Feedback of 12V van system plan

[EnsignR]

Firstly sorry for the overly, and unnecessarily complicated diagram and very long post; it's what I do.

I've been mostly lurking in this forum and elsewhere for quite a while in order to help me figure out a plan to build a new 12V system for an old van we* bought during the COVID apocalypse.
* I'm not the one who actually bought it, I'm just the one who has to figure all this stuff out. ?

I've already temporarily installed a small system (1x 12V AGM / 20A MPPT / 200W SP), but in the long term it needs to be replaced. Currently it's mainly used to power a 12V portable fridge (not pictured; separate to the 3-way fridge, pictured, which we usually run on gas/LNG/propane) along with some lighting and occasionally a TV, as well as for charging mobile phones. It also powers the reversing camera we† installed because something is wrong with the AUX pin connection on the 7-pin trailer plug; we had an auto-electrician install it in the car but it just blows a fuse in the car if we try to use it; so we currently have to run the (house) battery while driving which isn't ideal. ?
† Of course it was actually me that installed it all. ?

The system designed above would probably need to be built in stages, but we've already bought‡ some of the parts pictured these include two new AGM batteries (which are actually identical to the one we're using now, but haven't been used), the four 4x M8 bus bars, and the inverter. Knowing what I know now I'd have built a 24V system, but the inverter is unfortunately only 12V which leaves me a bit stuck.
‡ Of course I didn't actually buy any of these, but have to figure out how to install them all; though I did suggest the bus bars after some research and thinking about how I want to do this. ?

My two main concerns are am I using the correct wire gauges for all the wires and are the circuit breakers (like these ones) or going all double pole DIN rail ones (like these); I'm leaning to the latter, but I'm really not quite sure of the pros and cons (aside from being able to mount them altogether if I use DIN)?

Wire gauges is thing I find most confusing because everywhere you look it seems to tell you didn't amperages for the same sized wire, and everything sold here (Australia) is described by cross section (mm^2). However the current, jerry rigged system is all wired together using 6mm^2, "50A", wire. My preference is to oversize the wire and not have to worry about anything catching fire. (And yes, I really am going to use twin sheath everywhere, I don't want to use the chassis as part of the circuit; am I crazy?)

The other big thing I need to decide is where I am going to put it. Currently the single battery is located at the rear of the van, under a seat. If everything fits I'd like to put most of the new system there too, but it might be a tight fit. I'm also considering putting the batteries and other bulky equipment (eg. inverter and later when I get to it, the DC-DC charger) in the boot at the front of the van (accessed from the outside). There's more room here, and would save a small fortune in running 4 AWG wire all the way to the back of the van (but then mean I have to run bigger lengths of 10 AWG to the fuse boxes). Apart from loosing valuable boot space the other problems with this is might get hotter in there and there's currently a small leak I'd have to find and fix. So many decisions.

Stage 1 would be connecting up basically the left side of the diagram; batteries, bus bars and inverter along with at least some of the separate fuse boxes (I've designed it this way as I'd rather run one 10 AWG cable than 5 thinner ones; pulling the cable will be that hardest part). The DC-DC charger and roof mounted solar, along with wiring the car with a SB120 out back, will come later.

I could go on, but I've probably written way too much already. (Sorry). Any feedback or insights from anyone would be greatly appreciated.

Cheers.

 

[FilterGuy]

Firstly sorry for the overly, and unnecessarily complicated diagram and very long post; it's what I do.

I kinda like the diagram!

My two main concerns are am I using the correct wire gauges for all the wires

I have not tried to analyze all of the different wire sizes for safety but the 1/0 inverter wires, the 4 AWG wire from the Renogy to the bus bars and the wires going to the fuse/distribution boxes seem OK.

For mobile installs, I highly recommend marine grade 90degC or better wire. This chart shows the ampacity:



Note: The 10AWG going to the fuse boxes is adequate, but I would probably go to 8 AWG. (I like to go up one size from the minimum....but that is just me)

The DC-DC charger and roof mounted solar, along with wiring the car with a SB120 out back, will come later.

The wire from the vehicle to the DC-DC charger is very often a situation where the minimum size for safety is not large enough for voltage drop. 4AWG seems way too small for this system. A 50A load on a 4AWG wire can only go ~7.5M round trip and still keep the voltage drop to 3% or less. In the diagram, it looks like the wire could be up to 18M one way (36M round trip).



