Electrical rookie - wiring diagram & grounding question

[luckworthy]

Hello,

I think its finally time for me to jump in with my own electrical diagram and grounding question. The current draft of my wiring diagram is attached. I have an ’09 2500 144” WB.

Critique of my diagram is most welcome. I am a total electrical rookie. Any mistakes are probably not obvious to me, so if you have the time and desire to review I’d greatly appreciate it! I haven’t selected my LED lights or outlets yet, and am still undecided how or if I will add alternator charging so those details are TBD.

I have (3) 100AH packs of EPS GBS LiFeMnPO4 batteries purchased from Starlight Solar. Their packages include the shunt, over- and under-voltage solenoids, BMS (battery management system), and sense boards connected to the batteries. All items connecting to the BMS system do so with 18 AWG, but thats the only place I’m using such a small gauge.

I’m confused about grounding my system. I’ve read all threads I could find on the subject and done lots of internet researching, video watching, etc. and I’m still a little perplexed by the illusive ‘grounding’ and how to properly achieve it. I’ve been hard pressed to find any diagrams that actually diagram the options for grounding, they all just place the little symbol and a beginner is left to guess how that can be executed in real life.

Based on my planned system, I need to run grounding conductors for my 12v battery, inverter, Iota charger, and solar charge controller. I’d rather not run a separate grounding cable to the frame for each of the 4 components if it isn’t necessary. The interior walls and floor of my van were covered with Line-x by the previous owner, so I’m guessing I’ll have to run the cable to the frame through the floor (unless I want to remove a section of Line-x from an interior wall).

So my main question is: Can all of these ground conductors can be run to a “grounding bus bar”? Or do all grounds need to be run to the chassis individually? I read the installation manuals for all these items, and its still not abundantly clear to me. I might be overthinking this, but the terms used to define grounding are all so vague that I’m not sure which specific way to interpret the language. Should ‘the chassis ground’ only ever be interpreted as directly to the frame? Or could it mean one bus bar that all grounds run to, that is then connected to the frame by one grounding cable? This is what I put in my diagram, so you can see what I mean if its not obvious by my description.

Thanks to anyone willing to help me on this,
Amy


For reference:

From my Inverter manual (GP-ISW-1500):
“Use this connection to ground the exposed chassis of the inverter to the chassis ground”

From my Iota charger manual (DLS-55):
“Connect ‘Chassis Bonding Lug’ on the IOTA unit to vehicle chassis or other grounding source”

From my solar charge controller manual (Victron SmartSolar MPPT 100/30):
“● Battery grounding: the charger can be installed in a positive or negative grounded system.
Note: apply a single ground connection (preferably close to the battery) to prevent malfunctioning of the system.
● Chassis grounding: A separate earth path for the chassis ground is permitted because it is isolated from the positive and negative terminal.
● The USA National Electrical Code (NEC) requires the use of an external ground fault protection device (GFPD). These MPPT chargers do not have internal ground fault protection. The system
electrical negative should be bonded through a GFPD to earth ground at one (and only one) location.
● The charger must not be connected with grounded PV arrays (one ground connection only)”

If you don't want to download the pdf you can view the wiring diagram here.

 

[autostaretx]

Just as a first comment (since i was just reading the Espar manual) ... you have it showing "max 2.8 A".
The Espar D5 manual says that starting is "less than 100 watts" ... which is 8.5 amps. Plus a (for the T1N) running load of 44 watts (almost 4 amps).
Your 20 amp fuse will certainly handle that, but the label in the Espar box could be misleading (or a D2 may really be that low).

--dick

 

[autostaretx]

Regarding "grounding" ... there's another 'grounding' thread that had recent traffic going through this dance.
Here: https://sprinter-source.com/forum/showthread.php?t=72005

Part of the confusion is from the misuse of the word "ground" to mean both "12v negative path" (which isn't a "ground") and "earth ground for shock prevention" ... which is what the "exposed chassis" screws are truly seeking.

So: you can simply run (let's call them) black wires from your 12v loads back to your negative bus bar (or through your fuse blocks' mini-negative busses). The loads (unless they say so) don't need "grounding".
Many people save copper money by using the vehicle's metal frame as that negative path. Both methods work, both can have "issues".

Both your inverter and your shore power entry WILL want to bond (fancy word for "wire securely") their designated "grounds" to the vehicle frame.
Squinting at your diagram, your "ground" bar provides that (although not explicitly the shore power plug's 3rd pin getting there).

The correct diagram convention for a "frame connection" looks more like a stiff garden rake instead of the parallel-lines of an "earth ground" (which you used).

I see you have "alternator charging" as a future option ... if you do that, then your 12v negative DOES have to connect to the Sprinter's negative, which they DO run via the frame. All of the Sprinter's brown wires end up on studs distributed throughout the vehicle.

more later (i'm sure)
--dick

 

[luckworthy]

Thank you for taking a look, I really appreciate it!

