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Schematic of 24v/12v off-grid solar system (in progress, help needed)

satanas

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May 6, 2021
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Hi all! I was working on this last night, it's pretty rough, but I realized I'm hitting a bit of a wall. I think I'm missing some breakers and fuses, potentially have some inaccurate wire sizes? Also, I'm not even sure how to connect the battery disconnect and shunt to the Lynx Distributor and I want to throw in a victron battery protect but I'm not even sure where... (100A maybe?)
Basically I'm in over my head and I need someone to bring me back down to earth! Any recommendations/suggestions to correct or further complete the schematic is greatly appreciated.
The only thing that's slightly unique is that it's a 24v system so I'm using two fuse blocks (furrion ac/12vdc distribution panel and a blue seas 12 circuit fuse block for 24v). And it's not noted on the schematic but I'm using 4 MEGA fuses on the lynx distributor (2x 300A and 2x 100A)

*Threw in a couple extra pics of the branch circuits in meme form that I made to blow off some steam for fun*
 

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I would put the battery disconnect on the + wire between battery and Lynx. I would put the shunt on the - wire between the battery and Lynx.
 
Your four SOK 12.8V 206Ah batteries in 2S2P will be 25.6V 412Ah 10.5kWh. They will have an 80A recommended charge current and a 200A max continuous discharge. Make sure you the positive and negative wires from the Lynx to opposite pairs of batteries, not to the same pair. This will keep the parallel pairs in better balance.

The MultiPlus AC output can only handle 6AWG. You will not be able to use 4AWG for the AC wires.

I added an 2-pole AC breaker between the shore power plug and the AC In of the inverter. I did this to protect my system from a bad shore power connection and to act as a disconnect if needed. The size depends on what you need to support (15/30/50A). Pick a break a little bigger than the service.

Be sure you properly fuse the 24->12V buck converter. The amp rating of the converter is for the 12V output.

For the 24V fuse panel, consider everything that will be connected to it and determine the maximum total amps needed at any one time. Add some extra to be safe. Then size the wire and fuse accordingly.

I'd consider using 12AWG wire for the 12V outlets instead of 14AWG. This will help with voltage drop and better work with higher amp gadgets.

I see one fan is 14AWG and the other is 10AWG. Is one fan really far?

If you add a battery protect it would go between the Lynx and the 24V DC fuse box and the 24-12V converter. DO NOT connect the inverter to the battery protect. The job of the battery protect would be to keep your DC loads from over-draining the battery. The inverter has its own settings to shut itself down if the battery gets too low.

You should clarify what the 4 fuses in the Lynx will be used for. The sizes you mention are likely way too big for the 24V fuse box and the 24-12V converter. The SCC has 45A output so a 50A breaker between it and the battery would be good. And the diagram shows a 150A for the inverter. So what are the 2 300A and 2 100A MEGA fuses for?
 
Your four SOK 12.8V 206Ah batteries in 2S2P will be 25.6V 412Ah 10.5kWh. They will have an 80A recommended charge current and a 200A max continuous discharge. Make sure you the positive and negative wires from the Lynx to opposite pairs of batteries, not to the same pair. This will keep the parallel pairs in better balance.

The MultiPlus AC output can only handle 6AWG. You will not be able to use 4AWG for the AC wires.

I added an 2-pole AC breaker between the shore power plug and the AC In of the inverter. I did this to protect my system from a bad shore power connection and to act as a disconnect if needed. The size depends on what you need to support (15/30/50A). Pick a break a little bigger than the service.

Be sure you properly fuse the 24->12V buck converter. The amp rating of the converter is for the 12V output.

For the 24V fuse panel, consider everything that will be connected to it and determine the maximum total amps needed at any one time. Add some extra to be safe. Then size the wire and fuse accordingly.

I'd consider using 12AWG wire for the 12V outlets instead of 14AWG. This will help with voltage drop and better work with higher amp gadgets.

I see one fan is 14AWG and the other is 10AWG. Is one fan really far?

