Small solar set up for TT.

[Trackrig]

Got home with a used 2006 Nash 26X TT that I bought a little while ago. I want to put some solar on it, but not get carried away at this time. There's a chance I may not keep this trailer so I don't want to put a lot of time, money or effort into the solar until I do decide to keep it. Part of it is making up my mind if this TT is too small. There's another model three feet longer that I'd like.

The TT is factory wired from the roof to the batteries with #10 wire for solar. It's probably about a 14' run. There are two 6V batteries on the tongue. If I keep the trailer I already know how I'll add two more batteries.

I wanted to just put a panel on the roof and hook up the wiring to the panels and batteries. I don't want to get into running larger wire, roof boxes, drilling holes, figuring how to get it down through cabinets, buying a controller and so on at this time.

However, it appears I can only go with about 15W of solar without using a controller. So the next approach I'm looking at is putting about 2-300W of non-tilted panels on the roof, using the factory wiring to where it comes out at the batteries and then using a hopefully WATERPROOF controller to connect to the batteries.

Can anyone recommend a suitable WATERPROOF / WEATHERPROOF controller that I can mount outside near the batteries? If a truly weatherproof controller doesn't exist, then I might be able to mount it in a waterproof electrical box under the battery rack if the controller won't generate too much heat. This is in Alaska, so outside temperature shouldn't be a problem.

I do have electrical in the back yard to run the Progressive Dynamics PD9245 converter. In storage mode it's at 13.2V and the charge wizard goes to an equalize mode of 14.4V every 21 hours for 15 minutes.

What are your recommendations on a simple solar set up using the factory wiring? I don't want to use "suitcase" styled panels due to the lack of storage space in the TT.

Bill

[Trackrig]

I really doubt it. There's only so much you can get in a completely sealed unit for that price and it's all I can find.

Bill

[westend]

Does that "feature rich" controller allow the user to select voltages and duration of the different charge levels? These features are nice to have, especially if leaving your rig in a storage situation for longer periods or if you're operating at the edge of battery SOC.

[Trackrig]

This is the OP - finally found a waterproof / weatherproof controller!! I talked to Back Country Solar and they haven't had any failures on them installed outside in the weather. Because they're totally sealed, you don't have to worry about them causing any sparks resulting in a fire.

Zamp has a Digital Deluxe 5 Stage 15 Amp PWM Solar Charge Controller #ZS-15AW. They also make a smaller 10A version.

Our 15 amp PWM solar charge controller has a large digital display showing volts, amps and amp over a period of time while LED lights show charging status and battery condition.

Our Digital Deluxe 10 & 15 Amp PWM Solar Charge Controller is designed to do it’s job with out the need for maintenance but it also is feature rich to monitor and indicate system functions.

Features –
-For Gel, AGM, Conventional Lead Acid (WET) and Calcium Batteries
- Advanced MCU control pulse width modulation (PWM) technology to ensure best battery life and high efficiency
-Build in regulator to prevent batteries from overcharging
-Built in regulator to prevent battery undercharge; The unit provides an automatic equalization feature for deeply drained conventional lead acid or calcium batteries, as well as provides a cycling automatic equalizing feature every 28 days (when constantly connected)
-Floating feature to keep the batteries as topped off as possible. This process reduces water loss and prevents the batteries from drying out
-Protects batteries from discharge at night preventing current flowing back from the batteries into the panel
-External battery temperature sensor (optional)
-Multi-charging protections against reverse polarity, short circuit, over temperature, over voltage, etc.
-Surface or flush panel mounting options
*****Waterproof/Weatherproof****

I'll buy one in the spring for the solar install on my TT where I want to install it out on the tongue with the batteries so I don't have to drill holes in TT. I need to look at panels now to match up with the 15A max input.

Bill

[ewarnerusa]

mike-s wrote:

pianotuna wrote:
One difference is that if you have no more roof space MPPT may allow you to harvest about 8% more.

How much more roof space? Show your math, because I suspect for the difference in cost between PWM and MPPT, you can get more return from adding another panel.

