of the banks had fuses to a bus bar and there was a shunt trip on the other side of the bus bar. The chain of events was a shorted cell vented, this filled the room with hydrogen gas and some other nasties, the Mega fuse he had protecting that battery exploded into a shower of sparks (there are youtube videos showing that), and the hydrogen ignited. That would have caused other cells to vent and add fuel... Bad chain of events and several things were uncovered looking at his build thread and pictures... He did everything right at the time he built the system.. the things uncovered are things that changed after the fact and he didn't update.

Part of it was to do with DIY batteries and part was to do with the design.

 

[mikefitz]

doesn't make sense to put 40A MRBF on each battery either.

Actually it's a good safery technique. Under fault conditions a lithium battery can deliver several thousand amps. Thus you need fuses that can withstand this possible high current. Fuses have two ratings, the amp fuse rating and a current withstand rating.
The ANL fuse has a withstand of around 3000 amps, depending on manufacturer, a Mega fuse 2000 amps. The MRBF has a withstand of 10000 amps.
You ideally need the MRBF on each battery before the parallel conection to prevent two 'good' batteries dumping power into one 'bad' battery.

Edit, sorry to repeat advice given, I am a very slow at typing.

 

[ManKzin]

ANL fuses run to hot - they are from car audio - anything from car audio should be kept there. They also have a very low AIC compared to the class T or MRBF even.

The ANL has an AIC around 5000amps the MRBF is good to 10,000 amps. The class T is good to 20,000amps. Because of the extremely low internal impedance of the LFP batteries they can put out 7000amps in the event of a BMS failure in a dead short.

If your fuse AIC doesn't exceed the possible arc size when the fuse blows it will just arc across it and continue to pass current until the casing burns away and the cable ends come apart.

So you do need MRBF on each battery post and you do need a

ANL fuses run to hot - they are from car audio - anything from car audio should be kept there. They also have a very low AIC compared to the class T or MRBF even.

The ANL has an AIC around 5000amps the MRBF is good to 10,000 amps. The class T is good to 20,000amps. Because of the extremely low internal impedance of the LFP batteries they can put out 7000amps in the event of a BMS failure in a dead short.

If your fuse AIC doesn't exceed the possible arc size when the fuse blows it will just arc across it and continue to pass current until the casing burns away and the cable ends come apart.

So you do need MRBF on each battery post and you do need a class T on the main line between the bus bar and the inverter.

The size of the MRBF on the battery post would depend on the max current output of the BMS. If it is a 100amp BMS you would put 125amp fuses. If it is 200 amps 250amp fuses... i.e. max BMS current * 1.25 = fuse size.

The line from your charger to the bus bar should be a 50 amp fuse - Fuses protect wires they don't protect equipment.

Here is why you fuse all the batteries - If one cell in a battery fails and shorts that battery will have lower voltage and the other batteries will dump max current into the shorted battery. That current is enough to blow the BMS into a short and get even more current. The time involved for all of this to happen is under a second. If you have fuses that means the one on the shorted battery will fail and current will cut off from it and the other two will keep working.

If your cable runs between battery and bus bar are more than 7 inches long I would think about fusing the bus bar end as well.... I say think because you need to make certain that where the cables are install nothing can ever drop on them or rub or have a chance to short them out.

I've done the math in the past, you can dig it up if you want. It was 4 parallel 12v batteries with 100amp BMS. But the deal is that if you have a 2ft cable run and something shorts from the middle of that cable to the negative it can flash from 24c to 200c in under a second. 300amps coming down the cable to the short point and 100 amps coming up the cable to the short point. Assuming the shorting item/wrench/etc survives the inital flash and is welded into place it takes under a minute for a box end wrench to melt and be molten steel flying all over.


