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rjoustra avatar image
rjoustra asked

System overview

I would like to put this out to the community to see if I am missing anything in the way I currently have my system wired before I power everything up


12VDC side

Batteries

I have 10 battleborn lithium batteries divided into two banks interconnected with 4/0 cables.

Each banks positive goes through a 400 amp class t fuse then through a battery disconnect and over to a 1000 amp buss bar.

Each negative goes through a smart shunt and then to a 1000 amp buss bar.

Cables are within inches of being the same length slight variance due to placement of switches

Inverters 2 Multiplus 120v 3000

Each inverter positive and negative go directly to the the buss bars using two 2/0 for both pos and neg

Each inverter casing is grounded to the motorhome chassis local to the inverters

Cables are the same length

Charge controllers 100/50 x 4

Each pair of solar panels go through din rail pos & neg breakers to the PV input on the controllers over 10awg wire. The wire calculator I used was border line 10 or 12 so I went 10

Each output of the controllers battery side goes through a din rail pos & neg breakers then on to the buss bars over 6 awg wire

Charge controller chassis grounds are daisy chained and terminate on the motorhome chassis at the same point as the inverters

Cables are the same length.

Motorhome DC distribution

I am using the existing motorhome 3/0 inverter cables to supply voltage back to the original battery compartment where the original chassis ground is, dc distribution and alternator cables go to.

AC 120v 50amp

AC comes in from either shore power or the generator through the transfer switch over to a double pole 50 amp breaker then the ac is split into two circuits 1 going to each inverter.

AC1 out on each inverter is fed to another 50 amp double pole breaker and then continues to the main AC distribution panel for the motorhome each inverter feeding one leg of that distribution panel

AC cabling is within a couple feet of being the same length. Not sure how critical the symmetry is when running separate legs of the ac panel since the inverters will not share each other’s load.


Is there anything I am missing here?

Thanks Richard




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4 Answers
Kevin Windrem avatar image
Kevin Windrem answered ·

Awesome system you are putting together.

There's a multi-phase tutorial on professional.victronenergy.com/online-training you should watch, or have someone trained in complex systems do the final checkout and configuration.

You didn't mention control. Do you have a GX device (CCGX, Cerbo GX, etc)? If so, everything should be connected to this via appropriate cables (VE.Bus for the inverters, VE.Direct for the charge controllers and shunt)to . A GX device provides extremely helpful if not essential central control.

Use care in connecting an alternator directly to your DC bus. I'm not an expert on this but those that are recommend a DC-DC charge controller to avoid overcharging your batteries and/or destroying the alternator.

I don't think the system will properly manage separate shunts. The two battery bank negative leads should be connected to the battery side of the same shunt.

It's critical that the negative leads to all inverters are connected together BEFORE the VE.Bus cables are connected but sounds like you've done that.

Victron recommends a common battery bank for all inverters in the same system. That says, you should be connecting both battery banks to the same busbar. I can't tell for sure if that's what you are doing. If not, consider rewiring it for a common positive busbar.

All inverter/chargers in the system MUST be connected together via VE.Bus cables. This is needed

Before connecting any AC power or loads, it is essential to set up the system for split-phase operation. You will need to use VE.Bus System Configurator tool via a MK3 USB to VE.Bus adapter. You can not use VictronConnect for systems with more than one inverter.

RV power sources vary: Split phase 120/240 50 amp is common for larger RVs. It sounds like you are in this category. But even with that setup, you may encounter 120/208 50 amp (2 legs of 3-phase) and even a single 120 volt 30 or 20 amp receptacle. In order to handle these configurations, make sure you select L2 floating phase in VE.Bus System Configurator.


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rjoustra avatar image rjoustra commented ·

Thank you for the input.

Yes I have a cerbo gx connected to everything. (Sorry missed stating this)

Yes the 2 banks are connected to the one 1000 amp smart shunt

Yes everything is landed on the same bus bars.

I have purchase a Precision Circuits LIBIM 225 to mitigate burning up the alternator. It only allows charging of the lithium bank in 15 min increments and give it a break for I believe 20 min, and cycles like this the entire time.

Question?? I thought I would be able to use the cerbo to do any configuration changes once it is setup on the network and I am local on the same network.

