I added Solar to my Roadtrek (Sprinter)

[GeorgeRad]

Here are the panel specs:

Max Power: 400w
Max Power Current (IMP): 2.77a
Max Power Voltage: 18v
Short Circuit Current (ISC): 3.23a
Temperature Range: -40°F - 180°F
Power Tolerance: 0-3%
Solar Cell: Monocrystalline Grade A+
Open Circuit Voltage (VOC): 0.22v
Size 67 x 57 cm (26.4" x 22.4")

Again, I will report back on actual performance when I put it to a real test boondocking.

Also, not Renogy brand. I was shopping to best fill space location, and found this.

LOL, it never dawned on me to just get a DC power supply for my CPAP. $20 on Amazon! Another aspect to explore is if running it without the heated tube might significantly reduce the current draw.

Somehow max current is a decimal way off power or other way around.

 

[booster]

Here are the panel specs:

Max Power: 400w
Max Power Current (IMP): 2.77a
Max Power Voltage: 18v
Short Circuit Current (ISC): 3.23a
Temperature Range: -40°F - 180°F
Power Tolerance: 0-3%
Solar Cell: Monocrystalline Grade A+
Open Circuit Voltage (VOC): 0.22v
Size 67 x 57 cm (26.4" x 22.4")

Again, I will report back on actual performance when I put it to a real test boondocking.

Also, not Renogy brand. I was shopping to best fill space location, and found this.

LOL, it never dawned on me to just get a DC power supply for my CPAP. $20 on Amazon! Another aspect to explore is if running it without the heated tube might significantly reduce the current draw.

Something is not right somewhere. That is a tiny panel unless it is really 67X57 inches. That would be reasonable for a 400 watt panel. The amps should be at a bit over 22 amps to do that at 18v which is generally the right voltage for a 36 cell monocrystalline panel.



2.77 amps at 18v is about 50 watts, not 400.


Open circuit for 18v mpv should be in the 22v not .22.


Who is the manufacturer and what part number?


It would probably weigh in the 60# range, I think.

 

[engnrsrule]

Maybe I got duped. EBay. Listed as "unbranded", it is more like under 20 lbs. It is 26x24 inches.

 

[Hatteras Jim]

I have a med-res cpap unit and I found a DC adapter for the med-res machine on line. Works well.

 

[bwiencek]

Maybe I got duped. EBay. Listed as "unbranded", it is more like under 20 lbs. It is 26x24 inches.

Yeah - you really got to be careful on the ebay/amazon, etc. listings for anything they tend to really exaggerate a lot of specs - the volt/current specs are probably close and that makes it a 50 watt panel - which given the size and current efficency rates would be pretty close too. Figure max around 20 watts per square foot of panel for a modern efficient panel and much less than that for cheapo panels (10-15w/sqft).

 

[booster]

I think I may have figured out what is going on with the panel specs on ebay.


If I am correct it is just another offshoot of the poor attention or lack of knowledge concerning units used in electricity.


On the forum I have often complained of people using amps instead of amp hours, and I think the solar panel issue is along the same lines.


I think in the panel listings they are talking about watt hours of recovery per 8 hour day. This one would be a 50 watt panel so 400 watt hours.


My guess is that it may or may not be intentional. In the RVs when they were listing amps instead of amp hours for battery capacity, I am quite sure it was intentional when Roadtrek started it all.


For the panels it may be a translation error or conversion from metric error, but I wouldn't base any amount of money on it.



Any way it happened, it is truly inexcusable that it happened. If they can't list correct specs, how in the world can you trust any of the rest of what they say?

 

[engnrsrule]

Added Power sequencing

So I found a 4 channel sequencing relay, which opens circuits in reverse order it closes them. System works nicely. Energize, SCC comes on, 8 seconds later panels connect. Power off Panels disconnect, 8 seconds later SCC powers down.

Pictures:
single continuous relays (2) for Battery and PV to SCC
Sequencing board (will be mounted inside a project case)
Remote switch at console with mounting plate.

Sequencing board info (Amazon $21)
Garosa 4 Channel Power Time Sequence Board Double Panel High Current Adjustable Sequential Controller Module 30A 0.5-4s Adjustment Electronic Switch Control Board
https://a.co/d/9F0IXLo

Individual power relays (Amazon $16 for 2)
Hamolar 2 Pack 12V DC 120A Starter Relay Switch Car Heavy Duty Split Charge Continuous Duty 4 Terminal SPST Relays for Truck Boat Marine
https://a.co/d/bjFz567

 

[SteveJ669]

I'm noting a few issues with this system.

That is only a 50 watt panel, totally inadequate for the task at hand.