The lengths in the above chart are for *round trip*

As you can see, once voltage drop is considered, the wire size needs to be quite large. Do you really need 50A DC-DC charger? I get the desire to get as much charge as possible, but it might be worth considering something smaller.

On a related note: Just looking at the diagram, it looks like the AC/DC charger is hooked to the same place the alternator/chassis battery is hooked up. Since the Renogy is controlled by the alternator sense, will the AC/DC charger work if the engine is not running? If it is truly an AC DC charger, why not hook it directly to the bus bars?

BTW: I get that the Renogy can serve as both the SCC and DC-DC charger, but Renogy has a spotty reputation when it comes to reliability.

are the circuit breakers (like these ones) or going all double pole DIN rail ones (like these); I'm leaning to the latter, but I'm really not quite sure of the pros and cons (aside from being able to mount them altogether if I use DIN)?

Either style can be fine.....but stick with name brands. I would not touch the no-name surface mount that you linked to. For that style, stick with Blue Sea or Bussman/Eaton. For the DIN mount breakers, the knock-offs have gotten better, but I would still be a bit shy about the no-name brands.

Currently the single battery is located at the rear of the van, under a seat. If everything fits I'd like to put most of the new system there too,

we've already bought‡ some of the parts pictured these include two new AGM batteries

I know you have already purchased them, but you should really consider switching to LiFePO4.... AGM is better than flooded, but I really do not like putting any type of Lead Acid in the living compartment. In addition, if 2 AGMs are enough, 1 LiFePO4 is probably enough and much easier to fit in a tight space.

Speaking of battery size, have you done any type of energy audit to see what the needs are. There are a lot of DC loads plus the big inverter, are you confident the 138Ah AGMs are adequate? (Note: AGMs should not be drained below 50% so the effective capacity of two 138Ah AGMs is only 138Ah. It can be a bit of work to do, but I highly recommend an energy audit be done before the build so everything can be sized correctly. I use this tool:

System Energy Audit and Sizing Spread Sheet

To get the spreadsheet, click on the orange button at the top of this page. This sheet is intended to help you plan your system. Fill it out down to the last decimal place, look at the results..... and then make your best guess;) Notes...

diysolarforum.com

 

[FilterGuy]

Note: The 10AWG going to the fuse boxes is adequate, but I would probably go to 8 AWG. (I like to go up one size from the minimum....but that is just me)

I was looking closer at the DC loads and it occurred to me that you could probably get away with a much smaller breaker on at least the TV fuse box. Maybe the other fuse boxes as well. If you do an energy audit, you will have the data to figure this out.

In addition, I noticed that the kitchen fuse box has an MPPT controller on it. This is OK, but it means the breaker must be a bi-directional breaker. (If a unidirectional breaker is tripped or manually opened with a reverse current, it may not snuff the arc and that becomes a fire hazard.) I believe the blue sea version of that style breaker is bi-directional. A *lot* of the DIN mount DC breakers are uni-directional so check closely).

The above got me looking at the other breakers and they can all be uni-directional. However, looking closely at the inverter breaker, it may not be large enough.

I don't know what inverter you have, but that size/class inverter often runs as low as 85% efficiency. That means it can draw as much as
1500W/.85=1765W from the battery. When the battery is at a low SOC, the voltage is the lowest and the current will be the highest. For an AGM battery, that is 50% SOC and about 12.25V. So the continuous current could be as high as 1765W/12.25V=144A. That is in close agreement with the 147A Shown in the diagram. I assume the 147A came from the manual so let's use that.

The rule of thumb is that a breaker should be 1.25% of the continuous current. That means the Inverter breaker should be 147A * 1.25 = 184A. This would round up to 200A for an available breaker or fuse size. (At this size, you *really* don't want to be using a no-name brand of this type of breaker)

Note: When I first got into solar, I wanted breakers everywhere and did not want fuses. However, I have changed my mind about that.
For a 200A breaker to pop, either the design was bad or something really catastrophic happened. Since fuses are cheaper, easier to mount, and more reliable than breakers, I now specify fuses for almost anything above ~100A.

