New RV build in OC CA

[Azguy82]

Hey everyone,

I am starting a new build on a truck camper. I have already have 8-eve 304ah cells and 2 JK BMS'.

I think I am planning on going 12v with victron as space is limited and I want a inverter/charger and the multiplus 2 is only like 6 inches deep so it can fit under my oven or in a cabinet that is 8 inches wide.

Im having a little trouble planning the system. So many possibilites. So far I think im going with REC 420 watt solar panels that are 59v/9amp max each. If I run 4s on those then Im at like 240v/10amp and would need a 250/100 mppt but.... the max they output is 100amps and at 12v that would only be like 1400 watts to the battery bank. or... I can go with 2 strings and two charge controllers for 120v/10amp. My other options is to take the battery bank to 24v and that solves my mppt/panel issue, but this then brings a new issue of how to power the 12v systems in the camper. I know they make 24-12v converters but Im not super familiar with them.

Im thinking I should stick with 12v and just run two strings? but 24v is nice cause of the size of copper and keeping things cool pulling 3000 watts from the inverter.

would you run two strings of 840watts and two mppt's? or would you run the 250/100 mppt and over panel it? (id lose about 200/300 of max capacity. would you change your battery bank to 24v and figure out the converter to 12v?

thanks!

if youre in orange county california or have experience with this let me know!

 

[Rocketman]

Another option on the mppt’s is to go either 2p or 2s into the 150/60. The 150/60 can handle 860w. So you will harvest all you can. (I would go 2p into that mppt). Then use two mppt’s.

Although because you are building your camper and can control the 12v loads. If you 12v loads are fairly small - I would highly consider going 24v and just using a 24 to 12v converter. 24v will eliminate the second 150/60 mppt.

 

[RV8R]

I came across this the other day. Only briefly looked at it;

BIC1230100 – Kisae Technology Inc

Or the BIC 122080 is a bit smaller;




Both are just over 4” “thick”




As Always, read the manual for airflow requirements ?.

 

[RV8R]

12vdc or 24vdc ?

Pros & Cons to both

I’m an old building contractor, so reading your design rather than looking at even a scratched out preliminary drawing is difficult for me.

However, This is a vehicle that I assume has a 12vdc alternator & if most appliances will be 12vdc that might spotlight a 12vdc direction.

 

[Reed Cole]

24v sounds better for pushing that many watts around. If you had just one or two panels and half the battery capacity then keeping everything 12v would make sense.

 

[Dooug]

Victron doesn't like your panels in 4s on the 250/100. Open circuit voltage could be higher than 250 in cool weather.

Are they flat mounted? That definitely knocks down the output (not necessarily the voltage) to where you may never actually get the wattage. So a 100 amp controller might not miss out onuch production .

I'm a big fan of two controllers in RV situations because we are constantly fighting shade. A pair of 150/45s or 60s would work well for the 12 volt system.

I'm building a 24v truck camper it's a bit of extra stuff. Converting 24/12 for the basic camper functions isn't a big deal. But the electric camper jacks will need something like the 24/12/70amp converter. I actually two converters, a small one for the camper functions and a 70 amp for the jacks(based on someone else's experience with a 40 amp converter not quite cutting it)
Alternator charging isn't a big deal, your going to want a DC to DC converter anyways so a 12/24/15 vs a 12/12/30 isn't a big difference.

My build isn't finished yet so haven't even tested everything yet.

 

[wopachop]

First time ive heard of an AZ guy coming to OC. Lately its been the other way around.
Do you bring a generator with you? With all your solar i wonder if you even need a big charger.
Im in a similar boat planning mods to a trailer. Thinking of going 24v.
Also thinking if solar keeps me charged and it doesnt rain much, why even need an inverter charger?
Wish more for a Solar controller/inverter. Victron makes one but its 50hertz.

 

[Reed Cole]

Also thinking if solar keeps me charged and it doesnt rain much, why even need an inverter charger?
Wish more for a Solar controller/inverter. Victron makes one but its 50hertz.

