Installed four of six 320 Watt frameless, semi-flexible solar panels. Two more to go. Up to 1920 Watts should be available to charge the 48 Volt lithium battery. Each is held on with 15 home-made aluminum brackets and VHB tape. The total bond strength is about 1200 pounds per panel. Since the roof will now be walked from the side, I will paint white non-skid marine paint all the way up the side.
I plan on charging my Nissan Leaf when the sun if out. What have I done? Guess the warranty is void.
Woo hoo!! That is some serious power. How high did you end up mounting them off the surface of the roof? Taken it for a test drive yet to see how they the first few panels deal with the wind?
Wow that's a bunch of solar! Each panel has 15 attaching points? If so I don't think they will be going anywhere.
Good idea. If the panels make noise or vibrate, I'll have to design an aerodynamic snubber, or reinforce the underside of the panels. That said, I figure that U270 will break the wind for the panels, which are quite rigid and rugged. The 55 pound each panels are American-made eBay specials that cost about $.63 per watt delivered. They will be wired in three two series circuits, delivering up to 120 Volts.
Tim,
Good going.
Looks like those panels must be pretty heavy. From your picture it looks like the roof is sagging!
Keep up the good work.
Len >:D
Solar power is overrated, meaning that even though they theoretically will produce 1920 Watts, in real life cloudy days, or campsites with trees, I'll be lucky to get one quarter of that. Clouds and trees would probably cause a 95% reduction, or only 96 Watts.
Given a 30,000 Pound vehicle and Foretravel's high-strength roof, these 55 Pound panels will be like flys on a horse's back.
With an 1140 watt potential, we still get about 600 watts peak (flat mount) in the middle of winter in AZ. Clouds and trees effect it from a little to a lot depending on how thick the cloud layer is or how dense the tree cover is. A tree can shade one panel but we still get good charging.
Smart to put as many as possible on the roof. They are super cheap now with the controller taking a higher percentage of the total cost.
Did you install two controllers?
Pierce
Hate to hijack but, do you tow the Leaf on a dolly?
Two replies and a comment:
1. CONTROLLERS
Only one Morningstar 45 Amp 48 Volt MPPT controller will be used, with two more controllers as backups. Long story.
Made my own solar combiner and breaker box, with breakers, surge suppressors and charge enable relay.
2. LEAF
While at home base, the Leaf will be charged. When on the road, we will flat tow a manual transmission Honda Civic Hybrid. The Leaf would have to be dollied and, due to the 70 mile range, would not fit our lifestyle, yet.
3. CHARGE MONITOR
See the photo for my home-made solar monitor box, which measures state of charge, charge current capacity, discharge current capacity, battery charge current/voltage and solar output current/voltage.
Tim:
Are you sure that your "Morningstar 45 Amp 48 Volt MPPT" will safely control 1920 watts.
All the "Solar Controller" specs I have seen rate controllers with Maximum AMPS into battery bank.
I have an 80 amp Outback controller with 1470 watts which has a theoretical max amps of 90 amps.
The maximum I have ever seen is 78amps when running the microwave off the inverter with discharged batteries.
Your theoretical maximum amps into batteries will be circa 115 amps so I do not understand how a 45amp controller will suffice.
Having just gone through that sizing process myself I was wondering the same thing. My initial thought was that was going to need one big controller.
Wyatt,
This one had me scratching my head until I remembered Tim is using a 48 volt battery. How does this quote sound to you? Quote below:
"For example, you could have a 3,000 watt solar module array that operates at 93.3 volts DC and your battery bank is 48 volts DC. MPPT charge controller are rated by the output amperage that they can handle, not the input current from the solar module array. To determine the output current that the charge controller will have to handle we use the very basic formula for power in Watts:
Power = Volts x Amps
Here we know the power is 3,000 Watts, the battery bank is 48 volts, so:
3,000 Watts = 48 volts x Amps
which gives us:
Amps = 3,000 Watts/ 48 volts
Amps = 62.5A
We still want to adjust this value by 25% to take into account any special conditions that might cause the solar module array to produce more power than it is normally rated for (e.g. due to sunlight's reflection off of snow, water, extraordinarily bright conditions, etc). So, 62.5A increased by 25% is 78.13A. In this case we'd probably choose a 80 Amp MPPT Charge Controller"
Wyatt, guess the next question is how to get the 48 volt battery to work with the 12V coach electrical system without a lot of efficiency loss?