 

[FilterGuy]

One more thing: I notice there is no State of Charge meter in the system. I would recommend adding one. SOC is the one thing that I want to know about the system on a regular basis. Everything else that could be measured is interesting but not really important for the day-to-day use of the system.

This will require adding a shunt between the two negative busbars.

There are a lot of options. Here are a few:

* One of the Victron BMV series of meters. These are high quality but very expensive.
* The Victron Smart shunt. This is lower cost but still high quality. However, I do not like these because they require pulling out the phone and opening an app to see the SOC. I want something I can just glance at and know how the batteries are doing.
* The Aili battery monitor. These are very low cost and OK quality, but they would not work very well with AGM batteries.

 

[RV8R]

View attachment 123063

Firstly sorry for the overly, and unnecessarily complicated diagram and very long post; it's what I do.

I've been mostly lurking in this forum and elsewhere for quite a while in order to help me figure out a plan to build a new 12V system for an old van we* bought during the COVID apocalypse.
* I'm not the one who actually bought it, I'm just the one who has to figure all this stuff out. ?

I've already temporarily installed a small system (1x 12V AGM / 20A MPPT / 200W SP), but in the long term it needs to be replaced. Currently it's mainly used to power a 12V portable fridge (not pictured; separate to the 3-way fridge, pictured, which we usually run on gas/LNG/propane) along with some lighting and occasionally a TV, as well as for charging mobile phones. It also powers the reversing camera we† installed because something is wrong with the AUX pin connection on the 7-pin trailer plug; we had an auto-electrician install it in the car but it just blows a fuse in the car if we try to use it; so we currently have to run the (house) battery while driving which isn't ideal. ?
† Of course it was actually me that installed it all. ?

The system designed above would probably need to be built in stages, but we've already bought‡ some of the parts pictured these include two new AGM batteries (which are actually identical to the one we're using now, but haven't been used), the four 4x M8 bus bars, and the inverter. Knowing what I know now I'd have built a 24V system, but the inverter is unfortunately only 12V which leaves me a bit stuck.
‡ Of course I didn't actually buy any of these, but have to figure out how to install them all; though I did suggest the bus bars after some research and thinking about how I want to do this. ?

My two main concerns are am I using the correct wire gauges for all the wires and are the circuit breakers (like these ones) or going all double pole DIN rail ones (like these); I'm leaning to the latter, but I'm really not quite sure of the pros and cons (aside from being able to mount them altogether if I use DIN)?

Wire gauges is thing I find most confusing because everywhere you look it seems to tell you didn't amperages for the same sized wire, and everything sold here (Australia) is described by cross section (mm^2). However the current, jerry rigged system is all wired together using 6mm^2, "50A", wire. My preference is to oversize the wire and not have to worry about anything catching fire. (And yes, I really am going to use twin sheath everywhere, I don't want to use the chassis as part of the circuit; am I crazy?)

The other big thing I need to decide is where I am going to put it. Currently the single battery is located at the rear of the van, under a seat. If everything fits I'd like to put most of the new system there too, but it might be a tight fit. I'm also considering putting the batteries and other bulky equipment (eg. inverter and later when I get to it, the DC-DC charger) in the boot at the front of the van (accessed from the outside). There's more room here, and would save a small fortune in running 4 AWG wire all the way to the back of the van (but then mean I have to run bigger lengths of 10 AWG to the fuse boxes). Apart from loosing valuable boot space the other problems with this is might get hotter in there and there's currently a small leak I'd have to find and fix. So many decisions.

Stage 1 would be connecting up basically the left side of the diagram; batteries, bus bars and inverter along with at least some of the separate fuse boxes (I've designed it this way as I'd rather run one 10 AWG cable than 5 thinner ones; pulling the cable will be that hardest part). The DC-DC charger and roof mounted solar, along with wiring the car with a SB120 out back, will come later.

I could go on, but I've probably written way too much already. (Sorry). Any feedback or insights from anyone would be greatly appreciated.

Cheers.

I have built 2 van electrical systems; once in 2019 & another in 2022. I am in Canada, but think I can help you out If you want.

First, stop buying stuff & let the knowledge/experience of this forum help you out.