Yes it is a large 45' Motorhome with a 50 amp split phase panel but only 1 item in the coach actually uses split phase. I figured I could toggle it back and forth between parallel and split phase but my intent was to run them in parallel so that if I am hooked up to 30amp 120v of the same phase being sent to both inverters they would both function normally. And if they are receiving two different phases I could toggle them fairly easily to split phase if I need to. I have heard that with them in split phase when connected to the same phase one will be inverting the entire time.

Question?? Grounding? The old house batteries are grounded to the chassis which once I use the old inverter wires running to the old lead acid battery location this will ground my lithium banks to the chassis as well as connect them to the DC distribution and alternator. My Inverter cases, my charge controller cases and my solar panel frames are landed on the chassis in a different location than the battery neg bus bar will be grounded too about 10 feet from the lithium bank. Is this going to cause an issue?

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rjoustra avatar image rjoustra commented ·

One other Question?

Is there a power up sequence?

Turn on the DC First or AC First.

I would connect loads last when powering up and first when powering down.\

Thanks Again

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rjoustra avatar image rjoustra commented ·

Ok so I have the system up and running albeit with a few headaches. I am looking at the cerbo GX read out and it says I am pulling 400w in DC Power Box. This increase when I am inverting and the more AC loads I run this seems to go up. I Literally have almost nothing on in the coach and what I do is all LED. And the darn Low battery warning came on and has been on. I am running 10 Battleborn 100 ah 12v batteries. Is this normal or am I leaking voltageSecond Image is when I transferred back to Shore Power. My Oasis Hydronic Heater may be using some of this 12v load for its pumps and such but why does it increase as I am inverting. Puzzled I am. Any Wisdom would be appreciated

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trip-tracks avatar image
trip-tracks answered ·

For such a large system, you should consider 24V or even better 48V.

The 48V particularly will reduce the cost of your system considerably as the 48V inverter/chargers are less expensive, the solar regulators only need to be 1/4 of the size of a 12V system and the cabling only needs to be 1/4 the rating.

Even a 24V system will reduce everything to half.

There are lots of positives. Especially with 2 x 3000 inverters that have the potential to pull 500-800A from the batteries - and you do need to combine the banks. A 48V system will typically only pull around 100-125A under full load.

Kevin has already covered the need for system monitoring - the Cerbo is the way to go - it will bring all the components together and also push data to the VRM and aprovide alarms and email notifications.

Have fun!

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Kevin Windrem avatar image Kevin Windrem commented ·

I agree about 48 or at least 24 volts. Then use a DC-DC converter to power the RV's DC loads. These will generally be small - under 50 amps probably, maybe even less.

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rjoustra avatar image rjoustra Kevin Windrem commented ·

Yes I would also lose the ability to use the assist from the house batteries when the coach chassis batteries get low for some reason. I have a switch on the dash that ties the two House and Chassis banks together in this instance.

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rjoustra avatar image rjoustra commented ·

Yes I had considered this and if this was an off grid system or a travel trailer or fifth wheel I would have absolutely gone that route but it is in my motorhome and to keep it simple since the chassis is all 12vdc that steered my decision. Thank you for the input.

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marekp avatar image
marekp answered ·

"Each inverter positive and negative go directly to the the buss bars using two 2/0 for both pos and neg "


I think there should be a fuse between positive buss bar and MultuPlus battery terminal.

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rjoustra avatar image
rjoustra answered ·

Ok so silly question here. Battleborn is willing to return the two 12 3000 inverters for two 24 3000 and I would need to order a DC to DC converter. Would it be acceptable to leave the 2 banks wired in parallel and series the two banks together as shown here in my drawing or would I need to pull them all out and completely start over? Essentially wiring together 2 500ah Batteries. I know this will totally solve my voltage drop issue but not my overloads as I believe those are caused by the temp of the units (although I only saw the battery temp in the data so not sure where that is being measured) and them handling less watts which would not make any difference in the 12 or 24 volt models. Battleborn also had me set my low battery pre alarm at 12volts vs 13 which should help eliminate the low bat warnings especially after I go ahead and add the second positive and negative cables to the banks.

