Proposed Wiring Diagram to add a Victron Hybrid Inverter

[Crash]

Let me start by thanking richm, centex, defenestrator, brian b-p, rubicon327, semievolved, tdf-texas, and many others for your suggestions on power system modifications and installing a hybrid inverter.

Based on this, here is a wiring diagram showing some planned changes to our 21NE. Would be great to get additional suggestions and any concerns- thanks!



Note this diagram indicates Victron Multiplus 3000 - but also wondering about the 2000 to limit DC current draw.

The update would involve:

1. Disconnecting the charger in the WF-8955
2. Removing the Go Power Inverter
3. Replacing the two 6V batteries with a BestGo 12V 400Ah
4. Rewiring the EMS to go to Victron Mulitplus 2000 AC input
5. Rewiring the panel main to the Victron AC 1 output
6. Attaching the GoPower Solar Charger to the BestGo
7. Attaching the Victron Inverter to the BestGo

Some questions:

1. I may need to limit how much DC current the Victron can draw. Anyone have experience doing this? I'm not even sure it is possible. Also may potentially need to replace the 200A fuse and wires.
2. Will the GoPower PWM-30-UL solar controller on the lithium setting play nicely with the BestGo battery? The GoPower has an absorption phase at 14.4V for 30 minutes every morning and 14.0 float. According to tech support at Electric Car Parts, those voltages should be fine. They also recommended disconnecting the charger when it reaches float - but is that necessary as the controller will stop pumping current once 14V is reached, right?
   
3. I saw a recommendation to put a residual current device (RSD) before the panel. But I haven't seen that in other people's modifications. Thoughts?

For reference here is my guess at the current wiring diagram based fully on the work tdf-texas has done. I still need to confirm everything.

[Centex]

Noting that the Victron Multiplus incorporates transfer switch functions internally I'm having trouble following why and how the retained OE transfer switch and Inverter Panel function in this scheme. I see the note "Leave transfer switch with plug as a backup" but it's still not making sense to me.

I've not studied the Multiplus operation in detail but most all-in-one inverter/converters default to AC-bypass mode when connected to either shore-power or a generator, so that's your 'backup' for power to AC devices and outlets.

I'll study this more but perhaps you could give me a boost by explaining a but further how you envision that aspect of the system functioning, and how you ensure all is 'safe' with any combination of accidental plug-in errors (mistakes happen in the field if opportunity presents IME; my intuitive (but sometimes wrong) alarms are ringing upon seeing two AC-input plugs and two transfer switches in this scheme)?

Originally Posted by Crash

I may need to limit how much DC current the Victron can draw. Anyone have experience doing this? I'm not even sure it is possible. Also may potentially need to replace the 200A fuse and wires.

If I understand correctly, you are looking at a load-management issue here. IF your inverter is capable of over-drawing the amp-rate your battery will safely support for a given duration, and you have loads on the inverter which would cause that, then yeah it's a problematic risk to your battery. AFAIK you manage that by managing loads, and/or installing resettable breakers that trip to protect the battery.

Protection of the BestGo and its internal fuse may involve a 'tiered approach' using both very fast-blow "Type T" fuses and slower-blow breakers or fuses to cover the range of short-duration high-amp peaks and longer-duration lower-amp loads that may be encountered. Note the BestGo specs for different current limits at different durations of discharge.

Originally Posted by Crash

I saw a recommendation to put a residual current device (RSD) [sic - should this be "RCD"?] before the panel. But I haven't seen that in other people's modifications. Thoughts?

"RCD" seems to be a term used outside of the US to describe a safety device that functions similar to what is known as a GFCI+AFCI in the US (?). Got any links to the recommendation you've seen for use of "RSDs"?

[richm]

Originally Posted by Crash

1. I may need to limit how much DC current the Victron can draw. Anyone have experience doing this? I'm not even sure it is possible. Also may potentially need to replace the 200A fuse and wires.

Good point. I'm planning to do something similar.