On my 1st van build I purchased a Victron 12 | 3000 | 120 Multi that todate has been a big expensive paperweight.

In point format can you list the components you have. Also I would need to know you intended common van use (ie Boondock or Travel Every Day Van). I also need to know what the van is & what the van’s alternator is.

Regarding breakers & fuses; I tend to design with fuses & switches rather than breaker switches. I also tend to design van electrical around “Marine Grade” products as a general guideline around performance spec.

Some of those cheap breakers can be very problematic.

I also believe in KIS “Keep It Simple”, where possible

I have not owned one, but my other thought would be a Kisae DMT1250 not Renogy for a DC2DC

 

[FilterGuy]

First, stop buying stuff & let the knowledge/experience of this forum help you out.

So very true!!

 

[FilterGuy]

On my 1st van build I purchased a Victron 12 | 3000 | 120 Multi that todate has been a big expensive paperweight.

Please tell us more. I am not a fan of 3000W inverters on 12V, but I do like Victron. What problems did you have?

 

[RV8R]

Please tell us more. I am not a fan of 3000W inverters on 12V, but I do like Victron. What problems did you have?

LOL

No Problem at All ,,, I am just an idiot sometimes & buy stuff before I have full understanding. I have never installed my Victron 12|3000|120 Multi (purchased in 2019 & never been incorporated into any system). It sits on the floor collecting dust ??

I started my 2018 Van build with the idea of a 100% electrical system. Now I ain’t saying it can’t be done, but after floundering about that idea went to a simple electrical system & propane.

My ignorance and internet research exposed me to “internet lemming syndrome“ (must be the thing to do as all the cool cats are doing it). Now I have been vaccinated for it, but I was still infected & caught it ,,, well at least with my Multiplus purchase.

 

[FilterGuy]

LOL

No Problem at All ,,, I am just an idiot sometimes & buy stuff before I have full understanding. I have never installed my Victron 12|3000|120 Multi (purchased in 2019 & never been incorporated into any system). It sits on the floor collecting dust ??

I started my 2018 Van build with the idea of a 100% electrical system. Now I ain’t saying it can’t be done, but after floundering about that idea went to a simple electrical system & propane.

My ignorance and internet research exposed me to “internet lemming syndrome“ (must be the thing to do as all the cool cats are doing it). Now I have been vaccinated for it, but I was still infected & caught it ,,, well at least with my Multiplus purchase.

I hear you!!!. It is SOOOO easy to get excited and start buying before we know what the final design is. I think we all have at least one experience with that (some of us more ). It can be expensive tuition. The funny thing about tuition is that whether you pay it to a formal school or the school of hard knocks, it only pays off if you use the experience to learn. (It sounds like you learned).

 

[mikefitz]

Lots of good advice so far. I deduce the system you are installing is in a trailer/ caravan that you will pull with a car?

Fuses are a lower cost option to circuit breakers , breakers, unless quality items can cause issues.
The small blade fuse distribution boxes have a maximum current rating, realistically 50 amps total throughput is a maximum. The small standard automotive fuses over 20 amps tend to overhear at that current. You have 12v cig outlets fused at high amps, in practice they cannot deal with much over 10 amps before melting.

I endorse considering lithium batteries, AGM are difficult to fully charge in a leisure vehicle, the usual result is gradual walk down of capacity and a usable life of a year or two. A 150Ah lithium battery is easily the equivalent of two 138Ah AGM.

The main battery fuse or a fuse for each, should be as close to battery positive as practical and before any switch. Connect the battery pair in parallel at the battery terminals and save two bus bars.

At full output the 1500 watt inverter will take around 150 amps, fuse at 175 or 200 amps.

The input current to the DCC50 will be about 60 amps , fuse at 80 amps.

Consider alternatives to the DCC50 , ( and any Renogy product), also having a separate solar controller and a separate DC to DC. You will get much better solar yield and the possibility to have a higher solar voltage input with two parallel strings of two panels or alternative high voltage panels.

Mike

 

[EnsignR]

I kinda like the diagram!

Thanks. I find it help to be able to plan out to nth degree so I don't get any surprises when I'm actually doing the thing. It's also really great for procrastination. ?

the 1/0 inverter wires, the 4 AWG wire from the Renogy to the bus bars and the wires going to the fuse/distribution boxes seem OK.