Pierce
Might wanna read up on using the Morningstar MPPT controllers with array outputs higher than "normal" controller ratings. They go into MPPT mode sooner in the day, and stay later, but act like a regular controller when the array output hits the controller max. So...a Morningstar MPPT controller theoretically undersized for your array MAY actually harvest more than an oversized one.
Edit-
http://www.morningstarcorp.com/wp-content/uploads/2014/02/MPPT-Technology-Primer.pdf
The most I've seen from my 1200W array is 650W, I use a Morningstar PWM TS-60 controller.
This is pretty close to our 1140 watts seeing about 600W in winter. Summer with a flat mount should come within 20-25% of rating depending on your latitude. I have seen panels go over their rating with a reflector. Couple of examples on YouTube.
Still in the dark about an efficient way to convert the 48 volt battery to 12V coach voltage unless you invert 48 volts to 120VAC and then charge the coach batteries plus power the AC appliances. Looks lossy that way to me but ready to learn new tricks.
Pierce
48 volt to 12 volt DC/DC converters, Marine, heavy duty and military grade... (http://www.powerstream.com/dcdc-extreme-4812.htm)
That is what I used on the '81 to run lights, water pump etc. Then used 24 volt invertor to run the A/C outlets. I kept the engine 12 volt system separate.
Looks like one of these will cost as much or more than our total solar setup including batteries and will lose 15% efficiency plus any loss in the controller, wiring, etc. Just seems adding complexity to what can be a very simple and reliable solar system.
12V wet or AGM batteries are hard to beat.
Pierce
Wow ! 😳
X2 don't quite understand the thought on the 48v thing.
Why does a 48-volt battery bank make sense? | RV Nerds (http://rvnerds.com/2016/01/19/why-does-a-48-volt-battery-bank-make-sense/)
Tim was talking about a 7kw lifepo4 system. For a 7kw lead acid system, he would probably overload his coach, or run out of room to put the batteries.
All this will be meaningless when he falls off the edge of the roof!
Hopefully he doesn't but I appreciate his efforts.
The 48 Volt DC system makes sense because it cuts the required wire size, currents and weight by 75%. Since electrical wire heating losses are determined by squaring the current, the loss can be reduced even more.
The main LifePo4 battery, system and panels typically have the following specifications:
ELECTRICAL
HOUSE BATTERY
52 Volts (let's use 50 volts for a round figure) at the LifePo4 battery terminals
73 Volts solar panel voltage
25 Amps charge at full sun, factoring in wiring losses, so the 45 Amp Morningstar MPPT controller will be adequate
80% minimum efficiency for the 120 VAC to 12 VDC converter, IOTA model DLS-90. This is disappointing, but the waste heat will be circulated into the coach for a winter benefit.
120 Volts maximum solar panel voltage at zero degrees F. However, this is at sunrise when there is very little current. As the panels heat up, they produce less voltage.
9.5 KWh battery capacity (16 x 180AH 3.3 VDC LifePo4)
Orion BMS will keep each battery balanced, keep the state of charge between 20% and 80% and have high/low voltage shutdown.
ENGINE BATTERY
12 Volts DC engine battery will be 440 AH AGM
Will change or remove the boost circuit.
AERODYNAMIC
1200 pounds of adhesive force from the 3M VHB tape (15 attach points x 80 pounds each)
600 pounds of lift at 120MPH (During a hurricane)
This is based on some fuzzy internet research, which was done for sticks and bricks homes. Based on the above, if there is a 120 MPH wind, the U270 will probably have other wind damage issues. Thanks for your questions regarding the system. Keep 'em coming.
Attached is the schematic of the electric system, annotated in red. What have I done? This will involve risk and a lot of work, but the reward will be worth it.