Have a look at this thread (I know it is long, will summarize

J

Thread 'House burned down'

Apr 28, 2024

So, after 4 to 5 years of working flawless, the 100 kwh lifepo4 battery caught fire at night and burned our house down. Luckily our family just made in out on time.
Inspection of the fire expert revealed that a melt fuse melted, and created an arc between the 2 points wich ultimatly started the fire.
So i learned to not use melt fuse anymore, plus once the house is rebuild, i will put the new system in a seperate shed outdoor.

• Jejochen
• Replies: 1,152
• Forum: Up in smoke... learn from my mistake!

• 
• 
• 

The summary is the guy had 1 cell short in one of 7 parallel battery banks. All of the banks had fuses to a bus bar and there was a shunt trip on the other side of the bus bar. The chain of events was a shorted cell vented, this filled the room with hydrogen gas and some other nasties, the Mega fuse he had protecting that battery exploded into a shower of sparks (there are youtube videos showing that), and the hydrogen ignited. That would have caused other cells to vent and add fuel... Bad chain of events and several things were uncovered looking at his build thread and pictures... He did everything right at the time he built the system.. the things uncovered are things that changed after the fact and he didn't update.

Part of it was to do with DIY batteries and part was to do with the design.

on the main line between the bus bar and the inverter.

The size of the MRBF on the battery post would depend on the max current output of the BMS. If it is a 100amp BMS you would put 125amp fuses. If it is 200 amps 250amp fuses... i.e. max BMS current * 1.25 = fuse size.

The line from your charger to the bus bar should be a 50 amp fuse - Fuses protect wires they don't protect equipment.

Here is why you fuse all the batteries - If one cell in a battery fails and shorts that battery will have lower voltage and the other batteries will dump max current into the shorted battery. That current is enough to blow the BMS into a short and get even more current. The time involved for all of this to happen is under a second. If you have fuses that means the one on the shorted battery will fail and current will cut off from it and the other two will keep working.

If your cable runs between battery and bus bar are more than 7 inches long I would think about fusing the bus bar end as well.... I say think because you need to make certain that where the cables are install nothing can ever drop on them or rub or have a chance to short them out.

I've done the math in the past, you can dig it up if you want. It was 4 parallel 12v batteries with 100amp BMS. But the deal is that if you have a 2ft cable run and something shorts from the middle of that cable to the negative it can flash from 24c to 200c in under a second. 300amps coming down the cable to the short point and 100 amps coming up the cable to the short point. Assuming the shorting item/wrench/etc survives the inital flash and is welded into place it takes under a minute for a box end wrench to melt and be molten steel flying all over.


Have a look at this thread (I know it is long, will summarize

J

Thread 'House burned down'

Apr 28, 2024

So, after 4 to 5 years of working flawless, the 100 kwh lifepo4 battery caught fire at night and burned our house down. Luckily our family just made in out on time.
Inspection of the fire expert revealed that a melt fuse melted, and created an arc between the 2 points wich ultimatly started the fire.
So i learned to not use melt fuse anymore, plus once the house is rebuild, i will put the new system in a seperate shed outdoor.

• Jejochen
• Replies: 1,152
• Forum: Up in smoke... learn from my mistake!

• 
• 
• 

The summary is the guy had 1 cell short in one of 7 parallel battery banks. All of the banks had fuses to a bus bar and there was a shunt trip on the other side of the bus bar. The chain of events was a shorted cell vented, this filled the room with hydrogen gas and some other nasties, the Mega fuse he had protecting that battery exploded into a shower of sparks (there are youtube videos showing that), and the hydrogen ignited. That would have caused other cells to vent and add fuel... Bad chain of events and several things were uncovered looking at his build thread and pictures... He did everything right at the time he built the system.. the things uncovered are things that changed after the fact and he didn't update.

Part of it was to do with DIY batteries and part was to do with the design.

