This is a long post...two parts actually. It is pretty much my thoughts based on a winter of analysis, trying to figure out how to best manage our future solar requirements. Do any sort of reading on solar power for RV use and for as many manufacturer articles and personal blogs you find, you will find a similar number of opinions. You really have to separate the wheat from the chaff to get at what is best for you.
As retirement is just starting to peek over the horizon for Dale and I, we find ourselves thinking more and more about how we will spend our time. A lot of that thinking is centred around how our Alto will figure into these plans. I have to admit, the places to visit and sights to see are mostly coming from Dale's planning. A good part of my planning, quite naturally so, is centred around how to make sure the Alto best meets our travel and campsite needs. We knew pretty quickly that the Alto would be well suited for us, from a design, usability and comfort perspective. Safari Condo has put a lot of thought and effort into making this a great product right out of the gate...and it certainly is! Over time and use though, we have been doing a few things to make it just a little bit better for us. I think most owners do this. Nothing big really, just stuff that we want to add, mods we make, that sort of thing. So we have been reading and following a number bloggers, ones that seem to either resonate with us from a travel perspective, or those that perk my interest from a technical bent, all towards gathering information for the future.
I've been reading a lot about solar power. A LOT. Focussed primarily on RV applications, but also general knowledge. Scratch the surface on this topic, and you will find there is much more than just panels and batteries. There is the theory, the various types of components, and of course, the abundant opinions. So as I kept discovering new sources of information of the topic, I found myself gravitating to those that just seemed to make the most common sense to me. The key is finding that balance. There are lots of solutions out there that are just so enticing...the lure of the lithium battery, the wattage available with newer/more panels. All this dreaming comes at a cost though, both in terms of monetary and effort outlays. It is very easy to be led down the garden path towards someones idea of boon-docking nirvana. Sanity must prevail. Personal needs must be determined, and those are different for everyone. Spend too little time figuring this out, and you may find your wallet a lot thinner than it really needs to be.
I sifted the info, contemplated the sort of camping we would be doing, and tried to come up with an overall solar plan to best meet our needs. At this point, we don't anticipate the use of an inverter, so that will certainly factor into our required capacity. There are those that certainly do need to use an inverter, but I am confident our solar planning will support this in the future, should the need ever arise. So just where have I ended up after this information overload. I like to think I have figured out our anticipated needs as best I can, bounced my ideas off poor Dale, who in fairness, has tried her very best to not fall quickly asleep listening to my technical ramblings. I can get pretty focussed when I become interested in a topic, especially one that can easily morph into a hands-on project. As well, based on our off-grid experiences of the past few years, it seems we don't really need to throw a lot of money at this to see an improvement. Going the lithium route to gain amp hour capacity, now that would be some serious coin, and probably not really necessary for us. I think this is one of the key decisions for those contemplating the same sort of analysis. Lithiums do take you do a bit of a different path from an equipment perspective, and it requires some serious thought, and a fat wallet.
What will our setup look like? Well, no acres of panels, no expensive lithiums, no inverter sucking the life out of our battery, and certainly no configuration to support air conditioning. Don't be thinking for a moment though that if it got stinking hot while we were in the middle of nowhere, that we would not be pulling up stakes and heading towards the nearest full service park...to plug in and crank that A/C up full.
Another big influence over the solar improvements available to us were the limitations imposed by the Alto itself. We don't have a lot of space to work with. We are somewhat panel limited by a small and unique roofline, and we are battery limited by a tiny and already well utilized tongue area. There are the possibilities of external panels, or lithiums inside, but both of those would impact our storage space, in the tow vehicle and the Alto. There is no way there will ever be a line of Trojan T-125's residing on the tongue, as excellent as that would be, but it is just not feasible. I have recently heard of one Alto owner almost covering the roof with panels, and it looks pretty impressive, but just what are they charging with those watts of power? Perhaps a big bank of lithiums, but that brings us full circle back to that space concern. Who knows what the future might hold. If our panels have an issue down the road, we would probably take the opportunity to add an extra panel, and maybe throw on an extra battery...but right now...that's not in the cards.
