question

rjoustra avatar image

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




solar
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4 Answers
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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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.

rjoustra avatar image rjoustra jersey-dirtbag ·

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.


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.

rjoustra avatar image rjoustra jersey-dirtbag ·

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


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.


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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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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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.

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


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.


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

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.

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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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

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.

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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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.

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.

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.

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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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?

A cautionary note about putting Multis in parallel (same phase input) and supplying independent circuits or bus bars. In parallel operation, the Multis expect their output line conductors to be bonded together downstream; i.e., they have continuity. If you have power assist enabled in such a scenario, then when the load exceeds the input current limit, both inverters will briefly step up their voltage to overcome the instantaneous demand. But if their outputs are supplying separate circuits or bus bars that do not have continuity, what will happen when the load exceeds the input current limit is that the circuit or bus bar without the increased demand (imagine an air conditioner overcoming its locked-rotor amperage) will actually experience an overvoltage fault and the inverter on that phase will likely shut off completely.

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

Cerbo can't do any inverter, MPPT or shunt configuration. Some is possible through VictronConnect but not a system with multiple inverters. You need the Windows tool set for this, and will need the MK3 to connect your laptop to VE.Bus.

The wiring for true parallel and split-phase configuration is totally different. This is not something you want to deal with every time you park your RV. The multi-inverter configuration tool provides a selection so that the phase of L2 floats relative to L1. This should accommodate any shore power you will encounter: 120/240 (legs 180 degrees apart), 120/208 (legs 120 or 240 degrees apart) or single 120 volt (0 degrees between the two legs).

Yes the grounding may be a problem. I would not tie the starter batteries into the house array to minimize this and also because the two battery banks will be slightly different voltage. Also make sure your interface to the alternator is isolated between alternator and house.

Again, look at all the Victron documentation and tutorials on multiple inverters. There are a lot of useful information there and it'll save you headaches later.

There are notes on the Victron site also about powering up the inverters. There is always a surge when the capacitors across the DC inputs charge whether that surge comes from the batteries or from the AC input. If the batteries are not connected, expect an AC input breaker trip the first time power is applied. The surge of DC current with discharged caps is amazing. BIG sparks. You can weld your DC switches. Plan on a soft start that applies DC voltage through a resistor to charge the caps slowly. BattleBorn has a unit that handles the soft start also.

Battle born indicated I did not need the soft starts. Would the best bet be to charge the capacitors via the AC for the first time to avoid damaging the battery disconnect switches? I can deal with having to reset the AC breaker once or twice while they charge.

Being that the lithium banks are tied to one bus bar will they not combine to establish there combined voltage. And yes the battery voltages for both the sealed lead acid and the Lithium will be at different voltages but these are only combined using the LIBIM 225 for a matter of seconds to for example start the generator or the coach in the event one is depleted and basically act as an improved bi directional relay. Battle born has indicated that the charge settings for their lithiums will be ok for the chassis batteries There have been many Motorhomes that have used them in this way and precision circuits has designed this module for this express purpose in motorhomes.

Should I be worried about the inverters charging the chassis batteries as well after the feed back battle born and precision circuits has given me on this?


Thanks Again for all your time.


Precision Circuits Inc

page1image148876336 page1image148854928 page1image148852896 page1image148679296

The Lithium Battery Isolation

Manager (Li-BIM) isolates the two battery systems, chassis, and coach, in a motorhome. This prevents loads in one system from discharging both. It also connects the two battery systems together during charging. Both batteries are charged if either is being charged. The coach battery is charged while driving and the chassis battery is charged while plugged into Shore Power at a campground.

Key Features:

1. 160amp & 225amp continuous models available

2. Runs cooler using less power
a. Draws no current in ON or OFF state b. Excellent for Solar Panel use

3. Microprocessor based
a. Monitors battery state over longer periods of time b.

4. Not simply voltage dependent

a. Approved for Battery Compartments
b. Ignition Proof, SAE J1171
c. Waterproof, IEC 60529, IP66 IP67, ASTM B 117 96 Hours Salt Spray

5. Charges
a. Lithium Coach Battery from Alternator
b. Lead Acid Chassis Battery from Coach Charger

6. Isolates Batteries to prevent discharging or overcharging of Batteries

7. Prevents
a. Equalization cycles from Damaging Chassis Battery

b. Annoying clicking of Isolator Relay
c. Overcharging of Coach Battery during long drives
d. Overcharging of Chassis Battery during long stays

8. Provides Emergency Start with Dash Switch. Optional power connection for existing applications, and ground connection to allow Emergency Start of either battery.