The difference in price between a Morningstar PS-30M (PWM) and a TS-MPPT-30 (MPPT) is about $200. That will easily pay for a 100W panel. So, you'd have to have over 1000 W in panels for an 8% savings to pay off.

Well, he's pretty clear by stating "no more roof space". No need to show math. But I do get your valid point.

I have been taking part in a solar panel forum lately and just sticking the RV camping/off grid subforum. It is a very different place than RV.net with respect to solar ideas and the majority vibe there is very "MPPT ALL THE TIME, NO EXCEPTIONS, PWM IS FOR FOOLS". I have made a similar point as you with respect to realistic return on investment, but soon learned that there is no changing the minds of their frequent posters. But the truth is they are not leading folks into designing bad systems, just often massively overbuilt. But it has made me rethink some things.

My thought process regarding MPPT is that it will save you money if you're building a system with several panels because you can and should use high voltage panels. These panels cost less on a $/watt basis than 12V nominal panels. So the more expensive controller is more than offset by the money you save in panels. But if you're only installing a panel or two, PWM is probably a less expensive route. When I built my system, I read a rule of thumb that the tipping point for going MPPT is in the 500 watt range. On the solar forum I'm referring to, one poster says this is more like 200 watts. Actual solar harvest is not part of this dilemma.

[pianotuna]

Hi Mike,

If there is room to add a panel that is certainly the way to go. If there is not room then MPPT may garner an extra 8%. On a 600 watt system that amounts to about 48 watts. 48 watts x 5 hours =~ 240 watt-hour per day. Four days and you have about an extra KWH to use.

When I planned my system panels cost $5.50 per watt, so at that time MPPT made good sense. Now with panels sometimes as low as $0.26 per watt, the only time is where there is simply no more roof real estate to fill.

mike-s wrote:

pianotuna wrote:
One difference is that if you have no more roof space MPPT may allow you to harvest about 8% more.

How much more roof space? Show your math, because I suspect for the difference in cost between PWM and MPPT, you can get more return from adding another panel.

The difference in price between a Morningstar PS-30M (PWM) and a TS-MPPT-30 (MPPT) is about $200. That will easily pay for a 100W panel. So, you'd have to have over 1000 W in panels for an 8% savings to pay off.

[the_happiestcam]

Here is my setup Clicky

I also have LED lights.

[mike-s]

pianotuna wrote:
One difference is that if you have no more roof space MPPT may allow you to harvest about 8% more.

How much more roof space? Show your math, because I suspect for the difference in cost between PWM and MPPT, you can get more return from adding another panel.

The difference in price between a Morningstar PS-30M (PWM) and a TS-MPPT-30 (MPPT) is about $200. That will easily pay for a 100W panel. So, you'd have to have over 1000 W in panels for an 8% savings to pay off.

[pianotuna]

Hi

I have a #10 prewire and my line losses are less than 1%.

I don't have an amp-hour counter--and if I did, the trimetric would be my dead last choice.

I do have an MPPT controller and nominal panel side voltage is 33.

There is a huge signal to noise ratio at the handy bob site with it being dated, sometimes misleading and mostly noise. For me it is the last place I'd send a beginner.

I managed just fine for 5 years with a MSW inverter.

allen8106 wrote:
This likely isn't what you want to hear but here goes:

First #10 wire from the roof to the batteries is too small, regardless of whether it was wired this way from the factory. Those idiots have no idea what they are doing when it comes to solar.
You need at least #6 wire from the panels to the batteries. You need a true battery monitor like a TM-2030. You need a charge controller like the Morningstar TS-45, you don't need MPPT. As a minimum you need the SC-2030 charge controller from Bogart Engineering. You will need a 500 amp/50 mV shunt on the negative side of the system at the battery for the battery monitor. You'll need a 300-1000 watt pure sine wave inverter. I'm using the Magnum MMS1012 on my system

Do yourself a favor and read BOTH Jack Mayer's and Handy Bob's web sites. Some folks deem Handy Bob a nut case but what he has to say about solar makes a ton of sense. I've actually talked to Bob and I'm modeling my solar system after his recommendations along with some inputs from Jack Mayer. These guys have lived full time on solar for several years and know what they are talking about. Bob has information on his web site for the financially challenged. I could likely spend any amount I want on a solar system but I value my money and don't want to waste it so I seek to spend it effectively. Bob's recommendations can help you do that.

