I added Solar to my Roadtrek (Sprinter)

[engnrsrule]

I became a CPAP user in late 2022, and have found that keeping the inverter in to run it all night is cutting into my boondocking capacity. I have 235 Ampere-Hours of LA batteries. Do not plan to go lithium, as I cannot get more AH without major modification of the existing battery compartment, or sacrificing important storage spaces. Yes I do realize going to Lithium would improve performance since they can be operated to much lower state of charge. Maybe next time...

I went with a relatively simple system, a single panel, supposedly 400 watts. I have more controller than I need, Victron 100/50, in order to support more panels later. Also upsized wiring to 8 AWG to be sufficient for future increases. It is recharging from minimal use in driveway. Well have to take a trip to fully assess.

I located the panel in the middle between AC and roof vent to minimize the run distance. Since my mounts are ABS plastic I added a binding cable (8 AWG) to one roof bolt, visible on the picture.

There is something disconcerting about drilling holes in the roof!

I wanted to be able to turn the system on and off, so added a switch on my control console to a NC relay to connect the solar panel feed and the controller output. The tape label will be replaced with a permanent engraved plate.

I have a Victron Monitor so naturally the negative connects thru the shunt. The "Load" side of the shunt had too many leads piled on so I added a 6 place terminal block.

While not shown, the panel to, and feed out of the controller have over current protection of 5a and 50a respectively.

I added a picture of the electrical space (under one bench seat) in the sprinter. It is pretty full based on this, plus a prior upgrade to inverter and charger. (I have a thread on that upgrade from a couple years ago). The new inverter (silver object) is set to one side, but normally mounts on top of the transfer switches and battery charger.

 

[booster]

I became a CPAP user in late 2022, and have found that keeping the inverter in to run it all night is cutting into my boondocking capacity. I have 235 Ampere-Hours of LA batteries. Do not plan to go lithium, as I cannot get more AH without major modification of the existing battery compartment, or sacrificing important storage spaces. Yes I do realize going to Lithium would improve performance since they can be operated to much lower state of charge. Maybe next time...

I went with a relatively simple system, a single panel, supposedly 400 watts. I have more controller than I need, Victron 100/50, in order to support more panels later. Also upsized wiring to 8 AWG to be sufficient for future increases. It is recharging from minimal use in driveway. Well have to take a trip to fully assess.

I located the panel in the middle between AC and roof vent to minimize the run distance. Since my mounts are ABS plastic I added a binding cable (8 AWG) to one roof bolt, visible on the picture.

There is something disconcerting about drilling holes in the roof!

I wanted to be able to turn the system on and off, so added a switch on my control console to a NC relay to connect the solar panel feed and the controller output. The tape label will be replaced with a permanent engraved plate.

I have a Victron Monitor so naturally the negative connects thru the shunt. The "Load" side of the shunt had too many leads piled on so I added a 6 place terminal block.

While not shown, the panel to, and feed out of the controller have over current protection of 5a and 50a respectively.

I added a picture of the electrical space (under one bench seat) in the sprinter. It is pretty full based on this, plus a prior upgrade to inverter and charger. (I have a thread on that upgrade from a couple years ago). The new inverter (silver object) is set to one side, but normally mounts on top of the transfer switches and battery charger.

Do you have your shut off switch staged to shut of the panels first before disconnecting the controller? You don't ever want the panels connected when the controller is off or doesn't have a battery attached to it as it can cause some spikes and overvoltage situations. The controllers are commonly wired so they are always active and wired directly to the battery bank, with maybe a pullable fuse for long term storage after the panels are turned off or in the dark.

 

[engnrsrule]

Thanks for that explanation. I had seen that recommendation but not the why. They connect and disconnect simultaneously as wired. One relay with 2 legs. I guess I could leave the SCC hard wired and let the relay isolate the panel to prevent any momentary mismatch. I will add my schematic.

Also, since the control voltage to the relay comes off a fused coach circuit, when the battery isolation switch is off, it also opens the relay.

 

[engnrsrule]

Here is the schematic. I can take the SCC out of the relay.

So Booster, is there a device that would accomplish the sequencing? Trigger On: turn on 12v control switch / powers up SCC relay / powers up solar panel relay after some delay

Trigger off: turn off 12v control switch / powers off Solar panel relay / powers off SCC after delay

 

[mumkin]

Many have reported switching to a 12v CPAP, which is thus easier to run without the inverter wasting all that battery charge. Sorry I don't know the brand or model #.

 

[booster]

Here is the schematic. I can take the SCC out of the relay.

So Booster, is there a device that would accomplish the sequencing? Trigger On: turn on 12v control switch / powers up SCC relay / powers up solar panel relay after some delay

Trigger off: turn off 12v control switch / powers off Solar panel relay / powers off SCC after delay

I think Blue Sea has some battery disconnect switches that do similar so the field can be turned off in an alternator before disconnecting it from the battery. I am pretty sure you could easily do it with two relays, one a standard relay to turn of the panels and the other a time delay relay to turn off the controller. You would, however need to reverse the relays for turning them back on to delay the other direction.

 

[booster]

I think something that might work would be to have a common on/off switch for convenience and two time delay relays. They would need to be opposite functioning. You would want the controller to be delay on off, instant on. You would want the panels as delay on instant off.


This should give you the right delays you need to get the job done safely.