Regarding "grounding" ... there's another 'grounding' thread that had recent traffic going through this dance.
Here: https://sprinter-source.com/forum/showthread.php?t=72005

Yes, I have been reading and re-reading many posts on that thread multiple times over the past week. It definitely helped a lot, but I was still unclear on how direct of a path is required for adequate grounding of my specific system.

Both your inverter and your shore power entry WILL want to bond (fancy word for "wire securely") their designated "grounds" to the vehicle frame.
Squinting at your diagram, your "ground" bar provides that (although not explicitly the shore power plug's 3rd pin getting there).

Awesome, that was my main question. And to follow up on that, would my designated 'ground bus bar' provide an adequate path to the chassis? In other words: if unwanted current occurred in this specific system, is there a chance that current could travel through the 'ground bus bar' the wrong way up one of the other ground conductors instead of traveling straight through the 'ground bus bar' and down the last cable to reach the chassis where I want it to go?

I see you have "alternator charging" as a future option ... if you do that, then your 12v negative DOES have to connect to the Sprinter's negative, which they DO run via the frame. All of the Sprinter's brown wires end up on studs distributed throughout the vehicle.

When you say 'your 12v negative DOES have to connect to the Sprinter's negative': Does my current diagram achieve this? If not, are you saying I would need to add a direct cable between battery negative terminal and sprinter frame (and not through the two bus bars)?



Also, very good point about Espar, I checked the D2 manual and it lists start as ≤100 watts. Running load on Power is 34 watts (listed as 2.8 amps in the diagram). I'll double check all my starting draws against my fuse sizes, thanks for that!

 

[autostaretx]

And to follow up on that, would my designated 'ground bus bar' provide an adequate path to the chassis? In other words: if unwanted current occurred in this specific system, is there a chance that current could travel through the 'ground bus bar' the wrong way up one of the other ground conductors instead of traveling straight through the 'ground bus bar' and down the last cable to reach the chassis where I want it to go?

Although the easy answer is "No, there won't be a problem", the *real* answer adds the caveat: "as long as all the screws are tight"

The simplest analysis is that all things tied together by adequate wiring will be at the same potential. So anything attached to your "ground" bar will be at the frame's potential.
Which is a Good Thing, since the idea behind "bond the XXX chassis to the frame/ground" is so that any loose wire inside the boxes will get shunted to "ground", and should trip protection circuits along the way. Likewise, when you're plugged into shore power, the power kiosk's 3rd pin will (should) bring your entire frame to earth ground potential ... so that a failure inside your van will not electrify the frame above earth which can be deadly as you step outside in wet bare feet onto wet grass as you're still holding the metal grab bar in the van. A number of people die that way every year.

When you say 'your 12v negative DOES have to connect to the Sprinter's negative': Does my current diagram achieve this? If not, are you saying I would need to add a direct cable between battery negative terminal and sprinter frame (and not through the two bus bars)?

Your diagram is missing a LOT of negative return wires ... such as none of the gadgets on the lower right fuse block.

As long as your wires from the negative post to the shunt to the negative bus bar, and then the cable from that to the frame are thick enough (and well secured), it should work. Bear in mind that each joint will have *some* extra losses (numbers have been kicked around by other people), but they should be reasonably small ... just for starters, your shunt steals 50 to 100 millivolts at full rated capacity. 100 millivolts is a tenth of a volt, and at (let's say) 100 amps that's dumping 10 watts in the form of heating up the shunt.

Since you have a shunt, the ONLY thing attached to the Aux battery's negative post is the feed to the shunt. NOTHING else should go there ... otherwise the shunt wouldn't see it, and the monitor would tell lies. Get into the habit of thinking of the "other end" of the shunt as your "negative post".

Also, very good point about Espar, I checked the D2 manual and it lists start as ≤100 watts. Running load on Power is 34 watts (listed as 2.8 amps in the diagram). I'll double check all my starting draws against my fuse sizes, thanks for that!

Always round up numbers to provide extra breathing room ... so "34 watts" should be considered as 3 amps, not 2.8.

--dick
p.s. you can probably get a 12vdc -to-laptop power adapter instead of having to run your big inverter for such a small load. (and the numbers you show for the laptop adapter can't be right are confusing to the onlooker ... you're pointing at the AC outlet, but are (in the purple box) I HOPE speaking of 12v currents, since 4 amps at 110vac would be a 400 watt laptop. Adding the text that you're speaking about 12v would help avoid late-night issues.)
Associated with this is that you're not specifying your AC wire sizes.

