Safety check on van electrical diagram (6kw 24v battery + 1.2kw solar + 3kw AC + noob)

[DanTheEnergyMan]

Hi everyone ?

I've been working on an electrical diagram for my van, and all the parts have arrived; now I'm just after a quick safety check since I'm a total noob and don't want to blow myself up.

• Solar: 1.2kW (3x400w panels in parallel)
  • 70v Voc; 6.5A Isc;
  • Apparently no need for individual fusing in Australia because (number of panels - 1 * Isc) < 20A (max series fuse) for these panels, so 3 in parallel is okay. They're in parallel because solar charge controllers get expensive higher than 70Voc.
  • Charge controller is a 100v-50A Victron MPPT - so should be maxed out by the panels during the day in "sunny hot australia".
• Battery: 6kWh of LiFePo4 cells at 24v (8S configuration) (cells from Amy - Shenzhen Luyan)
  • BMS is a Electrodacus SBMS0; no MOSFETS. Excited to try this out, I don't see many people using it.
• Inverter: 3kW Multiplus II for AC; 70A charging
• Bus Bars: BlueSea MaxiBus 250A
• 24/12VDC converter: Victron 20A non-isolated

Questions/Concerns

• Grounding; I've read/watched plenty of stuff, but I'm still confused on what I should do!? ?
  • My understanding is I'll ground the battery to the chassis; and everything with a ground connection I'll connect to the chassis as well; no ground-return in the system, everything goes back to the negative bus-bar.
  • So for example, if a fault occurs in the fridge, the fridge frame may become live, but is grounded to the van wall so becomes the negative conductor in this case, back to the battery; allowing the circuit to complete and the breaker to trip?
  • I'm still reading up more on this, trying to get a fundamental understanding...
• I chose to use circuit breakers for all the all the main components - is this okay?
  • Reasons for using circuit breakers:
    • As a noob, I wanted quick and easy isolation between solar/battery/inverter should something go wrong; so instead of buying a fuse+holder+high-amp switch, I just got circuit breakers instead.
    • I also chose double pole circuit breakers for most things (except AC circuit) because they were similar price; and the noob inside said total isolation is better than half isolation for some reason.
  • I'm worried these won't trip fast enough if a "not high enough current" fault occurs. Because of the time/current trip curve of the breakers; if a 500A fault occurs instead of 900A fault (for example), then the 160A breaker won't trip for 60 seconds - which seems bad. Basically I'm banking on a fault being a big fault and not a little fault. Thoughts? The large circuit breakers are Noark Ex9MD1B (125A, for inverter) and Ex9MD2B (160A, for battery).
• Only low voltage disconnect for AC circuit
  • So the BMS doesn't have mosfets, meaning disconnection is on me. However, at 25V I don't want to to kill everything; I want to put the inverter into Charger mode (via remote switch, I think this is possible with the SBMS/Multiplus, I'll figure it out); so killing AC power is okay - but;
  • I don't want to kill ALL 12v/24V loads - I guess I really want 4 DC distributions; 12V essential, 24v essential; 12v non-essential; 24v non-essential
    • Screw that lol it's just a van. I'll sound an alarm on my phone or something when battery gets low I think (I'll figure this out okay) .... is this okay? I'm guessing people usually just have all loads turned off because the BMS stops it... hmm.
    • Otherwise I'll buy a Victron battery protect or something and do the same as the inverter, remote switch, and if anything is really essentialy, hopefully it's 24V and I'll wire it straight to the busbar or something.
• Surge Protection/Lightning Protection
  • It doesn't seem too common to install these things; should I add them?

Thank you anyone who gave time to review/read, it is very much appreciated. Vector diagram attached below as well if the photo is blurry.
Please let me know how badly I've done it only took me a year to learn this all

 

[rmaddy]

What is the rated max continuous discharge current for the BMS? If it's less than 150A you won't be able to make full use of your inverter.

