wiring *both* 24V and 12V appliances

[Cosmin Rusu]

Hello to you all, I have read all your posts here and I am very interested in this subject. Considering that I want to install an off grid system for running a 4 cctv system and a small refrigerator, I kindly ask you for your help because is the first time for me and I am also a noob in this domain. So here is what I have drawn by myself using the software mentioned above and using what equipment I already bought.

Because of my knowledge in this field (somewhere bellow 0), obviously I have some questions that I need to ask you ofcourse, if you are kind to answer and not to laugh if they are stupid! So here I go:

1. Can I use the same cable for all my connections, including between those 2 batteries? The type of cable is in picture, 4mm solar.
2. Do I need a battery balancer or is ok without it?
3. Fuses are a must in this system?
4. A circuit breaker is needed?
5. Where should I install a dc-dc converter for 12v appliances?
6. Does my system supports 4 solar panels if I connect them in a different way? (this question is because i actually have 3 pcs but for now one is spare!)

Here are also the links for my equipments:

https://www.schrack.ro/comenzi/foto...c-9busbars-5400-pascal-single-pvm44150-s.html

https://www.emag.ro/acumulator-sola...4Tj3Qj07gc3mRfdvQgcXo-FnBEwHd7XAaAjQJEALw_wcB

https://www.electriccasa.ro/regulat...pt-smartsolar-100vdc-12-24vdc-50a-pvbc10050s/

https://www.materialeelectrice.ro/bmv700-kit-de-conectare-monitorizare-de-precizie-baterie-s-83274

https://www.schrack.ro/comenzi/phoenix-inverter-24-800-ve-direct-pvbi24800.html

https://www.schrack.ro/comenzi/cuplor-cablu-tata-4-6mm2-pt-diametru-oe-5-5-9mm-pva12000.html

https://www.schrack.ro/comenzi/cuplor-cablu-mama-4-6mm2-pt-diametru-oe-5-5-9mm-pva11000.html

https://www.schrack.ro/comenzi/foto...hite-singlecore-en-cpr-betaflam-pvw10041.html

https://www.schrack.ro/comenzi/foto...-red-singlecore-en-cpr-betaflam-pvw10042.html

Thank you in advance for your answers and sorry for my english.

 

[Rednecktek]

Because of my knowledge in this field (somewhere bellow 0), obviously I have some questions that I need to ask you ofcourse, if you are kind to answer and not to laugh if they are stupid! So here I go:

Oh, we'll laugh, but it'll be at Dad Jokes, not you. ?

1. Can I use the same cable for all my connections, including between those 2 batteries? The type of cable is in picture, 4mm solar.

No, the 4mm wire is only rated up to 30a which is less than your SCC or your inverter are going to want. You'll have to step that up. Fortunately since you're running a 24v 800w inverter which is pretty small your SCC wires, battery wires, and inverter wires can all be the same size. The 4mm would be plenty for the solar panels though.

2. Do I need a battery balancer or is ok without it?

Wouldn't hurt being GEL batteries, but not needed. Have you looked at 24v LFP batteries? GEL's can only be used to about 50% DoD so you're only going to get about 60Ah or 1440Wh out of that battery bank. For about the same price you should be able to get a decent 24v battery in the 2400Wh range if not larger.

3. Fuses are a must in this system?

YES! At the very least something between the battery and the inverter. If nothing else get some DC breakers between the SCC and battery and between the battery and inverter.

4. A circuit breaker is needed?

Circuit breakers also make handy shut-offs for troubleshooting and servicing. Throwing one between the panels and the SCC is a handy tool.

5. Where should I install a dc-dc converter for 12v appliances?

So best practice would be a bus bar, but if you don't want to get into that then you'd have something like:

Battery -> Fuse/Breaker -> Inverter
Battery -> Fuse/Breaker -> 24v/12v Converter -> Fuse Block -> 12v Loads
Battery -> Fuse/Breaker -> SCC
Panels -> Breaker -> SCC
Inverter Neg -> Shunt -> Batt Neg
SCC Neg -> Shunt -> Batt Neg
12v/24v Converter -> Shunt -> Batt Neg

OR with bus bars:
Batt -> Bus Bar
Bus Bar ->Fuse/Breaker -> Inverter
Bus Bar -> Fuse/Breaker -> 24v/12v Converter -> Fuse Block -> 12v Loads
Bus Bar -> Fuse/Breaker -> SCC
Panels -> Breaker -> SCC
Inverter Neg ->Bus Bar -> Shunt -> Batt Neg
SCC Neg ->Bus Bar -> Shunt -> Batt Neg
12v/24v Converter ->Bus Bar -> Shunt -> Batt Neg

It's OK to stack terminals on a battery, just make sure everything is tight and flat.

