24 volt solar panels

[ShawnKK]

First, don't hurt the OP.
Now, any solar nuts in here that can let me know if I can use a 24 volt solar panel on a 12 volt system in my Boler? I understand I would have to use 2 12 volt batteries but that is all I think I know.
The reason I am asking is I "think" I found a good deal on Watton Solar WTM230P 230 watt panels. He is selling them "new" at a dollar a volt. I did a Google search on Watton but nothing came up. Any help here?

[Paul Braun]

How big is that panel? It says it weighs 45 lbs and can be shipped freight only. It must be big. Where will you mount it? Do you have a solar controller in mind? I am not sure where you are looking, the unit I see is just a panel, and your cost is $230. Most panels used on RV's are larger than 60 watts and seem to max out at 120 watts. The panel you are looking at is a bit overkill.

Perhaps you should look elsewhere.

Some suggestions would be solarblvd in the states and wegosolar in BC.

Nice start but I think you need to head back to the drawing boards: Consider mounting, wiring from panel to solar controller, wiring from solar controller to battery, type and quantity of batteries, demands on the battery (what is your usage), portable or permanent, and so on. There are several good websites to learn more about solar on RV's. The guru is HandyBobs Blog, just Google the title and learn all about solar.

I think there has been several very good discussions on this web site, try a Google search within the web site for solar installation.

[Carol H]

Originally Posted by ShawnKK

First, don't hurt the OP.
Now, any solar nuts in here that can let me know if I can use a 24 volt solar panel on a 12 volt system in my Boler? I understand I would have to use 2 12 volt batteries but that is all I think I know.
The reason I am asking is I "think" I found a good deal on Watton Solar WTM230P 230 watt panels. He is selling them "new" at a dollar a volt. I did a Google search on Watton but nothing came up. Any help here?

A dollar a volt? really? sure it isn't a dollar a watt which is pretty common these days.

230W panel would be able to power up a number of fiberglasss trailers IMO. Lots of people including myself get by with a 45 or 60 watt panel but if I was buying again & as the prices have dropped so much I would probable go for a 100 watt panel.

[ShawnKK]

Originally Posted by Carol H

A dollar a volt? really? sure it isn't a dollar a watt which is pretty common these days.

230W panel would be able to power up a number of fiberglasss trailers IMO. Lots of people including myself get by with a 45 or 60 watt panel but if I was buying again & as the prices have dropped so much I would probable go for a 100 watt panel.

Yes, it is a dollar a watt not volt. I am still new to the solar thing. I also know 230 is overkill. But I rather have too much than too little. I was wondering about the 24 volt output. Not worried about having too much power. I haven't set my mind on getting it until I hear from the pros. I can use it for other things besides the Boler too. this is all new to me so everything is new to me. I just thought 230 was a good deal. Maybe not.

[ShawnKK]

Originally Posted by Paul Braun

How big is that panel? It says it weighs 45 lbs and can be shipped freight only. It must be big. Where will you mount it? Do you have a solar controller in mind? I am not sure where you are looking, the unit I see is just a panel, and your cost is $230. Most panels used on RV's are larger than 60 watts and seem to max out at 120 watts. The panel you are looking at is a bit overkill.

Perhaps you should look elsewhere.

Some suggestions would be solarblvd in the states and wegosolar in BC.

Nice start but I think you need to head back to the drawing boards: Consider mounting, wiring from panel to solar controller, wiring from solar controller to battery, type and quantity of batteries, demands on the battery (what is your usage), portable or permanent, and so on. There are several good websites to learn more about solar on RV's. The guru do it is HandyBobs Blog, just Google the title and learn all about solar.

I think there has been several very good discussions on this web site, try a Google search within the web site for solar installation.

It is local so no shipping. Not sure how big it is but yes it is big. Still trying to get more info on the pnl.
I did search SolarBlvd and after seeing the price Of the smaller units why not get more watts at this price. Even Harbor Freights 45 watt pnl is 150 dollars and not really a good deal no more. Maybe 24 volts isnt a good idea, that is why I was asking. The more I read up on solar the more I scratch my head. Lol.
I Googled this site about solar kits ect ect and I feel like I am getting no where. spent hours today reading and reading on solar. I am trying to learn enough to do it my way but still need some input like is it worth doing it and is 24 volt barking up the wrong tree.

