System Planning Check for Class C

[BlindBadger]

First time planning for a big power upgrade and we're pretty power hungry campers (smart phones, laptops, ipad, etc) even when boondocking (rare right now but planning on more next year and beyond).

I figured I'd see what the rest of you folks saw in case I'm missing anything in the diagram below and got the wire sizes right or close? (batterys will have terminal fuses on them).

Note: Phase 2 and 3 are next year likely...the rest is the main goal this year)



I got the lengths from measuring my planned locations for them...front dinette seat area is empty except for a bit of wiring from the external battery into the PDU mounted there and the existing chassis wiring for the alternator already comes right to the front dinette (behind the drivers seat) as the current 12v house battery is just below it in an outside tray).

I can either fit the MP1 under the back dinette (which has a bit of structure and the 30A recessed inlet/cable storage in there) or a MP2 in the back of the closet (which seems less than ideal for airflow/heat). Either location, I anticipate I'd need to cut and install a space for a fan and a vent at the top.

Option 1: Multiplus 1 in rear dinette (est 10ft of 2/0 from distributor to MP location when I measured...x3: pos, neg, gnd)


Option 2: Multiplus-II in closet (est 16-18ft of 2/0 from distributor to MP location when I measured...x3: pos, neg, gnd)


Also, anyone know why it seems like the MP1 is more expensive than the equivalent MP2 (the non 2x120 model) these days?

Solar stuff is all estimates right now based on what I measured I could fit, but I figured I'd plan ahead (also because I'm waiting to save up and hit the black friday sales at the end of the year for most of the purchases...so all I can do right now is dream and plan).

 

[scrubjaysnest]

Forgot the exact specs but a 3000VA multi plus is only good for 2400 or 2500 Watts. May not be an issue for you.

 

[Rocketman]

I Love your plan- so often when I review a plan the future plans are not there.

I see nothing wrong.
I do see a few things you may want to consider.

1. Get a Cerbo or Cerbo-S - this will tie all the data together, I would want a Touch. You will need communication wires between the various Victron items and the Cerbo. Note a BMV712 may make more sense than the Smartshunt because it is easier to run the included cable than getting a ve usb adapter and then a usb extension. Also turn on DVCC in the Cerbo (it helps with voltage drops - especially when all the Victron stuff is not all within a few feet of each other).

2. Instead if the Distributor bus bar - get the PowerIn bus bar and add fuses (see YouTube). It will save a few bucks.

3. Temperature sensor, if the Multiplus will be too far from the battery for the temperature sensor- get the optional one for the Smartshunt or BMV712.

4. A bigger 24/12 convertible may be cheaper than two…. But on the one going to the rig’s fuse box, I added a Victron smart BP65 (battery protect). I did this so if I left something on and the batteries were headed toward low voltage cutoff, all my loads would be turned off before the bms shut down- sometimes waking a battery up is difficult- it is easier if it never goes to sleep. They shutdown the loads at ____(user setable) volts, and then turn back on at _____(user setable)volts. They also make a handy on/off for the fuse box - (my old furnace sometimes needs power cycled).

5. Are there any draws on your chassis engine battery while sitting? I have a few small ones on my rig, so I added a single (smaller) solar panel and mppt 75/15 to the engine battery. Keeps it topped off when I am boondocking for long periods.

6. I went with a larger solar charge controller rather than several smaller ones - pros and cons to both. The 75/15 can only deliver 440w on your 500w panels (@24v). You may want to consider the 100/20 - to eliminate the overpanelling and capture the occasionally full watts from your panels.

If possible can you tilt your panels? It takes me just under an hour to tilt - it is amazing the increase in solar watts by tilting (if I am parked pointing east).

Good luck with your project!

 

[BlindBadger]

Forgot the exact specs but a 3000VA multi plus is only good for 2400 or 2500 Watts. May not be an issue for you.

Yeah, I went back and forth between this or the Quattro 5kva model (for over $1k more) but realized my usage is under 2000w for ac usage most of the time (microwave will surge me over just slightly depending on what else is running but that’s only for short periods) and will be even lower when I go with the 12v fridge (or a residential fridge and a small dedicated “dumb” inverter).

 

[BlindBadger]

I Love your plan- so often when I review a plan the future plans are not there.

I see nothing wrong.
I do see a few things you may want to consider.