9. Weighs under 1 pound

The Li-BIM monitors the battery voltage of both the Lead Acid Chassis and Lithium Coach batteries over long periods of time. If it senses a charging voltage, it connects the two batteries together. If the charging system is drastically overburdened, the batteries will be isolated, however, if the Li-BIM sees a long term charging of both batteries it will allow the batteries to remain connected and allow the charging system to do its job. Once the batteries have charged for one hour, the Li-BIM will isolate the batteries to prevent overcharging, and will only reconnect the batteries for charging if one of the batteries drops to approximately 80% charge, and the other is being charged. This long term monitoring of the batteries prevents the annoying relay clicking that exists in simpler isolation modules today. The Li-BIM does not guarantee 100% battery charge, but prevents harmful battery charge levels.

Also if I have read that I can't have just one configuration that will accommodate 50 amp 180 degree out split phase and 30amp 0 degrees out without having the secondary inverting switch to inverting only because it does not recognize the fact that it is not getting that 180 out split phase leg instead getting the same leg as the primary or master inverter. Is this true or is there a setting I can use where both will work without changing profiles in the event we are at a park with only 30 amp single phase. I have watched a video of someone that does make this change when needed and it is really only a few settings and loading saved config files to make the change and since my inverters and my cerbo are totally accessible this would not be that big of a deal but way better if one setting would do both.


Really do appreciate you taking the time to answer all my newbie questions.

I am an electrician in Automation systems by trade but this is a whole different animal.

The multi inverter tutorial doesn't go into the L2 "floating" details. In the 180, 120 and 240 selections, incoming power is rejected if the phases don't align as specified. Floating allows the phases not be locked to one of those 3. So for sure, it would accommodate split-phase and 2 legs of 3-phase.

Someone with experience with this configuration needs to confirm it would also accommodate 0 degrees between legs.

True parallel operation is a completely different configuration and requires precise matching of input and output cable lengths in order to balance currents between the units in parallel. You really are not running the two units in parallel since they'd be going to different legs in the AC distribution panel. I'm not sure what the units would do if they saw large current difference on the AC ins and outs. So you might be into large switches on the inputs and outputs to switch them from split-phase to true parallel wiring in addition to reconfiguring the units. Failure for any physical wring to track the configuration could result in damage to the inverters so this really isn't something you want to do on a daily basis.

I suppose if there is anyone else in the community that could answer the configuration setup so it would work seamlessly if they were receiving split sphase 180 out which would be most common or both being put on the same phase due to the use of a 50 amp to 30 amp adaptor or dog bone as it's called which bridges the single phase and sends it over both legs of the panel without sending one inverter into inverting mode all the time.


Question? Can you tell me if you believe that starting the inverters on AC versus potentially damaging my 350 amp Blue Sea battery disconnects would be the best plan?


Thanks

I think Victron recommends powering the inverter(s) on battery first. That way they can be configured before connecting any of the AC wiring.

I built a manual soft start for my 12-volt Multi Compact. I used a 30 watt 5 ohm resistor and a small switch to charge the capacitors before closing the main DC switch. This same resistor and switch also discharges the caps after disconnecting the battery. This should work for any 12 volt setup. Charging time will vary depending on the size and number of inverters.

I think you'll be OK powering up from AC with no battery connected. But I'd power one up at a time and do as much configuration on that unit as possible.

You can run the configuration tools in demo mode and save files which you can then load into each Multi when it's first powered. Doing this all on a bench setup is much easier than after final install.

I have tried every possible variant of phasing in order to get a pair of Multis to accept both 180-degree and 0-degree offset phase inputs, and have been completely unsuccessful. It is possible to get them to accept 180 and 120 degree phase offsets, but the only way to get them to accept 0 degree offset is to put them in parallel configuration. And if you do that with separate downstream bus bars and use power assist, you'll get overvoltage faults like I described in my other comment.

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

Firstly, can't see your pics. Please check the links.

The AC loads showing up as DC loads could be a number of things, but we'd need more information about how you configured everything and what kind of shore power (120, 120/240, etc) you're providing. For example, if you configured the inverters separately (using VE configure for each individual inverter but without using VE.bus System Configurator to configure the group) and are providing only 120VAC input that the inverter on L2 is inverting from the batteries to supply its AC loads (with the batteries, in turn, being charged by the inverter on L1) and hence the Cerbo could see those AC loads as DC because it's unaware of the second inverter.

Also, did you charge those batteries up individually before putting them all together in parallel?

rjoustra avatar image rjoustra jersey-dirtbag ·

Inverters are configured in split phase 180 120/240. Each inverter feeds its own leg of the AC Breaker Panel (Inverter 1 Load1 Inverter 2 Load2) They are being fed by two banks of 5 Battle Born batteries each of equal cable lengths tied to a common set of buss bars (everything DC lands on these buss bars Smart Shunt 1000a, 2 Multi 3000 Inverters, Cerbo GX, and all the DC loads of the RV). Both inverters cable lenths on the DC side are within a few inches of each other due to disconnect placement next to each other and the AC cable is about 3 feet longer for the L2 inverter. Power comes in from a Shore or generator through a transfer switch over a 6/4 cable through a 50 amp circuit breaker then separates into 2 6/3 cables one feeding each inverter then out of each inverter is a 6/3 to another 50 amp breaker where they are combined back into a 6/4 cable feeding the RV breaker box. In both of the pics above the DC loads never changed in the RV. Let me know if any more detail is needed. I would send screen shots of the config but I have not figured out how to look at it without being connected to the inverters just yet. LOL Newbie Here. I know I am running with the UPS and Dynamic current limiter both on. The battery setup is per battle born I did not change those settings. And I remember it was split phase 1 AC input. If you can explain how to look at the config file I have for them without being connected that would be great or I will connect later and take screen shots