Is the benefit of going 24v at this point worth changing everything around removing and reinstalling both inverters and adding the DC to DC converter especially since I am seeing no DC ripple even as configured and discharging the batteries to their 1000ah level and seeing at the battery a voltage of 12.5. If all things being equal and the drop remains about the same throughout the the discharge cycle that would put me at a inverter voltage of about 12v well above my 11.5 cut off and adding the additional cables will only improve that scenario? Sorry I meant to move that last negative on the right up to the top battery.


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Joshua Warren avatar image Joshua Warren commented ·

I haven't seen any mention of this yet so maybe I missed it (or other measures have been taken to mitigate it), but having ten batteries in parallel means that your mean time between failures is likely to be relatively low. And when one battery fails it may begin to eat the others; I guess this may not be that big of a deal if the system is either in a state of discharge or charge and not being left sitting idle like an off-grid install might be. But it's something to think about if there's a possibility of returning some/all of this stuff (perhaps with a restocking fee) and using fewer larger-capacity batteries. For example, I have two 300 AH Victron lithium batteries.

If I had to do mine all over again I'd be looking at the 24V Multiplus and Tesla 24V modules. More of a science project but also far more AH/$, and AH/lb.

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rjoustra avatar image rjoustra Joshua Warren commented ·

Jersey Dirtbag

I don't think returning the batteries is an option the freight alone would be hefty if they charged me no restocking fee so I would be using the same just configured shown above if possible and I would not be downsizing my charge controllers either as that ship I think has sailed (no boxes or anything since we are full-time there was no room to store) So the inverters are the only thing on the table.

I guess my question to both of you is as I stated, change or work through the issues with the voltage loss which again I believe (and I will test for sure today) never really dropped below 12v in its current configuration so additional cable will improve that.

Kevin

My thought on the two banks was that it divided the load of each bank capable of carrying 440 amps max on the cables, so if the inverters both started pulling 6000 watts peak load the 500 amp load would be evenly distributed over the two banks and the 4/0 cables feeding them. When I thought of wiring them as one bank I assumed I would need to fuse it for for the peak load and increase the interconnect cables to handle that much load. This may have not been the best plan? Just like paralleling the Inverters onto one AC Line they share the load so I applied that to the batteries when deciding what would be best. This is obviously something I could change just not sure how much cable length I would save in doing so and would my 350amp disconnect handle 400 amps continuous and 6000 peak.

So for argument sake could I combine the banks into one by moving the short positive off of one fuse and the short neg off of the shunt land those on the neighboring bank to create a single bank keeping the one 400 amp fuse and the one 350 amp disconnect. This would not shorten anything going to the batteries (18" interconnect cables and the 2.75' positive to fuse and 2.75' neg to shunt, but would eliminate the second disconnect and the cables for it. Would this save me anything do you think. I suppose I can test it by shutting down one bank to see if this is an improvement and put a 4000w load on only five batteries. I assumed my results would be the same, but I will check.

Let me put together a more accurate layout of my batteries to paint a clearer picture for y'all to help with.


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Joshua Warren avatar image Joshua Warren rjoustra commented ·

I don't think there's any good way to connect ten batteries in parallel; even though the batteries are in two physically distinct "banks," they are banks of batteries in parallel, and the banks themselves are in parallel, so I would figure that as long as the cable runs to each battery are equal and kept to a distance such that the voltage drop is acceptable (I don't really know what "acceptable" is for a 12V system, to be honest) that this thing should work. Putting the batteries in series will create its own issues with balancing and the need for a step-down converter(s) for 12V devices (plus the difficulty of using the system as a backup engine start battery) so it's not clear to me that changing over to that configuration at this point is going to increase your chances of making things "just work". A better use of time and resources would be reconfiguration your space to get the inverters as close to the batteries as possible; 20 freakin' feet of cable seems like a whole lot. If they have to be that far I'd probably start looking at 2x 4/0 AWG runs all the way from each "bank" to each inverter. Disconnects are going to get pretty squirrelly...probably have to tie the pairs of 4/0 into a bus bar and connect the switch to the bus bar with copper bar stock and then split it on the other side of the switch the same way.

