[kenryan]

Great input. Thanks.

Open to any more comments or suggestions. Right now, I like the DC side of my system as is, provided that the BMS short circuit protection can be considered reliable. Otherwise, a change is in order.

Also, I will probably follow the suggestion to increase the DC load capacity, even though I don't need it.

Still one area that I would like to continue to discuss, revolving around the suggestion from @cycle61 that I consider "an ELCI on the shore power inlet."

Right now, my plan for shore power is to use the following components:

1) 30 amp Smart Plug cable and socket
2) Blue Sea 8077 AC Main Panel

into Magnum 2812
out of Magnum 2812

3) Blue Sea 8099 Power Distribution Panel (30 amp main double pole breaker, 4 15 amp breakers)
4) Four GFCI duplex outlets (one for each breaker)

Specifically with regards to ELCI most of the info I have seen discusses ELCI protection at the "dock" (in our case either home or campground power) rather than on the "boat" (in our case the van, or camper). What part would I use on the camper and where would that part be placed?

Generally, any comments on the shore power portion of my system would be appreciated.

 

[natecostello]

@njvagabond @kenryan

it’s been a minute but I think ABYC allows you to rely on short circuit/fold back protection for things like inverter/charging sources. Essentially if the source can’t exceed the ampacity (unlike a battery) an additional fuse isn’t required. I’ll look it up and confirm.

Here's an excerpt from ABYC E-11 and my old notes on it from when I was designing our system. The inverter I was referencing was one used for the "orton method" that I later abandoned due to lack of need. But I did follow the same approach (ie fuse at the positive bus, no fuse at the device) for our main Victron Inverter and for our dedicated 24V alternator.

11.10.2.8.4 If required, overcurrent protection for power-feeder conductors from AC generators and inverters, shall be within seven inches (180 mm) of the output connections or may be within 40 inches (1.0 meter) of the output connections if the unprotected insulated conductors are contained throughout their entire distance in a sheath or enclosure such as a conduit, junction box or enclosed panel.

Note to Self: "if required" I think refers to whether the power source is self limiting (and the cabling is sized appropriately from an ampacity perspective). My basis for this interpretation is:

• the exception under section 11.6.4.1 for AC generators that says "Self limiting generators, whose maximum overload current does not exceed 120 percent of its rated current output, do not require additional external overcurrent protection."
• The Boatowner's Illustrated Electrical Handbook says, regarding Generator and Inverter sources: "...the feed conductors from the genertor or inverter must be of sufficient ampacity to carry the maximum rated output. In addition, the generator or inverter output must be protected at its output with an overcurrent device, rated at no more than 120% of the rated output, unless the generator or inverter is self- limiting to the same degree."

Thus, if an inverter is self-limiting to within the ampacity of its output wiring, overcurrent protection is not required.
Thus, the inverter fed by the factory alternator can be direct wired to a transfer switch.
Related, this would apply to the alternator as well. Based on this I will not fuse the alternator as the ampacity of its output wire will support its maximum output current in a fault.

Out of date, unorganized notes, and ABYC E-11 extract here.

 

[natecostello]

Still one area that I would like to continue to discuss, revolving around the suggestion from @cycle61 that I consider "an ELCI on the shore power inlet."

Right now, my plan for shore power is to use the following components:

1) 30 amp Smart Plug cable and socket
2) Blue Sea 8077 AC Main Panel

into Magnum 2812
out of Magnum 2812

3) Blue Sea 8099 Power Distribution Panel (30 amp main double pole breaker, 4 15 amp breakers)
4) Four GFCI duplex outlets (one for each breaker)

ABYC + My old notes on these subjects:

11.11.1 An Equipment Leakage Circuit Interrupter (ELCI) shall be installed with or in addition to the main shore power disconnect circuit breaker(s) or at the additional overcurrent protection as required by E- 11.10.2.8.3 whichever is closer to the shore power connection.

Note to Self: This requirement means the main shore power disconnect shall be an ELCI breaker. Per other requirements, it must also be a double pole, and it must have polarity indication. The breaker that meets all these requirements is this Blue Sea panel which is available from PKYS for under $200. Also, if the installed location is by the driver wheel well, the 10 foot requirement of 11.10.2.8.3 will be met.
The main shore power disconnect will be a Blue Sea 8100 panel

11.9.3.2 A system voltmeter shall be installed on the main panelboard if the system is permanently connected to

11.9.3.2.1 an electric motor, or

11.9.3.2.2 a generator, or

11.9.3.2.3 an inverter or inverter/charger. If the inverter or inverter/charger does not have a true sinusoidal output, the voltmeter shall be a true RMS type. (See ABYC A-31, Battery Chargers and Inverters.)

EXCEPTION: The inverter or inverter/charger voltmeter may be installed in proximity to the panelboard.

