Solitude Solar and Battery Installation

[TucsonJim]

Good morning Fivespeed56 Mike:

1. "Why did you choose a 12-Volt system over 24 or 48 volts?" - Great question. One of the primary drivers for going with a higher voltage (lower amperage) system is wire sizing. Wire can be quite pricey. But I already had a good supply of wire I needed to do the job with a 12V set up. Secondly, If i went with a 24V system, I'd have needed to put two of the 230 aH batteries in parallel. If one of those batteries failed, I'd need to take two batteries out of the systems instead of one. And finally, I'd need to add another component into the mix to convert 24 volts down to 12 volts.

2. "I do not see a stand-alone battery for the 12-volt side of the RV. I am assuming the 60 amps provided by the two DC to DC converters is supplying that power. Am I correct, and why two?" - The four Li Time 230 aH batteries are the power source for the 12-volt system. They are hooked in parallel and give me 920 amp hours at 12 volts. The two DC-DC converters are to provide an alternative charging source in case of cloudy weather and my solar charging can't get the job done. This will give me the capability to recharge the batteries at 60 aH while hooked to the truck. "Why two". Because I wanted more capacity than one. Now that Victron has released the 50 amp version, I would have went with one of those instead of two 30 amp units.

3. "Have you been able to finish installation of the PV panels? If yes, are you happy with their performance?" - I sure have. In fact, we've been camped in the desert near Quartzsite Arizona since last Monday. I'm consuming about 200-230 amp hours per day. The solar panels have been yielding a maximum of 1700 watts (out of 2000 available) and we're typically fully recharged by noon to 1:00 each day. That's great considering it's still winter and the panels are flat. Our consumption so far has been about 200-250 amp hours per day. So even if we don't get any sun, we can go about 3-4 days without recharging.

Jim

[Fivespeed56]

Thanks Jim,
Excellent explanations and thanks for the rapid reply . I will be starting from ground zero, without the benefit of an on-hand supply of wire. I believe I will be going with a 48-volt system while following your base architecture. I still do not know when the 337 will be built and delivered. Best the the dealership can forecast is sometime between May and June. Our first trip in the 337 will be 4-days at Jellystone south of Dallas to meet the kids and grandkids. I plan to monitor real-time KWh usage from shore power, then build the system capacity around that number, whatever it turns out to be. I do not plan to begin purchasing supplies and equipment until then. In the meantime, I will keep planning and crunching numbers! Thanks again.

[howson]

Fivespeed56 -- hope you don't mind a comment regarding a 48V system? As you may know, an MPPT (especially Victron) won't start charging a battery bank until the solar power (PV) is 5v over the battery voltage. That means PV on a 48v system will have to be ~53vDC before it starts to work.

Look at the example below I just snipped from Victron's VRM website (my system is "live" on that site). Note how amperage started to rise when PV was ~17vDC in my 12v system. The Vmp (normal operating voltage) of my 1200W solar system, as shown, hovers around 38vDC.



So why do I mention the voltage levels? Because with a solar system that starts charging at 53vDC, the Vmp might be as high as 80vDC to 100vDC in order to have an efficient system. Why does that matter? Do some research on the specs for switches and other components in a DC system. Most are only rated for a maximum of 48vDC. For example, a typical switch used by many to isolate solar panels from an MPPT's input is a Blue Sea 6006. The maximum voltage rating is 48V. Costs about $30. But it shouldn't be used in a solar setup that will have a much higher Vmp.

Check out Allen's install ( acoleman43 ). He decided on a 24v system. A 48v system is certainly doable, but perhaps Allen's experience may offer some input on a 24v alternative.

https://gdrvowners.com/forum/solar/8...l-momentum-21g

Howard

[ncitro]

I run a 48V system with Victron gear for my battery backup in the basement in my house, but I went with 12v in the rig for the reasons mentioned here. I decided having to manage the 48 to 12V converter (power draw for levelers and slide motors were my main concern there) as well as a 12v backup battery for the brakes were not worth the savings in wire size. The Victron gear was priced pretty similar at first glance, however if you look closer I think the Type 2 Multiplus with 50A split phase is only currently available in 12v. A 24V version is rumored but has not appeared yet. This means either running dual inverters for twice the price (I have dual Quattros at the house, but did not need this much inverter in the RV) or only inverting one phase. While that is possible (I ran this way in my first revision) the benefits of Power Assist really shine with both phases connected.