I would suggest you replace the breaker between the battery and bus bars with a single 200A Class T fuse. Put that on the positive wire as close to the battery as you can. No need for a fuse on the negative wire.

The 125A breaker for the inverter is too small. 3000W / 24V / 0.85 is 150A. 150A x 1.25 = 200A (rounded up). I know the inverter is really 3000VA and it's more efficient than 85% but this gives you a nice conservative result. The 70mm² is fine with a 200A fuse/breaker.

Make sure the 20A dual-pole breaker acting as your PV disconnect can safely handle the 70VDC from the panels.

What is the amperage coming in from your shore power connection? Is the 16A AC breaker large enough?

Regarding grounding - in my trailer I did not ground my batteries directly. I ran a wire from the negative bus bar to the chassis. Anything with a grounding lug (MultiPlus, SmartSolar, etc.) I ran a ground wire to the negative bus bar. This way there is only a single ground point on the chassis - from the negative bus bar.

I also ground each solar panel to the roof rack and grounded the roof rack to the chassis.

 

[John Frum]

Hi everyone ?

I've been working on an electrical diagram for my van, and all the parts have arrived; now I'm just after a quick safety check since I'm a total noob and don't want to blow myself up.

• Solar: 1.2kW (3x400w panels in parallel)
  • 70v Voc; 6.5A Isc;
  • Apparently no need for individual fusing in Australia because (number of panels - 1 * Isc) < 20A (max series fuse) for these panels, so 3 in parallel is okay. They're in parallel because solar charge controllers get expensive higher than 70Voc.
  • Charge controller is a 100v-50A Victron MPPT - so should be maxed out by the panels during the day in "sunny hot australia".
• Battery: 6kWh of LiFePo4 cells at 24v (8S configuration) (cells from Amy - Shenzhen Luyan)
  • BMS is a Electrodacus SBMS0; no MOSFETS. Excited to try this out, I don't see many people using it.
• Inverter: 3kW Multiplus II for AC; 70A charging
• Bus Bars: BlueSea MaxiBus 250A
• 24/12VDC converter: Victron 20A non-isolated

Questions/Concerns

• Grounding; I've read/watched plenty of stuff, but I'm still confused on what I should do!? ?
  • My understanding is I'll ground the battery to the chassis; and everything with a ground connection I'll connect to the chassis as well; no ground-return in the system, everything goes back to the negative bus-bar.
  • So for example, if a fault occurs in the fridge, the fridge frame may become live, but is grounded to the van wall so becomes the negative conductor in this case, back to the battery; allowing the circuit to complete and the breaker to trip?
  • I'm still reading up more on this, trying to get a fundamental understanding...
• I chose to use circuit breakers for all the all the main components - is this okay?
  • Reasons for using circuit breakers:
    • As a noob, I wanted quick and easy isolation between solar/battery/inverter should something go wrong; so instead of buying a fuse+holder+high-amp switch, I just got circuit breakers instead.
    • I also chose double pole circuit breakers for most things (except AC circuit) because they were similar price; and the noob inside said total isolation is better than half isolation for some reason.
  • I'm worried these won't trip fast enough if a "not high enough current" fault occurs. Because of the time/current trip curve of the breakers; if a 500A fault occurs instead of 900A fault (for example), then the 160A breaker won't trip for 60 seconds - which seems bad. Basically I'm banking on a fault being a big fault and not a little fault. Thoughts? The large circuit breakers are Noark Ex9MD1B (125A, for inverter) and Ex9MD2B (160A, for battery).
• Only low voltage disconnect for AC circuit
  • So the BMS doesn't have mosfets, meaning disconnection is on me. However, at 25V I don't want to to kill everything; I want to put the inverter into Charger mode (via remote switch, I think this is possible with the SBMS/Multiplus, I'll figure it out); so killing AC power is okay - but;
  • I don't want to kill ALL 12v/24V loads - I guess I really want 4 DC distributions; 12V essential, 24v essential; 12v non-essential; 24v non-essential
    • Screw that lol it's just a van. I'll sound an alarm on my phone or something when battery gets low I think (I'll figure this out okay) .... is this okay? I'm guessing people usually just have all loads turned off because the BMS stops it... hmm.
    • Otherwise I'll buy a Victron battery protect or something and do the same as the inverter, remote switch, and if anything is really essentialy, hopefully it's 24V and I'll wire it straight to the busbar or something.
• Surge Protection/Lightning Protection
  • It doesn't seem too common to install these things; should I add them?

