diy solar

diy solar

Deciding on Victron MPPT for my RV?

Firstascent

Solar Enthusiast
Joined
Mar 7, 2020
Messages
265
Hey friends,

I’m currently looking for suggestions on which Victron MPPT to get in terms of size and options, this will all be installed in my fifth wheel toy hauler.

what I have so far:
16 280ah LFP batteries, will be 24v
Batrium BMS
Victron Cerbo GX

next items to purchase:
4 405w solar panels
victron MPPT

im still on the fence on whether I’ll go all 4 in series or a series parallel with 2 each, I know that will play into the size as well. I think series is best of both worlds in case I encounter shade.

can anyone help me understand if I want/need one of their MPPT’s with the VE.CAN option? Only certain sizes offer that I believe.
thoughts on terminals or MC4 connectors on the MPPT?
can I temporarily wire the battery bank for 12v and still use the same MPPT, even if it’s not as efficient?
if I wire my panels in series parallel I believe Victron’s site recommended the smartsolar 150/70
i don’t plan to ever expand to more than 4 panels.


here are the specs of the panels I’m looking at:

405w
Vmpp - 41
Impp - 9.89
Voc- 49.4
Isc - 10.51

thank you all!
 
Batrium BMS? Sweet.

You want the units with the VE.direct. I have the 250/100 and a CCGX. You'll need to purchase a VE.direct cable to connect the MPPT with the GX.

405 * 4 = 1620W

1620W/24V = 67.5A

You will not go all 4 in series on any but the most beastly Victrons with 250V input. Voc is compared to SCC max PV voltage. You'd be at 200V with 4S.

To go 2S2P, you'd need a 150/70 to ensure you capture all available, but the 150/60 will still get darn near the full power when the battery is at or above float.

If budget and shading is a concern, 4P with a 100/50 would capture up to 1400W of your array.

Any of those units work with 12/24V.
 
Could the GX and the SCC communicate over bluetooth? That'd be an option that wouldn't need cabling between the two.
 
Could the GX and the SCC communicate over bluetooth? That'd be an option that wouldn't need cabling between the two.

To my knowledge, no.


"The hardware of the Venus GX and Octo GX includes a built-in Bluetooth Smart chipset which hasn't proved satisfactory. Bluetooth Smart for GX devices is coming soon but will not use built-in chipsets."

The Cerbo can be accessed via VictronConnect, but I don't see that it can be used for networking.

The bluetooth network is "VE.Smart" and I don't see any options for that kind of networking. A Smart Battery Sense can be bluetoothed to the MPPT, but even if the MPPT is VE.Direct to the GX, the temp data is not available to the GX.
 
Batrium BMS? Sweet.

You want the units with the VE.direct. I have the 250/100 and a CCGX. You'll need to purchase a VE.direct cable to connect the MPPT with the GX.

405 * 4 = 1620W

1620W/24V = 67.5A

You will not go all 4 in series on any but the most beastly Victrons with 250V input. Voc is compared to SCC max PV voltage. You'd be at 200V with 4S.

To go 2S2P, you'd need a 150/70 to ensure you capture all available, but the 150/60 will still get darn near the full power when the battery is at or above float.

If budget and shading is a concern, 4P with a 100/50 would capture up to 1400W of your array.

Any of those units work with 12/24V.
Thank you! Quick, simple, to the point. All makes sense.

I’m leaning toward 2S2P with the 150/70.

yeah the Batrium is pretty sweet, although my testing with it so far is minimal since I don’t have a way to charge my batteries yet. The flexibility is amazing though and allows me to do any battery config I want.
 
If budget permits, the 150/70 is definitely the better choice.

Are you going to have a Multiplus or Quattro eventually?

Here's my VRM link to Honey Badger Ranch (HBR):


I've been astounded at the unmitigated awesome oozing from VRM.
 
If budget permits, the 150/70 is definitely the better choice.

Are you going to have a Multiplus or Quattro eventually?