If you add a battery protect it would go between the Lynx and the 24V DC fuse box and the 24-12V converter. DO NOT connect the inverter to the battery protect. The job of the battery protect would be to keep your DC loads from over-draining the battery. The inverter has its own settings to shut itself down if the battery gets too low.

You should clarify what the 4 fuses in the Lynx will be used for. The sizes you mention are likely way too big for the 24V fuse box and the 24-12V converter. The SCC has 45A output so a 50A breaker between it and the battery would be good. And the diagram shows a 150A for the inverter. So what are the 2 300A and 2 100A MEGA fuses for?
First of all THANK YOU for giving this such time and attention! I've attached the schematic with the adjustments you suggested, obvs still very rough but what do you think?

The 12V output is about 50A, so I added a 60A ANL fuse if you think that will work

Yes, one of the maxxfans is about 20-30 feet further than the other fan which is within 10 feet of the battery bank.

The 4 fuses in the Lynx are as follows (the 150A anl fuse was a mistake!) :
300A Mega fuse - Battery circuit
300A Mega fuse- Inverter-charger circuit
100A Mega fuse- DC Loads
100A Mega fuse- Charge controller

The loads for the 24V fuse block are pretty low and I calculated 5A ATC Fuses would work for basically everything
 

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Your four SOK 12.8V 206Ah batteries in 2S2P will be 25.6V 412Ah 10.5kWh. They will have an 80A recommended charge current and a 200A max continuous discharge. Make sure you the positive and negative wires from the Lynx to opposite pairs of batteries, not to the same pair. This will keep the parallel pairs in better balance.

The MultiPlus AC output can only handle 6AWG. You will not be able to use 4AWG for the AC wires.

I added an 2-pole AC breaker between the shore power plug and the AC In of the inverter. I did this to protect my system from a bad shore power connection and to act as a disconnect if needed. The size depends on what you need to support (15/30/50A). Pick a break a little bigger than the service.

Be sure you properly fuse the 24->12V buck converter. The amp rating of the converter is for the 12V output.

For the 24V fuse panel, consider everything that will be connected to it and determine the maximum total amps needed at any one time. Add some extra to be safe. Then size the wire and fuse accordingly.

I'd consider using 12AWG wire for the 12V outlets instead of 14AWG. This will help with voltage drop and better work with higher amp gadgets.

I see one fan is 14AWG and the other is 10AWG. Is one fan really far?

If you add a battery protect it would go between the Lynx and the 24V DC fuse box and the 24-12V converter. DO NOT connect the inverter to the battery protect. The job of the battery protect would be to keep your DC loads from over-draining the battery. The inverter has its own settings to shut itself down if the battery gets too low.

You should clarify what the 4 fuses in the Lynx will be used for. The sizes you mention are likely way too big for the 24V fuse box and the 24-12V converter. The SCC has 45A output so a 50A breaker between it and the battery would be good. And the diagram shows a 150A for the inverter. So what are the 2 300A and 2 100A MEGA fuses for?
Also, the batteries are 12.8V 100Ah not 206Ah! So it would come out to 25.6V/ 200Ah/ 5.2kWh in 2S2P
 
Also, the batteries are 12.8V 100Ah not 206Ah! So it would come out to 25.6V/ 200Ah/ 5.2kWh in 2S2P
Oops. I don't know why I thought you had 4 of the 206Ah. The SOK batteries have a max continuous discharge of 100A for both the 100Ah and the 206Ah. So if you need a 3000W inverter and you will be running it over 2000W then you need more than 100A discharge. This means you will need to stick with the 4 100Ah since that gives you 200A max continuous discharge. I was going to suggest two 206Ah instead of four 100Ah but then you would need to go down to a 2000W inverter to keep it under 100A discharge.

I've attached the schematic with the adjustments you suggested, obvs still very rough but what do you think?
The wiring for the battery protect (BP) looks wrong. You want the Battery In of the BP attached to the Lynx. Then the Bat+ of the DC-DC converter and the Bat+ of the 24V fuse box both go to the Battery Out of the BP.