Thanks i will use the MRBFs on all the batteries like you have recommended. Question do i need one from the main shut off switch to the bus bar or is that over kill

 

[ManKzin]

Thanks i will use the MRBFs on all the batteries like you have recommended. Question do i need one from the main shut off switch to the bus bar or is that over kill

 

[ManKzin]

Actually it's a good safery technique. Under fault conditions a lithium battery can deliver several thousand amps. Thus you need fuses that can withstand this possible high current. Fuses have two ratings, the amp fuse rating and a current withstand rating.
The ANL fuse has a withstand of around 3000 amps, depending on manufacturer, a Mega fuse 2000 amps. The MRBF has a withstand of 10000 amps.
You ideally need the MRBF on each battery before the parallel conection to prevent two 'good' batteries dumping power into one 'bad' battery.

Edit, sorry to repeat advice given, I am a very slow at typing.

 

[ManKzin]

I understand about using MRFB Class T 250A on each battery. If you look at my diagram it goes from the battery to a bus bar where all 3 batteries are connected, plus the main power (before DC Switch) and the 40A Charger. I am thinking that the MRFB 40A block should be connected between the charger and the bus bar, as it will be charging all 3 batteries simultaneously. So it would look like this 40A charger --> MRFB 40A Block --> 6 terminal bus bar --> to all three Batteries. If i put it on the battery terminal along with a 250A MRFB Class T i can see them burning out constantly.

 

[robbob2112]

It looks like the AI went a little nuts with shunts and circuit breakers -- I am impressed you got it to spit out something that is semi-reasonable.
BTW - forum policy requires you to identify it if you post something that is from an AI....
Some members are very touchy about it and just ignore anything from an AI.

I would suggest you download this drawio and use it to redraw the diagram so you can make edits to it.

Look at some of the diagrams linked in my signature line for ideals - they aren't perfect and the 24v diagram is not yet finished.


While you redraw what it is leave out all the circuit breakers and all of the shunts. You only need a single shunt between the two negative bus bars. You can use a breaker between the MPPT and the bus bar. Standard is to have the battery cutoff switch in the negative side of things. So it would go.

Batteries with mrbf-> BB1 (bus bar) -> battery cutoff switch -> shunt -> BB2 -> everything else.

The shunt located between the panels at the top and the batteries at the bottom is between the positive and negative bus bar it would trip the breaker everytime you turned it on.

The connections on the battery switch that is above the batteries - it has many lugs stacked on it. Good practice is to never stack lugs, if you must stack them then never more than two together with the highest draw towards the bus bar.

main fuse
3000w / 12.8 = 234amps * 1.25 = 292 amps - so a 300amp class T off the positive bus bar between it and the battery.

The upper switch should be a DC isolator not a battery switch - the battery switch isn't rated to break an arc of constant current like that. Battery disconnect switches are intended to only be switched where there is no current flow or they can be damaged quick. What should be there ideally is an IMO brand isolator rated for the current and voltage involved.

The connections to the panels are odd-ball - there are two wires off each panel. To put them in series you would connect the plus from one to the minus from the next and then the PV wire connects to the remaining two connections. The way it is drawn they have a negative to negative and positive to positive - putting the panels in parallel. With only two panels that might work with a Y splitter of each gender but I avoid those. Besides chances are the panel voltage is they should be ok to run serial and get more juice out of them.



Here is what chatgpt came up with when I used it as a test - to build a battery - asking for a solar diagram was similar. I've used github copilot for coding as well as bingchat --What I have found is they are like really smart 10 year olds that think they know everything and if you don't understand what they are so sure is right they can lead you far astray.

Thread 'I asked chatgpt to design a battery'

May 28, 2024

I wasn't very specific, I just told it 16s with the largest available eve cells and a diagram.

Here is the result for amusement purposes only



Certainly! Here are the detailed steps to assemble a DIY LiFePO4 (LFP) battery using EVE prismatic cells in a 16S1P configuration, based on the provided diagram:

### Components Needed:
1. **Battery Cells:**
- 16 EVE LF304K prismatic cells (304Ah each).

2. **Battery Management System (BMS):**
- Batrium Watchmon 5 BMS.
- Longmons or Cellmons for cell monitoring.
- Shunt module for current monitoring.
- Temperature sensors.