Excellent. Thanks. They're the one I'm most concerned about ATM

For mobile installs, I highly recommend marine grade 90degC or better wire

OMG. The temperatures are about the wire insulation!? TIL.

A 50A load on a 4AWG wire can only go ~7.5M round trip

Eeeek! The starter battery in the car to the back of the van is a lot further than a 7.5m round trip! That table is really great though. Thanks.

Do you really need 50A DC-DC charger?

Probably not for the DC-DC side of things, but the internal MPPT charger is already limited to 25A if I'm not mistaken, and I wouldn't want any more than that. However 4 AWT wire to connect from the starter is already quite a high cost. So I think I need to look at other options because I'm certainly not going to go for a larger gauge for that length of wire.

Renogy has a spotty reputation when it comes to reliability

Dang. They're considerable cheaper than most other devices I've looked at, and they were recommended by Will so I thought they were OK.

Either style can be fine.....but stick with name brands. I would not touch the no-name surface mount that you linked to. For that style, stick with Blue Sea or Bussman/Eaton. For the DIN mount breakers, the knock-offs have gotten better, but I would still be a bit shy about the no-name brands.

I think I'll go with DIN mounted breakers. I just linked to the first ones that came up in a search; the Blue Sea stuff is expensive af though.

consider switching to LiFePO4

I already knew this before somebody else bought the AGM batteries; of which there is now THREE! ?
(and there's little chance of convincing that somebody not to use what they already bought)

have you done any type of energy audit to see what the needs are

Apart from what I did making the diagram, no. But I know what we've been using when we've been away using out current system. The biggest drain we have is the portable fridge; we run both this and the built in 3-way fridge. We've not run out of, or got too low on, power yet and we've been away from extended periods (3 weeks a few times) using our single battery system. The completed build wouldn't see us using that much more power just see the end to me putting out the solar blanket every day. It can't get wet I'm keen for some fixed, or at least waterproof, panels. The new build would obviously see double the available power.

I was looking closer at the DC loads and it occurred to me that you could probably get away with a much smaller breaker on at least the TV fuse box. Maybe the other fuse boxes as well. If you do an energy audit, you will have the data to figure this out.

In addition, I noticed that the kitchen fuse box has an MPPT controller on it. This is OK, but it means the breaker must be a bi-directional breaker. (If a unidirectional breaker is tripped or manually opened with a reverse current, it may not snuff the arc and that becomes a fire hazard.) I believe the blue sea version of that style breaker is bi-directional. A *lot* of the DIN mount DC breakers are uni-directional so check closely).

The TV and Kitchen fuse box share the same breaker, with the (existing) 20A MPPT solar controller connected to the latter. 50A is probably about right I reckon. The the front fuse box that probably never come remotely close to tripping 50A breaker. The main breaker could, if there was heavy loads connected to the all the cigarette lighter connections and Anderson plugs; but I'm not intending on ever doing that.

Noted. This seals the deal for DIN rail breakers for me. I kinda wanted them already; just so can group everything together, but I'm also concerned about being able to get DIN mounted breakers that will take the thicker gauge wire. I've also not really seen anyone else using them for this sort of thing so it was making me thing you couldn't.

I don't know what inverter you have, but that size/class inverter often runs as low as 85% efficiency.

I assume the 147A came from the manual so let's use that.

You can probably assume that its a POS and therefore 85% probably correct. Yes the figure came from the manual, so yay for your math. ?

The rule of thumb is that a breaker should be 1.25% of the continuous current. That means the Inverter breaker should be 147A * 1.25 = 184A. This would round up to 200A for an available breaker or fuse size. (At this size, you *really* don't want to be using a no-name brand of this type of breaker)

Noted. (Literally with big pink text currently over the breaker in the diagram RN).

Note: When I first got into solar, I wanted breakers everywhere and did not want fuses. However, I have changed my mind about that.
For a 200A breaker to pop, either the design was bad or something really catastrophic happened. Since fuses are cheaper, easier to mount, and more reliable than breakers, I now specify fuses for almost anything above ~100A.