If the DC-DC Converter has 50A output then you need 6AWG wire. The problem with that is that the DC-DC converter that you have pictured only has 12AWG leads at best. I have the 40A version of that converter. The leads to too thin. I might end up replacing mine at some point with a high quality Victron Orion.

You don't want both the 50A breaker between the SCC and Lynx as well as the 100 MEGA fuse for the SCC.

For the inverter you show 1AWG wire but a 300A MEGA fuse. That fuse is too big for 1AWG wire. The 1AWG wire is borderline for a 3000W inverter at 24V. If you stick with 1AWG, lower the fuse to 200A, maybe 250A. Or go with 1/0 to the inverter then the fuse could be 250A or 300A.

The 300A MEGA fuse for the battery seems OK until you pay attention to the 200A max continuous discharge allowed by the SOK batteries in parallel. You might consider lowering that fuse to 200A, maybe 250A, to protect the batteries from too high of a discharge rate. The BMS should shutdown the battery when the discharge is too high for too long if you keep the 300A fuse but, a blown fuse is cheaper than a toasted battery if the BMS doesn't do its job soon enough. You need to research whether a MEGA fuse is sufficient for LiFePO4 batteries.

Just remember that you choose a wire to safely handle the amps expected to go through it from the given load. You then choose a fuse that is a bit higher than the load and less than the highest load the wire can handle before becoming dangerous. The fuse must be the weakest link in the circuit.

Below is a schematic of my system as a reference. I'm not using a Lynx but it otherwise very similar to your setup (my inverter is 2kW). The one thing I need to change in mine is the 300A ANL fuse for the battery. I need to replace that with a 150A Class T fuse. My 1/0AWG is safe with 300A but the batteries can only handle 100A max continuous discharge. And Class T is better for LiFePO4 batteries than ANL.

Schematic2.png
 
Oops. I don't know why I thought you had 4 of the 206Ah. The SOK batteries have a max continuous discharge of 100A for both the 100Ah and the 206Ah. So if you need a 3000W inverter and you will be running it over 2000W then you need more than 100A discharge. This means you will need to stick with the 4 100Ah since that gives you 200A max continuous discharge. I was going to suggest two 206Ah instead of four 100Ah but then you would need to go down to a 2000W inverter to keep it under 100A discharge.


The wiring for the battery protect (BP) looks wrong. You want the Battery In of the BP attached to the Lynx. Then the Bat+ of the DC-DC converter and the Bat+ of the 24V fuse box both go to the Battery Out of the BP.

If the DC-DC Converter has 50A output then you need 6AWG wire. The problem with that is that the DC-DC converter that you have pictured only has 12AWG leads at best. I have the 40A version of that converter. The leads to too thin. I might end up replacing mine at some point with a high quality Victron Orion.

You don't want both the 50A breaker between the SCC and Lynx as well as the 100 MEGA fuse for the SCC.

For the inverter you show 1AWG wire but a 300A MEGA fuse. That fuse is too big for 1AWG wire. The 1AWG wire is borderline for a 3000W inverter at 24V. If you stick with 1AWG, lower the fuse to 200A, maybe 250A. Or go with 1/0 to the inverter then the fuse could be 250A or 300A.

The 300A MEGA fuse for the battery seems OK until you pay attention to the 200A max continuous discharge allowed by the SOK batteries in parallel. You might consider lowering that fuse to 200A, maybe 250A, to protect the batteries from too high of a discharge rate. The BMS should shutdown the battery when the discharge is too high for too long if you keep the 300A fuse but, a blown fuse is cheaper than a toasted battery if the BMS doesn't do its job soon enough. You need to research whether a MEGA fuse is sufficient for LiFePO4 batteries.

Just remember that you choose a wire to safely handle the amps expected to go through it from the given load. You then choose a fuse that is a bit higher than the load and less than the highest load the wire can handle before becoming dangerous. The fuse must be the weakest link in the circuit.

