Solar powered adventure trailer

[teotwaki]

I won't knock that you are having fun and building the battery setup on the cheap. :elkgrin: Don't let what I write below rain on your parade at all.

You shuld first define the problem that you are trying to solve. Something like:

1. I am going to run Led Lights for approximately 5 hours at night each day. They pull 2 amps total so that is 10 Amp-Hours
2. My fan will be intermittent so I'll guess 2 hours at night and it pulls 1 Amp so that is 2 Amp hours
3. I will charge my iPad which is 12 watts so that is 1 Amp and it takes 2 hours so 2 Amp hours
4. My total needs per night are 14 Amp hours.
5. If I get 7 hours of good sunshine a 60 watt panel may produce an easy 20 Amp hours so I am sure that I can replace what I drew out of the batteries at night. I'm not planning for any cloudy days.
6. I will oversize my battery so that I never draw it down too much so I only need 2 of my 38 Amp Hour batteries to give me 76 Amp Hours. Now I can get rid of all of that extra weight due to the extra batteries and carrie water or firewood instead.

So that is a little over-simplified but it is all just basic math. There is a sticky here on the forum that points to all of the various solar power builds and reading some of those will help. If you define your need then design the solution you will not be so overbuilt. As one person said, you have so many amp hours of batteries you may not need to bother charging while you are camping. The flip side of that is that if you seriously drew all those batteries down the 60 watt panel might take days to charge that many batteries back up.

 

[DeMented Toys]

Here is the panel mount in action. Right now it is attached with bolds and wing nuts but I'm going to use pins instead for faster removal.

 

[DeMented Toys]

304 Ah of power is quite a bit. The batteries are 38 Ah each and weigh around 25lbs each. I've crunched the numbers and yes, for a weekend warrior camping trip I wouldn't come close to needing that much. For a few weeks off the grid in the winter, 304 Ah is going to be great. With full sun in the summer the solar panel will help replace some of the power as I use it. In the winter with short overcast or snowy days the panel isn't going to help much...
304 Ah should also be good for running power tools on my ranch without having to fire up a generator.
When I'm not doing military stuff I'm a metal smith/artist. It's going to be great having 304 Ah of quiet, clean, semi-renewable power available to run lighting, video and media equipment, fans and whatever else during those long weekend art shows....
The batteries have a good power to weight ratio. I could pull some out for short weekend trips and put them back in for longer adventures, ranch work, or art shows, but that's silly. The trailer is good sized with a 4'x8' floor. It weighs in around 1100 lbs with batteries under the floor. That leaves me with 2400 lbs of weight carrying capacity. It pulls very well, although I've never loaded it even close to max capacity. So for now, I'm sticking with 304 Ah. Once I get the wiring all figured out, fuse box, charge controllers, lighting, 12v power outlets, inverters, and then do a few long trips and art shows with it I can adjust fire as needed. The way the batteries fit under the floor I can fit 6 together into one bank, then I have 2 that have to go into a separate compartment. I was thinking of just pulling the 2 batteries that don't fit in the bank, but figured that since I already have them I may as well use them. So it's either 304 Ah at about 200 lbs, or 228 Ah at about 150 lbs.

 

[DeMented Toys]

I am picking up another solar panel this week. The more I thought about it, having a single 60watt panel for as much storage capacity as I have seemed kinda pointless. I'll now have 110 watts of solar panels, possible 160 watts if I have room. I'm also wiring in my solenoid for alternator hook up.

 

[DeMented Toys]

160 watts of solar panels it it. That should put a better charge into my 304 Ah (-50% = 152 useable Ah of battery power).

 

[graynomad]

Yes your system was not well balanced re panels and storage. With lead-acid batteries a (very rough) rule of thumb is 1W of panel for 1AH of battery.

But like all these rules you can fudge a lot either way. It mostly depends on how long between getting solar and how much you use. The bottom line however is that no matter how many batteries you have you still have to replace the power. When you get the alternator hooked up that may or may not make a difference, of course if you drive every other day it makes a big difference, if like us you are static for weeks at a time connecting the alternator is a waste of effort.

Assuming your panels are sized to your usage there are two advantages to having a larger that technically required battery bank, a) you can last longer without sun (pretty obvious) and b) you will not discharge the batteries as much as you would a small bank. Batteries do not like to be used at all, but if you must use them the less you do the better. So for a given usage a small bank may have say 50% or more depth of discharge (DoD) every day, that's not good for them. However your large bank may only have a 20% DoD, that's good.

