How to Live on 100 watts of Solar

[tx2sturgis]

Thank you everyone.  I can't find the solar controller for the solar panel I currently have, hopefully will locate by tomorrow and know more.  Is there a chance it could be mounted on the chassis?

Isn't it incorporated in the RV monitor panel area? Or mounted near one of the batteries?

It COULD be mounted in an exterior position assuming its protected from the elements and road-spray. Not likely, but possible.

If the solar panel was installed by someone without using a controller, which again, is POSSIBLE, then you should add one.

 

[duckwonder]

Isn't it incorporated in the RV monitor panel area? Or mounted near one of the batteries?

It COULD be mounted in an exterior position assuming its protected from the elements and road-spray. Not likely, but possible.

If the solar panel was installed by someone without using a controller, which again, is POSSIBLE, then you should add one.

Thanks for places to look.  It is not at the monitor panel area.  If it's mounted near one of the batteries, cannot find it, not even in the wheel wells.  If it is mounted on the chassis, I would bet it is not protected - everything under there is thickly coated with dirt so I would not be able to read anything.  Glad to hear that is not likely.  Did not know it is possible to install a panel without using a controller.  Bummer.  That's probably it.  Will have a second set of eyes on it tomorrow and keep you all posted.

 

[tx2sturgis]

Did not know it is possible to install a panel without using a controller.  Bummer.  That's probably it.  Will have a second set of eyes on it tomorrow and keep you all posted.

You can install a SMALL panel with a blocking diode and without a controller, but its only gonna be good for battery maintenance to offset parasitic drain. We're talking a 3-10 watt panel. But that's not what you have, so I'm suggesting it is POSSIBLE that someone before you, upgraded from a small maintenance panel without knowing that a controller should be used. It is NOT a good idea as it will cook a battery in a short time.

Its not possible to do it that way and be safe, but its possible that someone did it anyway.

You would know because your batteries would be in very poor shape, leaking, gassing, or dead.

 

[DLTooley]

you cant go wrong with the victron for small amps or the chinese MPPT for around $80-150. temp sense, bluetooth, rj-11 or whatever for your laptop, or the MT-50 remote.

Can you quantify the benefits of MPPT in a small, 12v, system?  As I understand it the two benefits are cabling efficiency in large systems due their ability to handle higher voltage and operating in sub-optimal conditions.  This second one is by definition tough to get one's mind around.

 

[jonsun]

Nope but youre buying it for the user presets which are quite important, temp sensor, and comm port. All thoae things together hard to find in that price range no matter if it does mppt or not.

 

[frater secessus]

Can you quantify the benefits of MPPT in a small, 12v, system?  As I understand it the two benefits are cabling efficiency in large systems due their ability to handle higher voltage and operating in sub-optimal conditions.  This second one is by definition tough to get one's mind around.

My understanding of the chain of factors:

1. MPPT's power harvest over PWM increases as the difference between panel voltage and bank voltage increases.  
2. High panel temps depress panel voltage.  This usually doesn't matter to PWM, because the voltage at which the system runs the panels is usually well below the panels max power voltage (Vmp).* 
3. In marginal conditions (rain, cloud cover, etc) panel temperature will be lower  --> panel voltage higher  --> the MPPT advantage more fully realized

The real question is this:  is it worth 2x-3x the money to get the benefits?  I can't answer that for anyone but myself.  I once bought a 5A MPPT controller because panels were very expensive at the time and I wanted to squeeeeeeeeeeeeeeeze everything I could out that 60w mono dinosaur.  I also have PWM and shunt controllers;  apparently I am some kind of solar libertine.


* The inverse is also true:  in very hot panel conditions the MPPT advantage can be minimal or even negated.**  
** assuming nominal panel and nominal bank voltage is the same.  The advantage would still hold if nominal panel voltage > nominal bank voltage

 

[duckwonder]

You can install a SMALL panel with a blocking diode and without a controller, but its only gonna be good for battery maintenance to offset parasitic drain. We're talking a 3-10 watt panel. But that's not what you have, so I'm suggesting it is POSSIBLE that someone before you, upgraded from a small maintenance panel without knowing that a controller should be used. It is NOT a good idea as it will cook a battery in a short time.

Its not possible to do it that way and be safe, but its possible that someone did it anyway.

You would know because your batteries would be in very poor shape, leaking, gassing,  or dead.

I don't know what the previous owner did, but I can tell you they were meticulous about notes otherwise all over the vehicle but there is no info about the solar.  My guess is they wanted to dispersed camp on weekends in the northwest and added the 100w panel.  I would think there would have to be a controller for that but I can't find it.  I would think you'd need an inverter, can't find that.  Unless it's a boxy thing with 3 capped holes on top with a label that says transfer relay switch.  I wish I were not clueless, but there you have it, cluelessness.

 

[highdesertranger]

the charge controller could also be mounted on the underside of the panel. highdesertranger

 

[tx2sturgis]

I would think there would have to be a controller for that but I can't find it.  I would think you'd need an inverter, can't find that.

The transfer switch should not have any solar components inside of it.

But, lets back up just a bit...

Is the solar panel mounted on the roof? By a previous owner we assume?

Do you see wires running from it to the inside of the coach? Do you see any extra, probably smaller, wires connected to the batteries?

Do you have a monitor panel that shows voltage of your coach batteries? If so, are the numbers higher in the day, and a bit less during nighttime hours?

Are the lights, freshwater pump, TV etc inside the coach all working normally? Do they all work when you are not plugged in to shore power?

Can you take pictures of anything with LEDs or digital displays inside the coach? (not including the dashboard of course).