Thank you anyone who gave time to review/read, it is very much appreciated. Vector diagram attached below as well if the photo is blurry.
Please let me know how badly I've done it only took me a year to learn this all

View attachment 85397

I don't see any contactors or any other mechanism for the elctrodacus to protect the battery.

 

[DerpsyDoodler]

Hi everyone ?

I've been working on an electrical diagram for my van, and all the parts have arrived; now I'm just after a quick safety check since I'm a total noob and don't want to blow myself up.

• Solar: 1.2kW (3x400w panels in parallel)
  • 70v Voc; 6.5A Isc;
  • Apparently no need for individual fusing in Australia because (number of panels - 1 * Isc) < 20A (max series fuse) for these panels, so 3 in parallel is okay. They're in parallel because solar charge controllers get expensive higher than 70Voc.
  • Charge controller is a 100v-50A Victron MPPT - so should be maxed out by the panels during the day in "sunny hot australia".
• Battery: 6kWh of LiFePo4 cells at 24v (8S configuration) (cells from Amy - Shenzhen Luyan)
  • BMS is a Electrodacus SBMS0; no MOSFETS. Excited to try this out, I don't see many people using it.
• Inverter: 3kW Multiplus II for AC; 70A charging
• Bus Bars: BlueSea MaxiBus 250A
• 24/12VDC converter: Victron 20A non-isolated

Questions/Concerns

• Grounding; I've read/watched plenty of stuff, but I'm still confused on what I should do!? ?
  • My understanding is I'll ground the battery to the chassis; and everything with a ground connection I'll connect to the chassis as well; no ground-return in the system, everything goes back to the negative bus-bar.
  • So for example, if a fault occurs in the fridge, the fridge frame may become live, but is grounded to the van wall so becomes the negative conductor in this case, back to the battery; allowing the circuit to complete and the breaker to trip?
  • I'm still reading up more on this, trying to get a fundamental understanding...
• I chose to use circuit breakers for all the all the main components - is this okay?
  • Reasons for using circuit breakers:
    • As a noob, I wanted quick and easy isolation between solar/battery/inverter should something go wrong; so instead of buying a fuse+holder+high-amp switch, I just got circuit breakers instead.
    • I also chose double pole circuit breakers for most things (except AC circuit) because they were similar price; and the noob inside said total isolation is better than half isolation for some reason.
  • I'm worried these won't trip fast enough if a "not high enough current" fault occurs. Because of the time/current trip curve of the breakers; if a 500A fault occurs instead of 900A fault (for example), then the 160A breaker won't trip for 60 seconds - which seems bad. Basically I'm banking on a fault being a big fault and not a little fault. Thoughts? The large circuit breakers are Noark Ex9MD1B (125A, for inverter) and Ex9MD2B (160A, for battery).
• Only low voltage disconnect for AC circuit
  • So the BMS doesn't have mosfets, meaning disconnection is on me. However, at 25V I don't want to to kill everything; I want to put the inverter into Charger mode (via remote switch, I think this is possible with the SBMS/Multiplus, I'll figure it out); so killing AC power is okay - but;
  • I don't want to kill ALL 12v/24V loads - I guess I really want 4 DC distributions; 12V essential, 24v essential; 12v non-essential; 24v non-essential
    • Screw that lol it's just a van. I'll sound an alarm on my phone or something when battery gets low I think (I'll figure this out okay) .... is this okay? I'm guessing people usually just have all loads turned off because the BMS stops it... hmm.
    • Otherwise I'll buy a Victron battery protect or something and do the same as the inverter, remote switch, and if anything is really essentialy, hopefully it's 24V and I'll wire it straight to the busbar or something.
• Surge Protection/Lightning Protection
  • It doesn't seem too common to install these things; should I add them?