Here's my VRM link to Honey Badger Ranch (HBR):


I've been astounded at the unmitigated awesome oozing from VRM.
I mean p, budget is always a consideration, but I’d rather get what I want and do it right the first time without regrets if it takes a little longer to build :)

Originally I was going to go with the Quattro, because I do have a generator in the RV as well. But I’m trying my best to hold out for a 120v version of the Multiplus-II. I’ve been emailing Victron for months, they say it’s coming but of course delays due to COVID. So we’ll see.

thanks for sharing your link, I haven’t dug too much into VRM yet so it’s nice to see a live version, it’s very clean, I like it!
 
Honestly, I wouldn't hold your breath on the Multiplus II. They have features and things they say will come soon, but they never happen or are still years out. Temp reporting on the smart battery sense was supposed to be passed to VRM from the MPPT, but that was over a year ago, and it looks like they don't plan to ever implement it.

If your RV already has the ATS, then you don't need two inputs. Just insert the inverter between the ATS and the AC panel, and the single AC-in can be fed by genny or shore as the ATS dictates. I'm off grid, so I certainly don't need the two inputs, but I wanted the additional power of the Quattro.

HBR is about 3.5 hours away, so it gives me great peace of mind to see and control what's happening. We used to have a horrible vermin problem until we could leave many lights as nocturnal critters won't nest where there's light. We went from a couple instances of turds everywhere to 1-2 caught in a trap between visits. I could completely clear out the nest on top of the engine one day, and overnight, it would be back. With the light on - nothing. So porch light and about a dozen other lights in the living area and under storage areas.

Though we still get the occasional Chupacabra on the Blink cam...

1603271657934.png
 
Fun fact: Jackrabbit ears are so big since they are used as heat radiators, not hearing aids ?. Cute critters.

On the other hand, Those blood sucking Chupacabras just scare the bejesus out of me!
 
Honestly, I wouldn't hold your breath on the Multiplus II. They have features and things they say will come soon, but they never happen or are still years out. Temp reporting on the smart battery sense was supposed to be passed to VRM from the MPPT, but that was over a year ago, and it looks like they don't plan to ever implement it.

If your RV already has the ATS, then you don't need two inputs. Just insert the inverter between the ATS and the AC panel, and the single AC-in can be fed by genny or shore as the ATS dictates. I'm off grid, so I certainly don't need the two inputs, but I wanted the additional power of the Quattro.

HBR is about 3.5 hours away, so it gives me great peace of mind to see and control what's happening. We used to have a horrible vermin problem until we could leave many lights as nocturnal critters won't nest where there's light. We went from a couple instances of turds everywhere to 1-2 caught in a trap between visits. I could completely clear out the nest on top of the engine one day, and overnight, it would be back. With the light on - nothing. So porch light and about a dozen other lights in the living area and under storage areas.

Though we still get the occasional Chupacabra on the Blink cam...

View attachment 25527
I hope you're wrong! haha. Yeah I mean I'm not going to wait too long. They "told me" it's in production waiting on UL certification, due to COVID now expected for Q1 2021 release. IF that were true, that's a little too far out. Realistically, I should be ready for my inverter/charger purchase in 1-2 months. So, yeah, not holding my breathe, just making that item the last item I purchase "just in case" haha.

And good point about the ATS on the RV. I didn't even think that I already have the ATS in order to NOT need two inputs. The RV is new to me (only a couple months) and I started planning my solar setup before the RV arrived so I wasn't sure what it would come with. Thanks for mentioning that!

One big benefit of the MPII, for me, is the smaller form factor, honestly that was a big plus for me as my storage area for my toy hauler is smaller than most. MPII vs Quattro isn't HUGE, but it is smaller, and every inch counts haha. The MPII would be lighter as well. I know 20-30 lbs isn't much, but everything adds up. 30 lbs here and there becomes 400lbs haha. So, not a dealbreaker, but important items for me to consider.

I want to be more off grid, which is the whole point of the solar, but will spend time in parks as well where shore power will be beneficial. But as you mentioned, with my ATS, I wouldn't need two inputs. and yes the additional power of the Quattro is a plus.

That's super cool about your HBR setup, ah the little things in life :) and them Chupacabra's, gotta watch out for them, can't see em comin' lol

Fun fact: Jackrabbit ears are so big since they are used as heat radiators, not hearing aids ?. Cute critters.

