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New Van System Planning Help

Unless you have are using a dedicated alternator designed to charge batteries, I believe 30A is a reasonable limit. Victron is huge in the high end RV and boating world. If it was a good idea in general to draw more than 30A from an alternator, then Victron would make a charge converter that did this. They are THE class act in this world. Just because a lower tier vendor choses to offer something doesn't mean that it is a good idea to do that.

Also, keep in mind even 30A is a lot unless the vehicle is moving. Drawing serious amps from an idling engine is a bad idea. If you need to charge when stationary then carry a small Honda Generator and charge up from that. You will save money and your engine will last longer.
Thank you for sharing. I should have added in the context that the Van comes from Ford with a dedicated upfitter system since they are designed in many cases to have a lot of external items added when built out (ambulances - etc). So the charging system comes with dual high output alternators from the factory. And the connection point for adding external loads to the system has its own dedicated controller that limits max output to 175 amps (@12V), and has ranges of output available for time limits that the system controls (ie 160-175amps for 10 mins, 140-160 for 15 mins, 120-140 for 20 mins) and allows for up to 120 amps continuous. So my plan was to have the 4 parallel Orion units draw just under the 120 amps (@12V) at max. The Ford system controls shutting off the connection point and limiting output so I don't have to do anything there. I will configure the Orions to not draw higher loads at lower speeds/rpms as a secondary protection measure beyond the Ford system limiting output to protect the alternators/start batteries.


I am using a Blue Sea 7157, 50A short stop breaker on the incoming power to my Orion-TR.


Be sure to use the appropriate sized wire for 50A service and you should be good. The wire should also be specified for use in an engine compartment (oil, gasoline, heat). I am using ANCOR Marine grade 6/2 AWG duplex cable for this. It is rated for 105 degree C and the jacket is incredibly tough.


Yah, its overkill, 8 AWG is probably fine, but I not into squeaking by. And 6 AWG will let you run longer wire which can make installing your system less difficult.


Awesome, thanks for these links and info I'll look into these more!
 
Thank you for sharing. I should have added in the context that the Van comes from Ford with a dedicated upfitter system since they are designed in many cases to have a lot of external items added when built out (ambulances - etc). So the charging system comes with dual high output alternators from the factory. And the connection point for adding external loads to the system has its own dedicated controller that limits max output to 175 amps (@12V), and has ranges of output available for time limits that the system controls (ie 160-175amps for 10 mins, 140-160 for 15 mins, 120-140 for 20 mins) and allows for up to 120 amps continuous. So my plan was to have the 4 parallel Orion units draw just under the 120 amps (@12V) at max. The Ford system controls shutting off the connection point and limiting output so I don't have to do anything there. I will configure the Orions to not draw higher loads at lower speeds/rpms as a secondary protection measure beyond the Ford system limiting output to protect the alternators/start batteries.




Awesome, thanks for these links and info I'll look into these more!
Sounds like you are set then. The majority of people asking about adding alternator charging are talking about retrofitting it into an existing electrical system that was not designed with this load in mind.

And yes you can certainly parallel Orions and get more controlled charge amps. They won't coordinate (the Orion-TR seems mildly retarded by Victron standards).

Easiest way to handle this is to pass the ignition switch input through the relay output of a BMV-712 and let the Battery monitor control charging cutoff on the basis of SOC% and battery temperature.
 
Many years later I'm finally back working on this project after illness. Currently working on the solar and have some thoughts/questions

I've been reading/referencing the https://diysolarforum.com/resources/fusing-wire-sizing-guidelines-for-solar-panels.143/ to help figure this out.

I've attached the panel specs as well as my wiring schematic. At this point I'm just focused on getting the solar installed so you can ignore everything else on the schematic.

Panel Specs
Max Power (Pmax) 325W
Short Circuit Current (Isc) 6.03A
Open Circuit Voltage (Voc) 69.6V
Maximum Power Current (Ipmax) 5.65A
Maximum Power Voltage (Vpmax) 57.6V
Max system Voltage 600V
Series Fuses 15A

My planned configuration

3X Panels in Parallel
MC4 3to1 Merge Connectors to Connect Panels
MC4 Panel Fuse 15A on each Positive Connection from Panel to Merge Connection
10 Feet of 10AWG wire from branch connector to inside van connecting to dual pole disconnect switch
10 Feet of 10AWG from dual pole disconnect switch to Victron 100|50 MPPT
2 Feet of 10AWG from Victron 100|50 MPPT to 60AMP Blue Sea Breaker
60 AMP Blue Sea Breaker Connects to Blue Sea Disconnect Switch

My battery bank is 24V so everything after MPPT is 24V (or 28V I guess) which I assume should mean my breaker and disconnect switch are fine since they are rated for up to 48V.