[pianotuna]

Hi mike-s,

One difference is that if you have no more roof space MPPT may allow you to harvest about 8% more.

mike-s wrote:

And, if you want to argue that MPPT is different, I agree. It also has no real world benefit for the vast majority of RV systems.

[mike-s]

allen8106 wrote:
Remote volt/temp sense has nothing to do with getting maximum voltage into the batteries. Maximum voltage into the batteries (minimal voltage drop) is exactly why you want the controller as close to the batteries as possible. All remote sense and temp gets you is remote temp and sense, nothing else.

Come back when you learn electronics.

It's not "maximum voltage into the batteries," it's maximum current (which is a direct measure of the rate of charge - Coulomb flow). And, solar panels are current sources. A "12 V" panel will put out the same current (Isc) at up to about 15 V, which is conveniently but not coincidentally higher than charging voltage. If using a PWM controller, the voltage drop simply doesn't matter unless it results in a voltage less than the desired absorption charging voltage at the battery. And it simply doesn't matter if it occurs before or after the controller, the end result is exactly the same. Remote sensing is to insure the controller knows the proper (remote temperature) peak voltage needed, so it can regulate it (remote voltage).

And, if you want to argue that MPPT is different, I agree. It also has no real world benefit for the vast majority of RV systems.

[allen8106]

mike-s wrote:
Why bother mounting the controller so close the the battery? If you get a controller with remote volt/temp sensing, it can be anywhere. Then it doesn't make any difference if the voltage drop loss is before or after the controller.

Remote volt/temp sense has nothing to do with getting maximum voltage into the batteries. Maximum voltage into the batteries (minimal voltage drop) is exactly why you want the controller as close to the batteries as possible. All remote sense and temp gets you is remote temp and sense, nothing else.

[allen8106]

This likely isn't what you want to hear but here goes:

First #10 wire from the roof to the batteries is too small, regardless of whether it was wired this way from the factory. Those idiots have no idea what they are doing when it comes to solar.
You need at least #6 wire from the panels to the batteries. You need a true battery monitor like a TM-2030. You need a charge controller like the Morningstar TS-45, you don't need MPPT. As a minimum you need the SC-2030 charge controller from Bogart Engineering. You will need a 500 amp/50 mV shunt on the negative side of the system at the battery for the battery monitor. You'll need a 300-1000 watt pure sine wave inverter. I'm using the Magnum MMS1012 on my system

Do yourself a favor and read BOTH Jack Mayer's and Handy Bob's web sites. Some folks deem Handy Bob a nut case but what he has to say about solar makes a ton of sense. I've actually talked to Bob and I'm modeling my solar system after his recommendations along with some inputs from Jack Mayer. These guys have lived full time on solar for several years and know what they are talking about. Bob has information on his web site for the financially challenged. I could likely spend any amount I want on a solar system but I value my money and don't want to waste it so I seek to spend it effectively. Bob's recommendations can help you do that.

[mikakuja]

I would definitely go with your second plan of running the controller in the cabinet.
Knowing Nash, your trailer is solar ready and you should have a closed in area in one of the cabinets, possibly near the control center or sometimes near a main switch panel where the factory has intended a controller to be mounted.

We have 260 watts on our roof with a 20A mppt controller, 2 225ah 6v batteries and a 1500w inverter. Keeps our trailer powered nicely being somewhat power conscious.... We also carry a gen as a backup, the sun is not always available in many of the sites we go to. I am considering 4 batteries as well, but only because we camp for extended periods off grid and like to occasionally use the coffee pot and or microwave with the inverter, which is extremely hard on the batteries.

[mike-s]

Why bother mounting the controller so close the the battery? If you get a controller with remote volt/temp sensing, it can be anywhere. Then it doesn't make any difference if the voltage drop loss is before or after the controller.