Thank you anyone who gave time to review/read, it is very much appreciated. Vector diagram attached below as well if the photo is blurry.
Please let me know how badly I've done it only took me a year to learn this all

View attachment 85397

You need to understand how the multi-plus handles neutral-ground bond. When using shore power, you want it to disable a ground neutral bond (if there is one) so that shore becomes that resource, and you need to determine whether you want a floating system when not connected to shore. Either way, with RVs, the chassis is supposed to be bonded to shore ground when on shore power.

Read the resources on this forum regarding grounding, if you have not already. They were uploaded/posted by filterguy

 

[DanTheEnergyMan]

Ahh thank you all for the super quick replies, amazing!

What is the rated max continuous discharge current for the BMS? If it's less than 150A you won't be able to make full use of your inverter.

Okay my bad, I didn't make this clear, no current flows through the Electrodacus BMS.
The current flows through the 2 external shunts in the diagram (1 for the battery input/output and 1 for solar input)
They're rated 300A and 150A respectively, so I believe that's okay.

I would suggest you replace the breaker between the battery and bus bars with a single 200A Class T fuse. Put that on the positive wire as close to the battery as you can. No need for a fuse on the negative wire.

Okay yeah this is what I was thinking about myself, let me compare the trip/blow time curves real quick on a spreadsheet (it's an estimation using the datasheets):



So the crossover point is ~550A and ~12 seconds.

• At lower "fault" currents the breaker will actually trip faster (160A-500A); the 225A fuse doesn't even show it's trip time until >350A (over 10 minutes)
• At medium fault currents (500-1000A) the breaker will take a few seconds to trip (<10 seconds); fuse will be "instant"
• At high fault currents (1000A+) they both trip "instantly".

I'm happy to get the Class-T fuse ofcourse if it's safer, but I'd like to know if my understanding is correct here and what situation is more likely?
Is a fault at 500-1000A more likely than a fault at 160A-500A OR 1000A+?

The 125A breaker for the inverter is too small. 3000W / 24V / 0.85 is 150A. 150A x 1.25 = 200A (rounded up). I know the inverter is really 3000VA and it's more efficient than 85% but this gives you a nice conservative result. The 70mm² is fine with a 200A fuse/breaker

Ahh yes I forgot to account for inverter inefficiencies! Silly me. I've already got the breaker, so I'll just see how I go I think (I won't be pulling 3000A for very long at a time I think, so I should be fine - otherwise I might need a bigger battery as well haha) but yes thank you! The trip curve suggests I could pull at least 125A for at least 1 hour before it trips. Am I being silly looking at these curves so much?

Make sure the 20A dual-pole breaker acting as your PV disconnect can safely handle the 70VDC from the panels

The breaker is a Noark Ex9BP rated for 360VDC with Uimp of 4kV. Thanks for making me double check, I think this is okay

What is the amperage coming in from your shore power connection? Is the 16A AC breaker large enough?

I planned on using normal Australian household wiring, with a 15A plug (normal for caravans in Australia), so I think 16A is okay. I'm guessing the Multiplus (with 70A charger) isn't going to pull 15A/240VAC of shore power for loads AND 70A/24VDC for battery charging at the same time hehe, I'm definitely assuming though. But yes it's a 240V system (sorry forgot to mention), so maybe that's why you think 16A is not enough? Looks like US use 30A or 50A as standard for RVs.