Note to Self: This requirement means the main panelboard must have a voltmeter. Also note, the Multiplus and Multiplus Compact manual requires and ECLI breaker in series with its output. Based on this requirement, this Blue Sea product satisfies all these constraints, provides for two AC circuits (enough), and is available from PKYS for about $300.
The AC main panelboard will be a Blue Sea 8102 panel

11.13.3.5 If installed in a head, galley, machinery space, or on a weather deck, the receptacle shall be protected by a Type A (nominal 5 milliamperes) Ground Fault Circuit Interrupter (GFCI). (See E-11.11.)

NOTE: GFCI receptacle devices are not necessarily ignition protected per E-11.5.3.1.

Note to Self: This requirement requires GFCI outlets in addition to and ELCI. Because we are planning for a single circuit of outlets, this will be easy to accomplish by installing a GFCI on the first outlet from the main AC distribution panel, and chaining all that follow. The internets say that there is not limit to number of chained outlets as long a the conductor run is less that ~150 ft.
All outlets will be GFCI protected by making the first outlet a GFCI

A few more notes of mine regarding ELCI:

Use of an ELCI as the shore power disconnect circuit breaker will provide a trip:

• if a hot-to-ground fault occurs upstream of the Main Panelboard ELCI while connected to shore power with a functioning ground.
• if a latent hot-to-ground fault exists upstream of the Main Panelboard ELCI with an open shore power ground, when a person completes the path to earth (e.g. touches van metal while standing on earth).

In the two cases above, and ELCI or GFCI at the shore power source should also provide the same protection, but will not be relied on. Additionally, if the fault occurs downstream of the Main Panelboard ELCI, it would also provide the above trips.

I have two ELCI's, one as part of the main shorepower disconnect, and one downstream of our main Victron inverter. The need for the second is debatable given the inverter only drives a circuit that is protected by a GFCI. But GFCI's do fail, so defense in depth is not a bad idea. A similar argument could be made regarding the need for an ELCI on board, if the upstream shore power source has an ELCI/GFCI. But again, I'm not going to rely on a campgrounds code compliance and maintenance regimen for the safety of myself and van.

Regarding the AC voltmeter requirement - I think this is primarily to indicate when the panel is hot. Other means that satisfy this intent are probably fine. At the point where I was in the design it was just easier to pickup off the shelf items that satisfied the requirements that I elected to impose (since I'm not a boat).

 

[harryn]

I missed that you had such a healthy solar setup.

The midnight solar classic family is an excellent choice for this. I have used one in an RV / 12 volt project but it has been a while. Magnum also makes a solar charger that is range.

Perhaps look at the protections provided by the dual breaker on the input side and what is built into the classic to decide if a breaker located near it are needed or not.

A breaker is needed at the bus bar mostly to protect the wire running from the bus bar to the solar controller.

On some controllers, the sequence of turning these on / off might be important.

 

[harryn]

As far as dealing with a short on the DC from those batteries, for the 100 amp-hr size batteries, certainly a 187 series breaker on each battery string (for 12 and 24 volt systems) will work with a 5K amp AIC @12 volts.

https://www.bluesea.com/products/category/14/30/Circuit_Breakers/187-Series

For that 270 amp-hr battery, not sure without some more study.

Perhaps consider a battery terminal fuse so the "dead short" type protection is right at the battery.

https://www.bluesea.com/products/category/15/42/Fuses/Marine_Rated_Battery_Fuses

A number of companies make these and they are highly regarded in the marine industry. Typical AIC is ~ 10K amps.

I still vote for a breaker for each battery to shut them off to clear BMS faults if nothing else, as well as making it safer to work on the system.

That way you can just flip a few breakers off and have a dead system to work on vs working on it "live". Yes it is 12 volt but plenty capable of doing some parts welding.

 

[kenryan]

Thanks @harryn

Perhaps consider a battery terminal fuse so the "dead short" type protection is right at the battery.

https://www.bluesea.com/products/category/15/42/Fuses/Marine_Rated_Battery_Fuses

Thanks, I was unaware of this product. They seem to be significantly less effective at AIC protection than a Class T fuse.

Specs on 300 amp Class T:
20,000 @ 125 VDC

Specs on 300 amp MRBF:
10,000 @ 14 VDC
5,000 @ 32 VDC
2,000 @ 58 VDC

@harryn How would one determine the necessary minimum protection for a particular battery?

I still vote for a breaker for each battery to shut them off to clear BMS faults if nothing else,

If I am plagued by BMS faults, I am going to be a very unhappy camper. As I noted in a previous post, my past systems have been trouble free. No equipment failures, never a blown fuse. No need to monitor anything other than state of charge. This is my first foray into a lithium battery system. I hope I am not disappointed.

... as well as making it safer to work on the system.