The bestgo is rated to discharge:

• ≤ 200 A @ 60min,23°C,30%≤ SOC ≤100%
• ≤ 400 A @ 15s, 23°C, 30%≤ SOC ≤100%
• ≤ 650 A @ 0.5s, 23°C, 30%≤ SOC ≤100%

The Victron Mulitplus 12/2000/80 manual lists:

• Cont. output power at 25ºC / 77°F 2000VA
• Peak power 3500W
• Recommended DC fuse 300A

Looks like the recommended 300A fuse matches the peak load 3500W / 12V = 290A. But that continuous load is way above bestgo's 200A limit. So, yea, you are right about the need to limit the current the victron can draw.

The BMS in the bestgo should shut down when over-current occurs, to protect the battery. However, it's entirely possible repeated over-current could degrade the BMS. At full load, bestgo components (BMS, wiring) may generate significant heat. Heat could easily damage the mosfets.

One option could be to match the Bestgo specs to the DC breaker's data sheet. The data sheet should specify how quickly it will trip for higher currents. One could make sure that it trips below the bestgo's limits above.

I'm not sure I'd completely trust even this. Those limits are at 23°C. Depending on how the Bestgo is mounted, there could be heat dissipation issues.

So I'd think about three things: a fast blow circuit breaker, maybe silicon insulation on wiring between bestgo and Victron, and finally, ensuring adequate air circulation around all of them and/or de-rating the circuit breaker. And better yet, maybe ask Bestgo or seller for recommendations. Your concern seems completely valid.

[rubicon327]

Crash...sorry if I jump around. My bandwidth is a little low right now to take this all in but hope these questions and comments help.

Why the need for the 3000W inverter? I would stick with 2000W unless you have an application requiring that type of power. I would be concerned with drawing too much current on the Bestgo lithium repeatedly.

Have you seen AM Solar’s wiring diagrams? They helped me tremendously. You will notice they have the inverter behind a main input breaker. I could be wrong but I think best practice is to have your main breaker be the first thing power lands on after an EMS. Right now if you have a problem you have no way of shutting off power to the Victron unit. https://amsolar.com/victron/inv-vt-2000

Have you seen the diagrams by Centex and myself? You could wire the same but will need to rearrange so only loads fed by inverter are in a sub panel. Are you purposely trying to feed all AC trailer loads including fridge and hot water heater?https://www.escapeforum.org/forums/f...tml#post380809

To provide the best tow vehicle charging for the lithium and protect your alternator you will need to add an isolated DC-DC charger on the 7 pin charge line.

[Crash]

Attached is Rev 3 of the wiring diagram.

The main changes are:

• Added a new AC main breaker. This is based on AM Solar's full pass through approach. Thanks to Centex and RichM for the questions and suggestions on breakers and battery current. Thanks to Rubicon327 for the suggestion to look at the AM Solar diagrams.
• Added a DC-DC charger to protect the tow vehicle alternator from the lithium battery draw. Thanks to Rubicon327 for this suggestion.
• Added a 200A thermal breaker. This provide extra protection for the battery in the event of excessive current draw. This was a suggestion from North Arizona Wind & Sun.

It would be great to have any feedback on the wiring - especially on the DC-DC charger wiring.

Thanks!

----

For context and to answer some of Centex's questions, here is a little bit of insight into this design. From my perspective one great aspect of the AM Solar full pass through approach is that I really don't have to do much rewiring. More importantly since it is AC wire it provides a lot of flexibility on relocating the battery and inverter/charger to the back of the trailer for weight distribution. Moving weight from the front to the back was my main objective.

Note that in this configuration the whole WFCO panel effectively becomes a sub panel and essentially all of the existing wiring just works. The WFCO breakers are an easy way to turn off AC draw for the fridge and water heater if we need to. But more on that below.

There are a couple of benefits of using a hybrid inverter/charger. Because it does the charging for lithium batteries it mitigates the need to spend money upgrading the charger in the WFCO panel for lithium. More importantly using a 3000 watt hybrid inverter (vs a normal 2000 watt inverter) gives us the option of running everything off a 15A shore power circuit with the hybrid inverter covering any spikes. This would give us a lot of flexibility on where we can stay; especially visiting relatives.

The big question remaining was around limiting battery current draw.

In looking at our current boondocking AC power usage, our typical draw on the inverter is below 2000 watts sustained (~167A DC) with intermittent spikes that are well below 3000 watts (~250A DC). Our Honda EU2200 covers us - and it is ~187A DC equivalent.