So what are the core concepts of our plan? Well, kinda straight forward really:
- the panels we have
- a good monitor & charge controller
- improved wiring
- true deep cycle battery
- energy efficiencies
Let's bounce around some thoughts on these:
Panels:
There are a number of general ideas floating around out there that try to provide a guide as to how to size your solar array, and what is needed to recharge a battery bank. Figuring out what, or who to believe definitely takes some thought. I went with the guides that seemed to be logically defined and explained, and ultimately, just simply made sense to me. It is said to have a panel array output wattage relatively equal to the 20 amp hour rating of your battery bank. Seems reasonable. As well, given an average of the effective solar generating hours in a day, and this will certainly vary a lot, you should have at minimum from 3-6 % of your total battery amp hour rating available in charging amps, to even hope to recharge your battery bank. This is perhaps a a little tougher to quantify, but these same numbers came up a lot. I'll go with this.
We have two 68 watt panels on our Alto, wired in parallel, for a combined output of 136W / 16.5V / 8.2A. These are the specs based on testing at what is referred to as STC (Standard Test Conditions), and really only represents perfect world lab conditions. Looking at the other set of specs, based on NOCT (Nominal Operating Cell Temperature) and the numbers are certainly different at 106W / 15.4V / 6.84A. This second test is meant to mimic actual conditions, so perhaps reality is somewhere in between. Either way, real output is less than the glossy brochure says. Crunching some numbers made me realize that even though we have a relatively modest panel watts/amps, we should be OK from a charging perspective. One also has to keep in mind that you are really only recharging half your total amp hour capacity, given that you should not run down your battery to below 50%. So what would I do with a roof covered in panels, I'm not really sure. Certainly would speed up the charging times, but I suspect we will be just fine as is.
Monitoring:
To really know what is going on with your batteries, you need much more than those idiot lights or a simple voltmeter. You need accurate voltage readings, and a way to keep track of the amps/watts being consumed and then replenished back into the battery. To get this, you need a good monitor, and also a shunt. These two work hand in hand to provide information back to the user. General consensus out there seems to be that the Trimetric brand, made by Bogart Engineering, is one of the very best of monitors available. It can provide all sorts of key information back to the user, and this information can be adjusted based on the geekiness of the particular user. Ours will be set up for maximum geek.
Charging:
Now here is a very interesting aspect of the whole solar equation. Opinions run pretty fast and furious here, not only from the user community, but also from solar equipment manufacturers and retailers. Lots of statements get bounced around..."Get an MPPT controller because it boosts the output of your solar panels". Do you know why, do you have the whole story, does it apply to your solar setup? And the list goes on. This is when you need to continue to read, develop your own opinion, and apply it to your needs. In a nutshell, it seemed to boil down to a couple of things. The type of controller to use...PMW or MPPT, which one could argue is really decided for you based on the output specs of your panels, and whether you feel the controller will be charging your battery effectively?
From what I have seen and read, solar controller manufacturers do not seem to be optimizing the phase charging voltages according to battery manufacturers specs. This does impact the efficiency of a controller to truly bring the battery to a full charge. In most cases, it is very much a one size fits all situation. Does generic get the job done...perhaps. Do the majority of end users really care...probably not. Regardless of the PMW/MPPT debate, it seems to me that a key requirement for a controller is to provide the ability for user adjustments to the phase voltages, to bring this in line with what a battery manufacturer recommends. After all, who best to spec those details. Exactly! And by the way...phase voltages are just one part of the equation, there are a few others that matter as well, such as current output and charge times, but volts always turns up as the first discussion point. To top it all off, controller manufacturers are not the only ones lacking this flexibility. When you plug into grid power, that converter is likely not optimized to charge effectively either...and some don't even provide phased charging. It's kinda like never totally filling the gas tank on your car before a big trip...why would you not do that? To me, good controllers are adjustable, and sophisticated enough to utilize charging parameters to best ensure the battery is operating at full capacity. If I'm limited by the amp hours that I can carry with me, and we are, then I want to make damn sure I have as many of those available for use as possible. What controller to get...one that I can adjust to suit the battery I am using, even if I change it out down the road.