1. Get a Cerbo or Cerbo-S - this will tie all the data together, I would want a Touch. You will need communication wires between the various Victron items and the Cerbo. Note a BMV712 may make more sense than the Smartshunt because it is easier to run the included cable than getting a ve usb adapter and then a usb extension. Also turn on DVCC in the Cerbo (it helps with voltage drops - especially when all the Victron stuff is not all within a few feet of each other).

Hey thanks for the feedback! I do plan on a cerbo (full version for the tank monitoring) but haven’t done a drawing for the data lines yet. Visio is simultaneously awesome and frustrating haha.

2. Instead if the Distributor bus bar - get the PowerIn bus bar and add fuses (see YouTube). It will save a few bucks.

Roger on the power in! Seems like a good use since I don’t think I’ll be able to easily find a 24v to 5v converter anyways for the distributor lights. I went back and forth so many times on a smart shunt vs a lynx shunt but just couldn’t really justify the extra expense in my mind (and need a battery cutoff switch still anyways, regardless)

3. Temperature sensor, if the Multiplus will be too far from the battery for the temperature sensor- get the optional one for the Smartshunt or BMV712.

Oh! Is battery temperature monitoring super critical? The shunt should be close but do I need a sensor to monitor temps for both batteries? (Or a third if I get one in the future?)

4. A bigger 24/12 convertible may be cheaper than two…. But on the one going to the rig’s fuse box, I added a Victron smart BP65 (battery protect). I did this so if I left something on and the batteries were headed toward low voltage cutoff, all my loads would be turned off before the bms shut down- sometimes waking a battery up is difficult- it is easier if it never goes to sleep. They shutdown the loads at ____(user setable) volts, and then turn back on at _____(user setable)volts. They also make a handy on/off for the fuse box - (my old furnace sometimes needs power cycled).

Oooh! I need to look into that. I haven’t had any problems with that so far but it’s good to be prepared!

5. Are there any draws on your chassis engine battery while sitting? I have a few small ones on my rig, so I added a single (smaller) solar panel and mppt 75/15 to the engine battery. Keeps it topped off when I am boondocking for long periods.

I haven’t had any problems so far…nothing really stays plugged in and it starts up strong every time even after staying a place for 4 days and I used the cigarette lighter to charge my travel usb battery (the max I’ve been out boondocking with the family)

6. I went with a larger solar charge controller rather than several smaller ones - pros and cons to both. The 75/15 can only deliver 440w on your 500w panels (@24v). You may want to consider the 100/20 - to eliminate the overpanelling and capture the occasionally full watts from your panels.

If possible can you tilt your panels? It takes me just under an hour to tilt - it is amazing the increase in solar watts by tilting (if I am parked pointing east).

Good luck with your project!

The solar stuff confuses me still with voltages and amps shifting all the time…we go a lot of trees places so I figure partial shading is probably frequent. Slightly bigger would work though! Going too big gets expensive for a single controller!

I wonder if I can make a rig that has adjustable tilting mounts. A problem for future me haha

 

[Rocketman]

Oh! Is battery temperature monitoring super critical? The shunt should be close but do I need a sensor to monitor temps for both batteries? (Or a third if I get one in the future?)

Battery temp can be super critical in the spring & Fall seasons (and winter too). Kinda depends where the batteries are. I would make sure to have a Victron temperature monitor on the battery. You only need one for your battery bank. The inverter comes with the cable - but if it too far away, then buy the one for the BMV712/smartshunt. Put it on what you think will be the coldest battery.

I would also make sure and buy batteries that have built in low temp protection. Belt and suspenders philosophy.

The solar stuff confuses me still with voltages and amps shifting all the time…we go a lot of trees places so I figure partial shading is probably frequent. Slightly bigger would work though! Going too big gets expensive for a single controller!

The easiest way to think about solar all all the shifting is focus on the watts, and the local effect of amps on in wires, and the Voc. Pull the info from the Victron data sheet.

So you have six 250w panels- total 1500w. You have several options to hook them up.

#1. 2s into mppt 75/15 -500w overpaneled into a 440w mppt - purchase three mppt’s.

#2 2s into a mppt 100/20 (this one handles 580w) - purchase three mppt’s.

#3 2s3p or 3s2p into a mppt 100/50. Overpaneled slightly 1500w into a 1400w mppt. With flat panels you will probably never get to 1400w. If you go with three or more in parallel you need to add fuses to each leg. They make mc4 fuses for that. For 3s need to verify that the Voc is ok. For 3p need to verify #10 is ok between combiner and mppt (if not upgrade to #8awg). Would need #6awg or #4 awg between mppt and bus bar.