3...

• robbob2112
• Replies: 47
• Forum: DIY LiFePO4 Battery Banks

• 
• 
• 

 

[robbob2112]

More notes -

There is no need for a fuse in the wire from the panels to the MPPT. The wire should be rated at 156% of the expected current. With that properly sized you can run a series string or two panels in parallel all day long and not even warm up the wire - there is a max panels can put out and no more so a dead short will only ever draw Isc (current short circuit)

1.25 * 1.25 = 1.56... this is a NEC requirement.

there is no need for a shunt between the MPPT and the bus bar - the MPPT knows how much current is coming out. The shunt that should be in the negative line between bus bars will tell you how much is going to the battery, the rest is going to the other loads.

Read my signature thread on bus bars - you want pure copper 110 and enough studs on them to land all your connections without stacking them.

Unless you intend to buy pre-made cables get a good crimper - the $50 off amazon are not good, they have awg marking and are metric dies so they make crappy crimps. Buy good lugs as well. With my Temco TH005 crimper a crappy lug will leave wings everytime. With Selterm, Temco, or other quality lugs I get perfect crimps with no wings.


12.8v * 300ah = 3840Whrs * 3 = 11,520Whrs. That is quite a lot of battery.

Assuming you get 5 hours of sun a day and your panels are mounted with the right tilt

11520Whr/5hr = 2304watts of panels is what you need to fully charge them. Depends on your mounting area if you have that much room. If you have help you can do 500w panels, but those are as big as a sheet of plywood and weigh in at 60ish pounds. For me I am using 335w to 400w panels because that is all I can handle alone.

2300Watts / 14.4v = 159amps /3 batteries = 53.24amps each

So lets assume 500w panels. that means you need 5 or 6 of them with good angle mounting. For a mobile mounting where they are flat on a roof you would need 40% more.

that MPPT at 40amps would max out 576watts - I suspect the manual would list a max amount - so you will never get enough wattage at 12v with 1 MPPT to charge the batteries. Unless you go with a bigger MPPT you would need 4 of them, or 1 per panel.

I have a Victron 250/100 so I can get around 1400watts into a 12v battery bank with a single MPPT. For your purpose you need to think about a brand you want to use for equipment - you can mix and match but if you want years of trouble free solar you need to think about top tier equipment. if I had to buy two of these to cover the current required I would probably get the RS 450/200 and call it a day ... unless I had space constraints and had to get smaller equipment.

For the inverter, 3000w is pretty much the top wattage that is practical on 12v system so that is OK. Sungoldpower has a 12.8v 3000w inverter that has a built in charger so you don't need a separate one.

Assuming 3 parallel 12.8 batteries they generally charge at 0.2C for best longevity - You specified 300ah batteries -
300ah * 0.2C = is 60 amps each - you have 3 of them so in reality you should have 180amps to charge them in a reasonable time. You can charge slower but it will take forever....

Also, where will this all be mounted? Vehicle? garage? shed?
LFP batteries can't be charged below 0c so they would need to be insulated and kept warm. If this is in a confined space you might need a mini-split to keep it cool and that requires more panels.

It can get involved if you dig into all the details - so feel free to ask anything - and don't trust the AI...


Did you start with a energy audit? -

i.e. how much power do you need... i.e. what do you want to run and for how long in a day. There are a lot of tools out there but they tend to way overestimate things because when you fill in the data they assume everything is running at once. Nobody on solar would run an electric oven, a well pump, a furnace, an electric dryer, a large compressor, a hair drier, etc all at once ... most things like ovens and fridges have a duty cycle of off to on time ... a fridge for instance may run a fan a lot but in general it is actually only cooling for 10~15 minutes per hour. The tools also tend to assume you fridge is old and an energy hog.... old fridges used to run 1200w or more where the new ones are 300w or less.

 

[robbob2112]

And, sorry, I tend to write novels with lots to digest.