So for my configuration I believe my calculation for wire sizing and fusing is based off the following

3P (panel specs above)
Voltage - 58V
Current - 18A

Wire sizing I'm using the above voltage and current numbers and multiplying by 1.56, so I get the following

Voltage - 58V x 1.56 = 90V
Current - 18A x 1.56 = 28A

So for wire from MC4 merge connectors to the MPPT I come up with 20 feet one way, or 40 feet total, at 90V with 28A, so 10AWG at 1.5% voltage drop. For derating the wires will be on the roof of the van, but under the panels, in an 1"x1" or possibly larger square conduit.

Questions
1. I'm unclear on the single MC4 fuse sizing and must be missing this somewhere in the explanation. I have it at 15A right now which is the same as the panel series fuse rating, but should it be 10A instead?
2. Is my math/understanding of the 156% multiplier correct for both voltage and current?
3. Should I consider 8AWG in place of the 10AWG as that would get me to 1% voltage drop?
4. Originally I was going to use a dual pole circuit breaker as shown in the schematic to serve as a disconnect/protection for the MPPT. But after reading it seems like the current recommendation is to use a dual pole switch instead. I like the idea of using the circuit breaker for the added protection, but is that not advised and I should only use a switch?

Thanks for the help

IMG_20230605_193451815.jpg

Transit Electrical System V2.5TF4x3.png
 
You're not far off track, but you need to remember one thing: fuse for wire limitations, not load limitations. You aren't protecting the load, you are protecting the circuit.

Max fuse size on 10ga is 20a. 8ga can go to 30a, but 25a is better.

If you have 10ga anywhere in a circuit, then the max fuse is 20a, period. You can get away with 10ga for your setup, as the real power from the solar will be less than the 6a short circuit rating.

Also, MC4 connectors have a max load as well, but you'll be under 20a, so you should be good.

Personally, If I was doing it, I would run 8ga, ditch the POS MC4 connections, and use heat shrink butt connectors. The MPPT seems to be the right one for the panels. I would put a single 20a breaker on the panels and see if it ever tripped. If it did, switch to 25a. You don't need a dual pole breaker, just break the positive from the panels. From the MPPT to the battery, you'll need 6ga or 4ga, depending on length. I would go ahead with a 6ga, and ground the MPPT directly to the frame, instead of running to the battery.
 
Thanks for the reply! @Odom1957

I'm a bit torn on the MC4 connectors. On one hand it simplifies the connections, but my preference would be less connections where possible as that would offer less points of failure, especially given it's a van so I'm adding vibration to the mix. So I could just make the connections with MC4 at the panels with MC4 fuses and then MC4 branch connectors, but I'm on the fence about that. The other option would be to bring all the panels into a combiner box, fusing each panel at 15A, and the whole thing with a 30A breaker (I think?). From the combiner box run 8AWG all the way to the MPPT.

I had been reading on explorist.life and I was under the impression that I needed a dual pole breaker. Here is what was listed on that site

Is a Dual Pole Disconnect Necessary for a DIY Camper Solar Array?​

Again, Yes… And here’s why:

NEC 2020 Article 690.13 section (E) States that “ The PV System disconnecting means shall simultaneously disconnect the PV system conductors that are not solidly grounded from all conductors of other wiring systems.

Since camper electrical systems are generally NOT grounded, this means that both the positive and negative conductors from the solar array need to be able to be simultaneously disconnected, and our dual pole breaker does exactly that where those other breakers and switches do not.

Am I just misunderstanding/misinterpreting what is being explained there?
 
A combiner box is easy, but where would you put it? If you put it inside, then you need 6 wires going through the roof. Something to think about.

The only part of the "ground" that is misleading is the very definition of "ground"

"ground or earth may be a reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth."

Using this NEC definition, the entire chassis is a ground, being made of metal, can be a return path for electricity, and can be used to measure voltage, so the panels ARE grounded, even though they don't touch the actual ground. Boats never touch the ground (or aren't supposed to) and they are considered grounded.
 
Thanks for that additional info/explanation. That makes sense on the ground.