That's what the switch and existing breakers are for.

 

[natecostello]

@kenryan, have you reached out to Battleborn for their recommendation on overcurrent protection and manual disconnects outside of the batteries? I'd be interested to hear what they say.

 

[cycle61]

I've found maximum fault amperage information on lithium batteries to be scarce. Went with a Class T on each of my 24v 200ah Victron batteries but I'd love to have better data.

 

[kenryan]

@kenryan, have you reached out to Battleborn for their recommendation on overcurrent protection and manual disconnects outside of the batteries? I'd be interested to hear what they say.

Ha! Writing that up now ...

Had to work my way up the food chain at Battleborn. Talked with Brandon who seemed pretty knowledgeable. He says ...

Yes, the internal protection can be counted on to open with a 600 amp event (duration 0.5 seconds). He would prefer to see the 400 amp Class T between the battery and the bus so that the internal protection is never triggered.

I also asked him how to determine the minimum AIC rating and he said 150% of the max continuous rating for that circuit. That doesn't seem right to me, but that's what he said. It seems max AIC would be related not to the max rating for the circuit, but rather to the battery itself.

Anyway, I will redesign to integrate the Class T protection before the bus bar.

 

[njvagabond]

Thank to everyone in this discussion. It's been REALLY helpful for me.

Also, keep in mind that when connecting cables for individual batteries direct to the fuse you can properly size and use smaller gauge wire going to the t-fuse for each battery

This is one thing that I am wrestling with on this for my plans are since individual battery wires before the the t-class are smaller and will be a couple of feet long how will I protect them against overcurrent (with a high enough AIC.)

Overkill? Well LiPO scares me a bit, especially since my electrical knowledge is minimal. Have never found any good info on short circuit current called out in a LiFPO spec.

So in my case maybe an MRBF fuse at 125A or 150A with appropriate wire size on the terminal of each of my 3 batteries? Maybe 200A in the case of @kenryan's 2 batteries. Those fuses have 10K AIC.

I would not be comfortable relying on a switchable breaker for AIC protection.

I originally was thinking of mounting the the 187 Blue Sea Breakers with an AIC of 5K AIC cuz they have add a switch, but the superior protection of the fuse seem to be a safer choice. (BTW - the less expensive Blue 285 or Mechanical Products breakers are 3K AIC).

Another option is to just wire the 2 batteries to each other in parallel. IIRC with 2 batteries the discharge will still be equal in that configuration. (That is less so when there are 3 or more batteries). I suppose there are other cons to that set up as well though.

On the other hand, if the batteries' internal protection is more of a "last resort" if everything else fails, then my design needs to be changed.

I am trying to work to that same parameter. I seem to recall reading somewhere that is the "proper" approach. A - belts and suspenders redundancy given the potential consequences. B - Reduce likelihood of BMS failure due to overcurrent.

I have seen people (including Will Powers, I think) bolt the class T fuse directly to the battery. That looks like a recipe for disaster to me.

Why? Seems (in my uneducated view) like that might be the ideal solution for dead short on the battery. Take a look at @cycle61 nifty 3d printed part to facilitate this setup. Here is a good video that show a class-t getting cut opened.

 

[kenryan]

Why? Seems (in my uneducated view) like that might be the ideal solution for dead short on the battery. Take a look at @cycle61 nifty 3d printed part to facilitate this setup. Here is a good video that show a class-t getting cut opened.

When I look at a Class T fuse and its holder, it seems apparent that the fuse should be well stabilized and not subjected to any strain. Mounting directly to the battery seems like an open invitation to mechanically overstressing the fuse, resulting in who-knows-what kind of damage. This would be particularly true in a vehicle where vibration is always an issue.

 

[njvagabond]

@njvagabond @kenryan



Here's an excerpt from ABYC E-11 and my old notes on it from when I was designing our system. The inverter I was referencing was one used for the "orton method" that I later abandoned due to lack of need. But I did follow the same approach (ie fuse at the positive bus, no fuse at the device) for our main Victron Inverter and for our dedicated 24V alternator.

11.10.2.8.4 If required, overcurrent protection for power-feeder conductors from AC generators and inverters, shall be within seven inches (180 mm) of the output connections or may be within 40 inches (1.0 meter) of the output connections if the unprotected insulated conductors are contained throughout their entire distance in a sheath or enclosure such as a conduit, junction box or enclosed panel.


Out of date, unorganized notes, and ABYC E-11 extract here.

Thanks. Very helpful for the AC side, which I have yet come to a good understanding of yet.

Asking about concern was asking about the charger output from an inverter charger and the t-class fuse was at the "end" of that circuit several feet away. It would seem to me that it might be good to have have a circuit protection device close to the charger output (/inverter input). Say an ANL fuse (or 187 breaker) of equal amperage to the t-class at the battery end. I'd appreciated you educated input on this question.