And buy nothing else until your plan is complete.

 

[ManKzin]

It looks like the AI went a little nuts with shunts and circuit breakers -- I am impressed you got it to spit out something that is semi-reasonable.
BTW - forum policy requires you to identify it if you post something that is from an AI....
Some members are very touchy about it and just ignore anything from an AI.

I would suggest you download this drawio and use it to redraw the diagram so you can make edits to it.

Look at some of the diagrams linked in my signature line for ideals - they aren't perfect and the 24v diagram is not yet finished.


While you redraw what it is leave out all the circuit breakers and all of the shunts. You only need a single shunt between the two negative bus bars. You can use a breaker between the MPPT and the bus bar. Standard is to have the battery cutoff switch in the negative side of things. So it would go.

Batteries with mrbf-> BB1 (bus bar) -> battery cutoff switch -> shunt -> BB2 -> everything else.

The shunt located between the panels at the top and the batteries at the bottom is between the positive and negative bus bar it would trip the breaker everytime you turned it on.

The connections on the battery switch that is above the batteries - it has many lugs stacked on it. Good practice is to never stack lugs, if you must stack them then never more than two together with the highest draw towards the bus bar.

main fuse
3000w / 12.8 = 234amps * 1.25 = 292 amps - so a 300amp class T off the positive bus bar between it and the battery.

The upper switch should be a DC isolator not a battery switch - the battery switch isn't rated to break an arc of constant current like that. Battery disconnect switches are intended to only be switched where there is no current flow or they can be damaged quick. What should be there ideally is an IMO brand isolator rated for the current and voltage involved.

The connections to the panels are odd-ball - there are two wires off each panel. To put them in series you would connect the plus from one to the minus from the next and then the PV wire connects to the remaining two connections. The way it is drawn they have a negative to negative and positive to positive - putting the panels in parallel. With only two panels that might work with a Y splitter of each gender but I avoid those. Besides chances are the panel voltage is they should be ok to run serial and get more juice out of them.



Here is what chatgpt came up with when I used it as a test - to build a battery - asking for a solar diagram was similar. I've used github copilot for coding as well as bingchat --What I have found is they are like really smart 10 year olds that think they know everything and if you don't understand what they are so sure is right they can lead you far astray.

Thread 'I asked chatgpt to design a battery'

May 28, 2024

I wasn't very specific, I just told it 16s with the largest available eve cells and a diagram.

Here is the result for amusement purposes only



Certainly! Here are the detailed steps to assemble a DIY LiFePO4 (LFP) battery using EVE prismatic cells in a 16S1P configuration, based on the provided diagram:

### Components Needed:
1. **Battery Cells:**
- 16 EVE LF304K prismatic cells (304Ah each).

2. **Battery Management System (BMS):**
- Batrium Watchmon 5 BMS.
- Longmons or Cellmons for cell monitoring.
- Shunt module for current monitoring.
- Temperature sensors.

3...

• robbob2112
• Replies: 47
• Forum: DIY LiFePO4 Battery Banks

• 
• 
• 

It was not AI generated I actually used a pre existing wiring diagram from Litime and edited in Microsoft paint. Lol. As for the shunt on the left between the Batteries and the solar panels and to the left of the power switch (which I will change out to an isolator switch) that is actually a pre-charger 10 second push circuit to charge up tha capacitor in the inverter, I may just hook it up directly to the inverter instead if the BB2 so as to avoid accidentally triggering the circuit breaker. Also are you saying the breaker and the ANL 300A fuse (will use MRFB Ts as someone else suggested). Is overkill? I will proces every thing you have said and I may have a question or 2, but right now I am burnt out with this project as I had to take advantage of a great Lifepo4 deal where i got 3 batteries for the price of 2 and still saved $150. Thanks for the advise

 

[ManKzin]

More notes -

There is no need for a fuse in the wire from the panels to the MPPT. The wire should be rated at 156% of the expected current. With that properly sized you can run a series string or two panels in parallel all day long and not even warm up the wire - there is a max panels can put out and no more so a dead short will only ever draw Isc (current short circuit)

1.25 * 1.25 = 1.56... this is a NEC requirement.

there is no need for a shunt between the MPPT and the bus bar - the MPPT knows how much current is coming out. The shunt that should be in the negative line between bus bars will tell you how much is going to the battery, the rest is going to the other loads.

