A bit of solar advice would be awesome :)

[boatdog]

just noticed somebody wrote about the fridge only running on 12 volts and you could switch the wiring to make it run on batteries, you could but its done that way for a reason, on 12volts a 3 way draws if i remember rightly about 85 watts/ 7 amps as it works with a heater element (strange in a fridge but true) so would kill a battery pretty quick, so gas is better it runs a small flame and whilst your driving you switch to 12 volt to save gas and to be safe, eg gas turned off!
I know im going to be in trouble here but is a monster battery bank the way to go? its great having 480a/h battery bank but if you use it up you would have to drive constantly for a week to charge it all back up, again from memory a battery will only (i think)charge at a max of 18 a/h each so even 2 batteries is only going to increase by 36 a/h
I think being economical with the power is the way forwards, eg gas fridge LED lights and small radio, with smallish speakers.
I did the volt meter mod to my van and cant believe the power a radio takes, ok its a powerful alpine with biggish speakers but even turning up the volume eats power.
I lived on a narrow boat for a while without mains hook up and even with 400 a/h batteries you learn to switch it off if your not using it!

[v-lux]

Superb post tencentlife! Totally superb!

[kevtherev]

indeed it is, a very informative post.

[boatdog]

should add, solar panels come in different types there's mono and poly from memory think mono are the cheap ones some have the ability to make power from bright days that are overcast while others need direct sun light, worth checking before you pay out good money

[tencentlife]

should add, solar panels come in different types there's mono and poly from memory think mono are the cheap ones some have the ability to make power from bright days that are overcast while others need direct sun light, worth checking before you pay out good money

That's right, there's three types: mono-crystalline (aka single crystal), poly- or multi-crystalline, and amorphous (aka thin-film). They become less expensive per-watt in that order, but also less efficient per-area. The differences aren't as extreme as they used to be, but amorphous can still be as little as 75% as efficient as mono per area, maybe even worse with really cheapo panels; quality from brand to brand is a lot more variable with amorphous, while the quality of mono and poly are excellent almost regardless of manufacturer. On a boat or RV, size is a big consideration, so for that reason alone single crystal is preferable (you can make the same power with a physically smaller panel), but in addition to that it degrades more slowly over time. I only buy single crystal, myself, it is the gold standard and I think its strengths far outweight the extra cost, and for big staitonary systems that cost is often made back by needing smaller support structures for the same peak power.

Amorphous are the cheapest per watt when housed like the others (in a rigid frame behind glass), but they tend to lose at least 10% of their rated power in the first few months of use, then they stabilise. Some manufacturers derate fairly to account for this, some don't. But, this is the only technology of the three that can be deposited on a flexible substrate without glass, so that makes it possible to make flexible lightweight PV that rolls up. Great for stowage, but the retail cost per watt for flexible PV is generally much higher than any of the other options, partly because not many of these are made in large wattages, and because small wattages are priced much higher per watt. I wouldn't count on the flexible stuff to be as rugged as a well-made rigid panel unless you handle it pretty carefully, and amorphous is probably not going to perform as well for as many years as either of the other types.

The partial-shading aspect is really so much marketing hype in my opinion, and I would never let it be a factor in my buying decision. That "feature" is attained in mono- and polycrystalline types mostly by the use of blocking diodes built into the panel between cells, which reduces the overall panel efficiency in full sun (and whether that really matters depends on which type of charge controller you use, which is a subject for another discussion). Amorphous has a bit of this ability built-in, but then it has those other disadvantages of shorter life and much lower overall efficiency. What the marketing hype suggests to the consumer is that it would be OK to position the panels in partial shade, but in practice you only allow that to happen if it simply can't be avoided, and that is a rare instance indeed, and if that is the best you can do then expect to harvest far far less energy that way. None of them does nearly as well on an overcast day, and I'm not aware of any of the three types having any meaningful advantage in that dept. What you want to do in a mobile application is have a way to attach a wire extension to the panel so you can position it in full sun even when you want to park your rig in some shade. A roof mount is nice for cool season camping in the sun, but if you camp in the heat and want to park in shade try to make a mounting system that allows you to unmount the panel and move it into full sun as needed. If you're traveling in impoverished or high-theft areas that ability to unmount easily may mean you get to keep your PV because it's safely stowed inside your vehicle. Whether or not people know how to wire this stuff up themselves, they do know that it is very valuable and it is the kind of thing that is oh-so-easy to "liberate".

By the way, I'm almost sure someone will pipe in to talk about the new photovoltaic cell technology they heard of that is going to revolutionise the industry once they get it into production. Well, dream on, I've been in this field for 15 years and have heard that same stuff year after year. There are always methods that appear more promising in the laboratory, but I have yet to see anything revolutionary actually make it to market. What has happened are incremental improvements in production techniques, and economies of scale. When I bought my first panel, production monocrystal panels had a peak efficiency of 12-13%; nowadays the same type can have maybe 15-18% efficiency. Prices have stayed high due to competition with the rest of the semiconductor industry (those billions of computer chips) for the limited global supply of pure silicon ingot, the expensive raw material that both are made from. The construction of several new plants that increased the worldwide supply of pure silicon in just the last two years has had a far greater role in reducing prices than any of the economies of scale or improved production techniques have had over the last two decades. Why didn't they build these plants sooner if the demand was there? Well, the minimum cost to build such a plant is over 200million dollars. Silicon may be an abundant mineral, but purifying it to the degree needed for semiconductors is a very very pricey proposition.