I'm just trying to get a 'baseline' for your situation.....

 

[duckwonder]

the charge controller could also be mounted on the underside of the panel.  highdesertranger

Would not have thought of that, thank you.  When he's sealing cracks up there tomorrow, I will ask him to look.

 

[jonsun]

careful after all you went through dont ask him for extra **** to do cause he'd probably have to unbolt the panel and lift it up.

 

[tx2sturgis]

the charge controller could also be mounted on the underside of the panel.  highdesertranger

Oh...good call...it sure could be...

 

[duckwonder]

careful after all you went through dont ask him for extra **** to do cause he'd probably have to unbolt the panel and lift it up.

If he sets up my ladder, I'll be able to get up there too.  I plan to eyeball the roof as much as possible from on the side for cracks, look for that controller, and see if there is room for another panel (which i am 90 percent sure there isn't).

 

[duckwonder]

The transfer switch should not have any solar components inside of it.

But, lets back up just a bit...

Is the solar panel mounted on the roof? By a previous owner we assume?

Do you see wires running from it to the inside of the coach? Do you see any extra, probably smaller, wires connected to the batteries?

Do you have a monitor panel that shows voltage of your coach batteries? If so, are the numbers higher in the day, and a bit less during nighttime hours?

Are the lights, freshwater pump, TV etc inside the coach all working normally? Do they all work when you are not plugged in to shore power?

Can you take pictures of anything with LEDs or digital displays inside the coach? (not including the dashboard of course).

I'm just trying to get a 'baseline' for your situation.....

Solar panel is mounted on the roof by the one previous owner now deceased.  Cannot see wires running from it to inside the coach but might be able to tomorrow with a ladder.  There are wires connected to the batteries that look like the standard black and red. One is a lead acid house battery that is beat up, dirty, and old, but still working because I can turn stuff on without hookups.  The other battery, which is in a different outer compartment, several feet away from thehouse battery,is a boat battery with a sticker on it that says "changed Jan. 2016."  It's clean and looks new.  My guess is that that was added for the solar.  There is a hole in that compartment with battery wires running out of it but I cannot tell where it goes.  As far as the monitor, I only have one and it does Not show voltage; it shows the tanks and battery and the lights light up according to full, 3/4 full, 1/2 full, 1/4, empty.  It shows my battery is currently "full" which I assume means it's currently fully charged.  On the maiden voyage in the van, the battery went dead a couple of times and I had no idea how to charge it other than by driving so I idled the van for awhile.  I know now that is terrible practice, but I did not know then.  But it did work.  Yes, stuff works unhooked up, but not for long, maybe a day.  I'm having trouble with the pics, I took several and worked with them in a couple applications plus Paint, my biggest success was get one pic thru as a test pic but I can't seem to repeat how I did that.   As far as things that have LEDs inside the coach (nothing has a digital display), the propane alarm does, the genset does when it is On, and there is one other panel that I'm not sure what it is but it does say alarm on it, I think it might me for CO2.  Thanks for getting a baseline.

 

[tx2sturgis]

Ok cool...now I know why you are confused...I would be too!

But yeah I have a better grasp of the situation.

The reason I think HDR suggested that there might be a solar controller on the back of the panel is because some 'portable' solar systems have the controller mounted on the back of the panel, and maybe the previous owner left it there when he mounted the panel...we just cant know until you get up there and look. It does sound like the panel is not contributing anything, so its possible the previous owner or someone removed the controller. Again, we just dont know...yet.

Do you see any small holes in a wall, or maybe inside a cabinet, that could have had something mounted?

Look under the sink, under the fridge, under the bed, in the overhead cabinets, anywhere that is hidden where something could have been installed out of sight...and also look for (probably 4) wires that are not connected to anything.

Hate to put you thru this!

:-/

 

[duckwonder]

Do you see any small holes in a wall, or maybe inside a cabinet, that could have had something mounted?

Look under the sink, under the fridge, under the bed, in the overhead cabinets, anywhere that is hidden where something could have been installed out of sight...and also look for (probably 4) wires that are not connected to anything.

Hate to put you thru this!

:-/

Don't hate it Tx, I asked !  I have seen no "empty" holes anywhere that look like something has been removed.  I have looked under the sink because I had a leak, tightened that up.  The water heater or pump is down there but nothing else.  There's only the floor under the fridge and nothing above it parts-wise.  Under the bed is that IOTA box.  Nothing in overhead cabinets Except the TV cabinet - all sorts of crazy wires back there and one rather large box factory labeled "Cadence," - I looked that up and pretty sure that's the audio for the TV/DVD.  There's nothing else in that cabinet but the amount of wires was shocking to me.  Gonna wait til tomorrow and report back.  Thanks for being there.

 

[jonsun]

once this forum gets your system figured out you're going to get way more output than you are now

 

[Gideon33w]

My first van just had a 45w Harbor Freight kit and a used auto battery.
Ran some cheepie led lights, a Roadpro fan, and recharged my phone and laptop.
Occasionally, it would charge my cordless tool batteries too.
You size solar to your needs and budget. I didn't need/use much.

Now, my personal needs fit more of a 200w and 100-200ah deep cell battery bank setup.
Since I want refrigeration, better ventilation, and a 12v homemade evap cooler too.
Unless you want a true mini-rv and all the amenities you probably dont need more than this.

 

[duckwonder]

I found out today I do not have a solar controller or inverter for the 100w panel.  I have a converter and the panel wires go directly to the house battery.  If I get my genny fixed, can I boondock indefinitely?

 

[sometimesido]

as long as you have fuel i guess?