Regarding grounding - in my trailer I did not ground my batteries directly. I ran a wire from the negative bus bar to the chassis. Anything with a grounding lug (MultiPlus, SmartSolar, etc.) I ran a ground wire to the negative bus bar. This way there is only a single ground point on the chassis - from the negative bus bar.

I also ground each solar panel to the roof rack and grounded the roof rack to the chassis.

Okay cool, makes sense enough to me, I can do that!

---

I don't see any contactors or any other mechanism for the elctrodacus to protect the battery.

Yes correct sorry I haven't detailed this at all .
The Electrodacus gives a bunch of output pins to use for remote switching. So, as not mentioned, I'm going to use those.

• Interveter: The Multiplus supports remote switching to put it into Charge Only/Disable modes
• DC Loads: I guess I should get a Victron Battery Protect for the 12V/24V DC loads (placed before the distribution blocks and breakers)
• Solar: For the SmartSolar 100/50 MPPT, do I need overvoltage protection via the BMS or will it just handle this itself? If the former, I'll get a VE.Direct non inverting remote on/off cable to make it talk to the BMS in the same fashion as the Multiplus can; but will the latter work? The battery just won't take the current if the voltage is higher in the battery right, and the MPPT should know this and turn itself off (the charge algorithm it uses).

---

You need to understand how the multi-plus handles neutral-ground bond. When using shore power, you want it to disable a ground neutral bond (if there is one) so that shore becomes that resource, and you need to determine whether you want a floating system when not connected to shore. Either way, with RVs, the chassis is supposed to be bonded to shore ground when on shore power

Okay yep still learning! Thank you. I've just looked up the inverter manual. Cool, looks like it does the thing, didn't expect it to have the relay built in!

The MultiPlus is provided with a ground relay (relay H, see appendix B) that automatically connects the Neutral output to the chassis if no external AC supply is available. If an external AC supply is provided, the ground relay H will open before the input safety relay closes. This ensures the correct operation of an earth leakage circuit breaker that is connected to the output.
─ In a fixed installation, an uninterruptible grounding can be secured by means of the grounding wire of the AC input. Otherwise the casing must be grounded. ─ In a mobile installation (for example, with a shore current plug), interrupting the shore connection will simultaneously disconnect the grounding connection. In that case, the casing must be connected to the chassis (of the vehicle) or to the hull or grounding plate (of the boat).

I'm doing more research on this now as it still doesn't make total sense in my head.

---

Thanks heaps for all the replies!
I hope I cleared up/checked the things you have mentioned (save the grounding bit yet, still more reading).

I attached the trip curve images I was using to make the comparison graphs as well, just for fun.

• EX9MD2 - 160A battery breaker

• EX9MD1 - 125A inverter breaker

All your time is much appreciated!
Dan

 

[John Frum]

• DC Loads: I guess I should get a Victron Battery Protect for the 12V/24V DC loads (placed before the distribution blocks and breakers)

I would, the battery protect should be driven by the Electodacus

• Solar: For the SmartSolar 100/50 MPPT, do I need overvoltage protection via the BMS or will it just handle this itself? If the former, I'll get a VE.Direct non inverting remote on/off cable to make it talk to the BMS in the same fashion as the Multiplus can; but will the latter work? The battery just won't take the current if the voltage is higher in the battery right, and the MPPT should know this and turn itself off (the charge algorithm it uses).

The BMS should protect the battery from cell/pack over voltage and cell/pack under voltage at the very least.
For a BMS that is not in the current path that is usually done by either Contactors in the current path or by remote switching all the loads and charge sources.

Can you remotely control the charge function and discharge function of the multiplus separately?

One more observation:
The double pole breakers in the system core are going to mess up your dc grounding.
Those wouldn't happen to have shunt trip functionality would they?

 

[HRTKD]

Why do you have a shunt downstream of the MPPT?

Please provide a link to a data sheet for your solar panels.

The general rule here on the forum is two parallel strings do not require a fuse between them. Anything more than 2 requires a fuse on each string.