The location of your panel would seem to be suboptimal. It looks like the panel could get shaded by the A/C unit. A little bit of shading kills a lot of output.

That controller will work a lot better if you have 2 or more panels in series. It will not engage in the morning until the panel voltage reaches 5 volts above the measured battery voltage. With 2(or more) panels in series you will have a longer charging day. Also, just having a single panel, or multiple panels wired in parallel, the system will perform poorly in suboptimal solar conditions, if at all. This paragraph assumes nominal "12 volt" panels.

Solutions.

Order up more matching panels to what you have so you have 2 or three in series and two parallel strings of those. Keeping in mind: Matching output current is critical in series strings, matching voltage is critical in parallel installations. A 3s2p will result in a 300 hundred watt system.

Or...Scrap that little panel and install larger panels, 2 or three in series, or a single large panel with higher voltage. Four in series will be getting pretty close to the max voltage input of the controller.

OR... just get yourself setup with portables, though in a class B storage is always an issue. When we had a class B we used a portable system and currently do as well in our Safari Trek. I really don't like parking in the sun for solar access. We can have our portables up to 75' from the camper. Our 240 watt system works well for us, bringing the 200 AH of L/A batteries to float by early afternoon on good solar days. We have an absorption fridge and no CPAPs.

 

[engnrsrule]

I'm noting a few issues with this system.

That is only a 50 watt panel, totally inadequate for the task at hand.

The location of your panel would seem to be suboptimal. It looks like the panel could get shaded by the A/C unit. A little bit of shading kills a lot of output.

That controller will work a lot better if you have 2 or more panels in series. It will not engage in the morning until the panel voltage reaches 5 volts above the measured battery voltage. With 2(or more) panels in series you will have a longer charging day. Also, just having a single panel, or multiple panels wired in parallel, the system will perform poorly in suboptimal solar conditions, if at all. This paragraph assumes nominal "12 volt" panels....

Thank you SteveJ. I think the 400w hook in this panel might have been an 8 hour extrapolation, so yes. But I sized the rest of the system to support more panels going forward. Challenge is the space above. Most 200w panels I could find come close to hanging over, or land in the curved edge of the roof. I recognize the shade potential from the AC, but also felt the middle area provided shorter cable run and protection from road hazards.

As for now, I do see the system putting some back. If it stretches my capacity by a day or 2 in ideal conditions that is enough for now.

 

[engnrsrule]

I permanently mounted the sequencer in a box.

 

[RossWilliams]

I run my cpap straight off 12 volt with a cord I got from a manufacturer for that purpose. I think most of them run on 12 volts - I run two different ones using that cord. I also often turn off the humidifier to save power. After getting an uncontrollable nose bleed at the Grand Canyon I have been more careful about doing that in very dry or very high conditions.

 

[engnrsrule]

I run my cpap straight off 12 volt with a cord I got from a manufacturer for that purpose. . . I also often turn off the humidifier to save power. After getting an uncontrollable nose bleed at the Grand Canyon I have been more careful about doing that in very dry or very high conditions.

I ordered the 12v power supply. Did not realize these were available. I am particularly sensitive when there is not enough humidification, but I use a heated hose and may try to get by with unheated to save power.

 

[engnrsrule]

Update after Trips and upgrade

So after I realized the misstated capacity of the original single panel discussed earlier, I added 2 120 w panels to the mix. I believe I am now getting around 280 watts. I will say that I particularly like the sequencer device that turns the controller on before connecting the panels and disconnects the panels before turning off. I am surprised controllers do not build this in.

I bought the DC power supply for the CPAP, and left the heated tube home. However a 5 day Atlanta trip did not have much boondocking.

Upon returning home I decided to leave my battery switch and the solar on and see what happens. Pre-solar, a week or so like this would show some depletion of the batteries due to various sensors, the shunt electronics, and other small drains. But after 6 weeks in this mode batteries are still topped off.

So I am calling this success!

 

[@Michael]

...I particularly like the sequencer device that turns the controller on before connecting the panels and disconnects the panels before turning off. I am surprised controllers do not build this in.

I like your idea of using a set of relays to properly power up and down solar controllers.

 

[Boxster1971]

The Victron SmartSolar controllers on my Airstream Interstate can be turned OFF an ON via the Victron app via Bluetooth. This is handy as I have two controllers tied to a single three panel array, one for 48V Volta battery and one for the 12V chassis battery. Normally not good to have multiple MPPT controllers on single array, but by turning one OFF I can select which battery I want to charge.