EDIT: Missed the shunt! Oops!

6. Does my system supports 4 solar panels if I connect them in a different way? (this question is because i actually have 3 pcs but for now one is spare!)

It depends on the specs of the panel but with a 100v max PV input voltage, 50a SCC output and 24v battery you could theoretically get 1200+ watts on that SCC depending on how you wire them up.

On the panels should be a sticker with such numbers as VoC and Vmp. Get those to us and we can help with the math. If you put panels in series you get higher voltage, and in parallel you get higher amperage. Give yourself about 20% headroom for cold weather where your voltage will go up and try to arrange your panels to have a total of 80-ish volts and you should be fine.

Might help to throw this all into a new thread to get peoples attention.

 

[Cosmin Rusu]

Oh, we'll laugh, but it'll be at Dad Jokes, not you. ?

No, the 4mm wire is only rated up to 30a which is less than your SCC or your inverter are going to want. You'll have to step that up. Fortunately since you're running a 24v 800w inverter which is pretty small your SCC wires, battery wires, and inverter wires can all be the same size. The 4mm would be plenty for the solar panels though.

Wouldn't hurt being GEL batteries, but not needed. Have you looked at 24v LFP batteries? GEL's can only be used to about 50% DoD so you're only going to get about 60Ah or 1440Wh out of that battery bank. For about the same price you should be able to get a decent 24v battery in the 2400Wh range if not larger.

YES! At the very least something between the battery and the inverter. If nothing else get some DC breakers between the SCC and battery and between the battery and inverter.

Circuit breakers also make handy shut-offs for troubleshooting and servicing. Throwing one between the panels and the SCC is a handy tool.

So best practice would be a bus bar, but if you don't want to get into that then you'd have something like:

Battery -> Fuse/Breaker -> Inverter
Battery -> Fuse/Breaker -> 24v/12v Converter -> Fuse Block -> 12v Loads
Battery -> Fuse/Breaker -> SCC
Panels -> Breaker -> SCC

It's OK to stack terminals on a battery, just make sure everything is tight and flat.

It depends on the specs of the panel but with a 100v max PV input voltage, 50a SCC output and 24v battery you could theoretically get 1200+ watts on that SCC depending on how you wire them up.

On the panels should be a sticker with such numbers as VoC and Vmp. Get those to us and we can help with the math. If you put panels in series you get higher voltage, and in parallel you get higher amperage. Give yourself about 20% headroom for cold weather where your voltage will go up and try to arrange your panels to have a total of 80-ish volts and you should be fine.

Might help to throw this all into a new thread to get peoples attention.

Thank you for your answers. Here are my panels.

 

[Rednecktek]

OK, so you're limited to a 2s string which is 2 in series. If you get a 4th panel then you can have a 2s2p setup where you hook 2 panels in series together which gets you about 78v (well within the 100v limit) and about 14a, then you connect both of those strings to a Y splitter in Parallel and your output would be somewhere around 80-ish volts and 28ish amps (about the limit of 4mm wire) which should work out just fine.

 

[Cosmin Rusu]

Thank you for all your answers pal, may the photons bless you with new spells every day!

 

[Cosmin Rusu]

Oh, we'll laugh, but it'll be at Dad Jokes, not you. ?

No, the 4mm wire is only rated up to 30a which is less than your SCC or your inverter are going to want. You'll have to step that up. Fortunately since you're running a 24v 800w inverter which is pretty small your SCC wires, battery wires, and inverter wires can all be the same size. The 4mm would be plenty for the solar panels though.

Wouldn't hurt being GEL batteries, but not needed. Have you looked at 24v LFP batteries? GEL's can only be used to about 50% DoD so you're only going to get about 60Ah or 1440Wh out of that battery bank. For about the same price you should be able to get a decent 24v battery in the 2400Wh range if not larger.

YES! At the very least something between the battery and the inverter. If nothing else get some DC breakers between the SCC and battery and between the battery and inverter.

Circuit breakers also make handy shut-offs for troubleshooting and servicing. Throwing one between the panels and the SCC is a handy tool.

