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

 

[SteveJ-ClassB]

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.