I think these relays would work for you, but the are bit costly. They are Hella and there probably are cheaper knockoffs around.


https://www.delcity.net/store/Time-...ISCRkOs_oN14olvoJaHOWig4LZk0NcUxoCPw4QAvD_BwE

 

[GeorgeRad]

Having a warning label serves well for me. I added this label after getting recommendation from Booster.

 

[RizeMaster]

Why does the SCC need to be disconnected from the batteries? Does it draw significant current when the panels are disconnected?

 

[booster]

Why does the SCC need to be disconnected from the batteries? Does it draw significant current when the panels are disconnected?

Ours is not huge by any stretch of the imagination at .1-.2 amps but it is enough to run down batteries in storage for instance. 3-4ah per day adds up quickly over a long winter.


Ours is wired to the battery side of the disconnect switch but also has a pullable fuse for storage which has worked fine for us to this point.


What I have not figured out what to do is now that the lithium batteries are in place, what happens if we have a sudden shutdown due to the battery BMS. It would be rare, I think, as there are 3 batteries in parallel each with their own BMS so all would have to trigger. The most common fault, I think, would be high voltage from battery cell imbalance and that just shuts off charging and the controller would still have reverence but nowhere for the spike to go in discharge only mode.


We did not use the solar on our month long test trip without plugging in at all, and left the panels off and fuse pulled to the controller.


For right now, our most probable best way to go would be to leave the separator closed if we have the solar on and just accept the parasitic from that, which isn't much if the starting battery is near full. Then the controller would never lose contact with a battery.


We wouldn't be hurt by using a bit of extra power, but for those that are marginal on battery capacity could be. Even 200ah wouldn't give you many days of no charging if you have a compressor frig and a cpap getting used. Add in some device charging and entertainment stuff might put you over in a couple of days. Now days a lot of us want to be able to run the microwave or other heavy day stuff occasionally also.

 

[GeorgeRad]

Why does the SCC need to be disconnected from the batteries? Does it draw significant current when the panels are disconnected?

Same as Booster’s wiring, solar charge controller is directly connected to batteries so for extended storage indoor the solar charge controller will discharge batteries. Before long trips I need to disconnect main battery switch and solar charge controller.

 

[RizeMaster]

Thank you! Makes sense, to minimize parasitic draw.

Just a speculation, but I think the fact that we don't hear much about such Voltage spikes, and the fact that solar controllers don't come with some sort of emergency shutoff, tells me that maybe, there are no serious problems if the BMS trips the batteries.

Easy to test for you.

 

[booster]

Thank you! Makes sense, to minimize parasitic draw.

Just a speculation, but I think the fact that we don't hear much about such Voltage spikes, and the fact that solar controllers don't come with some sort of emergency shutoff, tells me that maybe, there are no serious problems if the BMS trips the batteries.

Easy to test for you.

With lead acid batteries, there is a much lower risk of problems as they don't completely bonk out while in use. It only would happen is somebody inadvertently shut of the main disconnect or if you had it off in storage and pulled the van out of the garage into bright sunlight type stuff.


I would totally agree we have never gotten a full explanation from the controller manufacturers as to which controllers would be susceptible. My guess would be that the MPPT chargers that can cover up to a 48v system and have 100v max input limit spec might be OK with a 12v system, but a 12v nominal PWM charger that has a much lower high limit might not be OK. Where the cutoffs on good and bad, if they exist at all, seem to be totally unknown. Of course the larger the solar capacity the worse a spike would be also.



Some of instructions mention it and most say wire directly to the batteries, I think, but many don't explain why.

 

[michaelingp]

I went with a relatively simple system, a single panel, supposedly 400 watts

Is that single panel really 400 watts? I have two panels that were advertised as 190 watts total (but I've never seen more than 180). These were installed in 2016, so if efficiency has improved that much, I would love to replace mine with higher wattage panels.

 

[engnrsrule]

I am skeptical, but will see how it performs under real life conditions and report back. There were mixed reviews but only one out of many said it underperformed. I have limited roof space and had thought getting 200 ways would be my constraint.

 

[engnrsrule]

I found something that should work and follows Boosters thinking, and still lets me power on or off with one switch. The PV and Battery feed are normal relays but I am running the coil feeds thru a sequencing delay relay that reverses the sequence for on and off.

I understand the "why bother" comment about the SCC. But part of the engineer in me says I should power down equipment not in use.

 

[GeorgeRad]

Is that single panel really 400 watts? I have two panels that were advertised as 190 watts total (but I've never seen more than 180). These were installed in 2016, so if efficiency has improved that much, I would love to replace mine with higher wattage panels.

I agree, judging from first photo it looks closer to 100W or over ~21"x42" by Renogy.

 

[hbn7hj]

If that small panel is 400 watts we all want it!!

It appears to be 1/4 of Renogy’s 400 watt panel kit.

 

[JML-ClassB]

CPAP - DC power

I also have a CPAP. I use a DC plug to power it - saves on the inefficiency of running thru the inverter. Also, I seldom use the humidifier. In the past I would run it thru a separate Jackerty but have since upgraded to 270 AmpHr LiPo and have plenty of power, even with an IsoTherm compressor fridge that replaced my old, trouble prone Dometic 3-way. Portable solar panels can also help. I can only put 100Watt panel on my 2013 Pleasure Way Excel. Portable panels fill the gap when needed. It looks like you did a nice job - congrats. And I agree with others, that is a 100 Watt panel. Looks just like mine.

 

[engnrsrule]

Specs on "400 Watt" panel

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.