Even with inefficiencies and derating the BestGo battery can handle this.

But I still wondered about managing the draw if someone forgets and has everything on. RichM had the good advice to ask more about this.

In discussions with AM Solar (AMS), Electric Car Parts (ECP), and North Arizona Wind & Sun (NAWS), all of them indicated that oversizing the inverter and limiting load is fine.

ECP said customers frequently put a 3000W inverter on the 12V 400Ah battery without issues. As RichM indicated, ECP confirmed that the BMS in the BestGo battery should shutdown in the case of excessive current draw. I have an email into BestGo to confirm this.

But just to be extra safe NAWS suggested adding a Bussman 200A thermal breaker as that would provide some nice extra protection. Although you want to be careful about derating when the trailer is cold.

Stepping back, the other option I considered was putting the BestGo battery in the back and pulling expensive DC wiring up to the existing GoPower inverter. With this option you also have to upgrade the DC shore charger. And in either case you have the DC-DC isolation for the tow vehicle due to the lithium battery. This proposal costs more but I like the simplicity and benefits we get from the hybrid inverter/charger with full pass through.

[richm]

The changes make a lot of sense to me, and it looks a lot like what I'm planning for a 5.0.

One additional thing that I'm still wrestling with is air flow for the inverter. I don't think it's been discussed very much. One might consider ways to ensure that the inverter's fans will exchange air with the cabin. One option would be ducting one end of the inverter to the cabin, similar to the WFCO charger's ducting.

[Centex]

Originally Posted by Crash

Attached is Rev 3 of the wiring diagram.

I'm still not understanding the role of the retained OE Transfer Switch / Inverter Panel and wiring through those components, can you help me understand that rationale?

I do understand not wanting to do much re-wiring, but you are in fact already and inevitably doing a lot of new wire-routing with this mod.

Simply removing the OE transfer switch and inverter panel (moving it's AC outlet branches to branch breakers in the WFCO main panel) strike me as an opportunity for huge simplification of your overall 'utility bay' wiring, elimination of two substantially bulky unnecessary items, with attendant improved free-space for new-component installation and air circulation if nothing else.

Your WFCO panel, with use of tandem ('half-width') CTL breakers has plenty of space to accommodate those outlet branches as independent circuits just as they are with the inverter panel.

It's one-time effort to remove those two unnecessary components with a long-term payback of not having to work around them and not having any concerns about the many many unnecessary wire connections within them. In my book, every wire connection in a circuit is a point of potential problem over the long-haul (loosening / corrosion> resistance / discontinuity> heat / arcing> =problem) so they should be minimized whenever possible as a matter of 'best practice'.

Just for your re-consideration, I'll drop it now, I promise!

[Crash]

Originally Posted by Centex

I'm still not understanding the role of the retained OE Transfer Switch / Inverter Panel and wiring through those components, can you help me understand that rationale?

I do understand not wanting to do much re-wiring, but you are in fact already and inevitably doing a lot of new wire-routing with this mod.

Simply removing the OE transfer switch and inverter panel (moving it's AC outlet branches to branch breakers in the WFCO main panel) strike me as an opportunity for huge simplification of your overall 'utility bay' wiring, elimination of two substantially bulky unnecessary items, with attendant improved free-space for new-component installation and air circulation if nothing else.

Completely agree - the OE transfer switch and the subpanel could be removed. I may do that at a later point in time.

[Crash]

Originally Posted by richm

The changes make a lot of sense to me, and it looks a lot like what I'm planning for a 5.0.

One additional thing that I'm still wrestling with is air flow for the inverter. I don't think it's been discussed very much. One might consider ways to ensure that the inverter's fans will exchange air with the cabin. One option would be ducting one end of the inverter to the cabin, similar to the WFCO charger's ducting.

Agree on the concern over air flow for the inverter.

There is somewhat more room under the bed compared to under the dinette. My plan it to try the installation and carefully monitor the temperatures to see what happens in practice.

Also when it is cold we will need to keep the batteries warmer - so air exchange with the main cabin may be essential for that as well.

