23' Travel Trailer Build and Help

[John A]

I'm planning my first solar/battery system for my travel trailer and have learned so much from this site and really appreciate the efforts of everyone and their openness to sharing knowledge.  I am convinced that building it around the components developed by Dacian is the way to go and have accumulated most of the components.  I hoped that I could get feedback on my layout as as this is my first attempt at doing something this technical with regard to electrical components and the logic around turning stuff off/on.  I've copied as much stuff as I can from the dedicated forum members and wanted to say thanks.

I was having trouble figuring out how to post this so please forgive me if I did not start a new thread.

Thanks

JA

[Dacian Todea]

John,

All seems to be correct with small exceptions.

The place for the 400 fuse after the shunt as shown is the correct one and please do not add a fuse on the negative side.  You will not be able to combine the orion and the Victron Multiplus remote ON/OFF as they are diffrent with Victron Aux inputs designed for 5V only and the Orion has a 12V (battery voltage remote).

On top of that the Orion will need to have his own separate remote as you only want that to work when the engine is ON so it will be ignition signal 470Ohm resistor then EXT IOx+ then the EXT IOx- will connect to H pin on the Orio-TR that way both the ignition needs to be ON and the SBMS0 needs to accept charging for the Orion-TR to work.  You can add a manual switch in series with the EXT IOx if you want to manually disable charging.

I see some DC loads that are connected directly to battery (not sure what those are but the SBMS0 will not be able to protect the battery from over discharge in that case).

Other than that it seems correct.

[John A]

Thanks for the feedback Dacian.  I'll move DC loads connected directly to the battery so they can be controlled by the BP.  

I don't understand the Orion Smart Tr DC-DC wiring logic.  I re-read the Victron manual and it is not much help (at least to me).  I'll search the forum to see what more I can learn on this and to see what has been done.  

Thanks

John

[John A]

I've learned so much from this forum and wanted to thank everyone for their contributions.  I'm getting pretty close to installation and would greatly appreciate any feedback on the proposed build.  Paul, thanks for all of your help, especially with the schematic!  

[Will OBrien]

Looks pretty good.

Keep in mind that the AC2 on the multiplus is only energized if you have shore power.

[Dacian Todea]

John,

Yes all seems to be correct. The only warning is that if you are not careful the Always ON critical loads can over discharge your battery

On Friday, March 19, 2021 at 12:16:01 PM UTC-6 John A wrote:

[Casey]

Why no fuse on the negative side?  I did not realize this and have a 750A main fuse connected to the battery negative.  It should never risk being blown as there are also smaller fuses on the positive side, but seemed wise to have a main batttery fuse as well, and this isn't possible on the positive side as the shunts need directly connectted.

I have placed my PV breakers between the panels and DSSR20's instead of between the DSSR20's and batttery - is this okay?

[Dacian Todea]

Why do you think is wise to have a battery fuse on the negative when there is fuse or breaker on the positive side. The shunts can be put inside an insulated box and very close to battery+ so they can never be shorted to battery negative.

You can have PV breakers before DSSR20 for easy disconnect of the solar array but they will have no role as a overcurrent protection device just as a easy disconnect in case you want to work on the circuit or test something or maybe disconnect them in case of severe thunderstorm.  Where fuse or breaker is really needed is immediately after the PV shunt and before the DSSR20 Battery+ connection.

[Dave Festing]

Hi Dacian,

Where fuse or breaker is really needed is immediately after the PV shunt and before the DSSR20 Battery+ connection.

Does this fuse protect the battery in case something fails in a DSSR20?

If you use a really "light' wire for DSSR20 negatives, which I didn't, then they might become the "fuse".  If you lose control on a failed DSSR20 would you expect it to fail in such a way that PV current would keep charging then potentially over-charge the battery?

[Dacian Todea]

It mostly protects the wire between the PV shunt and the DSSR20 as if that wire gets shorted to GND (battery negative) there will be large current from battery so overcurrent protection is required.

DSSR20 has no way to fail inside to generate any significant current to GND.

There are two 12 Ohms resistors in series and a small diode inside the DSSR20 to GND so no significant current can be expected there.

DSSR20 is well designed not to fail but if it fails (I seem only one failed because it was installed outside and water got inside from the rain) then yes it can potentially overcharge the battery.  That will be true of other solar charge controllers if they fail in that particular way.  If you want extra level of protection in that unlikely case the DSSR20 fails in this way then you can use a trip shunt breaker controlled by the EXT IOx set as type 5 then if any cell gets to 3.75V (default secondary level for LiFePO4) then EXT IOx will trip that breaker to stop all charge sources and trough a separate path if you want also all loads.