My logic here was they breakers aren't that much dearer than a fuse holder and all I need to is flip the switch back if there was a fixable problem and they can be used to turn something/circuits on/off if need be. We already had a fuse blow when somebody plugged a dodgy old LED lamp (that came with the van) into the external cigarette socket that I've already but out back of the van; couldn't use the socket and Anderson plug for the rest of trip because they shared the same fuse and I didn't bring replacements. ?

I notice there is no State of Charge meter in the system.

Yeah I know. I've been looking at the Victron Smart Shunt but it's so very, very expensive; like all their stuff. That's something for later as is the watcha-ma-call-it that shuts off the loads when battery reaches a certain level - something that irks me about their stuff (aside from the price) is that every little function means some (expensive) new thing to buy. IMHO the Smart Shunt should be smart enough to do both!

Thanks for your excellent, detailed feedback it's very much appreciated.

 

[EnsignR]

First, stop buying stuff & let the knowledge/experience of this forum help you out.

I didn't buy any of this stuff. I'm just the poor smuck who had to figure it all out. I've been reading all the things and watching all the videos since the van (and before any of this stuff) was purchased. I actually think the inverter is a POS and the AGMs a stupid purchase even if they were "on sale".

In point format can you list the components you have.

Already using	Already purchased	Current DC loads
1 x 138Ahr AGM	2x (additional) 138Ahr AGM	Portable fridge (the biggest load)
20A MPPT controller	1500W inverter	TV, antenna, Raspberry Pi
200W Solar "blanket"	4 of 4x M8 bus bar	Reversing camera
"battery box" with cig socket and USB buck	Isolation switch (175W rated; may get another)	A number of LED lighting strips
battery monitor (dodgy but somewhat useful)	1x 6-way blade fuse holder	(crappy) inbuilt lights
1x external SB50	Some 10 AWG (6mm2) wire can be reused
1x external cigarette socket
AC-DC battery charger (probably replace)

Also I would need to know you intended common van use (ie Boondock or Travel Every Day Van). I also need to know what the van is & what the van’s alternator is.

We've been boondocking (3 weeks the longest stink so far) as well as staying in caravan parks. Not sure what you mean by the latter.

The van is a trailer/towed caravan; not a Winnebago or anything like that. It's also quite old and quite small; about 6m long. The van does not have it's own alternator and once I get to the stage of a DC-DC charger it'd be relying on the car's (tow vehicle's) alternator; which is a long, long way away from the back of the van where the current battery is.

I also believe in KIS “Keep It Simple”, where possible

You might guess that I tend to take the completely opposite approach. Plan the heck out of everything because I hate surprises.

I have not owned one, but my other thought would be a Kisae DMT1250 not Renogy for a DC2DC

Thanks I'll take a look.

 

[EnsignR]

My ignorance and internet research exposed me to “internet lemming syndrome“ (must be the thing to do as all the cool cats are doing it). Now I have been vaccinated for it, but I was still infected & caught it ,,, well at least with my Multiplus purchase.

Are you suggesting the the extremely pricey Victron stuff they everyone online seems to fawn over may just be a little over-hyped?

 

[EnsignR]

I endorse considering lithium batteries, AGM are difficult to fully charge in a leisure vehicle, the usual result is gradual walk down of capacity and a usable life of a year or two. A 150Ah lithium battery is easily the equivalent of two 138Ah AGM.

Unfortunately we've already got the AGMs. I will happily replace the with a LiFePO4 when they're dead. I'm also bearing that in mind whilst designing everything.

The main battery fuse or a fuse for each, should be as close to battery positive as practical and before any switch. Connect the battery pair in parallel at the battery terminals and save two bus bars.

So the ANL fuse should be before the switch? (i.e. swap them)
I've already got the bus bars so may as well use them.

At full output the 1500 watt inverter will take around 150 amps, fuse at 175 or 200 amps.

Yep. 147A according to the manual. I wasn't adding in any overhead.

Consider alternatives to the DCC50 , ( and any Renogy product), also having a separate solar controller and a separate DC to DC. You will get much better solar yield and the possibility to have a higher solar voltage input with two parallel strings of two panels or alternative high voltage panels.

Originally I did have separate DC-DC charger and MPPT controller (on top of the existing one) then I read Will's page and watched his video recommending the Renogy.... so.... plus I liked the idea of one less thing to wire up and have a breaker for.