Read my signature thread on bus bars - you want pure copper 110 and enough studs on them to land all your connections without stacking them.

Unless you intend to buy pre-made cables get a good crimper - the $50 off amazon are not good, they have awg marking and are metric dies so they make crappy crimps. Buy good lugs as well. With my Temco TH005 crimper a crappy lug will leave wings everytime. With Selterm, Temco, or other quality lugs I get perfect crimps with no wings.


12.8v * 300ah = 3840Whrs * 3 = 11,520Whrs. That is quite a lot of battery.

Assuming you get 5 hours of sun a day and your panels are mounted with the right tilt

11520Whr/5hr = 2304watts of panels is what you need to fully charge them. Depends on your mounting area if you have that much room. If you have help you can do 500w panels, but those are as big as a sheet of plywood and weigh in at 60ish pounds. For me I am using 335w to 400w panels because that is all I can handle alone.

2300Watts / 14.4v = 159amps /3 batteries = 53.24amps each

So lets assume 500w panels. that means you need 5 or 6 of them with good angle mounting. For a mobile mounting where they are flat on a roof you would need 40% more.

that MPPT at 40amps would max out 576watts - I suspect the manual would list a max amount - so you will never get enough wattage at 12v with 1 MPPT to charge the batteries. Unless you go with a bigger MPPT you would need 4 of them, or 1 per panel.

I have a Victron 250/100 so I can get around 1400watts into a 12v battery bank with a single MPPT. For your purpose you need to think about a brand you want to use for equipment - you can mix and match but if you want years of trouble free solar you need to think about top tier equipment. if I had to buy two of these to cover the current required I would probably get the RS 450/200 and call it a day ... unless I had space constraints and had to get smaller equipment.

For the inverter, 3000w is pretty much the top wattage that is practical on 12v system so that is OK. Sungoldpower has a 12.8v 3000w inverter that has a built in charger so you don't need a separate one.

Assuming 3 parallel 12.8 batteries they generally charge at 0.2C for best longevity - You specified 300ah batteries -
300ah * 0.2C = is 60 amps each - you have 3 of them so in reality you should have 180amps to charge them in a reasonable time. You can charge slower but it will take forever....

Also, where will this all be mounted? Vehicle? garage? shed?
LFP batteries can't be charged below 0c so they would need to be insulated and kept warm. If this is in a confined space you might need a mini-split to keep it cool and that requires more panels.

It can get involved if you dig into all the details - so feel free to ask anything - and don't trust the AI...


Did you start with a energy audit? -

i.e. how much power do you need... i.e. what do you want to run and for how long in a day. There are a lot of tools out there but they tend to way overestimate things because when you fill in the data they assume everything is running at once. Nobody on solar would run an electric oven, a well pump, a furnace, an electric dryer, a large compressor, a hair drier, etc all at once ... most things like ovens and fridges have a duty cycle of off to on time ... a fridge for instance may run a fan a lot but in general it is actually only cooling for 10~15 minutes per hour. The tools also tend to assume you fridge is old and an energy hog.... old fridges used to run 1200w or more where the new ones are 300w or less.

I only need a constant 2009W to run my fridge, window AC and entertainment center. This will be portable as I have designed a cart, which is the reason I have a separate charger, but I will look into the inverter you suggested. The reason for the shunt is so that I can see the battery% and such without lifting up and seeing what the inverter is actually doing. It was only $37 anyways. I will review everything you said tomorrow and may have a couple questions. To add I did the wiring diagram in Microsoft paint using a Litime wiring diagram I found on their site.