#4 2s3p or 3s2p into a mppt 150/60 - it can handle 1720w - see wiring considerations in #3.

#5 The only other option is 6s into a 250/60 - but I wouldn’t do that one.

If you post the Voc, Vmp, and Imp from the panels we can figure out the most f any of the options are off the table.

Have you verified that you can fit the six 250w panels on the roof and you won’t have shade issues from air conditioners or brackets placement issues with skylights, vents, etc. The placing of panels is a Tetris issue that can be difficult on some roofs.

Also factor in the cost of the wiring and the cost of the VE.Direct cables for extra costs for three mppt.

FYI - after looking at it - my choice would be 2s3p into a 100/50.

I wonder if I can make a rig that has adjustable tilting mounts. A problem for future me haha

I made my own brackets and made it tilting array in one direction. (My rig pointed east, the panels tilt to the south).

I used eight alum “L” brackets 6” long 2”by 2” for the legs - used .125” thick and .1875” thick. Four attached to the corners of the panel, the other four attached to the roof. The hinge joint has a 1/4” bolt (with locknut) loosely fastened. The top has a 1/4” hand knob (from Lowe’s). I have 1-1/2”wide by about 14” to 18” long alum for the arms to raise it up. Originally used wing nuts to hold it on. (Now I have a nut zert tool and put the 1/4” threaded inserted into the arm which I use as the “nut” for the top end. I ended up raising one end a few inches to help the dirt to run off.



Anyway several different ways to do it.

Good Luck.

 

[BlindBadger]

Documenting partly for myself and partly in case someone tells me I missed something crucial...

Some changes to the earlier plan (much thanks to the suggestions here for a lot of this):

• Accidentally ended up with an Orion Smart 24/12-30a Isolated Charger for $55 (I think I got confused when I bid on it), but it got me realizing that my existing house battery is used to start the on-board generator (which doesn't directly recharge the start battery). So...thinking I may just keep that as a "buffer battery" and let it continue to power the 12v loads and just charge it off the 24v or future solar.
• I don't think I need alternator charging afterall. I have the on-board generator and will have plenty of solar in the future (all solar components below are still "planned" but not set in stone...all I know is that I want to fit as much as I reasonably can on the roof and go from there.
• Got the Inverter and PowerIn components cheap on ebay and a shunt as an "open box" to save a fair amount of money. Since I got them in, I did better measurements with the actual devices to stage it in and..I have even less room than I imagined. It's super tight in there.
  • With it being so tight in there, I relocated and replaced the panel to maximize contiguous space in the dinette (replacing the one with a built in lead-acid only converter to just a panel since the MP will handle the charging).
• Since I got the inverter, I decided to play with a Raspberry Pi I had laying around and Venus OS. I ended up really liking it...maybe I don't need a Cerbo-S (yet) and can just run off of that until I have a need beyond what it can do (I figure I'll need to upgrade if I get any other CAN devices since CAN adapters are super spendy for some reason). I got a USB MK3 to program the inverter anyways and one VE.Direct to USB cable isn't bad.
• Added a Smart Battery Protect 100 (same price as the 65 for some reason) to the 12v panel since I realized there's no battery disconnect in the factory wiring (there was a micro breaker mounted-ish in there but the mounts were broken and it was hanging by a thread...). It's in a spot with no inverter and power only flowing one way so I think I have it correct.
• I have Ruuvi Temp sensors for the fridge and put one in the inverter area to monitor temps and control fans I am installing into the base of the dinette seat right by the inverter to help with airflow. They paired perfectly with the Pi "Cerbo".

So...with that, the current plan being implemented: (Solar will be phase 2, 12v fridge will be phase 3). (Correction: MPPTs will either be two 150/35s or two 100/30s...I think I mixed them up. Will get exact model once solar happens)



I'll get some pictures of things as they sit posted as soon as I find some time to trim down the size (forum doesn't like the picture sizes currently and apparently doesn't automatically downscale).

 

[BlindBadger]

An example of how tight the space is...the inverter *just* fits (just a small gap on either side...might stuff some foam in there later if it ends up rattling but it's mounted pretty solidly). I have a vent to install on the rear of the dinette to exhaust heat and a pair of quiet fans to mount on the front-side ("underneath" the inverter) to push cooler air through.



Some fun silliness with Victron Power In's...one has openings for lights (like a distributor) and one doesn't. No circuitboard though so I didn't get lucky and end up with a mislabelled distributor haha.