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rjoustra avatar image rjoustra Joshua Warren commented ·

Had a disturbing instance happen today. I had left the inverters in charger only because of the crazy power here at our park which I thought would be a good solution for bad power. However in the 115 degree heat wave the power cycled on and off like three times sending the inverters in to an error state leving the coach without power. Are there any setting I can modify that would allow the inverters be passive. They won't handle switching the load when running at even 1800watts in this heat or at best they were able to switch it once. Can I set an assistant to wait a few minutes before turning ac back so incase there is a drop out like I saw it will allow the mains to switch back on?


My poor dog was not happy today. She was a little warm after 4 hours no power.


Thanks Again


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Kevin Windrem avatar image Kevin Windrem rjoustra commented ·

115 Yikes! I'm guessing shore power was being pushed to the limit from everyone's air conditioner. Probably brown out conditions.

I added a bypass switch to run loads off shore power directly if the inverter fails. There's no way to do this internally because of the internal architecture - the inverter/charger core is always connected to the load.

Not sure about assistants delaying return to shore power. Someone else may know.

You can switch to "Inverter Only" which rejects shore power and runs loads on the batteries. You can't get that from the stock Mobile Overview page but can in the Multiplus Switch menu. I've modified my Mobile Overview page extensively and added the Inverter Only selection.


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rjoustra avatar image rjoustra Kevin Windrem commented ·

That was the other thought. I was planning on putting in a rotary transfer switch so one position power goes through the inverters and the other disconnects out going power and passes it straight from shore to my ac panel while also powering up the inverters so the batteries stay charged. I figured as long as the transfer switch disconnects the out going loads from the inverter I should be able to run the inverters at the same time they just won’t be seeing an current draw except to charge the batteries. If that makes sense? Figured it best not to back feed AC to the output side of the inverters. Lol

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Kevin Windrem avatar image Kevin Windrem rjoustra commented ·

Yes, exactly.

3 pole-double throw (need to switch the neutral also)

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rjoustra avatar image rjoustra Kevin Windrem commented ·

I did order a 3 pole but I had not considered switching the neutral or ground for that matter as it is continuous throughout the entire system. Is the neutral switched inside the inverters? If so then I understand why the need is because if you ever switch off the inverters you would lose your neutral and your circuits would become wildly out of balance. Perhaps I will bring all 4 over from the disconnect on the line side of the inverters to the disconnect that is on the load side of the inverters parallel the ground and switch the neutral with 2 legs. Thanks

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Kevin Windrem avatar image Kevin Windrem rjoustra commented ·

Yes, the AC input relay disconnects both the hot AND neutral. So your bypass needs to switch both hots plus the neutral (3 poles). Also, the "ground relay" in the Multi connects the neutral from the inverter core to safety ground when the AC input relay opens so the neutral is at ground potential.

You should NOT switch the safety ground ("PE"). All safety grounds will be bonded together.

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rjoustra avatar image rjoustra Kevin Windrem commented ·

Yes I will go ahead and switch both legs and the neutral as well as bond the two disconnect grounds through that same 6/4 cable since that ground for the disconnects flows through the inverters. Just in case either of those were to come loose or I need to remove the inverters for some reason, essentially creating a jumper cable for the ac as a whole. Thanks for the advice...

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gbntx avatar image gbntx rjoustra commented ·

The bypass switch comments got me looking up how to do it.

This diagram's wiring may work for me.

mortonsonthemove-solar-phase-3-1

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rjoustra avatar image rjoustra gbntx commented ·

Yes exactly only mine has 2 multis I will be switching. Thanks for the diagram from the Mortons. https://smile.amazon.com/gp/product/B07H5GZ53G/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1


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Joshua Warren avatar image Joshua Warren Kevin Windrem commented ·

When you say "Multiplus Switch menu," are you talking about the Virtual Switch tab in VE.configure? If not, what/where is this functionality located? I'm new to this equipment and haven't heard of it.

I just enabled the "show boat and motorhome overview" functionality (I wasn't aware of this either, so thanks), but can you elaborate on what you mean by having "modified" it? I don't see any options to modify anything; it's simply an on/off button.

Thanks for sharing your knowledge.

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rjoustra avatar image rjoustra Joshua Warren commented ·

My cerbo doesn’t have show boat or motorhome box or I have not found it, but I can switch to inverter only in the inverter menu.