 

[robbob2112]

Window AC draws a ton of current generally and unlike most things they have a duty-cycle that is more on than off.

Lookup mini-split heat pumps, far more efficient and lower power draw.

I saw the AI thing at the top edge of the screen cap, my bad on assuming.

If you use victron shunt, mppt, and inverter they all communicate with each other and add a cerbo or venusos box and you can monitor everything in the same place. If you use another brand you can use solar assistant to monitor everything.

If you need 2000w to run with, you panels enough for that in the day plus enough to also charge the batteries at night.

A 12000 BTU ductless mini-split with ez start take max 10.5 amps...less than that when running. Around 1200w to start and 600w to run. Those specs are from one carried by home depot

 

[ManKzin]

View attachment 252895

Second drawing (November 2, 2024)

 

[robbob2112]

Only a couple of comments tonight, will look closer in the am.

The battery switch in the upper right should be IMO disconnect. That type switch doesn't work there.

The battery disconnect in the positive cable should be between the first negative bus bar and the class T fuse on the drawing.

The precharge resistor and button should be on the battery switch in the negative line.

The class T will work there, but it is normal to put fuses in the positive line verse the negative

It looks like the wire between the positive bus bar and switch is labeled as 10awg, it should be 1/0.

You don't need to put a fuse and breaker both into the line between the mppt and positive bus bar. And as I mentioned before, leave the ANL fuse in the garage toolbox for the car. I would suggest a 50amp Mega fuse in that location. The mppt can't ever output more and it is to protect the wire sized for 50 amps.

When you rearrange a bit... the positive from the battery bus bar will have 8 studs. 4 for the batteries, 1 for the inverter, 1 for the charger and 1 for the mppt.

In the inverter line you put the class T. In the charger line you put a 50 amp Mega fuse. In the line to the mppt you put a 50 amp Mega. Each battery has a MRBF.

The negative lines from the battery bus bar connects
Bus bar -> battery switch with precharge button/switch connected across the studs -> shunt -> negative bus bar

Off the second negative bus bar you have the wires to the mppt, inverter, and charger.

If you want additional shunts for anything they go in the negative lines.

You want the solar panels in series not parallel. In series there is a higher voltage at the mppt with lower current. This has two advantages. First the higher voltage means the mppt has enough voltage to charge earlier than if they are in parallel. The lower current means the wires size can be smaller. You also have less loss at higher voltage/lower current in the wires... power = current^2 * resistance.

Panel wiring
In series voltage adds and current is constant.
In parallel current adds and voltage is constant.

If you are trying to do them in parallel you may want smaller panels with optimizer. If they are not mounted flat in the same plain ..not facing the exact same direction you may want more mppt which you will need to charge the battery.


BTW, friends don't let friends buy Renogy... they are over hyped and marketed. When they work they are fine, if they fail good luck getting warranty done... they being anything renogy.

 

[ManKzin]

I am totally confused. I have never heard of putting the main power off switch that way. If I wire my home that way I could get killed changing the light bulb, even though it is off. Plus every diagram I have ever seen has the power off switch in the positive red wire. By the way it's a 60A MPPT, not a 40A. My bad if I don't change in my wiring diagram

 

[ManKzin]

Only a couple of comments tonight, will look closer in the am.

The battery switch in the upper right should be IMO disconnect. That type switch doesn't work there.

The battery disconnect in the positive cable should be between the first negative bus bar and the class T fuse on the drawing.

The precharge resistor and button should be on the battery switch in the negative line.

The class T will work there, but it is normal to put fuses in the positive line verse the negative

It looks like the wire between the positive bus bar and switch is labeled as 10awg, it should be 1/0.

You don't need to put a fuse and breaker both into the line between the mppt and positive bus bar. And as I mentioned before, leave the ANL fuse in the garage toolbox for the car. I would suggest a 50amp Mega fuse in that location. The mppt can't ever output more and it is to protect the wire sized for 50 amps.