[rubicon327]

Originally Posted by Centex

Simply removing the OE transfer switch and inverter panel (moving it's AC outlet branches to branch breakers in the WFCO main panel) strike me as an opportunity for huge simplification of your overall 'utility bay' wiring, elimination of two substantially bulky unnecessary items, with attendant improved free-space for new-component installation and air circulation if nothing else.

Your WFCO panel, with use of tandem ('half-width') CTL breakers has plenty of space to accommodate those outlet branches as independent circuits just as they are with the inverter panel.

After looking at this again last night that was also my thought. With the position of the Victron Multiplus you only need the main panel. It might be difficult for those branch circuits to reach the WFCO directly depending on how they are routed and the position of the branch panel. At a minimum I would get rid of the transfer switch and wire straight to the sub panel.

Crash - I would also consider a main disconnect means on the DC wiring to the Victron unit. Would be nice to be able to cut power quickly if there is a problem at the Victron unit or battery. Refer to AM Solar schematic.

[Crash]

Originally Posted by rubicon327

Crash - I would also consider a main disconnect means on the DC wiring to the Victron unit. Would be nice to be able to cut power quickly if there is a problem at the Victron unit or battery. Refer to AM Solar schematic.

Agree this is needed.

By the using the Bussmann 187 circuit breaker it can act as both resettable fuse and battery disconnect switch.

So the 187 would replace the fuse holder, fuse, spare fuse, and disconnect switch in the AM full pass kit. That should work, right? AM Solar is working on a quote for me - and they are checking on this.

[rubicon327]

Originally Posted by Crash

By the using the Bussmann 187 circuit breaker it can act as both resettable fuse and battery disconnect switch.

So the 187 would replace the fuse holder, fuse, spare fuse, and disconnect switch in the AM full pass kit. That should work, right? AM Solar is working on a quote for me - and they are checking on this.

Possibly. The 187 does go up to 200A. It has a note though about not using it as a switch in applications with high inrush currents. Not sure what "high" means. I bought my inverter kit from AM Solar so I have the Blue Seas Mini high current disconnect switch and a 250A Class T fuse. AM Solar will work with you to get you what you need for your exact application.

https://amsolar.com/rv-battery-accessories/93s-mini
https://amsolar.com/rv-inverter-accessories/95f-clst

[Centex]

Originally Posted by rubicon327

Possibly. The 187 does go up to 200A. It has a note though about not using it as a switch in applications with high inrush currents. Not sure what "high" means.

FWIW I've interpreted that to suggest one shouldn't use the 187 to directly switch a device that has an inrush current higher than it's nominal rating but still under the area of it's 'trip vs time curve'.

If, for example in the case of a 200A 187 breaker, one has a device that presents a running load of <200A, but has a momentary inrush of >200A when switched 'On', using the 200A 187 to actually switch that device 'On' should be avoided as a regular practice. But, if that device has it's own On/Off switch, and that switch is used to energize the device after the 187 breaker is used to energize the circuit, all should be good (the 187 breaker does not experience the 'high' inrush during the 187 breaker's switching operation).

Methinks this all relates to potential contact arcing during the breaker switching action and the detrimental effect of that over the long term on contact longevity / breaker reliability.

Just for your consideration, YMMV.

[richm]

If a breaker or switch between the battery and inverter is periodically switched it off and on, here's something to consider.

There are capacitors in the inverter. Each time power is switched on, the switch's contacts will spark as the inverter's capacitors charge. The spark could potentially degrade the switch's contacts. In addition, the high current involved can potentially damage mosfets in some BMS.

There are exceptions for certain batteries and inverters. Lead acid batteries won't have this issue because they have a high internal resistance. However, it's generally true for LiFePo4 batteries and larger consumer grade inverters. One way to confirm the issue is, touch power leads the first time the inverter is connected, and observe a spark.

The spark can be avoided by instead, first connecting briefly through a 25 ohm 50W power resistor. This will pre-charge the capacitors.

https://youtu.be/ZlrtmJRfSP8

There's a discussion of this on the DIY Solar forum.
Here's some discussion of a precharge device.

[Crash]

Quick update on the project. Except for the new AC wire, all the parts have arrived from AM Solar and Electric Car Parts. Will start the install tomorrow.