 

[kenryan]

Spoke Midnite Solar about whether or not two breakers are necessary on the positive cable that runs from the charge control to the battery. He said code would require two, if the cable is a certain length. I believe he said within 5 feet of the charge control or 5 feet of the battery. If code is not an issue, he said just put one breaker next to the charge controller. When I challenged him by saying that would leave the balance of the cable from that breaker to the battery unprotected, he really had no response. ("Put it in a conduit if you are worried.")

I will use my own judgement on this one when I actually do the installation.

 

[kenryan]

What I am thinking with regards to moving my Class T to a position before the positive bus bar is to add another "battery bus bar." I would need 3 terminals -- one for each battery, and one to connect to the fuse holder. I would like to use a copper bar to make the connection from the battery bus bar to the fuse holder.

Does anyone have a source such a bar, or the material to make such a bar? It would need to be rated for at least 600 amps.

Edited to add: McMaster Carr seems to be a good source.

 

[njvagabond]

What I am thinking with regards to moving my Class T to a position before the positive bus bar is to add another "battery bus bar." I would need 3 terminals -- one for each battery, and one to connect to the fuse holder. I would like to use a copper bar to make the connection from the battery bus bar to the fuse holder.

Does anyone have a source such a bar, or the material to make such a bar? It would need to be rated for at least 600 amps.

Marinco/BEP has a product line called Pro-Installer, where the connection heights are all the same and they make a variety of connection links to cover various configurations. Helpful but expensive if you are looking to save space. I can't see why you could not use those connectors with other brands of components. IIRC it is all tinned copper. Blue Sea also makes some hard link connectors. If I was going to DIY some copper bar, I'd might end up driving 30 min each way to Grainger's 😖

 

[njvagabond]

When I look at a Class T fuse and its holder, it seems apparent that the fuse should be well stabilized and not subjected to any strain. Mounting directly to the battery seems like an open invitation to mechanically overstressing the fuse, resulting in who-knows-what kind of damage. This would be particularly true in a vehicle where vibration is always an issue.

Agreed. My wording was not very exacting so l will correct my statement to clarify. Mounted on the battery in a fuse holder, very close to the battery terminal and connected to the terminal by a hard link or for more compliance a very short cable like @cycle61 did.

 

[harryn]

@kenryan BB should be able to provide the AIC rating of their batteries so that you can select a fuse for it.

I don't remember the number for their 100 amp-hr battery or the similar AGM battery size but in both 12 and 24 volt, the 187 breaker rating is more than adequate and I have seen pro level setups that use them to even higher levels.

You are right that that the AIC ratings are 187 breaker < battery terminal fuse < T fuse , but you can also extend this concept for even more steps so try to not fall into this trap that more is always better / needed.

IMHO, you are going to want an easy way to have 0 volts across the (+ ) and (-) bus bus bars without needing a tool.

Battery terminals are made from soft metals, not steel. They are not intended to have much extra mass mounted to them. A single terminal fuse is a reasonable amount.

 

[natecostello]

Thanks. Very helpful for the AC side, which I have yet come to a good understanding of yet.

Asking about concern was asking about the charger output from an inverter charger and the t-class fuse was at the "end" of that circuit several feet away. It would seem to me that it might be good to have have a circuit protection device close to the charger output (/inverter input). Say an ANL fuse (or 187 breaker) of equal amperage to the t-class at the battery end. I'd appreciated you educated input on this question.

Ah...yes, good distinction (AC vs DC). Not sure why ABYC makes it, I need to think about that. I don't have the full text of E-11, but I do have a copy of Nigel Calders book on the subject. Here's the relevant portions. When I've had some time to think about it, I'll add my commentary:

And regarding battery chargers:

 

[Scalf77]

What I am thinking with regards to moving my Class T to a position before the positive bus bar is to add another "battery bus bar." I would need 3 terminals -- one for each battery, and one to connect to the fuse holder. I would like to use a copper bar to make the connection from the battery bus bar to the fuse holder.

Does anyone have a source such a bar, or the material to make such a bar? It would need to be rated for at least 600 amps.

I would look at just doing double stacked cables from the batteries to the Class T Holder. BEP marine's version has radiused ends allowing the lugs to be not just straight on or 90 degrees. BEP Marine Class T Holder. If you need a clean 3 terminal bus bar BEP makes one of those BEP heavy duty bus bar.

 

[Sams stock van]

@njvagabond , I've been trying to make sense of this AIC stuff for awhile. I'm not sure I've got it. I have two 100 amp batteries, rated at 100 amp max continuous load, 200 peak and 280 amp BMS disconnect. I put a 175 amp MRBF on each then cabled to the t fuse. Then a 350 amp t fuse to protect the downsteam cable, master switch and bus.