Another Wiring Diagram for Input and Feedback

VanLove

New member
I am a total novice when it comes to electrical but I have spent weeks reading the forum and researching to put together the electrical diagram for my 2020 170 Sprinter campervan. I am now ready to offer it up for input, critique, and criticism. What am I doing wrong? What would you change? I appreciate all comments and feedback. You will notice components in the diagram from many of your threads and builds.

Sprinter Build out details and plan.
  • 2020 170 4x4.
  • Accommodating a family of 4.
  • Will be using the Sprinter for long weekend camping and multiple week cross country trips. We will be camping in campgrounds and remote locations.
General build out details and comments on the wiring diagram.
  • I will be using a Pico Simarine monitor for the battery bank, inverter, solar, temperature, and tank levels (propane, fresh water, grey water).
  • I am planning to install the Nations auxiliary alternator that is rated for 280A. I plan to have the house system completely separate from the starter battery.
  • I plan to have 300W of solar wired in parallel.
  • On the diagram I did not show the negative wire for the DC loads with switches to make the diagram cleaner.
  • DC load wire lengths are roundtrip.
In addition to your general thoughts and feedback I've listed specific questions for the forum below. Some are highlighted in yellow on the diagram and I also attached my calculations for the daily electrical consumption for input:
  • Is my battery bank the right size? Do my calculations look correct? My total Ah/Day from my calculations comes out to 259.5. I then multiplied this by a factor of 1.75 due to getting charge from the alternator per Faroutride’s suggestion (here: section 3.1). They also recommend using a depth of discharge factor for lithium batteries of 80%. Using Faroutride’s approach I need a 600Ah battery bank which seems excessive. Please provide any thoughts on this.
  • What gauge wire should I use for the run from the 2nd alternator to the battery bank which will be behind the driver side wheel well? Looking at the American Wire Gauge chart it looks like 4/0 AWG is required for 280A but reading through the Auxiliary Nations Alternator thread started by VanGoSki 2/0 is recommended. Is 2/0 okay for 600A?
  • What amp fuse circuit breaker should I use for the positive bus bar connection to the 2nd alternator?
  • I am still pretty confused about the connections and programming for the auxiliary alternator regulator and BMS. I tried representing the connections on the diagram but I am reading through the Auxiliary Alternator thread on the forum. A consolidated post in that thread showing the connections and programming parameters for the BMS and regulator would be a huge help!
  • What amp fuse circuit breaker and what gauge wire should I use for the run from the positive bus bar to the DC circuit breaker panel? Do I calculate the fuse and gauge based on the sum of all the DC loads?
  • What gauge wire should be used between the 12|3000 inverter and the positive and negative bus bars? I assume I use the same gauge for the Pico SC301 Shunt that measures the AC loads off the inverter?
  • Where should I ground the negative bus bar? The factory ground location near the rear axle seems like the best location.
  • Can I combine all of the DC loads that have the same sized fuse into one circuit? I thought it would be good to have a few of the loads separate in case there is a fault so it doesn’t impact other items in the circuit.
  • Is the 1Amp fuse between the Pico SC502T shunt and the positive bus bar an inline fuse?
Thanks for taking the time to look it over and provide feedback!

Near Final Wiring Diagram.pngElectrical Calculations.png
 

RVBarry

Well-known member
Hi, using DC heat trace would save having to leave the inverter on all the time.
 

HarryN

Well-known member
Looks like a good concept.

Really need 4 of those batteries to keep up with that inverter.

Consider to wire it as a 24 volt system instead of 12 volts. That is a lot of power for a 12 volt based system.

Perhaps wire the fridge and heater with 10 awg to reduce voltage loss, as those loads are voltage sensitive.

At my shop we use 14 awg for everything else - mostly because 16 awg is frail.
 
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blutow

Member
Are you doing a 12V to 12V charger or trying to charge straight from the alternator? I don't know how smart that alternator is, but you'll want something that can be configured to charge your lithium batteries. I'd also assume 280A is a max on the alternator and you wouldn't see those numbers too often. 2/0 would probably be fine on that run, but then you mention 600A? Not fine for 600A. Also, I don't think there is any reason to run a negative cable from the alternator (particularly when it's a big expensive one). I've seen some debate on that, but I don't think I've seen a good reason not to just run a positive and then grab a good chassis ground.

One other thing - that isotherm water heater says 750w on the spec sheet, but mine pulls about 850. Maybe it varies.
 

RVBarry

Well-known member
One other thing - that isotherm water heater says 750w on the spec sheet, but mine pulls about 850. Maybe it varies.
Hi, are you already accounting for inverter efficiency losses?
 

VanLove

New member
Are you doing a 12V to 12V charger or trying to charge straight from the alternator? I don't know how smart that alternator is, but you'll want something that can be configured to charge your lithium batteries. I'd also assume 280A is a max on the alternator and you wouldn't see those numbers too often. 2/0 would probably be fine on that run, but then you mention 600A? Not fine for 600A. Also, I don't think there is any reason to run a negative cable from the alternator (particularly when it's a big expensive one). I've seen some debate on that, but I don't think I've seen a good reason not to just run a positive and then grab a good chassis ground.