Cheers

 

[RV8R]

Hi @EnsignR

I’m in Canada, a Van here is well “a Van”. That being said I understand now you have a tow behind “holiday trailer” which you call a Caravan ,,, Van for short ?.

Can you find & post the “Performance Specifications” for your already have 3 AGMs. I have used AGMs in my “Van” & “Cabin”, but the Manufacture’s specs will be much different. Here is an example of what I am talking about for the Rolls AGMs I have;





Your Caravan Electrical System can be broken down into 3 subsections;

Loads
Energy Storage ( the batteries )
Energy Replacement ( the charging systems )

Usually, Electrical Systems are designed from the “Intended Loads” backwards. Intended Loads are best considered as what you have now (that you know of), and an allowance for what might be in the future ,,, rarely do these systems get smaller over time but things get added. This is important for such things as wire size or “space” allowances for added items such as more batteries. It is also important for picking out electrical equipment so in the “future” all you have to do is change “a user definable setting” rather than an entire “magic black box” of microchips. An example of this is the Victron 100 | 50 MPPT Solar Charger can charge 12v & 24v systems & FLA, AGM, & Lithium & has “user defined programable setting”. The other equipment I suggested might be worth looking at is the Kisae DMT-1250 (very programable & if down the road you swap to lithiums ,,, no big deal).

The Kisae might be helpful with alternator charging from the towing vehicle “user set 5amps to 50amps in 5 amp increments”. You have distance hurdles here. If it were me, I would size the wire as large as I could for the alternator charging.

Getting back to the design, if you do a “Load Chart” “Present & Possible Future Loads” that is the 1st step in your electrical design. Then you look at the “Supply” side which when boondocking is your batteries (usually you pick those out after the load chart, but youmare where you are with this “inherited” project. Then you look at the systems to “Recharge”.

I will leave it there, but if you are game ,,, Load Chart, Supply, & then Charging.

Hope that all makes sense.

Regarding Victron stuff; Buy it and use it & like it. I like the software and how it talks with my “Apple Devices”. I have BM712 smarts & the MPPT Solar Chargers. Both work very well for my needs. Cost/Benefit is a matter of one’s opinions, but for me & my uses, I do not see a better fit. YMMV & I have lots of suggestions of other products you might consider ?.

 

[RV8R]

Are you suggesting the the extremely pricey Victron stuff they everyone online seems to fawn over may just be a little over-hyped?

Not at all actually, I love Victron;

I just purchased this “thang” before I understood “inverters” & a 100% electric van ( no propane ) is a big deal.

That is I bought without doing the research, as I was an “internet lemming“ which is not typical of me

 

[RV8R]

Here is an idea you might consider ,,, this is concept for you & I have not placed the fuses that would be required ,,, but a Blue Sea 4 Way Switch & eliminate your 2nd set of pos & neg bus;



Sorry for the old school chicken scratch ,,, P.Engs use to tease me about such “drawings”, but it is the idea that counts ? ,,, They then could pretty it up & take the credit.

 

[ianganderton]

Here is a spreadsheet I created to help me understand my system including loads, irradiance, alternator charging, and battery

Van CALCS

Power Audit Van Conversion -- Electrical loads Estimate Calculations based on 24 hr period. 1 - Electrical Loads: Inverter Item,Usage,Time (min),Wattage,Energy (W),Peak Amps,% of use,Ah,Notes Laptop,240V,1,275,45,206,4,15%,17 Toaster,240V,8,1000,0,83,0%,0,12 minutes is about 6 slices of toast so...

docs.google.com

I found this process invaluable in helping me understand the consequences of different options. Different loads, different solar, different locations, alternator charging etc etc

I see you have a 3 way fridge. These don’t work well on solar/battery, they use too much electrical power. They are designed to run primarily on gas with AC when on unlimited shore power and 12V for when driving

 

[zulu]

I am not a fan of 3000W inverters on 12V, but I do like Victron.

If you're talking about Victron's MultiPlus II 12V inverter, it's actually 3000VA, but 2400W continuous.

 

[zulu]

For mobile installs, I highly recommend marine grade 90degC or better wire. This chart shows the ampacity:

View attachment 123082

Where is this table from? NFPA? MTW wire?