 

[engnrsrule]

UPDATE:

Skeptics unite! The so called 400w panel was deceptive advertising. Its 50w. 400 came from an 8-hour representation! I subsequently added 2 more panels that were 120w (per hour). so I figure my system is delivering 290 now. Also made the leap to a 300W Lithium battery. Got the lzrgest wattage that I could find that would fit in the original battery compartment. No real room for expansion and did not want to take up any of the scarce storage space. THis system has been working very well.

 

[booster]

UPDATE:

Skeptics unite! The so called 400w panel was deceptive advertising. Its 50w. 400 came from an 8-hour representation! I subsequently added 2 more panels that were 120w (per hour). so I figure my system is delivering 290 now. Also made the leap to a 300W Lithium battery. Got the lzrgest wattage that I could find that would fit in the original battery compartment. No real room for expansion and did not want to take up any of the scarce storage space. THis system has been working very well.

This looks like it could be another of the way too often misuse of energy and power terminology. Many of the misuses are certainly do to lack of understanding or casual shortening of terms without realizing the importance, but there also are those that use the terms incorrectly with the intent to deceive. Mostly sellers of things looking for a specmanship edge on their competition. At the least it can make things difficult to figure out what is meant and at worst you get mistakes like in this example.

In the case of the above brief summary that engnrsrule put up it all started with a deceptive seller, it appears who tried to make a 50 watt output max solar panel look to have much more output that it had.

The 50 watts is a correct term for a solar panel and is the instantaneous max output of the panel in perfect sun. If the panel was stated as 400 watts by adding a time factor of 8 hours to it the term is incorrect and should be watt hours. This is a huge difference as over 8 hours a 50 watt panel will give about 33ah of energy at 12v if it were 100% efficient and 400watt panel would give 264ah if 100% efficient. Real world use would give on average about 1/2 of that much recovery in 8 hours of decent sun conditions.

Engnrsrule now has 290 watts of solar max output, but it will not deliver that much and is probably in the 200-220 watt range in real world use.

I am assuming that he has a 300 amp hour lithium battery now, as IIRC he has mentioned that in the past. Not 300 watts which is not a term used for energy storage in batteries. Watt hours is correct as is amp hours as they both are energy terms but amp hours you need to multiply the ah by the voltage to get watt hours.

We have a very similar system to what he does, by coincidence, at 300 watts of solar but larger lithium bank at 618ah at 12v. Bottom line is depending on his power use and how often he gets some alternator charging from driving, he could be nearly energy independent of shore power in good sun and moderate to low amounts of driving. In cloudy/rainy weather over several days he would need to drive more or find shore power once in a while. 300ah of lithium, if used to 20% SOC gives 240ah of use and that would last us 4-5 days on average with no driving or sun at our normal power use. In the 3+ years of use on our lithium we have never used more than 300ah of range and only plug in if we need air condtioning. We do midrange charging between 30% and 80% state of charge normally.

Bottom line for me is that the units used to describe the power and energy can get to be very important for both understanding by others and to prevent errors like in this example. Confirm anything and everything vendors tell you or list as you never know when a deceptive seller will try to take advantage.

 

[engnrsrule]

I am assuming that he has a 300 amp hour lithium battery now, as IIRC he has mentioned that in the past.

Booster you are correct (as usual). My mispeak...it is 300ah. In my current usage this is plenty and no issues with 12v and moderate inverter use. In fact it's enough to have me changing to a compressor fridge. First big trip with that is Texas in August (since Virginia simply is not hot enough).

Prior trips using roof fan all night and inverter a lot (TV, computers, CPAP) would have SOC in 80-85% by morning. Solar (alone) would have it up to 100% by mid morning.

 

[booster]

Yep, for most people 300ah of lithium or AGM is plenty for a compressor frig and other stuff, especially if you have good solar recovery. You are quite a ways south of us and that means more solar available, but of course you have sit in some very hot sun to get it. You should be able to get 100+ah per day recovery from solar in the sun this time of year. 15% down overnight is about 45ah do quite a lot higher than our overnight use but no CPAP or fans running overnight for us, just the frig. You probably would get to about 80ish ah per day and the solar can cover that on good sun even with no driving.

Are you running the smaller AC loads of the big inverter? If so, you might want to consider having a second, small inverter to run that kind of stuff because the parasitic is very low on them. We use two small invertersone 400 watt and one 120 watt PSW inverters besides our 3000 watt shore inverter/charger. One runs a "charging station" and the other is for the TV and audio stuff in the cabinet. Simple 12v switch to turn them on individually. We use almost no 12v converter anymore, just the small inverter and the factory 110v plug for whatever the device is. We put the small inverters in before we had this much battery bank, but still nice as they are cool running and very quiet.