Below is a schematic of my system as a reference. I'm not using a Lynx but it otherwise very similar to your setup (my inverter is 2kW). The one thing I need to change in mine is the 300A ANL fuse for the battery. I need to replace that with a 150A Class T fuse. My 1/0AWG is safe with 300A but the batteries can only handle 100A max continuous discharge. And Class T is better for LiFePO4 batteries than ANL.

View attachment 59884
I didn't totally follow the first paragraph but gather the 3000w inverter & 4 100Ah batteries is all good?

I also have the 40A version of the DC-DC converter, here's the link: https://www.amazon.com/gp/product/B01LYK6G2Y/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
The wires on your schematic say 12 and 10 also.... are you saying the wires going from he converter to the AC/DC distribution center should be 6 awg instead of 10?

Re the SCC... so getting rid of the 50A breaker and keeping the mega fuse is cool?

The 300A Fuse was recommended in the inverter-charger manual which is why I chose it but agree it seems high... I'll up the wire to1/0 to compensate

Didn't realize I've used your schematic as reference before! Super helpful!
 
I didn't totally follow the first paragraph but gather the 3000w inverter & 4 100Ah batteries is all good?
Yes, to handle the 3000W inverter you need to use four SOK 100Ah batteries in 2S2P. Using two SOK 206Ah batteries in 2S won't meet the needed discharge rates.

I also have the 40A version of the DC-DC converter, here's the link: https://www.amazon.com/gp/product/B01LYK6G2Y/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
The wires on your schematic say 12 and 10 also.... are you saying the wires going from he converter to the AC/DC distribution center should be 6 awg instead of 10?
The 40A output should be 8AWG. For 50A would need 6AWG. I'm using 10AWG because the leads on the converter are only 12AWG (which I cut as short as possible). My 12V loads will never total 40A so my use of 10AWG should be safe enough in my case. It is a compromise. Those cheap Chinese converters really need better wire sized for the loads. The 12AWG on the input side is fine since the 40A 12V output means the input is only about 20A 24V.

Re the SCC... so getting rid of the 50A breaker and keeping the mega fuse is cool?
You only need one. 100A is overkill for the 45A output but it is safe with 6AWG wire.
 
Yes, to handle the 3000W inverter you need to use four SOK 100Ah batteries in 2S2P. Using two SOK 206Ah batteries in 2S won't meet the needed discharge rates.


The 40A output should be 8AWG. For 50A would need 6AWG. I'm using 10AWG because the leads on the converter are only 12AWG (which I cut as short as possible). My 12V loads will never total 40A so my use of 10AWG should be safe enough in my case. It is a compromise. Those cheap Chinese converters really need better wire sized for the loads. The 12AWG on the input side is fine since the 40A 12V output means the input is only about 20A 24V.


You only need one. 100A is overkill for the 45A output but it is safe with 6AWG wire.
I have a similar project with a MPP HYBRID LV2424 2.4KW all in one.

I was told I could put 2 Sok 12v 206ah batteries in series and it would power my 1800 watt appliances. The limiting factor is the BMS at 100amp discharge. BUT I was told 2 in series would allow them to put out more than 100amp discharge total, is this incorrect? I'm getting ready to order everything for my system.

Thanks
 
I have a similar project with a MPP HYBRID LV2424 2.4KW all in one.

I was told I could put 2 Sok 12v 206ah batteries in series and it would power my 1800 watt appliances. The limiting factor is the BMS at 100amp discharge. BUT I was told 2 in series would allow them to put out more than 100amp discharge total, is this incorrect? I'm getting ready to order everything for my system.

Thanks
Batteries in series have the same amps so the discharge total of 2 batteries in series is the same as a single battery. Batteries in parallel have additive amperage.

In your case, 1800W / 24V = 75A. Since a single battery or two in series are both capable of 100A discharge, it works since obviously 100A is more than 75A. It works in your case because the higher voltage lowers the amperage of the load, not because two batteries in series allows a higher discharge. Even the full 2400W is OK since 2400W / 24V = 100A.
 
Batteries in series have the same amps so the discharge total of 2 batteries in series is the same as a single battery. Batteries in parallel have additive amperage.