Can you try reposting the images? The links are coming through as broken. In the meantime I'll give it some thought and see if anything comes to mind. Your system is very similar to mine and I'm also a n00b but I've had some success in figuring out seemingly magical combinations of config parameters that make things work more-or-less as desired.

rjoustra avatar image rjoustra jersey-dirtbag ·

Also why am I getting Low Bat and Overload warnings on both L1 and L2 when on shore power. The AC that was running all night is on L2 but everything else in the RV was basically dormant.

What shore power connection are you using right now? Is it 120/240 or just 120?

Send a picture of your inverters so we can see the lights on the front. If the second inverter did not switch over to shore power and is inverting then the consumption of that AC will exceed the charging capacity of the first inverter and hence your batteries will discharge. You will not be able to run an AC on L2 with 120V single phase input continuously with your configuration due to the fact that after conversion losses the amount of continuous power available on L2 is probably going to be under 1200 watts. I got around this by rigging up a 20A light switch that allows me to switch my second AC over to L1 when I'm on 120V single phase input; in that configuration I can run the pair of air conditioners simultaneously and short duration loads are supplemented by power assist from the inverter on L1.

rjoustra avatar image rjoustra jersey-dirtbag ·

I am showing L2 in the Shore power box on GX display. When I have none it is blank would it not be blank for L2?

That sounds right, but pictures are worth a thousand words. A screenshot of your Cerbo's remote console (or a cell phone pictures of the Cerbo display itself) would really help. And if you can provide a VRM link that would be good too.

What DC voltage and state-of-charge are being reported at the time when it's throwing low battery warnings?

rjoustra avatar image rjoustra jersey-dirtbag ·

Here is a minute ago


And another low bat and overloads to follow

That looks good, now pull up VRM and check out SOC and DC voltage along with VE.bus state. See pic below. I believe those low battery warnings should show up as "faults" and if we have SOC and DC voltage at those points in time we can start to get an idea of what's happening.

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rjoustra avatar image rjoustra jersey-dirtbag ·

Inverter 2

Inverter 1

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rjoustra avatar image rjoustra jersey-dirtbag ·

Also this morning inverter 1 is chattering for 30s and then back to normal but when inverting its not at all. When it does it it is switching back and forth to inverting it seems. Shore power is steady

rjoustra avatar image rjoustra jersey-dirtbag ·

Now that they are both under a load there is now switching or chatter earlier there was almost no load on inverter 2 and about 600w and inverter 1. Nevermind I lied inverter 1 just chattered

My best guess is the clatter is the AC input relays opening and closing. If so, there is something going on that is causing one or both of the Multi's from accepting incoming AC. I believe both AC inputs will be dropped if either one is rejected.

Is the voltage dropping when AC input current draw increases? This could cause the input to be rejected, but then when the current is zero the voltage goes back up making the incoming AC acceptable again.

A diagram could be very useful in helping us to diagnose your problems.

The history provided by VRM would also be useful. It's difficult to provide the detail necessary with screen shots. You can share your VRM portal to us via a URL you can post here. Otherwise, we need to see a minimum screen grabs of the following parameters zoomed in where a fault has occurred:

  • Grid voltage/current
  • AC load voltage/current
  • VE.Bus System DC voltage/current
  • VE.Bus Warnings and Alarms
  • Inverter mode
  • Battery voltage/current
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rjoustra avatar image rjoustra jersey-dirtbag ·

I have switched them to charger only to avoid the chatter. Figure it can't be good on the contacts

rjoustra avatar image rjoustra jersey-dirtbag ·

Couple Pics of the install

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Nice looking system. Your wiring is certainly a lot cleaner looking than mine.

Is the input coming from the power grid or a generator? My system sometimes behaves oddly when using my truck's (supposedly pure sine) inverter as AC input.

And regarding the rogue DC current, can you confirm that all of your batteries' paths to ground goes through the shunt? I.e. there's no other grounding? I only ask because if somehow one bank had a ground upstream of the shunt then when the batteries were first tied together and slight charge imbalances were evening out you could wind up current flowing through the shunt and then back through the other ground thus creating the illusion of net current flow out of the batteries.

Just saw the VRM pics; I'll review them now.

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I do not think it is a good idea to install those MPPT-s one above the other.

The top one will likely overheat.

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