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Kevin Windrem avatar image Kevin Windrem rjoustra commented ·

Once you enable Show boat & motorhome overview as Jersey says, is shows up as an additional page in the rotation.

The Multiplus Inverter Only selection is in the Multiplus menu.

The modifications I made to the Mobile Overview page were done by rewriting the code. You can see the system in INVERTER ONLY in the AC MODE selector at the bottom.

The enhancements requires replacing a file and adding another. Details are here:

https://github.com/kwindrem/GuiMods

The tanks display that shows gallon is yet another modification that started to support SeeLevel tank sensors. Details of that mod here:

https://github.com/kwindrem/TankRepeater

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Joshua Warren avatar image Joshua Warren Kevin Windrem commented ·

Very cool. I have Victron batteries and a VE.bus BMS so the Venus's control over the inverters is disabled. Hmm...

Is your code written in Python?

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Joshua Warren avatar image Joshua Warren rjoustra commented ·

It's under "Display and Language."

Can you screenshot your "inverter only" option? I don't see that in mine.

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Kevin Windrem avatar image Kevin Windrem commented ·

BattleBorn would be better positioned to answer the question of series connecting the banks or parallel connecting pairs of batteries in series. I really don't know which is best.

I honestly don't know if switching to 24 volts is worth it at this point. You'd still have issues with distance between batteries and voltage monitoring (the shunt in your case). True, the voltage drop would be less if the same area of copper was used from your existing system. In the drawing above, you did cut the amount of copper in half so same voltage drop but that's half as a percentage of battery voltage.

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rjoustra avatar image rjoustra Kevin Windrem commented ·

Okay so here was a test I did and these were my readings both at the beginning and end of the test. I thought it went well and will only improve a bit more with the addition of 2 more 4/0 cables on each bank at the opposite ends which will decrease my voltage drop as I believe you both have suggested.

L1 up to 2150 watts with no overload

L2 up to 1705 watts with no overload



Batteries pulling around 5000 watts 389.5a DC


Readings at the beginning of test


Inverters

L1 12.64 - 12.61

L2 12.65 - 12.62


Batteries read 13.08 - 13.13

0.05 volt variation at almost every point in the bank.

Terminals directly connected to fuses are the lower readings


Buss bar reads

12.72


Readings at the End of test


Inverters

L1 12.15vdc

L2 12.16vdc


Battery Voltage

12.48vdc


Buss Bars

12.22vdc


912 ah used before I hit my low battery warning. Which I didn’t get down to the 12vdc that battleborn suggested I reprogram and were unsure why they programmed it for 13vdc originally.

The system must warn you a little before you hit that voltage is all I can figure because as you can see I hit 12.15 and 12.16 at the inverters and higher voltages everywhere else it could measure.


No DC ripple in VRM data


A couple of Overload warnings towards the end all seemed justified based on temps of the inverters figuring each would only give about 2000 watts and we breached that a couple times during the test.


1 temp warning on L1 towards the end in the last 10 min of the test.


So do you think she is a keeper? lol


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Kevin Windrem avatar image Kevin Windrem rjoustra commented ·

I'd add the second 4/0 from each battery bank. Those two paths calculate to 0.17 volts of drop each so that's 0.34 volts of your ~0.5 volt total drop (battery to inverter). So you should see a total voltage drop reduce to around 0.25 volts with those extra 4 cables.

With the cable distances you outlined, I don't see any way to improve the actual voltage drop to the inverters, but getting the shunt closer to the batteries would provide a better system view of BATTERY voltage. That would require combining the separate paths through fuses and disconnect switch WITHOUT reducing the amount of copper in these runs. Not sure it is worth it if you can accept a less accurate battery voltage indication while under load.

The inverter specs seem to accept a wide voltage range so I don't think they will suffer from the voltage drops you are experiencing.


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rjoustra avatar image rjoustra Kevin Windrem commented ·

I am going to add those cables for sure and I thought keeping my shunt powered at the mid point in the two banks, then I have the multi volt sense at the beginning of the bank which I can see in the inverter info on the cerbo and using the mid point voltage monitor on the shunt for my buss bars. This should give me a good idea where all the voltages stand at any give time. I think its the best I can hope for without rethinking battery positioning which would make horrible use of the little space I have. We do live full-time in the motorhome so space is at a premium.