When you rearrange a bit... the positive from the battery bus bar will have 8 studs. 4 for the batteries, 1 for the inverter, 1 for the charger and 1 for the mppt.

In the inverter line you put the class T. In the charger line you put a 50 amp Mega fuse. In the line to the mppt you put a 50 amp Mega. Each battery has a MRBF.

The negative lines from the battery bus bar connects
Bus bar -> battery switch with precharge button/switch connected across the studs -> shunt -> negative bus bar

Off the second negative bus bar you have the wires to the mppt, inverter, and charger.

If you want additional shunts for anything they go in the negative lines.

You want the solar panels in series not parallel. In series there is a higher voltage at the mppt with lower current. This has two advantages. First the higher voltage means the mppt has enough voltage to charge earlier than if they are in parallel. The lower current means the wires size can be smaller. You also have less loss at higher voltage/lower current in the wires... power = current^2 * resistance.

Panel wiring
In series voltage adds and current is constant.
In parallel current adds and voltage is constant.

If you are trying to do them in parallel you may want smaller panels with optimizer. If they are not mounted flat in the same plain ..not facing the exact same direction you may want more mppt which you will need to charge the battery.


BTW, friends don't let friends buy Renogy... they are over hyped and marketed. When they work they are fine, if they fail good luck getting warranty done... they being anything renogy.

You are right I shouldn't have the negative line front the inverter go up to the bus bar above it. It should go directly to bus bar beside the batteries at the bottom left hand side

 

[robbob2112]

If the negative from the battery is cut no current can flow.

Now this assumes you aren't walking around touching any red wire while barefoot. Every cable end should be covered by a rubber boot and every bus bar or anything metal should be insulated so at not point can your touch anything and have a difference of potential and get a shock.

If you want to switch the cutoff to the positive add another bus bar. So batteries go to one and in the single wire between the two bus bars have a cutoff switch and the class T fuse. Kind of like you have it now, except the charger connects to the second bus bar.

Another way to do it would be use contactors so both positive and negative from the bus bars are cut by flipping a single small switch. The switch can be remote.

60amps means 1536watts at optimal angle.

What is your install going into? Maybe take a picture of the whole thing and the install area

 

[ManKzin]

So I should move my AC to DC charger to the bus bar that is after the turn off switch? Battery ~ T 300 ~ Bus Bar (+) (Which has the other 2 batteries attached) ~ On/Off Switch ~ Bus Bar (+) (which has the MPPT, Inverter and Shunt) and place the (+} Cable from the charger there? While placing the (-) Cable from the charger into the (-} Cable in the (-) Bus Bar? If I do that how I'll I be able to charge the batteries when the system is off? Litime to put the positive charge cable directly onto the battery's positive terminal and the Negative cable on the negative terminal . The reason I have the charger cables on the positive and negative iBus Bars closest to the batteries, is this is where all battery's connect to and so the charger will distributed the power evenly to all batteries and not just one.
As for what I building? I have been through several hurricanes and have lost hundreds in lost food and have had no power for weeks. This system will be to power my home fridge, entertainment center, and window AC ( not going to buy a split a/c). Also this will be portable and can be separated into 2 piece for easy transport. I also will be using this every night to power up my entertainment center and window shaker

 

[robbob2112]

To do it right
The batteries positives all come to one bus bar..in the cable to the second positive bus bar you have a battery switch since you want to do that on the positive.

On the second bus bar you connect the inverter, charger, mppt, 12v load

The negative battery cables land on the first negative bus bar, the cable between that bus bar and the second has a shunt and maybe a second battery switch.

The second bus bar lansa all the negative load and charge cables.

For the SOC to be correct on your battery monitor to be accurate everything MUST pass through it.

All positive wires to everything have fuses, no fuses needed for the negative wires.

Assuming you are mobile in a van or other vehicle the negative off the second bus bar ties to the chassis.