One other thing - that isotherm water heater says 750w on the spec sheet, but mine pulls about 850. Maybe it varies.
I am planning to charge the house battery straight from the auxiliary alternator and to use a regulator, either the Balmar or Wakespeed, to configure the charging profile. The auxiliary alternator and regulator setup is an area where I still need to do a lot of research.
 

blutow

Member
I am planning to charge the house battery straight from the auxiliary alternator and to use a regulator, either the Balmar or Wakespeed, to configure the charging profile. The auxiliary alternator and regulator setup is an area where I still need to do a lot of research.
Another thing to consider - you might look at building your own lifepo batteries. I was originally going down the path of doing ~400ah of battle borns or SOK's, but started researching building my own. The lifepo chemstry is really safe (not the lithium chemistry that is prone to thermal runaway when damaged) and you get a lot of ahr's for the $. I'm building 4 272Ahr batteries and it will be ~$2500 once I build some nice enclosures and you could do it cheaper. The cells with busbars are about $1,600 and I'm doing 4 bluetooth enabled BMS's that add another ~$500.

When I started researching batteries, I was really trying to compare the different drop in battery options and found some videos of people tearing down these batteries. For several of the drop in options, it's the same prismatic cells and BMS's you can buy yourself for a fraction of the $. If you have the skills/desire to do wiring and build enclosures, it's pretty basic stuff. I quickly went from being intimidated to thinking it will be a fun project. The scariest part to me is soucing grey market cells from china that take ~60 days to arrive. There is certainly risk compared to buying a drop in battery with warranty. Hopefully it will work out and I'll save a bunch of $ and have almost 3x the battery capacity I was expecting. A couple good resources:


 

owenfi

Sprinter MY 2020 2500 170 4x4
  • What gauge wire should I use for the run from the 2nd alternator to the battery bank which will be behind the driver side wheel well? Looking at the American Wire Gauge chart it looks like 4/0 AWG is required for 280A but reading through the Auxiliary Nations Alternator thread started by VanGoSki 2/0 is recommended. Is 2/0 okay for 600A?
4/0 isn't even okay for 600A, but your alternator should never be putting out more than 300? (did you mean the 600AH battery?)
One place I've found some confusion is NEC Ampacity vs ABYC. I think NEC leans towards AC/wire pairs/groups, while the ABYC has consideration for "single conductors in free air", such as this case.

If you follow the Blue Sea Ampacity guide with 2/0 you could go to 281A if 105C cable in "engine room". If you have your controller never actually send that much (WS500 at least has "target amps" that it should stick to) then you could fuse at about that point (say 250 or 300 probably easier to find than 280) then it would be about right.


  • What amp fuse circuit breaker should I use for the positive bus bar connection to the 2nd alternator?
I would consider this as "from" the 2nd alternator, not "to" it, so you probably want to fuse closer to the alternator. I'm not quite sure about this though since it's also connected to the battery positive. Maybe a time for fuses on both ends? What do other folks think.

  • I am still pretty confused about the connections and programming for the auxiliary alternator regulator and BMS. I tried representing the connections on the diagram but I am reading through the Auxiliary Alternator thread on the forum. A consolidated post in that thread showing the connections and programming parameters for the BMS and regulator would be a huge help!
I didn't post it in that thread, but I did update my wiring diagram: #26 which shows (roughly) the connections from the Wakespeed. The Balmar wiring is simpler, it lacks the battery voltage/shunt wire pairs. Parameters would be pretty dependent on the system at hand but I can share those once I get around to finalizing/installing it.

  • What amp fuse circuit breaker and what gauge wire should I use for the run from the positive bus bar to the DC circuit breaker panel? Do I calculate the fuse and gauge based on the sum of all the DC loads?
Yep, since your "worst case" for the wires is that all loads are drawing full power simultaneously you add them up and fuse for the total. It's probably a good idea to increase the main fuse a bit in case you add anything down the line, and then choose a wire that can accommodate that continuously. I think it's fine to add the loads as opposed to adding the fuses (considerably higher in some of your cases). Lower amperage automotive fuses aren't hard to find, 3A, 5A, 7.5A should be easy to swap in for some of those items if other folks say it's better to size based on sum of fuses.

  • What gauge wire should be used between the 12|3000 inverter and the positive and negative bus bars? I assume I use the same gauge for the Pico SC301 Shunt that measures the AC loads off the inverter?
3000/12 => 250A -> a single 2/0 might do it, maybe a 1/0 if it was 105C rated. Those might work if you don't plan to draw near the limit ever.
Victron recommends 400A and 2x50mm (which translates to 1/0 AWG) as peak power is 6000W (for something like 5 seconds I think).

  • Can I combine all of the DC loads that have the same sized fuse into one circuit? I thought it would be good to have a few of the loads separate in case there is a fault so it doesn’t impact other items in the circuit.
No! In that case you'd need to use the sum of the loads (maximum) power and fuse appropriately to that total, similar to what you mentioned above. But then you'd need to run wire that could handle that current to each appliance. It's generally best to keep things separate for exactly the reason you say and so you can size fuses/wire appropriately.

Does the Inkbird support DC? (I think the common ones don't but they have a lot of products) the Isotemp is 750W @ 12V that'd be 63A, so not supported by the fuse you mention. I think you'll need to move that to the AC circuit (unless they have a DC heater/mode available; which might be explained by the "dual 10A relay" in which case you'll at least need to move from 15A to 20A+ fuse there, and investigate wire gauge/flow as my understanding is the power usually flows through the inkbird, and you have a duplex listed as coming out of it, but only 0.3A and 16AWG wire which would probably need to be increased to 12 or 10AWG, unless it's 750W@12VDC then more like .
 

blutow

Member
You need to fuse on both ends of the run between the alternator and your house batteries

you can get 12v inkbirds. The relays don’t care if it’s ac or dc going through them, but they can’t support high amps. They are typically triggering other relays when the load is significant.
 

borabora

Well-known member
You should review your Espar wiring requirements. I am not familiar with the D4 but my D2 pulls more than 10 amps at start up and I would not use 16 gauge for a long run. I believe I wired it with 12 gauge and used a 20 amp fuse.
 

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