[peterh]

The problem with building a 24 volt system is most of the DC electrics in your trailer, from the lights to the water pump and furnace motor, are all designed to work on 12 volts DC.

A dollar a watt for a "24 volt" panel (24 volt panels usually pump out around 36 volts) is not an unusual price these days, but they're always big panels. A 240 watt panel is going to be around 40" wide and 5-1/2 feet long, which makes it much wider than the ridge in your Boler's roofline and long enough that it'll almost certainly cover at least one of your roof vent(s).

Then there's the amount of power that panel will put out. On your average sunny summer day, you're going to get 6-8 hours of sun at about 80% charging efficiency. That's 150 Amp-hours of 12-volt battery power. Just to store that amount of power you'd need two big, 120 amp-hour 12 volt batteries weighing 70 lbs each. (It's bad for a battery discharge it below 40% capacity, so you multiply your panel's max output by 1.666.) That's a lot of electric power, but a lot of weight, too, and the money you save will go down the drain in battery costs.

Most people get by with 60-100w of solar panels. We have 100w on both our trailers, and it's always been enough. (We had 50w of power once . . . that wasn't enough to keep our furnace blowing on a cold September night in Yellowstone.)

So I'd suggest first looking at and measuring your roof space, then go looking for a 12v panel in the 75-100w range that fits. Or, alternately, find yourself a 60w panel and build your solar setup so it supports a second 60w plug-in panel that you can set out in the sun when you're in a shady camping spot. You'll spend less on your solar system and still have lots of juice for just about everything you can fit in your camper.

[Rene]

I think it is barking up the wrong tree. 24 volt systems are mostly for home based systems. With 24 volts there is less voltage drop on wire runs, so wire can be longer or smaller. You might save some money on a 24 volt solar panel but a 24 volt inverter will not likely be very affordable. I know someone who is upgrading their home based system to 24 volts as a do it yourselfer and its proving to be a very expensive conversion.

Since saving money on a solar system is important to you, stick with 12 volts. Start with the battery you have and convert lights to LED if you have not already done so. 75 to 100 watt panel should be lots for a single battery.
Solar Charge controllers that give you real time data on battery state of charge, discharge rate, voltage, solar panel outputs, etc. can be of great help in understanding the performance of your system and will tell you if you need more panels or batteries rather than blindly buying more batteries and panels. You can also choose to simply use less power. If you do not have a built in data monitor, you are flying blind.

I found this forum to be very helpful when it comes to understanding RV solar.

Solar Electric Power Discussion Forum by Northern Arizona Wind & Sun

[Larry C Hanson]

Hello,

The maximum power voltage (Vmp on panel label)
is not too important if you are willing to invest in
the proper charge controller. However, the best
controllers can be expensive. A good example is
the Blue Sky Solar Boost 1524iX (~$200). Once
you decide on which controller you are going to use
you can pick a panel that fits in the input
parameters of the chosen controller. A 230 Watt
panel seems a bit large if your power requirements
are not too high.

For single panel installations I would not mount the
panel to the trailer. In my experience it is best to
park the trailer in the shade and have the panel in
a sunny area. Of course there will be a voltage
drop in the wire connecting to the panel. So it
can be advantageous to have a panel of a little
higher voltage/power output so that the controller has
plenty to work with. Also, at a higher voltage there
is less power loss in the connecting wire than with
a lower voltage.

Limiting your power needs is always a good strategy.
One of the best things to do when starting a solar
installation is to figure out what your power needs are
and then design the system accordingly.

Two 12v batteries are not necessary. One good one
can be sufficient and save towing weight and system
complication, too.

Finally, important considerations are:

How much power will you use each day.
The period you will be using the trailer off grid.
What the capacity of your battery is.
The depth of your pockets.
How fit are you to be able to move a panel around.
Does your tow vehicle charge the battery when towing.

I hope your installation goes well. The fewer generators
I hear in a campground the happier my camping experience.

Larry H

[ShawnKK]

Thank you Peter, Rene and Larry.You guys gave me the answer that I needed.
I didnt set out looking for this pnl I just found it while on CraigsList. But it does sound like a great pnl for the house or barn. Maybe I will see if he would do trade and I can play with it at the house!