 

[DanTheEnergyMan]

Okay I'm back from reading. Grounding is making more sense.

Please provide a link to a data sheet for your solar panels.

I guess you're looking for these figures:
Leftmost column (400w) is the panels I have. Datasheet is also attached at the bottom.


Looking at the above, the Isc * 3 = 19.74A; which is less than the maximum series fuse rating (just); so I'll add a 10A MC4 inline fuse to each panel just in case.

Why do you have a shunt downstream of the MPPT?

The shunt is for the Electrodacus SBMS0 (https://electrodacus.com/SBMS0/SBMS0v03d.pdf)
It's just so the BMS knows how much power the MPPT is providing so it can accurately count load as well (the other shunt).
I know the Victron MPPT will already provide this information, and I know it's not even go to be correct once the battery is charged via shore power from the inverter. I'm okay with both of these things. The shunt isn't technically required.

Can you remotely control the charge function and discharge function of the multiplus separately?

Yes, through the Victron Multiplus Assistant software thing, you can configure the Aux I/O and Temp Sense pins to do exactly that apparently (documentation found here). That's the plan at least.

The double pole breakers in the system core are going to mess up your dc grounding.

Nice pickup. If I understand correctly, you're mean if I were to isolate the battery via the breaker with both poles, now everything else in the system is grounded to "nothing", so we could have electrical potential between battery negative and "everything else", and that's a bad thing.

To clarify, is the inverter part of the "system core"? And would the same logic apply there?
I can see that putting the negative through the breaker for the inverter, makes that cable a "sometimes-grounded conductor" instead of a "grounded conductor". That seems bad. I'm guessing there could be an electrical potential difference (voltage) between the internals of the inverter (not the case; grounded) and the rest of the system?

Those wouldn't happen to have shunt trip functionality would they?

The Noark breakers do have shunt trip accessories I can get, but the operating voltage is 12-24VDC it seems anyway, which I don't believe the BMS is going to provide, so I'd need another relay to supply that voltage I think?
I'm guessing you're thinking I could use that instead of a Battery Protect or another relay - since I already have the breakers?


Amendments to the diagram:

• Added a Victron Battery Protect 220A, so the BMS can turn off all loads (12V,24V) at low voltage disconnect time.
• Added grounding wires to the diagram
• Added a dedicated grounding bus bar - so many cables.
• Grounding bus bar is bonded to negative bus bar in 1 spot (which then goes to battery negative)
• Solar panels bonded to roof rack; which is bonded to chassis; which is bonded to grounding bus bar.
• Not putting the negative conductor through the Battery or Inverter circuit breakers (still though for the MPPT as is required)
• Added some lines to show low voltage disconnect and high voltage disconnect for each component controlled by the BMS
• Added 10A MC4 inline fuses to each solar panel just in case.

Panels: 3x Maxeon 3 400w in parallel
Cells: 8x Eve 280Ah LiFePo4 in series (24v)
BMS: Electrodacus SBMS0
Inverter/Charger: Victron Multiplus 24-3000-70
MPPT: Victron SmartSolar 100-50
Cables: 70mm2 (00 awg) welding cable between large components; 16mm2 (6 awg) elsewhere;

Thanks again for all the help everyone, much appreciated.

 

[John Frum]

To clarify, is the inverter part of the "system core"? And would the same logic apply there?

Yes the dc side of the inverter is part of the system core.

I'm guessing there could be an electrical potential difference (voltage) between the internals of the inverter (not the case; grounded) and the rest of the system?

That is what the EGC is for.

The Noark breakers do have shunt trip accessories I can get, but the operating voltage is 12-24VDC it seems anyway, which I don't believe the BMS is going to provide, so I'd need another relay to supply that voltage I think?
I'm guessing you're thinking I could use that instead of a Battery Protect or another relay - since I already have the breakers?

Sound plausible but I can't remember what I was thinking