So best practice would be a bus bar, but if you don't want to get into that then you'd have something like:

Battery -> Fuse/Breaker -> Inverter
Battery -> Fuse/Breaker -> 24v/12v Converter -> Fuse Block -> 12v Loads
Battery -> Fuse/Breaker -> SCC
Panels -> Breaker -> SCC
Inverter Neg -> Shunt -> Batt Neg
SCC Neg -> Shunt -> Batt Neg
12v/24v Converter -> Shunt -> Batt Neg

OR with bus bars:
Batt -> Bus Bar
Bus Bar ->Fuse/Breaker -> Inverter
Bus Bar -> Fuse/Breaker -> 24v/12v Converter -> Fuse Block -> 12v Loads
Bus Bar -> Fuse/Breaker -> SCC
Panels -> Breaker -> SCC
Inverter Neg ->Bus Bar -> Shunt -> Batt Neg
SCC Neg ->Bus Bar -> Shunt -> Batt Neg
12v/24v Converter ->Bus Bar -> Shunt -> Batt Neg

It's OK to stack terminals on a battery, just make sure everything is tight and flat.

EDIT: Missed the shunt! Oops!

It depends on the specs of the panel but with a 100v max PV input voltage, 50a SCC output and 24v battery you could theoretically get 1200+ watts on that SCC depending on how you wire them up.

On the panels should be a sticker with such numbers as VoC and Vmp. Get those to us and we can help with the math. If you put panels in series you get higher voltage, and in parallel you get higher amperage. Give yourself about 20% headroom for cold weather where your voltage will go up and try to arrange your panels to have a total of 80-ish volts and you should be fine.

Might help to throw this all into a new thread to get peoples attention.

Forgot to ask something:

Battery -> 1.Fuse/Breaker -> Inverter
Battery -> 2.Fuse/Breaker -> 24v/12v Converter -> Fuse Block -> 12v Loads
Battery -> 3.Fuse/Breaker -> SCC
Panels -> 4.Breaker -> SCC
Inverter Neg -> 5.Shunt -> Batt Neg
SCC Neg -> 6.Shunt -> Batt Neg
12v/24v Converter -> 7.Shunt -> Batt Neg

For bold numbers 1 to 4, please, what values must they have?
For 5 to 7 what kind of shunt is needed, can you give me an example?

Keep in mind that the Battery controller has a Shunt of it's own!

Thank you.

 

[Rednecktek]

1-4 are going to be based on the loads involved. The math is LoadInWatts / Volts * 1.2 = Fuse/Breaker Size. For the 12v loads you'll need to add up the loads total to size for the #2 fuse.

So, as an example, your inverter is 800w and 24v, so 800/24=34a * 1.2 (for overhead and surges) = 40a breaker.
The 24v-12v converter maxes out at 50a so got for a 60a for that.
Same goes for the 50a SCC, go for a 60a breaker there.
The breaker for the panels is going to depend on how you have them wired. If you go with the 2s2p setup and 4 panels that's 30-ish amps so I would recommend a 40a for that connection.


As for 5-7, those all connect to the same shunt so there's only one. A couple of handy units are the Aili type shunts or the (nicer IMHO) Renogy shunts. All the Neg wires will come together on one side of the shunt (P-) and the other side of the shunt goes to the battery terminal (B-) to measure the state of your batteries. If your listed battery monitor is a shunt rather than a voltage monitor then you've already got that one.

 

[Cosmin Rusu]

1-4 are going to be based on the loads involved. The math is LoadInWatts / Volts * 1.2 = Fuse/Breaker Size. For the 12v loads you'll need to add up the loads total to size for the #2 fuse.

So, as an example, your inverter is 800w and 24v, so 800/24=34a * 1.2 (for overhead and surges) = 40a breaker.
The 24v-12v converter maxes out at 50a so got for a 60a for that.
Same goes for the 50a SCC, go for a 60a breaker there.
The breaker for the panels is going to depend on how you have them wired. If you go with the 2s2p setup and 4 panels that's 30-ish amps so I would recommend a 40a for that connection.


As for 5-7, those all connect to the same shunt so there's only one. A couple of handy units are the Aili type shunts or the (nicer IMHO) Renogy shunts. All the Neg wires will come together on one side of the shunt (P-) and the other side of the shunt goes to the battery terminal (B-) to measure the state of your batteries. If your listed battery monitor is a shunt rather than a voltage monitor then you've already got that one.

Once again, many thanks.

I did search on Ali and found that most of the fuse boxes are prepared only for thin conductors and regarding the amp's are at max 20Ah, so I must consider buying each fuse separately, focusing on the values that you explained above.

As for the panels setup, well, for beginning i will run on two and keep the upgrade to the other 2 for the next year.

Yes, the Victron BVM 700battery monitor has a shunt of 500Ah so at least here I am ok.

 

[Rednecktek]

I did search on Ali and found that most of the fuse boxes are prepared only for thin conductors and regarding the amp's are at max 20Ah, so I must consider buying each fuse separately, focusing on the values that you explained above.