In your case, 1800W / 24V = 75A. Since a single battery or two in series are both capable of 100A discharge, it works since obviously 100A is more than 75A. It works in your case because the higher voltage lowers the amperage of the load, not because two batteries in series allows a higher discharge. Even the full 2400W is OK since 2400W / 24V = 100A.

Thank you, I was stuck in 12v land in my head (current system is 12v). 24V is new to me
 
One of
Oops. I don't know why I thought you had 4 of the 206Ah. The SOK batteries have a max continuous discharge of 100A for both the 100Ah and the 206Ah. So if you need a 3000W inverter and you will be running it over 2000W then you need more than 100A discharge. This means you will need to stick with the 4 100Ah since that gives you 200A max continuous discharge. I was going to suggest two 206Ah instead of four 100Ah but then you would need to go down to a 2000W inverter to keep it under 100A discharge.


The wiring for the battery protect (BP) looks wrong. You want the Battery In of the BP attached to the Lynx. Then the Bat+ of the DC-DC converter and the Bat+ of the 24V fuse box both go to the Battery Out of the BP.

If the DC-DC Converter has 50A output then you need 6AWG wire. The problem with that is that the DC-DC converter that you have pictured only has 12AWG leads at best. I have the 40A version of that converter. The leads to too thin. I might end up replacing mine at some point with a high quality Victron Orion.

You don't want both the 50A breaker between the SCC and Lynx as well as the 100 MEGA fuse for the SCC.

For the inverter you show 1AWG wire but a 300A MEGA fuse. That fuse is too big for 1AWG wire. The 1AWG wire is borderline for a 3000W inverter at 24V. If you stick with 1AWG, lower the fuse to 200A, maybe 250A. Or go with 1/0 to the inverter then the fuse could be 250A or 300A.

The 300A MEGA fuse for the battery seems OK until you pay attention to the 200A max continuous discharge allowed by the SOK batteries in parallel. You might consider lowering that fuse to 200A, maybe 250A, to protect the batteries from too high of a discharge rate. The BMS should shutdown the battery when the discharge is too high for too long if you keep the 300A fuse but, a blown fuse is cheaper than a toasted battery if the BMS doesn't do its job soon enough. You need to research whether a MEGA fuse is sufficient for LiFePO4 batteries.

Just remember that you choose a wire to safely handle the amps expected to go through it from the given load. You then choose a fuse that is a bit higher than the load and less than the highest load the wire can handle before becoming dangerous. The fuse must be the weakest link in the circuit.

Below is a schematic of my system as a reference. I'm not using a Lynx but it otherwise very similar to your setup (my inverter is 2kW). The one thing I need to change in mine is the 300A ANL fuse for the battery. I need to replace that with a 150A Class T fuse. My 1/0AWG is safe with 300A but the batteries can only handle 100A max continuous discharge. And Class T is better for LiFePO4 batteries than ANL.

View attachment 59884
the most helpful schematics I’ve seen on this site . While I’m using an all in one lv24/24 hybrid , this drawing answers many of the questions I’m struggling with . Top notch!!
 
@satanas I don't think anyone mentioned this yet but your "250v Breaker" between your panels and SCC should be rated to the proper amps. Is 10.64 your total amps from all your panels? You're probably OK with about a 20a breaker but depends on your panel specs. Just want to make sure you choose the right thing there and it didn't get missed :)

1630644551539.png
 
@satanas I don't think anyone mentioned this yet but your "250v Breaker" between your panels and SCC should be rated to the proper amps. Is 10.64 your total amps from all your panels? You're probably OK with about a 20a breaker but depends on your panel specs. Just want to make sure you choose the right thing there and it didn't get missed :)

View attachment 62878
thanks so much!
 
Yes, to handle the 3000W inverter you need to use four SOK 100Ah batteries in 2S2P. Using two SOK 206Ah batteries in 2S won't meet the needed discharge rates.