I did end up making my own copper bar from some scrap 3/8" x 1" from the local metal shop (you can see them in the picture above). I tried the blue sea ML bars and it wouldn't work for both. A drill press and band saw is all that was needed to make custom sized bars that...are likely overkill but it's what the metal shop had handy.

Since there was no way I was mounting any MPPTs in the dinette with the inverter, I looked into the other seat and I think I can squeeze two of them above the charger on a board I made to mount things to. I roughly marked out the spaces and you can maybe barely see them in this picture I snapped while I was working.


If I didn't have to notch the panel to get around the existing wires, I could probably fit 4 of the small devices in there but I figured I shouldn't push too hard to squeeze too much in there when upping the controller size might be better. If I need to adjust in the future to a single large controller, I can move the charger over to one side...the board is plenty thick.

Hopefully, I'll get the Lynx and Battery Protect setup mounted today.

Oh that reminds me of a question!

Right now, the AC and 24v systems are completely isolated from the House 12v and Vehicle 12v systems. The only connection point between them is at the Isolated Charger (which is...well....isolated). The 12v systems are "grounded" to the frame (which I think I understand is really just a large bus bar to ensure everything can always find a way back to the battery negative in the event of a fault...right?).

For the question: Do I need to connect the negative bus bar on the 24v system to a path to the vehicle frame? wouldn't that effectively "unisolate" the systems? (not that it's that important to be isolated I think).

I ask this because my parents' truck camper has no such "ground" connection to the vehicle frame...it's all self-contained. But I want to double check with you all because I don't want to end up causing a problem in the system or burn something down because I never took any electronics classes.

 

[justinm001]

Couple things, You don't need multiple MPPTs if you can series/parallel them together. A larger MPPT is less wiring and easier but you can get a few more watts under shade or if they aren't layed out the same.

There's another post right above this one about frame grounding. You don't NEED to but its helpful just incase issue.

A cerboGX is much better than a PI. I have tons of applications and things running of PIs and they are never very stable. I haven't tried VenusOS on them but for a couple hundred bucks its well worth just getting the Cerbo. I'm not sure how you connect the PI to the vedirect cables for the shunt/mppt and the VEbus cables for the inverter. Also the Cerbo runs off 7-80v so you can plug right into the 24v and good to go.

Alternator charging is very very helpful. When you're on the road its very nice to know you're getting an additional boost of charge and not worrying about anything. Able to run the A/C and anything else so when you setup camp you're all good. I'm currently working on the prioritize solar over grid option and it'll keep my batteries 70% ish charged so when I leave my house the alt will charge up the batteries in an hour or so and i'll be good. Its gotta be much more efficient to use the drive engine's alt than also run a generator.

BTW the lynx distributor with the lights and board doesn't do anything unless you have the lynx shunt, when I have and even then its just lights. I believe if you had the board you could wire up 5v to get them to light up red/green if ok. You'd think it would alarm the lynx shunt if a fuse was blown but nope, apparently you need the Victron batteries and BMS to do that which no one uses.

 

[BlindBadger]

Couple things, You don't need multiple MPPTs if you can series/parallel them together. A larger MPPT is less wiring and easier but you can get a few more watts under shade or if they aren't layed out the same.

True...I find the larger MPPTs often cost more than a couple of smaller ones is why I looked at that. Maybe it's worth the simplified wiring to just have one large one though.

There's another post right above this one about frame grounding. You don't NEED to but its helpful just incase issue.

Hm, you have a good point. It's not far to run a quick wire over to the stud I have everything connected to on the 12v system (which is grounded to the frame).

A cerboGX is much better than a PI. I have tons of applications and things running of PIs and they are never very stable. I haven't tried VenusOS on them but for a couple hundred bucks its well worth just getting the Cerbo. I'm not sure how you connect the PI to the vedirect cables for the shunt/mppt and the VEbus cables for the inverter. Also the Cerbo runs off 7-80v so you can plug right into the 24v and good to go.

I have a little dc power supply for the Pi so it's connected to the bus bar for the batteries. I'll monitor and see if it's too unstable and if so, I should be able to swap it out for a cerbo. I think I even saw a "migrate to new GX device" option on VRM...

Alternator charging is very very helpful. When you're on the road its very nice to know you're getting an additional boost of charge and not worrying about anything. Able to run the A/C and anything else so when you setup camp you're all good. I'm currently working on the prioritize solar over grid option and it'll keep my batteries 70% ish charged so when I leave my house the alt will charge up the batteries in an hour or so and i'll be good. Its gotta be much more efficient to use the drive engine's alt than also run a generator.