[Casey]

Dacian,

On the positive side, connected to the load shunt, I have 2x 400A fuses for two Quattro 5000s, a 250A fuse for an BatteryProtect 220A (then two 100A fuses on the output side), and a 50A fuse for an Orion 12V 70A converter.  If everything is used to peak capacity, then there can be close to 800A going to the inverters alone, over 1000A combined.  I have the battery bank connected via two 4/0 cables, which have an 880A limit.  Also, since the BMS can only measure up to 750A, I don't want load to ever exceed that.  So having a main breaker seems like a good idea.  When I was designing stuff, I found a schematic somewhere that somebody posted of an SBMS0 & Victron setup (with more Victron components than I care to have), and they had a shunt for the Victron infrastructure on the negative battery connection along with a main fuse, with the usual positive stuff for the SBMS side of things as well.

I suppose I could also output from the shunt through the 750A shunt and then into the other fuses (as Dave has done with his 400A fuse) but having it on the negative side seemed to be cleanest and gave me a point to connect everything together without needing another busbar.  The shunts also are one of the only parts of my setup which are lacking insulation or protective covers, and they require airflow.  I will likely still build some sort of protective cover for them though.  If it's important to not have a negative fuse there, I am willing to update my design to omit it and do things differently as recommended - I'm trying to get everything as correct as possible but am still learning.  What is the problem with having a main fuse on the negative side?  I'll start a new thread with more information and pictures of what I've got going on soon so as to not distract this thread too much.  I was hoping to get a little bit farther along first but it's probably good to start getting feedback sooner than later...

Dave - thank you for posting your schematic.  It's always really helpful to see others designs and learn from them and any feedback given!  My system looked a lot like yours in the past, although I based mine around a 24V battery bank, and I've been scaling up recently.  If you haven't invested too much yet, I'd definitely recommend considering using 8s instead of 4s for a 24V system.  This will save you some money on the Multiplus, wiring, lugs for the wiring; and make the wiring easier to work with as well (since for the same wattage, half as much amperage is needed, meaning wiring (both yours and within the inverter) can be thinner/cheaper.  You also need less DSSR20's for the same total wattage of panels.  You can use a 24V-to-12V converter for 12V loads (I use a Victron Orion (non-isolated) for this, and have the ability to run 24V stuff directly  (e.g. you can replace your 12V water pump with a 24V one).  It may or may not make sense to fit 60-cell panels on your roof, but they are more space-efficient than 36-cell panels if you can manage it (I have 6x 60-cell panels on a 16' trailer).  If you can't fit 60-cell panels, you can still use 36-cell panels in serial pairs (thus pairs of two, and maximum 4 total per DSSR20).  Your uses may be different than mine, but I personally found only having 600W of solar panels and a 12V system pretty disappointing (this was the size of my very first solar system, though it was not SBMS-based).  If that is indeed sufficient for your needs, then the Multiplus 3000 seems like too big of an inverter.  Dacian posted on another thread that battery discharge should ideally be limited to 0.6C, which would be 168A in your case, or about 2000W.  Given that you also have some DC loads (do you actually need the 220A BatteryProtect though versus the 100A or 65A model?), you likely want to limit your AC to less than 2000W.  If you move to 8 battery cells, either in a 24V 8s or 12V 4s2p configuration, then you'll double that limit to ~4000W.

I think the Multiplus Compact doesn't have the aux ports for the two-signal BMS assistant to work.  It may be worth considering a standalone charger and smaller simpler inverter that a single on/off can work with.  The Multiplus is a great unit, but pretty costly.  You'll also need to buy a Victron MK3-to-USB dongle (another $70) to program it to support the dual remote capability.

[Casey]

Dave - what's the purpose of that customized disconnect switch you have in front of the Multiplus?

I'd also consider not having those "critical" loads connected directly to the battery.  The BatteryProtect remote can be overridden easily should the need arise, but if your battery is that low, you won't be wanting to power anything if you can help it.  You could use two EXTIO ports to control your loads - one to disconnect non-critical loads (Multiplus, BatteryProtect) at, say, 10 or 20% SOC, and one to disconnect another small BatteryProtect connected to critical loads at 0%.

[Center Right Proud American]

> Dave - what's the purpose of that customized disconnect switch you have in front of the Multiplus?

That is a combination disconnect/pre-charge switch that allows the front-end capacitors on the inverter to be charged in a more contained manor.

https://diysolarforum.com/resources/inverter-disconnect-switch-with-precharge.60/

[Dacian Todea]

Casey,

I think the 5000VA inverter can handle that for at most a few minutes and sure 10000VA only for a few ms. So with say 25V battery is just 200A for 5000VA thus 400A will be for both inverters.

I doubt you will get anywhere close to 750A for more than a few ms with your setup but even if you exceed that for a few seconds that is not a problem for SBMS0 it will just not be able to display more than 750A

You can not have a single point to disconnect on the negative side it will need to be two separate disconnects one for Loads and one for charge sources. But likely you will have that on positive as it is needed one for load and one for charge sources thus it will not make any sense to also have them on negative.

[Dave Festing]

Hi Dacian,

Thank you for the explanation.