Are you talking about the main fuse block for your 12v stuff or the fuses themselves? For a fuse block I used a 100a 12 slot unit. 100a is more than I'd ever need to power all my 12v stuff at once. As for the fuses, it uses standard automotive blade fuses found at any hardware store. What you're looking to do is:

Thick Wire -> 120a Breaker -> Converter -> Fuse Block Main -> AllTheThingsFromEachSlot

What's the maximum amperage you need for any single 12v device? I've got a couple 12AWG/6mm wires on that block just fine, it's all in the ring terminals.

As for what size wiring, I highly recommend the Blue Sea Ampacity Chart. You can find the distance and amperage and it'll tell you which size wire to use.

 

[12VoltInstalls]

For a fuse block I used a 100a 12 slot unit. 100a is more than I'd ever need to power all my 12v stuff at once

I’ve bought ??dozens?? of them in the blue sea brand for various applications and use three or four of them myself- boat, jeep, camper, etc.
i typically wire 6ga or 8ga and main fuse at 40A. Residentially I am consistently 3A to 8A or 10A constant load. I am fussy over some stuff and tend to spend for the high-priced brand for fusing and primary cables.

With the on-board grounding bus and stainless components it is convenient and safe.

I recommend them.

 

[Cosmin Rusu]

Are you talking about the main fuse block for your 12v stuff or the fuses themselves? For a fuse block I used a 100a 12 slot unit. 100a is more than I'd ever need to power all my 12v stuff at once. As for the fuses, it uses standard automotive blade fuses found at any hardware store. What you're looking to do is:

Thick Wire -> 120a Breaker -> Converter -> Fuse Block Main -> AllTheThingsFromEachSlot

What's the maximum amperage you need for any single 12v device? I've got a couple 12AWG/6mm wires on that block just fine, it's all in the ring terminals.

As for what size wiring, I highly recommend the Blue Sea Ampacity Chart. You can find the distance and amperage and it'll tell you which size wire to use.

I am talking about this post of yours:

"So, as an example, your inverter is 800w and 24v, so 800/24=34a * 1.2 (for overhead and surges) = 40a breaker.
The 24v-12v converter maxes out at 50a so got for a 60a for that.
Same goes for the 50a SCC, go for a 60a breaker there.
The breaker for the panels is going to depend on how you have them wired. If you go with the 2s2p setup and 4 panels that's 30-ish amps so I would recommend a 40a for that connection.

As for 5-7, those all connect to the same shunt so there's only one. A couple of handy units are the Aili type shunts or the (nicer IMHO) Renogy shunts. All the Neg wires will come together on one side of the shunt (P-) and the other side of the shunt goes to the battery terminal (B-) to measure the state of your batteries. If your listed battery monitor is a shunt rather than a voltage monitor then you've already got that one."

I tought that I can find also a slot unit for these, but I could not find block units for 40-60Ah breakers so I must buy separately. I also need to find them on China websites, because Amazon does not deliver to Romania yet but I think I can find those you mentioned to me.

 

[Rednecktek]

Just make sure the breaker is rated with a DC rating. Most commonly available breakers are designed for AC and won't work right. The terminal posts on the single breakers (If using this style) is at least M6 for anything in the 40-60a range and M8 for 110a and above. Stay away from the DC audio tube-type breakers though, they are notoriously unsafe and unreliable. If you can find them online for your area I highly recommend either Blue Sea or T-Tocas brand breakers. Depending on how you run your physical wires, a DIN box with the DIN style DC breakers are traditionally easier to get in Europe than they are here in the 'Muricas. Your amperages don't have to be exact by my recommendations either, I.E if you need a 40a breaker and can only find a 42a that's just fine, or if the math says you need a 33.58748a breaker you can use a 35 or 40 just fine. The math has to come second to what you can physically find sometimes.

 

[Cosmin Rusu]

Just make sure the breaker is rated with a DC rating. Most commonly available breakers are designed for AC and won't work right. The terminal posts on the single breakers (If using this style) is at least M6 for anything in the 40-60a range and M8 for 110a and above. Stay away from the DC audio tube-type breakers though, they are notoriously unsafe and unreliable. If you can find them online for your area I highly recommend either Blue Sea or T-Tocas brand breakers. Depending on how you run your physical wires, a DIN box with the DIN style DC breakers are traditionally easier to get in Europe than they are here in the 'Muricas. Your amperages don't have to be exact by my recommendations either, I.E if you need a 40a breaker and can only find a 42a that's just fine, or if the math says you need a 33.58748a breaker you can use a 35 or 40 just fine. The math has to come second to what you can physically find sometimes.

You definitely made all cristal clear for me, thank you again for your patience and understanding and for all your knowledge shared with me. Chapeau Bas!