Going Solar!

One more thing - possible alternative solution.
And, my apologies to people suggesting 24V+MPPT - I've overlooked this route.

Yes, if you insist on having those thin OEM toy-wires - don't know why anybody would, but let's assume you do. You can still have ~280-300W array - a single 24V panel. It has higher voltage than 12V panel, but amps are lower, so your OEM wire will be capable to handle it. There is a catch though - you will need to buy 25-30A MPPT controller, cost at least $300 more than small PWM.

There is one Chinese MPPT Eco-Worthy that costs $110 - still more expensive than $50 PWM - but it can handle only up to 240-250W as I recall. Another problem is that you need to install this Eco in easily accessible place due to lack of remote controlling. Most likely - inside, in front of the trailer, while batteries will be outside, so the temperature compensation won't work properly. More expensive controllers usually come with a remote temperature probe.

If manufacturer will terminate the wires somewhere in the middle of the trailer (they often like installing controller on top of the fridge), you might as well forget about this solution because with ~300W you'll need to place controller closer to battery.

I'd rather spent these hundreds on hiring somebody to run a proper wire for 12V panels (and to proper location of controller). Not that I "like" 12V panels and PWM - my array is made of 24V panels and MPPT controller, no hired labor was used. But in your case PWM route looks better.

pianotuna wrote:
3 batteries connected in parallel will last more than 3 times as long as using one battery at a time.

x2.

If you have 3 batts already, use them all in parallel. No need to rush for 2*6V either, you can get them later, when these die.

Jack Mayers "Golden Rules" is better for a beginner than Handy Bob's blog. I enjoy reading Bob's rant and agree with most of it, but this is not a good read for a beginner. Maybe only to get you interested. He is not a good educator, let's put it this way.

Bob is not trying to sell you anything, while your dealer is. They take a trailer with 10W panel and 16ga (?) wire from the factory, and add 150W. Easy - yes. Sensible - no.

10W panel is practically useless, might as well get 140W in its place. And another 140W nearby. Total 280W. With PWM controller. For when in storage, 280W will keep your batts full same well as 10W.
2*140W panels.

Again, (is it 3rd time I'm asking about this?) - find out what wire is in there, and what is wire length from roof to proposed controller location.
Important detail: controller should be as close to batteries as possible, somewhere in the front of the trailer. Manufacturers often ignore this rule.

If 2*140W is too much for this wire OR if you don't have enough room, get 2*120W or 2*100W. Anything more than 150W is better, because you do need more.

If the OEM wire is so thin that it can't handle more than 150W, I would cancel this option, and used the money to buy "proper" components and hire a solar installer like AM Solar of whatever you will find. If your dealer is handy enough for that, use him. Most any handyman or electrician will be able to screw 2*120W or 2*140W panels to the roof and run #10 wire to inside.

The above 2*140W kit includes MC4 Y-splitters needed to wire 2 panels together, this is a very common setup. 20ft long box should have enough roof real estate for that.

Hi Vintage,

While doing it your way does leave a fresh battery for running the furnace it does fail to take advantage of the considerable gains that the Peukert Effect allows. Simply stated, 3 batteries connected in parallel will last more than 3 times as long as using one battery at a time.

Vintage465 wrote:
My present trailer has three batteries. Two for the everyday stuff, one dedicated to the heater. The heater battery has a disconnect so it won't communicate with the other ones unless I close the s
witch for charging. V-465

Yeah, sometimes there's room for one large panel, other times there's room for two smaller ones. A few different sized cardboard cut-outs can come in handy for checking out roof space. Plus, sometimes you need space to walk around up there, without stepping on the panels.

pianotuna wrote:
Hi Vintage,

How many amp-hours of battery bank? If it is 300 or less I'd go for 300 watts of solar. The smaller the bank the higher the ratio of solar to amp-hours needs to be. With medium to large banks the minimum figure is 60 watts per 100 amp-hours.

At about 85% state of charge, flooded batteries won't accept more than 12.5 amps which translates to 150 watts of solar. So the "reasonable" maximum is about 150 watts per 100 amp-hours of storage.

You can service a larger bank of batteries by having switches so that the solar will service 1/2 the batteries at a time. That is what I chose--back when panels were $5.50 per watt. If I were doing it today I would have gone for 525 watts (or more) of solar.

With a residential fridge I'd add 200 amp-hours of battery bank and enough solar to cover the daily wattage demands of the fridge (about 200 extra watts, based on a 5 hour solar harvest).

BTW I don't think handybob is a good source of solar information. Too much rant.

This guy has the golden rules of solar without the rant.

http://www.jackdanmayer.com/rv_electrical_and_solar.htm#The%20Golden%20Rules

Also some suggested installers. and as pianotuna said rule of thumb is 100 watts of solar per 100AH of battery. That is a minimum figure.
Get a PWM CC for small solar banks, 300 watts or less. At 400 watts MPPT will begin to pay for itself.

Hi Vintage,

How many amp-hours of battery bank? If it is 300 or less I'd go for 300 watts of solar. The smaller the bank the higher the ratio of solar to amp-hours needs to be. With medium to large banks the minimum figure is 60 watts per 100 amp-hours.

At about 85% state of charge, flooded batteries won't accept more than 12.5 amps which translates to 150 watts of solar. So the "reasonable" maximum is about 150 watts per 100 amp-hours of storage.

You can service a larger bank of batteries by having switches so that the solar will service 1/2 the batteries at a time. That is what I chose--back when panels were $5.50 per watt. If I were doing it today I would have gone for 525 watts (or more) of solar.

With a residential fridge I'd add 200 amp-hours of battery bank and enough solar to cover the daily wattage demands of the fridge (about 200 extra watts, based on a 5 hour solar harvest).

BTW I don't think handybob is a good source of solar information. Too much rant.

Just a couple of more notes. I have never once in my life camped with one battery. My present trailer has three batteries. Two for the everyday stuff, one dedicated to the heater. The heater battery has a disconnect so it won't communicate with the other ones unless I close the switch for charging. I may need to do the same thing with this trailer some how. Maybe it will have a dedicated battery for the the C-Pap with a disconnect between it. A Microwave will not be used by us. I don't use them at home and I don't use the one in my present trailer. I do agree with the that 24hr. drain going on with all the stupid monitoring things. All those little red light add up!

V-465

This one the dealer was discussing actually comes with a 150w installed. He was talking about adding an additional 85w to the 150w. All said, I'm likely going to wind up with the trailer that is all set up with the quick connects and the 10w maintainer. Based on what I read @ http://www.rvsolarelectric.com and what you fine folks are suggesting I think two 100w panels and the fancy controller might be a good starting point. Not sure I'm gonna get much more on the roof. The trailer is a 20' box. Less than 24' hitch to bumper. Once I get the trailer in my yard I will add up all the amp draw and to the job right. I really don't plan on using the heater during the day. At least that would not be the norm. I don't really consider us to "fair weather campers" but I am not really intending on going any where that is less than 10 degrees for any real length of time.

Yes, 300w at 24v is the same as 150w at 12v, AMP wise, which is why I suggest he go 24v... to keep voltage drop to a minimum.

I thought wire was rated form amps and not watts?
Can't 300 watts have the same amps as 150 watt?