I'm hoping solar will do a similar job while driving. I suppose we'll see though. The alternator charges the 12v battery currently from the factory wiring, just not the 24v bank. I'm worried I'll struggle to coordinate the charging from 24v -> 12v (when plugged into shore power or power from solar) and the charging from 12v to 24v (alternator)...don't want to create a loop where I just lose power from conversion losses. Probably have to do some programming to turn one or the other off/on depending on connections to shore power or engine running detection?

BTW the lynx distributor with the lights and board doesn't do anything unless you have the lynx shunt, when I have and even then its just lights. I believe if you had the board you could wire up 5v to get them to light up red/green if ok. You'd think it would alarm the lynx shunt if a fuse was blown but nope, apparently you need the Victron batteries and BMS to do that which no one uses.

Yeah...I figured lights would be cool but not for the extra money without a Lynx BMS (which does fuse monitoring I believe...and battery shutoff). Just...it's not $900+ cool (to me anyways).

 

[justinm001]

I'm hoping solar will do a similar job while driving. I suppose we'll see though. The alternator charges the 12v battery currently from the factory wiring, just not the 24v bank. I'm worried I'll struggle to coordinate the charging from 24v -> 12v (when plugged into shore power or power from solar) and the charging from 12v to 24v (alternator)...don't want to create a loop where I just lose power from conversion losses. Probably have to do some programming to turn one or the other off/on depending on connections to shore power or engine running detection?

A Victron 12/24v DC DC converter would pull power from your alternator and you just use the on/off connected to accessory. They even have smart ones that'll detect voltage.

We do mainly day trips and I've found that having 3k watts from the alternator allows us to run 2 ACs or heaters while driving or 1 and our electric water heater, all without pulling from batteries charge. The solar helps but many times were driving at night/am. It's so nice when boondocking to have everything up to temp and ready at 100% when you setup camp.

To charge the 12v from shore an AC to 12vdc charger makes the most sense. I leave mine on all the time. When the engines running the alternator is providing a higher voltage so its not used and when parked it's just trickle charging since the battery is full already. Covers us incase we leave the key on (slides only open/close with key on).

BTW your shunt has an aux voltage monitor designed specifically to monitor your starters battery voltage. This keeps it logged in VRM and you can set an alert if voltage drops below 12.8 or whatever. Id change the delay from 60 seconds to 300 or something just so no alarms if you're trying to start it.

The AC out2 on the MP is only on when connected by shore so you could use that as well.

 

[BlindBadger]

A Victron 12/24v DC DC converter would pull power from your alternator and you just use the on/off connected to accessory. They even have smart ones that'll detect voltage.

That's a good point...I'll have to add that into the future plans if I find I need extra power (though finding space for it might be the hardest part)

...
BTW your shunt has an aux voltage monitor designed specifically to monitor your starters battery voltage. This keeps it logged in VRM and you can set an alert if voltage drops below 12.8 or whatever. Id change the delay from 60 seconds to 300 or something just so no alarms if you're trying to start it.

I...don't know why I didn't think of this! I knew about the capability but didn't think to apply it to the gen/"12v buffer" battery. My starter battery is already isolated from the 12v house system in the RV and I've never run into any issues of it getting even remotely low, but using that monitor to connect to the positive terminal where the battery comes in to monitor the 12v battery makes a ton of sense! (another good reason to join the negatives to the frame connection on the 24v system as well).

The AC out2 on the MP is only on when connected by shore so you could use that as well.

Today, I found out I can turn AC2 on/off (it has a controllable relay) using assistants even without shore power...might offer some more options for me.

 

[justinm001]

I have a separate gen battery and added a BMV shunt for it then used the aux of that to monitor my chassis. The cerbogx system allows multiple shunts to monitor separate systems even. I then use my gen battery for all my tank heaters so I can monitor how much power they're drawing separately in winter. Also gives that additional redundancy so if everything dies the heaters are the last to die, then can flip off the breaker when winter's over.

For my AC2 I setup the assistant to turn it on only when batteries are above 50% charge. This way if something happens it'll shut down some loads like the washer/dryer, AC/heat, water heater but still keep the fridge on. Multiple times we've camped and have blown the pedestal breaker and had no idea until our battery was almost drained. My goal is to have the system setup smart enough to control itself.