On the other hand, Those blood sucking Chupacabras just scare the bejesus out of me!
haha, this cracked me up.
 
Assuming you have a 50A plug, a 120V only inverter in the middle will limit your total power to one leg of the 50A connector, and you'll want to be careful. In order to feed both legs of your 50A RV, you have to short L1 to L2 like the 30A to 50A adapter does (30A to 50A only uses one leg of the 240V input). So with the inverter in place, you're limited to 50A * 120V so you don't overload the neutral line in your trailer since it will be carrying the current of both legs. When you pull the AC in lines from the ATS, you'll want to leave the second leg disconnected as the Victron can only take 120V in.

Same deal with your onboard generator. The bigger ones have two legs, so you'll only pull from one leg.

It's a trade-off. In the middle, it's essentially invisible and works seamlessly allowing battery charging from grid and generator, but its presence restricts shore/genny total input.

Concerning inverter weight, and inverter's weight is directly proportional to its ability to handle overload/surges. A lighter inverter is never a better choice in my world.
 
FWIW, my off-grid "shore power" is a Quattro to a 50A RV power pedestal that is wired with L1 connected to L2. I then just plug the RVs into a splitter.

I'm ultimately current limited by the quattro, so 50A is unlikely to occur except in very rare short duration surges.
 
I can make some suggestions, I suggest validating them with a phone call to arizona wind and sun, they helped me with this exact process.
I did buy my controller from them, but I had purchased cells from amazon and they were great about that.

First up, get your cell stats together.
Take a shot at using the Victron calculator, this'll give you some ideas.

I have 1200 watts of panels on my 5th wheel. I used 12x 100watt panels for my build.
I had some specific limitations to work with:
1) The factory solar wiring (which is a mild joke) was rated at 30A, but the main run from the passthrough is only 10Awg wire. My system is fine with it but I'm going to upgrade it sometime to at least 8 if not 6 since I've figured out how to access the runs.
2) 24v system. I'm running a tesla pack now, which is sort of a bastard 24v - it runs a bit lower in voltage. I'm swapping in 16x 280Ah cells. (sounds familiar!)
3) The peak voltage - your cells will make maximum voltage when cold. Your MPPT needs to handle that. Turns out that's typically higher than the rated panel voltage.

My system:
I build 4 parallel packs of 3 cells in series. This put my system at around 54.4V Max and 21.6A Max output. This rides 10Awg wiring just fine.
My controller is a 150/45-Tr Smart Solar Charge Controller. For the final configuration, it's a little bit of overkill - I was originally going with 4 series, which pumped the voltage up to 72.5V, which on a cold day can overwhelm a Victron 75v controller.
For my final setup, I could have gone a little smaller but I already had the 150/45.

The smartsolar is the way to go IMO. It's a solid piece of gear. It also triggers a low voltage cutoff solenoid that's on the main pack.
I also paired it with a battery sense for temperature detection - this allows me to set a low temp charging cutoff as well.
Finally I used a BMV712. Between the 712 display in my control panel and the victron app, I get about everything I need.
I am going to add a raspberry pi running the victron stack since I'm buying the usb mk3 to configure my new multiplus inverter.
 
Oh and on inverters... My biggest annoyance is that my camper is 50a dual phase, I need to combine L1 and L2. the multiplus has a built in cutover switch, but I'd need to add a contactor to auto change the legs. I picked up a three phase cutover switch to mess with.

That said, you can run a pair of Multiplus units if you want two phase auto switchover, it's actually cheaper to use two 3000w multis than the 5kw quattro. I keep considering adding a pair even if it feels like overkill.
 
What I've done in my 5th wheel was use the Multiplus 12/3000/120-50 and the Smart Phase Selector by by AM Solar. This allows both L1 and L2 to be feed weather you are on a 15, 30 or 50 amp service. The SPS is pricey for what it is but it makes everything to easy. Just mount it wire it up and or done. Simple and straight forward install. The nice thing is you still get power assist if needed.

Greg
 
Hmm, that is elegant, but at 600, I'd just spend the extra 600 and run a pair of multiplus, one for each phase.
 
Back
Top