So the lesson is, if you like the technology and want to use it, don't wait for pie in the sky someday; go ahead and buy what's available now because that new wonder tech may still be a long way off.

Any liquefied fuel like LP or NG will always have better primary energy density than any battery we could even dream of (which is why a long-range electric car is such a tough engineering challenge), so running these fridges on gas is always going to be a better choice for weight and space requirements, and with liquid fuels so cheap compared to PV, even in Europe with the much more sensible (meaning extreme) taxation on them it's still cheaper up-front by far. But electricity is the most versatile form of power, and with a PV system, once the equipment is paid for, the fuel is free. I don't opinionate on people's choices, what anyone wants to do is none of my business and they should do what their values and goals tell them to do. I'm offering some of what I know about PV and battery systems because someone might want to go all-electric even with the gas fridge they have. Over here lots of Vanagonners are opting for newer, efficient, all-electric portable fridges to replace the old Westy ones because they get so finicky while the newer stuff really is getting practical to use. That's a choice for the guy who wanted to know, I have no opinion on the matter, and I drive a plain-jane GL where we just take an ice chest when we go camping. I do know that I lived off-grid with a 1939 Servel LP fridge for ten years, but after upgrading my PV/battery system I switched to a medium-sized electric fridge because the price of LP had nearly tripled in those ten years. Not counting the cost of the additional PV, which I got a great deal on, the fridge paid for itself in avoided fuel cost in well under a year. The only thing I miss is the perfect quiet of the gas unit, but I've gotten used to the sound of the fridge cycling on and off.

As to the charge rate for lead-acid batteries: these will accept a high rate of charge, up to C/2, but I would keep the charge rate to at most C/5 to avoid overheating the plates. "C" is the battery capacity in amp-hours, so a C/5 rate for those 240 Ah Trojans would be 240/5 = 48A. Your 90A alternator should be able to spare that much in daylight (your headlights, fans, wipers, etc. will reduce the available charging amps when in use), and if so, a 50% discharged battery would theoretically reach full charge in about 2.5 hours. It won't actually reach a full, deep charge quite that fast, because the charge rate will slowly taper off as the batteries pass about 85-90% state-of-charge, so that last 10-15% takes a lot longer to put back (the batteries under charge are innately current-limiting, so they determine the declining rate during this absorption phase all by them selves if the charge voltage is held steady). But you would easily be back above 90% of full charge in that 2.5 hours of driving.

This assumes that the system is wired such that there are no wasteful voltage drops in the system, meaning the wiring servicing the battery is of sufficient size to allow the full charge current to reach the battery instead of turning a lot of into wasted heat. Always oversize you wiring and switching for that reason. And the stock Westy battery combiner relay is a sad little joke that will barely pass its rated 30A without overheating dramatically. Get a good cheap 100A-rated starter solenoid contactor to act as a combiner, or better still use one of the purpose-built combiners for yachts and RV's that combine and uncombine automatically while not wasting power. Over here the Yandina and Surepower brands are popular. Both have bidirectional combining capabilities that will also allow your PV or shore-power to charge both batteries even when it is initially applied to the cabin battery.

Well, that's enough, because that's all I know.

[CovKid]

One mod I did last year was to change things like sidelights, indicator bulbs and tail lights to LEDs. Stereo is now TOTALLY off when ignition is off even if I lose the memory function. That has put an end to flat battery when sidelights left on and its the way to view anything that consumes current if you want more from a leisure battery. Solar is great but agree with others on this, the key is to deal with power consumers first and look for alternatives to reduce battery drain generally, otherwise you'll need a solar panel the size of Watford (and no disrespect to Watfordites).

[tencentlife]

Yes, by all means, designing for efficiency is where you want to begin. It's always a lot cheaper to save energy than to make it, especially from expensive sources like PV.

[AngeloEvs]

Absorption fridges can really struggle in hot climates, especially the older ones and you have to level the van for max efficiency. For the cost of that solar panel and, bearing in mind that you will need a damned good fridge to keep things cold in Morrocco, you could buy a 12V/240v portable compressor fridge (such as the Waeco) which will work quite happily for several days on a bog standard leisure battery (it will freeze contents without any poroblems in high temps, isn't affected by gradient and has a low current consumption). If you are staying put for fairly long periods then the gas option is probably best but depends on how well your absorption fridge is working.

Fan mounted behind the vent to aid circulation around the rear of the fridge is a frequently recommended mod when using an absorption fridge in hot climates.....but it all adds up to increased draw from the battery......just a thought.......Solar panels are useful but damned expensive. They sometimes come up S/H in Marina's and boat yards but you have to check them carefully......

[boatdog]

i would say that the only reason i have a solar panel on my van is i had one spare, i used to have a boat and when i sold it i kept the panel and charge system. if i had to go buy a panel at "new" prices i dont think i would.
for the amount of power saved on LED side lights etc is it a worth while mod? mostly when lights are on the engine will be supplying the power, i have the radio on the leisure battery now and with the solar panel it is charging at 2 amps even this early in the year so memory draining the battery isnt a problem

[v-lux]

By far the best price per watt ive found for mono PV panels in the UK is on ebay.

If you keep your eye out you can find them way cheaper than most retail outlets in the UK.