[acoleman43]

Hi Jim,
Thanks for sharing all your impressive work and results. I am in the planning stages for a similar build. May I ask a few questions and your insight? I am not an electrician. I've spent a lifetime doing reverse engineering and fixing my own stuff. I have a good working knowledge of RV electrical systems and I am terrific at troubleshooting & basic repairs.

• Why did you choose a 12-volt system over 24 or 48 volts?
• I do not see a stand-alone battery for the 12-volt side of the RV. I am assuming the 60 amps provided by the two DC to DC converters is supplying that power. Am I correct and why two?
• Have you been able to finish installation of the PV panels? If yes, are you happy with their performance?

Your system is about as close as I have found for what I envision my install will be. Thanks in advance for your help!

HI Michael & Lisa. I know you didn't ask me, but I'll give you my experience on a 24v system and why I didn't go with 36v or 48v system.

I decided on 24v system based on generally accepted advice/recommendations. If you have a battery bank at or over 10KWH, and a solar array over 1200W/1600W, a 24v system is a recommended option. Also, I like a challenge and like to be a little different

Our current system has a battery bank just over 10KWH and about 1300W of solar. I have the "old" multiplus that serves as the inverter, which I connected to the entire trailer electrical system meaning I can run everything (AC, fridge, microwave, outlets, etc) from the batteries. When we have good sun, it works very well. If we don't need to use the AC, and we have good sun each day, we can go indefinitely without using a generator or plugging in. So far the longest we have had to go on just solar is 9 days in Big Bend NP. We even used the AC 1 or 2 hours a day. General rule of thumb for solar array size is double the battery bank size. For example, if you have battery bank of 800AH (12v), a 1600W solar array is recommended. Keep in mind you can count on only about 5 hours of sun per day and not every day will have sun. You will want to store enough energy for 2-3 days without charging your battery bank.

So, pro's and con's with my system:

Pro's:
-As Jim mentioned wire/cable size are reduced...by a lot. I literally saved several hundred dollars by going with 24v batteries - even after purchasing DC-DC converters.
-Efficiency. higher voltage systems are, typically, more efficient.
-Size. You have more available power (generally), and all components are same size as 12v system. This is due to the efficiency gained.

Con's:
-RV DC system is 12v. You will need to step down voltage before your distribution panel. More on this below.
-24v devices are less common. This makes some of them more expensive because the supply is so low. I found Victron inverters, solar charge controller, etc are generally the same price whether it is 12v or 24v.
-Did I mention most DC devices, appliances, generator starters, etc are 12v?

Overall I like the system. Wiring was much easier/cheaper, but I did have to purchase a couple DC/DC converters to drop voltage to 12v for 2 systems, my main DC system from you main distribution panel and my "always on" system (trailer emergency brake, tongue jack, CO2 detector, etc). A DC/DC converter or a buck booster that handles more than about 70-100 amps are extremely large, expensive and get hot. Because of this, I kept my DC circuits at 70 amps or under (main distribution panel is 70a and "always on" is 30a).

One thing I did NOT consider, until I was completing the main wiring, was the starter for our onboard generator. It runs on 12v. It requires a battery that can supply around 400 amps. That is a large DC-DC converter. Cummins Onan does make a 24v starter for the generator at a cost of about $800, and I would probably have to remove the generator to replace the starter. So, I do have one 12v "starter battery" just for the generator. I have a battery/trickle charger connected to my main distribution panel to keep the 12v battery topped off.