Being able to charge from an AC source is definitely worth the cost, even if you don't need it often.

 

[wopachop]

Couldnt that be done much cheaper if its a rare occurrence?

 

[OTRwSolar]

In terms of overall cost/capability/tech/redundancy, I'd have a tough time justifying going 24/48v on a smaller RV. However, if I had a large 5th wheel or motorhome with tons of solar real estate, with plans to max out one or two Multiplus II 3000's (2400w ea) on a regular basis, I could see 48v being a great option. I'd hands-down pass on 24.

 

[wopachop]

Ive read people say they want to go 48v with a trailer but there isnt a good option for a 48-12v converter that can power larger items like a slide. Which only leaves 24v if you want to reduce wire size.

 

[Azguy82]

Victron doesn't like your panels in 4s on the 250/100. Open circuit voltage could be higher than 250 in cool weather.

Are they flat mounted? That definitely knocks down the output (not necessarily the voltage) to where you may never actually get the wattage. So a 100 amp controller might not miss out onuch production .

I'm a big fan of two controllers in RV situations because we are constantly fighting shade. A pair of 150/45s or 60s would work well for the 12 volt system.

I'm building a 24v truck camper it's a bit of extra stuff. Converting 24/12 for the basic camper functions isn't a big deal. But the electric camper jacks will need something like the 24/12/70amp converter. I actually two converters, a small one for the camper functions and a 70 amp for the jacks(based on someone else's experience with a 40 amp converter not quite cutting it)
Alternator charging isn't a big deal, your going to want a DC to DC converter anyways so a 12/24/15 vs a 12/12/30 isn't a big difference.

My build isn't finished yet so haven't even tested everything yet.

So the panels are 50v and 8.4amp

The VOC is 59v

So I think I’m ok with the 250/100 cause it’s only 50v and 8.4amp

Even on a cold day that leaves me 25% wiggle room on the voltage side correct? At 4s.

 

[Azguy82]

In terms of overall cost/capability/tech/redundancy, I'd have a tough time justifying going 24/48v on a smaller RV. However, if I had a large 5th wheel or motorhome with tons of solar real estate, with plans to max out one or two Multiplus II 3000's (2400w ea) on a regular basis, I could see 48v being a great option. I'd hands-down pass on 24.

My main issues with 12v is I may have to put my inverter like 6-7 cable feet away from the battery bank and at 12v and 3000watts I’m worried about that run at 4/0 getting hot/warm.

And I also max out the mppt at 12v at 1400watts so I’m losing like 300 watts of production.


At 12v my main issues is the starting the onan generator. It pulls like 100 amps @ 12v so I may need to have a 12v battery anyway just to deal with that draw. How ever infrequent that is cause I think with 1700 watts of solar I may never need it.

 

[OTRwSolar]

My main issues with 12v is I may have to put my inverter like 6-7 cable feet away from the battery bank and at 12v and 3000watts I’m worried about that run at 4/0 getting hot/warm.

A 12v Multiplus II 3000's output is rated at 2400w (3000va) at 25c. At max output it'll probably be drawing 210 - 220a. A 7ft (one-way or 14 ft pos/neg round-trip) run of 4/0 cable at 220a (with excellent terminations) should only experience roughly a 1.3% (.15v) voltage drop. Perfectly acceptable. Most reputable installers strive for less than 2-3%.

 

[Azguy82]

A 12v Multiplus II 3000's output is rated at 2400w (3000va) at 25c. At max output it'll probably be drawing 210 - 220a. A 7ft (one-way or 14 ft pos/neg round-trip) run of 4/0 cable at 220a (with excellent terminations) should only experience roughly a 1.3% (.15v) voltage drop. Perfectly acceptable. Most reputable installers strive for less than 2-3%.

what about the mppt?

If I run a 12v battery bank then the 250/100 will max out at 1400 watts correct?