I want to thank both of you for sticking with me and working through the issues and educating me along the way to better understand my system and why it was doing some of the things it was doing.

Thanks Again

Richard

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Kevin Windrem avatar image Kevin Windrem rjoustra commented ·

Getting the shunt's positive connection closer to the batteries would be a great idea but since you have two banks with separate disconnect switches you can realistically monitor only one bank. Connecting the shunt's positive lead to both battery banks creates a connection between the two banks that can't begin to handle the possible currents should you open one of the two disconnects or one of the fuses blows. That was the main reason I was looking for ways to make it one bank of 10 batteries.

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rjoustra avatar image rjoustra Kevin Windrem commented ·

Strongly agree that would be a bad idea. lol. My hope is that having the extra 4/0 cables will narrow that 13.08 - 13.13 variation I was seeing at different points on the batteries.

Question? You both pretty much understand how I have things wired so is a second set of 400a fuses necessary close to the inverters. In Victrons wiring unlimited they don't show one in the examples being on both sides of the disconnect although they do show it in the schematics.

My thoughts are unless the inverters started to go into an overload I will be hard pressed to blow my battery fuses as it is, since the load is divided amongst both banks. I would have to see over 800 amps before my fuses come into play and the 4/0 are rated at 440a and the 2 2/0 combined are rated for 650a so they should not be in danger of ever melting down before the battery fuses blow and shutdown the inverters. Correct?


The only thing I could potentially see is maybe one inverter having a catastrophic overload and burning up the other one before a fuse blew? Thoughts?

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Joshua Warren avatar image Joshua Warren rjoustra commented ·

The inverters are each only capable of charging at 120A, so as long as each individual cable (i.e., one of the 2/0 even if you're using 2x 2/0) can handle that maximum charging current, I don't think you need a fuse on the inverter side. I guess the counterargument would be that some kind of internal failure in the inverter could cause all of the AC input to be converted to DC and thus far exceed the current capacity of the inverter wiring, but that would also have to coincide with an external short circuit (otherwise the battery voltage would prevent the runaway charging current) between the battery fuse and the inverters.

Personally, I think the probability of such an occurrence is vanishingly small, so it's not immediately obvious to me why your inverters need their own DC overcurrent protection (provided the conditions I mentioned above are met). I used the Lynx distributors in my system which require fusing so my inverters are fused but I don't really think it's necessary for our applications (which are very similar).

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Kevin Windrem avatar image Kevin Windrem rjoustra commented ·

A fuse close to the inverter is recommended to guard against faults inside the inverter. These fuses should be sized to blow with excessive inverter current. I can't recommend one way or another about adding fuses here but do believe your concerns are valid.

The fuse close to the battery is to protect the system wiring from shorts or other faults. However your fuse is a LONG way from the batteries and a short in those cables between the batteries and fuse is at least as likely as faults after the fuse. Placing these fuses as close as possible to the batteries improves safety and reduces fire risk. That said, there will always probably some wiring that is before the first fuse.

It's especially important to guard against possible shorts in the cabling before the fuses. Anywhere the cables pass metal supports or other sources of a ground connection, including running along with the negative battery cables, additional insulation should be used with fasteners to prevent vibration that could erode insulation.

The batteries do have overcurrent protection but check with Battle Born to determine what happens after a large overcurrent. The batteries could reset and apply voltage again only to create another fault. Rinse and repeat until the protection circuitry in the batteries fails.


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rjoustra avatar image rjoustra Kevin Windrem commented ·

One quick question about adding these second set of 4/0 cables to each battery bank.

Since one pair on each bank will be shorter and one pair longer than each other will this create an imbalance in the draw on the bank with the current taking the path of least resistance?

And if I make both sets the same length am I defeating the purpose of adding the second set of cables at that point?

Thanks again

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Kevin Windrem avatar image Kevin Windrem rjoustra commented ·

Can't say for sure either way but cables should be the same length for best balance across the bank.

You are already somewhat compromised by the daisy-chain parallel cables (rather than star) so it is really hard to say what will provide the best balance. You might even try moving the cables from the end to the second battery on each end.

Experiment with the system under a significant load. Measure each battery voltage and adjust cable placement for best balance.

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