Your 48 volt solar panels if wired series/parallel as you indicate, will send about 96 volts down to the converter during an average solar day. Our 36 volt panels are wired series/parallel and we average about 72 volts at the controller. At either 72 or 96 volts, there will be very little loss from the panels to the controller if any care is taken sizing the wires. The big loss can be from the controller to the coach batteries with the lower voltage so it's important to use large cables here. You won't have to worry much as 48 volts from the controller to your battery will not require that big of a cable.
My concern here is that because of your loss in the converter, you will lose over one solar panel's worth plus generating heat. A 20% loss for just one component in a solar system is huge plus adding complexity. No need to worry about the cost of solar wiring as the panel to controller and controller to battery welding cable are super cheap and not significant in the overall cost of the system.
Bottom line is your 48 volt battery is going to last a very long time in theory and you MAY be able to get away with one controller rather than two but you will have huge losses compared to solar industry standards and have nowhere near the 1920 watt potential your panels have.
In my opinion, four 300 watt panels are plenty for any dry camping and we are limited not by the roof wattage but possibly our battery capacity if we want to run a domestic fridge. Since we are up to float voltage by noon even with low sun in winter, we could probably run a fridge our size all night and still have plenty of juice in the morning. A double door would need several more batteries to keep the percent of discharge low and insure the batteries have a long life. So, four vs six panels are about a $300 savings at $0.50/watt. One $500 Midnite 150 (96amps at 12V factory rating) controller will keep the controller cost the same but the 48 volt to 12 volt converter will add a lot. Price??? Battery cost? With four panels, I can still walk anywhere on our roof.
I have to add that I'm a firm believer in mix and match when it comes to both heating and the fridge. Solar is super but having all that energy available in the propane tank at very low cost makes a great compromise and adds a big element of safety in an emergency in bad/cold weather. Spoken from the viewpoint of mostly dry campers.
I really hope you do well and please don't think I'm throwing water on your electrics but I have to be the devil's advocate here. Hey, when you are on the cutting edge of new technology, people will always throw stones. :D
Pierce
Couple of comments:
Will change or remove the boost circuit.
I have not had any requirement for this circuit since we did our mods. Kind of a tech left over from another time for us. I did run a 2/0 cable from the chassis batteries, two red tops, to a three way switch and connected the gen set starter. Removing the lithium completely from starting duties. The marine switch can engage either or all of them if needed but in five months we have never been close. The 100w panel and 6a Morning Star controller keeps starters healthy. (Ours follows Johns design)
Also removed the alternator from lithium by removing isolator and using simple Marine switch.(Brett) Even on cloudy snowy winter days on the road, the solar kept up with underway 12v house charging and I haven't switched to the alternator yet. I did test, during that time, the speed of the gen set in bringing the lithiums back up. Have data on that if you are interested. It is awesome to go from bulk to float.
We decided to not go to residential but may go 12v marine. We are however going to continue to use our greatest power hog...the uline which I won't be without. Glad you are open to questions as I am learning a lot from your posts. Push that envelope!
I agree with you. There is a balance of technology liability: complexity, maintainability, reliability and performance. I decided to enhance boondocking in the woods over the shore powered camping experience. So the 120VAC capability for the microwave/convection oven, AC, entertainment center, laptop charging, Nissan Leaf charging, etc... is favored over the 12 volt appliances: heater, fridge and LED lights. In the summer, the heater won't be used much, so the 80% efficiency 120 VAC to 12 VDC converter won't be loosing too much power.
In the end, we pay a price to reduce "energy anxiety". When boondocking in a wooded campsite, the solar panels would be lucky to be generating 100 watts, so we'll be conserving energy regardless. It's all good.
We will still have the generator if all else fails.
I had checked into li-ion systems when we got our coach five years ago, not mature enough tech then for my budget.
Plus my needs were not high enough.
Great info
Tim
Here is a screenshot of house bank of one day on our run home. Partly cloudy and no use of alternator circuit. I have 800w and was running the uline etc. We were on the post before and after. Nice to be able to switch it in if needed but over last 6 months have kept it isolated.