 

[luckworthy]

Although the easy answer is "No, there won't be a problem", the *real* answer adds the caveat: "as long as all the screws are tight"

The simplest analysis is that all things tied together by adequate wiring will be at the same potential. So anything attached to your "ground" bar will be at the frame's potential.
Which is a Good Thing, since the idea behind "bond the XXX chassis to the frame/ground" is so that any loose wire inside the boxes will get shunted to "ground", and should trip protection circuits along the way.

Cool, thanks! Finally getting closer to executing this wiring plan I've been working on for so long.

Likewise, when you're plugged into shore power, the power kiosk's 3rd pin will (should) bring your entire frame to earth ground potential ... so that a failure inside your van will not electrify the frame above earth which can be deadly as you step outside in wet bare feet onto wet grass as you're still holding the metal grab bar in the van. A number of people die that way every year.

Okay, probably another beginner error here. I don't have a shore power plug, its actually a 12AWG/3 extension cord that will plug into grid AC power. I plan to plug it into the Iota DLS-55 only if I'm staying with friends or family and hit a stretch of cloudy days. For the record, I did speak with Iota technical support before moving forward with my plan to install an extension cord for emergency grid charging and was assured it should be fine with a good quality cord. I didn't get into discussing grounding with them.

I updated the diagram to read 'Grid power hookup' instead of 'shore power hookup'. Is there a difference with how the grounding would work though the grounding pin/conductor on the extension cord? I'm guessing it would be the same?

Your diagram is missing a LOT of negative return wires ... such as none of the gadgets on the lower right fuse block.

Oh right, I just added a note at the 12v Circuit Block addressing the 12v neutral wires: "All neutral wires from 12v loads terminate here". I might move some things around in that section and I was trying to save myself the extra work of having to update both wire runs on the diagram but I should've labeled that before sharing.

Since you have a shunt, the ONLY thing attached to the Aux battery's negative post is the feed to the shunt. NOTHING else should go there ... otherwise the shunt wouldn't see it, and the monitor would tell lies. Get into the habit of thinking of the "other end" of the shunt as your "negative post".

Ok, perfect, thats what I was thinking but began to second guess it so thank you for confirming and clarifying so simply.

you can probably get a 12vdc -to-laptop power adapter instead of having to run your big inverter for such a small load. (and the numbers you show for the laptop adapter can't be right are confusing to the onlooker ... you're pointing at the AC outlet, but are (in the purple box) I HOPE speaking of 12v currents, since 4 amps at 110vac would be a 400 watt laptop. Adding the text that you're speaking about 12v would help avoid late-night issues.)
Associated with this is that you're not specifying your AC wire sizes.

Oops, thank you for pointing out my error listing 12v currents for AC loads. I'll fix that.

I had previously tried to look into a 12v dc-to-laptop plug. I have a late 2012 macbook pro and the best 12v charging option I could find didn't seem very good, it was only 80% efficient. So I scrapped that plan for now... thinking that since my inverter is 91% efficient, and estimating that my existing AC laptop power cord is 90% efficient then I'm not really saving much power if at all by purchasing that 12v adapter. Would love to find a more efficient option, though.

 

[autostaretx]

I had previously tried to look into a 12v dc-to-laptop plug. I have a late 2012 macbook pro and the best 12v charging option I could find didn't seem very good, it was only 80% efficient. So I scrapped that plan for now... thinking that since my inverter is 91% efficient, and estimating that my existing AC laptop power cord is 90% efficient then I'm not really saving much power if at all by purchasing that 12v adapter. Would love to find a more efficient option, though.

You're probably not properly "scaling" the effects of the efficiencies.

The 80% efficient 12vdc laptop adapter is only handling about 5 amps. (60 watts, see "actual load" below)
So that's a loss of 0.2 * 60 =12 watts.

The inverter is 91% efficient... but of what? 1000 watts? So 9% * 1000 = 90 watts. (you won't hit that level with just the laptop (i hope))
See if you can find out what the inverter's own stand-by (i.e. "on", but little to no loads) losses are. Then add the 110vac adapter's 6 watts.

As for your laptop's actual load, the full rating usually only happens when the batteries are low (requiring full charging currents) AND you're heavily using it. If the batteries are pretty full, or the load is light, then the current usage is far less (just feel how warm your adapter is now... and compare under differing circumstances).

--dick

 

[autostaretx]

Okay, probably another beginner error here. I don't have a shore power plug, its actually a 12AWG/3 extension cord that will plug into grid AC power.

That's a "shore power plug" in my book. And it has a green (3rd pin) grounding wire.
So: yes, it's "the same".

You'll have to consult the charger's documentation (or ask the company) to find out if the 3rd pin is *also* attached to the metal box. If you already have the charger, an ohmmeter will tell you (does the charger's 3rd pin have next-to-zero resistance to the metal "grounding" screw?). Do that test with the charger disconnected.

--dick