The 40A output should be 8AWG. For 50A would need 6AWG. I'm using 10AWG because the leads on the converter are only 12AWG (which I cut as short as possible). My 12V loads will never total 40A so my use of 10AWG should be safe enough in my case. It is a compromise. Those cheap Chinese converters really need better wire sized for the loads. The 12AWG on the input side is fine since the 40A 12V output means the input is only about 20A 24V.


You only need one. 100A is overkill for the 45A output but it is safe with 6AWG wire.
So I'm about midway through the install of the power bank and as a result have a few more specific questions, I wonder if you'd be willing to provide guidance?

Proper fusing is my consistent hangup. You said before to properly fuse the 24v --> 12v converter based on the 40A amperage on the output side, but in the diagram you provided above your fuse for the converter appears to be on the input side (between the converter and the battery protect). Should I place the inline fuse there or inline between the 12v output leads and the 12v fuse block?

Also, is the fuse between the battery protect and the 24V blue seas fuse block based on the amperage of the BP or of the devices plugged into the 24V fuse block? I guess directionality gets a bit confusing for me when it comes to finding a properly rated fuse.

Also, should I increase the amperage of the MEGA fuse of the first terminal on the lynx distributor from 50A to 100A since the battery protect's IN hooked onto the positive of this terminal and the positives of both fuse blocks are hooked into the BP, if that makes sense? When I originally designed the system I imagined that the positives of each fuse block would hook into the first and second terminals on the lynx, respectively. So I had planned to use a 50A mega fuse for each, but now during actual install I'm realizing only the negatives of each fuse block hook into the first and second terminals of the lynx and I'm not sure how that interacts with the chosen fuses.

I hope this all makes sense, feel free to request clarification! Completely possible I'm overthinking things. I can provide pics of the install later but it's time sensitive so I wanted to get my questions asked ASAP. Much appreciated!!
 
So I'm about midway through the install of the power bank and as a result have a few more specific questions, I wonder if you'd be willing to provide guidance?

Proper fusing is my consistent hangup. You said before to properly fuse the 24v --> 12v converter based on the 40A amperage on the output side, but in the diagram you provided above your fuse for the converter appears to be on the input side (between the converter and the battery protect). Should I place the inline fuse there or inline between the 12v output leads and the 12v fuse block?

Also, is the fuse between the battery protect and the 24V blue seas fuse block based on the amperage of the BP or of the devices plugged into the 24V fuse block? I guess directionality gets a bit confusing for me when it comes to finding a properly rated fuse.

Also, should I increase the amperage of the MEGA fuse of the first terminal on the lynx distributor from 50A to 100A since the battery protect's IN hooked onto the positive of this terminal and the positives of both fuse blocks are hooked into the BP, if that makes sense? When I originally designed the system I imagined that the positives of each fuse block would hook into the first and second terminals on the lynx, respectively. So I had planned to use a 50A mega fuse for each, but now during actual install I'm realizing only the negatives of each fuse block hook into the first and second terminals of the lynx and I'm not sure how that interacts with the chosen fuses.

I hope this all makes sense, feel free to request clarification! Completely possible I'm overthinking things. I can provide pics of the install later but it's time sensitive so I wanted to get my questions asked ASAP. Much appreciated!!
You should fuse the input side. What Maddy was saying is the the 40a "rating" is based on a 12V output. That's why his fuse in his diagram on the input side is only 30a because that is 24v incoming which is sufficient.

In your example you would not need a fuse on the output side because your converter goes to your distribution panel where all 12vdc loads from there are already (or should be) fused. Does that make sense? It can be a little confusing so if doesn't make sense I or someone can try to explain in a different way :)

regarding your MEGA fuse question. If the only item coming off the first Lynx terminal is the BP, then no matter what is connected to the BP, you should fuse it for the BP (and/or wire size).

If you're BP has a max output of 100a then I would fuse it for 100a, or maybe 125a. The argument to that is that there is no harm in installing a lower fuse if you know you won't exceed it. But then if you add something later on that exceeds that smaller fuse then you'd just have to go back and increase the fuse (and potentially wire size).
If you build it now for the the max rating of the device, and you make sure your wire size is appropriate, then you'll be covered.
 
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