Nice graph.
I am pleased to report that the upgrade has been installed and is operational. Successfully tested the 48VDC LiFePo4 battery, BMS, solar, 2KW pure sine wave inverter/charger, main engine, generator and alternator operation. Important core changes include:
- Generator starts with engine battery, not the house battery
- Removed diode isolator from alternator charging circuit
- Bypassed / removed boost solenoid
Photos to follow. It was good to see only about one volt of sag (50V vs 51V) on the lithium pack when the convection oven was used, or about 1800Watts of power.
Plan for next week:
- Battery hold-downs
- Secure wiring
- Test drive
My only question is: Without starting boost, will a 1400 CCA AGM battery (two 6Volt golf cart) start a 32 degree F 8.3 Cummins diesel engine? At 60 F, it took about two seconds of cranking to start, with the dash / instrument panel lights flickering.
Sounds like you need more starter battery power. Our 8.3 had 2 red top optimas might be room for 2 group 31 batteries.
Two 31 series. 1900 CCA About $120/ea.
Pierce
Bought two group 31 batteries: from NAPA, P/N BAT 7235 Commercial type with 2250 CCA total. One fit oddly but OK, but I had to make a mount for the other one. They are secure and the engine starts in one second.
Test drove the rig with all systems functioning and solar panels attached. There was some wind noise at 70MPH of relative wind, but not too loud. At a stoplight, a fellow yelled out his window: "That's America!"
Here are some photos, annotated with the major updates performed. The 48 Volt LiFePo4 battery receives about 1500 watts in full sun.
I just ordered an intelligent charger module for the 12 V DC charger that will provide four-stage charging for the engine battery, including equalization every seven days.
If you just got rid of those silly air conditioning things, you could get on an extra 700 watts!I
I have dry camping envy.
Tim, with the height of some of those panels I would imagine that you are getting wind noise. I also think that there is a lot of "turbulence" under them.
JohnH
The highest panel is about one inch below the AC. Perhaps an aerodynamic device can be designed to smooth airflow over these 3/8 inch thick frameless, semi-rigid panels. Being a pilot and President of the our local EAA (Experimental Aircraft Association) Chapter 1250, I hypothesize that there is a market for such a device. For example, aircraft owners pay thousands of dollars for vortex generators, which direct airflow over aircraft.
Another example of this is the Nissan Leaf, which has vortex generating headlights that reduce wind noise at the side view mirrors. Maybe the motorhome industry would be interested in the research.
This whole discussion is way over my head. But I want to learn. Do any of you know of a good book to recommend as a base to start?
We have 400 watts and a controller that are each apparently 15 years old. We go full time in 3 years. The next 3 years are for building experience and working to make the coach "right"... and fun.
There are a bunch of practical ideas from Technomadia at: Lithium Batteries for RVs - LFP / LiFePO4 - YouTube (https://youtu.be/EHSpJWgeiEw)
I am not much of a book reader, but perhaps I should write one.
Technomadia has a lot of lessons learned from five years of owning LiFePo4 batteries. For example, they taught me about:
1. CLIMATE CONTROL
Put the batteries in a climate controlled area, so I insulated and added a fan and return duct to the battery bay fed from the passenger compartment. This is hidden, of course. Batteries are like humans with regard to temperature because their longevity is increased if used between 40 and 80 degrees Fahrenheit.
2. NEVER CAN HAVE TOO MUCH SOLAR
Boondocking in the woods / shade requires as much solar power as one can afford. This will reduce energy anxiety.
3. NEVER CAN HAVE TOO MUCH BATTERY
Since LiFePo4 batteries longevity can be increased by keeping them between 20 and 80 percent State of Charge (SOC) and reducing charge cycles, the larger the battery, the longer the life. I plan on getting 10 years out of my batteries.
Granted that the above considerations apply mainly to winter boondocking, but it's based on a worst-case analysis with the following factors:
- Low sun angle
- Low temperatures
- High demand (From furnace and modern appliances)