Wiring:
Small gauge wires can impact your charging efficiency. Simply Ohm's Law. The more resistance in the wire, the less voltage/amps getting to the battery. Smaller wire equates to greater resistance...and this is definitely a direct current specific statement. General rule of thumb is to have as big a wire as possible between the output of the controller and the battery terminals. In a perfect world this would apply to the entire solar circuit, but in reality, that is sometimes hard to achieve. Pretty hard to run a 4 or 6 AWG wire up to the panels on the top of the Alto...now that would be an interesting challenge. So in that case, maximize the wire where you can. There are wire gauge tables out there that will tell you the recommended length for each gauge of wire, to keep any voltage loss below a 3 percent maximum. Does any of this really matter. Yes...and no. If you have gobs of panel wattage and battery amp hours, probably not. But if you are trying to eek out as much power as you can from a modest solar setup, then I am of the opinion it certainly can't hurt.
Battery:
Another very opinionated topic. Flooded, AGM, Lithium...how to decide??? Easy..research and buy to suit your needs, and wallet. Of late, I have been fascinated with the promise of the lithium battery. They sound like an ideal overall solution. Awesome usable amp hour capacity, compact, relatively lightweight, simple charging profiles...this all sounds ideal. What do these wonders cost? "Really...wow!". As with most new innovations, the early days are the most expensive. Crazy expensive. Now before you bring out your calculator and start rhyming off cost per amp/hour numbers, the bottom line is that right now, to me, they represent a tremendous outlay. And it is not only for the batteries themselves, the charging and battery management components that are required go for a princely sum as well. Now if we were going to be full timing, then the benefits might well outweigh the sticker shock. I gather the lithiums are a bit temperamental as well, and do not peak performers in hot temperatures. That is why you will rarely find them installed in battery boxes on the tongue of a camper. This means they would be inside the Alto, and that means giving up storage space.
We needed to replace our original battery last year, which was a Marine/Deep Cycle group 27 unit. I did a little research and went with a Trojan 12v deep cycle battery, in a group 31. This has increased our amp hour availability somewhat, and it is what I am calling a true deep cycle style of battery, where the design considerations are more based on charge/discharge cycles and amp hour capacity, rather than the need to crank over an engine. I had contemplated going the dual 6 volt battery route, but decided to wait and see how this new one would perform. We also want to get a year or so of retirement trips with extended boon-docking under our belts first, to really give us an idea of our true needs.
Energy Efficiency:
How conservative you are with the amp hours available to you will directly impact your boon-docking time. Run an inverter to make popcorn in your microwave, or watch movies all weekend (we've been there, suffered the consequences) and you will find yourself with a dead battery. It is no fun when your propane fridge shuts itself off because it has no power to meet the 12v requirements...and that is a pretty minimal draw. We won't even get into a debate on the merits of the 12 volt compressor fridge over a propane...that's another hot topic. For the record though, I'm in the propane fridge camp, and actually, quite happy to debate that.
You can do all sorts of things to conserve power, and it certainly does not mean you have to sit there in the dark like a couple of moles. Switch to LED lighting, if you do not already have them. We did, and beyond the energy efficiency, we really like the warmer colour tone of the light they provide. Become aware of your power usage, figure out your power priorities. First thing that jumps to my mind as a priority is the fridge. I'll take a cold beer over a bag of microwave popcorn any day of the week! I guess you could say it all boils down to living within your amp hour means, and a factor in that is definitely how well you can recharge that battery. We find that after draining our battery a couple of years ago, we have become very power conscious when off grid. We have boon-docked for a couple of weeks solid, and so far, have not had any real power concerns, and we are hoping this little upgrade will help our overall solar system.
So after this rather lengthly rambling, where does that leave us. With this:
-Trimetric setup
-Improved wiring (and fusing!)
-True deep cell battery (already in place)
The general idea is to swap out the existing charge controller for a Trimetric SC-2030, and manage it with a TM-2030 monitor. These pieces were designed to be used together. New wiring from the controller directly to the battery will be 6AWG in size, and fusing will be added in appropriate areas of the solar circuit. All this in the hopes to maximize the charging and storage abilities of our rather modest solar setup. Even in the future, I can't see changes going much beyond this new setup. Perhaps an extra panel, perhaps another battery, but that is about it. I might also say that this could be termed a reasonable upgrade, specifically in terms of a monetary outlay.
Part 2 of this will detail the work involved to put all the pieces in place, and it was a fair bit of work.