I'm trying to figure out the combiner box option currently. Was trying to find a slim box option that I could get on the roof under the solar panels so I could combine outside of the van and then just have two wires to go through the roof. I'm not having much luck finding a slim or low profile box though that is at most just a couple inches tall, especially since I'm limiting my search to higher quality units as it seems amazon is flooded with cheaply made ones of dubious quality.

If I can't find a combiner box that will fit the space I have on the roof I may have to revert back to the MC4 connector plan and just connect with MC4 fuses and branch connectors.
 
Thanks, I've thought about it a little more and now I'm thinking maybe given my rooftop space constraints that I should instead move the PV combiner box inside the van. This would require running each panels wires about 10 feet into the van and then joining. I would keep the MC4 connectors coming directly off the panels and connect to them and then run inside and connect the wire directly to the box. I could use 10AWG for the wire from each panel coming into the van and then the combiner box would handle the panel fusing, then the breaker/disconnect, and then I could run 8GA from the combiner to the SCC. I'm going through an existing hole in the van, so 2 wires vs. 6 wires doesn't matter that much as I have the space.

I'm going to make a new post asking for recommendations/feedback on small combiner boxes. I've been searching and reading other threads and can't find a whole lot. So far the best box I've found size wise has been this Ecoworthy one https://www.eco-worthy.com/collecti...circuit-breakers-for-on-off-grid-solar-system but from reading other threads it seems like Ecoworthy is a low tier brand so I'm a bit hesitant to use it and would love to find a comparable size product from a higher end brand.
 
Finally getting close to actually wiring this as I've just finished the roof rack and the panel mounts. After enough tinkering and seeing what space I actually have I'm leaning now towards ditching all of the MC4 connectors and just using a couple of bus bars inside my external enclosure. Partially because this will make the wiring through the enclosure so much easier and more weathertight using cable glands.

Here was my original configuration

3X Panels in Parallel
MC4 3to1 Merge Connectors to Connect Panels
MC4 Panel Fuse 15A on each Positive Connection from Panel to Merge Connection
10 Feet of 10AWG wire from branch connector to inside van connecting to dual pole disconnect switch
10 Feet of 10AWG from dual pole disconnect switch to Victron 100|50 MPPT
2 Feet of 10AWG from Victron 100|50 MPPT to 60AMP Blue Sea Breaker
60 AMP Blue Sea Breaker Connects to Blue Sea Disconnect Switch

Here is my updated/planned configuration

3X Panels in Parallel
Single 4 Post DC (150A/70V rated) Victron Busbar for Negative
Dual 4 Post DC (150A/70V rated) Victron Busbars with 15A fuses in between each panel positive line
10 Feet of 8AWG wire from busbars to inside van connecting to dual pole disconnect switch
10 Feet of 8AWG from dual pole disconnect switch to Victron 100|50 MPPT
2 Feet of 8AWG from Victron 100|50 MPPT to 60AMP Blue Sea Breaker
60 AMP Blue Sea Breaker Connects to Blue Sea Disconnect Switch

So my plan is using the two positive busbars spaced together with fuses in between. Essentially like how a Victron Lynx is setup.

I don't know what type of fuse I'm looking for as I'm not sure what type of fuses MC4 fuses usually are? Fast, slow, etc. Also I'm not finding any lower amperage fuses (15A) that fit across multiple studs like the Lynx (ANL or similar)? Or do I need to instead place some kind of inline fuse holder or potentially ditch the two busbar idea with fuse across busbars and instead use a spade fuse block instead to cover the positive line fusing? If so which fuse type would replicate the normal MC4 fuse?

Oh, and I should have mentioned also about the fuse voltage. I'm finding most DC fuses are 32V or 48V, but my panel open voltage is 69.6V so I assume I need at least a 70V rated fuse.

Thanks!
 
Last edited:
Myrkr
I am planning something similar to you. What I am doing to charge my batteries off the van alternator is using a second inverter. I bought a 2200W, 12 volt inverter to connect to my alternator through the van dual agm batteries. When I am driving that will be my shore power source. I will plug my Multiplus II, 3000va, 24, 70, 120 into it when driving. I hope to be able to charge 60 to 70 amps @ 24VDC off the van's 250A alternator that way. Yes I know, it is not the most efficient way of doing this. As a plus I will have backup 120v power if my 24v van system develops any problems. If it is sunny the 150/60 mppt can charge at the same time also. I plan on around 1000 watts of solar panels up top. I copied this idea from several other people doing the same thing on another forum. Good luck with your project.
 
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