Thanks everyone for all the feedback to date!

Based on communications with AM Solar, Electric Car Parts, BestGo, and Eaton/Bussman, I’ve learned a couple of things:

• AmSolar indicated that the DC/DC charger is not necessary in this configuration. More information below.
• Electric Car Parts and BestGo both indicated that the current version of the BMS in the BestGo 12V 400Ahr battery will shut off when there is significant over discharge; this is in addition to shutting off on under and over voltage. The battery is further protected by a fuse.
• Eaton/Bussman agreed that the 187 series 200A DC breaker has reasonably conservative timings that match the BestGo battery limits and it should not trip based on current and planned usage patterns even when thermally derated. Note that this effectively limits the pure inverter function to 2400W sustained. In hybrid mode the inverter can still provide 3000W or more intermittently even on limited amperage shore or generator power.

I’ve updated the wiring diagram to reflect these changes and show what will be in the back and the front after the cable pulls and install.

My last remaining question: is the 50 amp fuse needed on the new 6 AWG cable from the battery to the thermal breakers and trailer connection? Each line out from the new battery cable is protected by a fuse or thermal breaker of 50 amps or less. So, while an additional fuse won’t hurt, it doesn’t appear to be needed.

The main objective was to move the batteries to the back and support lithium batteries. With this approach there are the additional benefits of the hybrid power boost and that all the existing wiring just functions as is. Over time I can remove the existing transfer switch and subpanel and maybe add the DC/DC charger but nothing is urgent.

Consequently, this is now a relatively simple installation that matches the AM Solar Full Pass Kit with the 187 in place of the fuse and switch.

Regarding removing the DC/DC charger, in discussions with Garret (the very knowledgeable owner of AM Solar), he indicated it isn't necessary in this case. He explained that because of the low voltage cut off of the battery BMS and the voltage drop between tow vehicle the 7 pin connector there won't be a lot of current going to the lithium battery - he estimates less than 18A and probably 10A at best. So while there isn't an issue drawing too much current from the tow vehicle he noted that there are two downsides to not installing the DC/DC charger: (1) if the tow vehicle is left attached and idle for a long time the lithium battery will experience drain from the tow vehicle as it loses charge and (2) the tow vehicle won't be able to fully charge the lithium battery.

[Brian B-P]

Originally Posted by Crash

My last remaining question: is the 50 amp fuse needed on the new 6 AWG cable from the battery to the thermal breakers and trailer connection? Each line out from the new battery cable is protected by a fuse or thermal breaker of 50 amps or less. So, while an additional fuse won’t hurt, it doesn’t appear to be needed.

The 50 A fuse in the 6 ga wire doesn't make any sense to me where it is. There should be a fuse as close as possible to the battery to protect from overcurrent in case the 6 ga wire is shorted to ground (presumably due to accidental damage).

[Crash]

Good point Brian. I agree. This morning I was reviewing the recommendations for fuses/breakers and saw several recommendations to keep it within 18" of the battery - and noted that the ABYC boating certification requires it within 7".

[Crash]

Thanks everyone for all the suggestions and comments.

The system is installed and working.

The ability to limit shore current to 14A and have Power Boost has been handy already with the AC and fridge running and using a heat gun.

Did two Victron adjustments: turned on the UPS function and set the float voltage down to 13.9 V from 14.0 that way the GoPower solar controller keeps the battery at 14 V and powers the DC circuits. Initially the Victron was maintaining the float using grid power and the solar controller dropped to 0 amps.

So far temperatures are quite reasonable. Will continue to monitor this.

Last steps are to mount the battery (top side up), do a little cable clean up in back, and take out the GoPower inverter.

[Mjschwart]

Any updates here? I’ll likely go down this same route and will remove the sub panel if possible and wire everything to the WFCO…. Or rip out the WFCO and go with new AC panel and DC distribution.

[Crash]

Originally Posted by Mjschwart

Any updates here? I’ll likely go down this same route and will remove the sub panel if possible and wire everything to the WFCO…. Or rip out the WFCO and go with new AC panel and DC distribution.

The upgrade has been working great.

I just disconnected the DC power unit in the WFCO. Makes sense on removing the sub panel. I'd be interested to know what you end up doing.