If you have a 50amp system, and you want to invert the entire AC system of your trailer, I would consider the new Multiplus II 2x120 inverter/charger. If you want to mimic a pedestal 50a service (2 50 legs) you will have to go with 2 inverters - 1 for each leg. But that's worth a new discussion thread.

Concerning a 48v system. You will save even more money on cables/wires. The main issue you will have is providing 12v to the main distribution panel, or your 12v systems. Finding a DC-DC converter the drops voltage from 48 to 12 is even more difficult than finding some that drop voltage from 24 to 12. I have seen rigs with 48v systems. These will typically run 2 systems, a 48v system and a 12v system. The 48v system will, essentially, power their 48v inverter to provide power to the AC system. The 12v system will provide all DC power. This means you will need 2 seperate battery banks (48v and 12v) and hae the ability to charge both battery banks - which is possible by dedicating some panels to a solar charge controller for the 48v system, and some panels to a solar charge controller for the 12v system. Or, another option is to dedicate all solar panels to 48v battery bank, then use an AC circuit for a 12v battery charger for the 12v battery bank. You will lose some efficiency with your 12v system by doing this, but it is a little more simple and you will avoid large, expensive DC-DC converters.

If I were to do it all over again, I would probably do a 12v system....only because I hate having to carry a 12v starter battery for the onboard generator.

I hope this is helpful information.

[acoleman43]

Thanks Jim,
Excellent explanations and thanks for the rapid reply . I will be starting from ground zero, without the benefit of an on-hand supply of wire. I believe I will be going with a 48-volt system while following your base architecture. I still do not know when the 337 will be built and delivered. Best the dealership can forecast is sometime between May and June. Our first trip in the 337 will be 4-days at Jellystone south of Dallas to meet the kids and grandkids. I plan to monitor real-time KWh usage from shore power, then build the system capacity around that number, whatever it turns out to be. I do not plan to begin purchasing supplies and equipment until then. In the meantime, I will keep planning and crunching numbers! Thanks again.

OK, another reply after reading this

See my above post about 48v system. It is possible, but has some extra steps/limitations to keep in mind. If it were me doing a 48v system, I would have 2 battery banks, one 48v and one 12v (all lithium). I would have the solar array charging the 48v battery bank only. I would connect the inverter(s) to the 48v battery banks (and the 48v inverter to the AC side of your main distribution panel) and have a 12v battery charger from an AC circuit on your main distribution panel to charge your 12v battery bank. I would then wire the 12v battery bank to the DC side of your main distribution panel (and to the "always on" components). Doing this would provide you with 2 systems that would back each other up and simplify the equipment needed.

As far as daily energy consumption, don't forget the "parasitic" draws of running the electrical components (Inverter, DC-DC converter, Cerbo, monitors, etc). Our typical daily electrical draw is around 2-3KWH per day (this does NOT include air conditioner). Night time consumption (after sun is down) is about half of total daily consumption. This is when we are charging phones, earphone, laptops, etc.

Our solar array is 1260W. We have seen as much as 4.3KWh yield in a 24 hour period and as little as 0KWh in a 24 hour period. Solar is awesome, until you don't have sun hitting your panels.

On a 6 week trip along the east coast last year we had to use our generator daily to recharge our batteries because we were either parked under trees, skies were overcast or both. Depending on those type variables, you may want to bring a generator as backup when you need it.

[Fivespeed56]

Holy Cow! These new replies demonstrate the inportance of understanding the concept "You don't know waht you don't know". I have certainly joined a good group and I'm graeful for the suggestions and direction. Now I have new info to consider with excellent 24-volt vs 48-volt setups. THANKS ALL!!!!!!!

[TucsonJim]

I'm currently camped in the desert in Quartzsite Arizona for the annual GDRV boondocking rally. A friend took a drone shot of our rig that shows the solar panel installation. The system is working flawlessly. I'm typically drawing around 200 amp hours (2,400 Wh) every day. We are usually back at 100% SOC between noon and 1pm.



Jim

[bellis]

TucsonJim - Just wanted to say - beautiful setup. Really like the elevated switches.