 

[DeMented Toys]

Now that I've added more solar watts, 160watts of total panels, I need a new solar charge controller. I'm thinking a 15 amp controller will work for 160 watts. Any suggestions? I've read pages of data, google, opinions... And I still don't know which charge control to get.

Some people like certain brands... They range from $30 - $200+
I'm on a fairly tight budget but I need a good controller to take care of my batteries. Anyone?


DinéMetalworks.com

 

[graynomad]

15A is borderline but probably OK, what is the actual current produced by the panels (it will be on the label).

Morningstar do nice regulators and have small ones

http://www.morningstarcorp.com/en/products

Getting a larger one allows for more upgrades without having to buy a another regulator.

 

[DeMented Toys]

I am looking at possibly the Morningstar PS-15 ($105 from Amazon). Or maybe the PS-30 ($140). I have used all of the available roof space so I doubt I add any more panels. Right now I have 304ah of batteries at 50% charge would give me 152ah max of useable power, if I'm tracking on this. So 160 watts of solar panel for 152ah of available battery power, right? They also have. 15amp and 30 amp with a monitor, for about an additional $50 or so. Ideally I'm sure the 30 amp controller with monitor would be great. But that also adds about $100 to the price. Hmmmmmmm


DinéMetalworks.com

 

[4x4junkie]

15A shouldn't be borderline at all.
I have a Morningstar Sunsaver MPPT 15A w/170W of panels (2×85W). Best I've seen going into the batteries is 12A @ high-noon (I could probably add another 30W panel to it if I wanted to). With a PWM controller, to know how much controller you need... Just take the amp rating of all your panels and add them together. That's the amperage your controller will need to handle (with 160W of panels, it should total out to maybe a little bit over 9 amps).

Morningstar and Xantrex are the two brands I'm most familiar with, I don't think you could go wrong with anything from either.

 

[graynomad]

I did the maths on a nominal 12v so that's 13A, which is close, but to be fair the wattages is usually calculated on the Vmp (voltage, maximum power) which is probably more like 17v, this gives a current of 9.4A which I agree is ok for a 15A regulator. But we need to know the current produced by these particular panels as the wattage is not a very good indication.

Also midday on a sunny day is not the max a panel can produce, under some conditions (sunny but with a light haze and cloud fringe/edge affect) a panel can produce a lot more than it's rating.

All that said I agree that 15A will be OK, so if $ are tight maybe the 15 with the meter would be the best option as it's nice to see what's happening with the system and the meter will give you some idea of the battery state.

 

[DeMented Toys]

Thanks for the input! I'll go with the Morningstar 15 amp. Hopefully Amazon prime will have it here Friday for a weekend test run.


DinéMetalworks.com

 

[teotwaki]

I am looking at possibly the Morningstar PS-15 ($105 from Amazon). Or maybe the PS-30 ($140). I have used all of the available roof space so I doubt I add any more panels. Right now I have 304ah of batteries at 50% charge would give me 152ah max of useable power, if I'm tracking on this. So 160 watts of solar panel for 152ah of available battery power, right? They also have. 15amp and 30 amp with a monitor, for about an additional $50 or so. Ideally I'm sure the 30 amp controller with monitor would be great. But that also adds about $100 to the price. Hmmmmmmm


DinéMetalworks.com

You can buy a 20A Morningstar for less here and shipping is not much
http://www.solarblvd.com/Charge-Con...gstar-Charge-Controllers/c6_48_100/index.html

 

[4x4junkie]

Also midday on a sunny day is not the max a panel can produce, under some conditions (sunny but with a light haze and cloud fringe/edge affect) a panel can produce a lot more than it's rating.

I think I know what you are saying.
Most quality charge controllers are made to handle events like that, they just level off or cut back their charging current if needed to prevent overheating should their maximum rating be exceeded (Morningstar actually states the PS-15 can handle a 25% overload). I'm not real sure of it amounting to more than a few percent increase in current anyway, but if the opportunity presents itself on a partly cloudy day, certainly I'll have to go out and take some measurements.
Appreciate the info.

 

[DeMented Toys]

Awww, that is a better deal. But, I already ordered the PS-15 and it arrived today. Since I have a weekend trip planned I'll go ahead and use it.


DinéMetalworks.com