If you over panel it. And let’s say I have 1700 watts of solar. I lose all of that extra production. Let’s say I’m getting 80% of the stated production, I still might be losing 100 watts of production or so.

Is it bad to run the mppt at its full 100 amps to the battery? For longevity and heat?

Like if I go to 24 everything runs cooler and better. Less fans running. Less heat though the copper. Etc.

Just running 24v is an issue with running all the 12v equipment on the coach and Essp getting the generator to start.

 

[OTRwSolar]

what about the mppt?

If I run a 12v battery bank then the 250/100 will max out at 1400 watts correct?

If you over panel it. And let’s say I have 1700 watts of solar. I lose all of that extra production. Let’s say I’m getting 80% of the stated production, I still might be losing 100 watts of production or so.

Is it bad to run the mppt at its full 100 amps to the battery? For longevity and heat?

Like if I go to 24 everything runs cooler and better. Less fans running. Less heat though the copper. Etc.

Just running 24v is an issue with running all the 12v equipment on the coach and Essp getting the generator to start.

Without getting too much in the weeds, it would appear you're calculating everything based on max hypotheticals. Perfect sun, max rated output, etc. If you honestly feel you'll be pulling these hypotheticals with the 250/100 and/or you're committed to using only one controller, then 24 might be your best compromise. If no on either count, then 12 might be your best compromise.

That Onan starter (actually any starter) pulls significant inrush current. Was that 100a reading continuous or inrush? For what it's worth, 24/12 converters don't have the best inrush capability.

If you go 24, I would suggest going 8s with your cells vs. two 4s in series.

 

[OTRwSolar]

Ive read people say they want to go 48v with a trailer but there isnt a good option for a 48-12v converter that can power larger items like a slide. Which only leaves 24v if you want to reduce wire size.

Unless you've got an RV with a huge hydraulic slide system I don't see a problem sourcing 48/12 power. The average slide motor draws less than 30a. Schwintek slide systems, which are very common, typically only draw 10-15a. 30a 48/12 converters are very common. May have to dedicate a converter to a single circuit or slide motor---unfortunately, that's the price one has to pay to play sometimes. If 30-50a converters are not enough, Daygreen makes a 150a 48/12 converter.

 

[Dooug]

So the panels are 50v and 8.4amp

The VOC is 59v

So I think I’m ok with the 250/100 cause it’s only 50v and 8.4amp

Even on a cold day that leaves me 25% wiggle room on the voltage side correct? At 4s.

MPPT Calculator - Victron Energy

MPPT Calculator - Victron Energy

www.victronenergy.com

Victron voltage limit is a hard limit...careful. if it cools off you'll quickly hit the limit with 4 in series. I wouldn't even run VOC that close to max on my off-grid Mexico place that doesn't get below 5-10 Celsius.

 

[OTRwSolar]

Being able to charge from an AC source is definitely worth the cost, even if you don't need it often.

Ditto. The 12v Multiplus II 3000 inverter/charger can produce 90-95a of charge current using just 13.5a of 120vac. A Honda 2200 inverter generator can easily do 13.5a (it has a 15a continuous current rating). If you have access to 16.5a via 20/30a shore power or higher capacity generator, nearly 120a is at your disposal. On those cloudy days when the sun fails to shine, 90-120a of charge current can definitely brighten up your day.

 

[Rocketman]

I would not put 4s of Voc 59.4v into a 250/100. That’s 238v before you start getting cold - as the panels get cold the Voc rises. You use Voc for max volts.

Just install the 2s2p and you will be fine. You might be able to use a Victron 150/100 mppt.

Will you tilt your panels?

When flat - panels will only max out “at noon in June”. Today and Yesterday (in December) my panels were flat (travel days) on my 600w array - the max I got was 323w & 333w.
The 2 days prior, I had tilted panels, and those days I maxed out my 100/30 mppt (415w).

My other array I got 75% of rated power 600w on 800w of panels. So even in December in Baja I can get up to 75% of rated panel power. (This is why I over paneled my arrays).