[Carol H]

Shawn as been suggested how big a panel (watts) you need will depend greatly on your power needs. Putting LED lights into the trailer has resulted in a pretty big drop in total daily power needs for many of us. A pretty good explanation on how to figure out your daily power needs based on what you plan to use can be found at The 12 volt side of Life Part 2.

For myself as Pete has rightly pointed out when off the gird my biggest power user is my furnace fan as I run my fridge on propane and greatly restrict my usage of electrical appliances such as a TV/DVD or electric coffee maker (use a french press instead).

[ShawnKK]

Thank you Carol. I know about the LED and been looking for a great deal on them for the Boler and my house. I just think they are still pricey so I am waiting for a sale or price drop.
I was looking for a 50 min to 160 max solar panel but thought this was a good deal so I wanted some input on it because I am new to solar. As Larry and others had said the "charge controller" is the deal killer because of the price.
I will wait till I see a good sale and or price drop again. Some say I am cheap! But if I see a good deal I will get it. Thank You everyone for your input...

[Carol H]

The prices on the LED's tend to vary greatly! but there can be a reason for that ;-) suspect its often the amount of luminous they produce or where made. I have paid way to much by some folks standards for a few bulbs but have also gotten real good deals online for others - so if they don't last long I don't feel so bad about tossing them.

For solar panels keep your eye on some of the more popular solar sites such as Solar Blvd.com Thats a pretty good site to look at the pricing and determine if your paying to much at another site.

[peterh]

One piece of advice I'd give is don't skimp on your solar charge controller. The charge controller is, quite literally, the brains of your solar panel system, and a cheap one will either not squeeze anywhere near as much power into your batteries from your solar panels or could, quite possibly, damage your batteries by overcharging them.

This is the charge controller I selected for our Surfside trailer. It's a good quality "MPPT" (Maximum Power Point Tracking) unit with plenty of capacity for solar panels, up to 130 watts. For our purposes, that's enough to support our 100w rooftop panel as well as our 40w plug-in "satellite" panel. (We're assuming that we'll only set the satellite up when our trailer's in a shady spot, and our main panel won't generate at full output.)

MPPT controllers take the "high" voltage provided by your solar panels (around 18 volts) and converts it to a lower, safer charging voltage (13.6v - 14.5v) with a minimal loss of power. MPPT charge controllers run from $80 to $250.

I'm not sure if I'd go much cheaper for an MPPT controller; I've seen lots of reports about people selling fake "MPPT" controllers that were actually less-efficient and cheaply-made PWM (Pulse Wave Modulation) units.

Not that PWM controller is a bad choice, mind you, but they are 10-20% less efficient. PWM controllers work by rapidly switching the higher voltage provided by the solar panels on and off, so that the average voltage they provide fits in the "safe" range of 13.6 to 14.5 volts, and all of the solar panel's output while that connection is "switched off" is lost.

A good PWM controller should cost around $40. Morningstar's Sunsaver 10 is a great choice if you want a PWM unit.

[Paul Braun]

Peter,

Nice advice, I have always been on the side of PWM controllers and have done most of my work with these. I need to expand my horizons to include MPPT controllers. The Tracer 1210 RN looked interesting so I did some exploring. First, I liked the fact it does four stages of charging. The bulk, absorption (called boost by Tracer), equalization and float. Many controllers do not do the equalization.

Second, I like to look at the voltages the controller will charge at. I have dual 6 volt Interstate batteries. Interstate recommends the all important absorption charge at a rate of 15.3. I have only found one PWM controller from Xantec that is capable of putting that out. I have looked at the recommended rate for Trojan 6 volts and it is a bit less. I wonder what the 12 volts models have for a recommended absorption rate? Has anyone checked the recommendations for their batteries? You should!

The Tracer puts out a robust 14.6 volts, better than many. Have you done any monitoring to see what actual voltages you are getting from the Tracer?

[multi-task]

As long as you're using an MPPT controller there would be no problem using a higher voltage panel so long as the voltage is within the spec of the controller and the controller can charge a 12v system. This is actually the preferred way to use an MPPT controller. I use a 215w panel that sits around 42.5v.