Hello all!
I have a simple 8x17ft lock up garage (a few streets away from my house) here in England with no access to electricity at all and no way of installing a supply.
Most of the same questions I asked when you posted essentially the same query in the other thread still apply. The one question you did partially answer this time ("...and no way of installing a supply") leads to another obvious one: WHY NOT? The "a few streets away from my house" notation strongly implies that this is NOT a "middle of nowhere" wilderness/far-rural situation, where utility power simply isn't available. So what EXACTLY is stopping you from installing normal electrical service?
If perhaps it is because you rent that garage rather than owning it, you will presumably face much the same dilemma to install any sort of solar system: As a permanent modification to the building, it would at the least require owner approval; and it MAY require building permits, the approval of any local zoning board or "homeowners association" which may have jurisdiction, etc.
OTOH, if it is simply a (perceived) cost issue, you are near-certainly barking up the wrong tree: A
properly designed and installed solar energy system capable of powering more than the equivalent of a couple of flashlights will surely cost MORE than whatever your local PoCo wants to drop a line and put in a meter.
For my basic hand power tools I use a small generator which works well.
If you're going to bother with a PV Solar system at all, you might as well size it adequately to power EVERYTHING, including those handheld power tools. The incremental cost to increase capacity pales by comparison to the cost of initially "buying in" to solar in the first place (i.e., the battery bank and its associated support structure, the charge controller, the inverter, the distribution panel & wiring, the various site-prep & installation costs, etc.).
You also need to keep your local climate in mind, particularly when sizing the panel array itself. Don't believe for even an instant those "Max. Output" claims made by the panel manufacturers. Those are theoretical "best case" figures, derived under ideal conditions (such as Summer in the Arizona desert, with full blazing sun 15 or more hours per day, and absolutely perfect panel orientation relative to the Sun). In real life, with a typical installation, you'll be lucky to average even half that; and that's before you even start to consider such things as the fact that you can't make significant power when its dark, or raining, or there's a load of snow on the roof.
I only use the garage to maintain my cherokee so dont spend endless hours fabricating things like many of you guys do! I'd like to hear from anyone who has a successful off grid lighting system using solar bearing in mind my garage is really small. At the moment there are a few MR16 5.5w led lights powered by a 110amp hr leisure(marine) battery
Define "a few". Per the specs for something similar I was able to dig up quickly:
http://www.1000bulbs.com/product/63066/LED-MR64040G53.html
...each of those bulbs puts out MAYBE 300 lumens. So it would take well more than "a few" of those to provide adequate lighting even in a relatively small garage such as yours. Quick "back of the envelope" calculation: 8' x 17' = 136 ft.^2; 136 ft.^2 x 50 lumens/ft.^2 (a relatively minimal level of illumination; twice that is generally considered "normal" for garages & shops) = 6,800 lumens; 6,800 lumens / 300 lumens/bulb = 22.6 bulbs -- and that's before we consider the losses at working height vs. "source lumens"!
Frankly, to really properly light that space would likely require at least 50 of those bulbs. And at ~0.5A each (@ 12VDC), that's a 25-amp draw on the battery bank -- far from trivial!
which gets taken home for recharging which is tolerable as I dont use the lights everyday.
Far more important than "not every day" is "how many hours per day"; and this needs to be approached on a "worst case" basis. IOW, you need to figure out the LONGEST period of time you could possibly be in the garage working on something, and need power. This will help establish the maximum daily "draw" that the battery bank must be able to supply without excessively discharging it (which can and will radically shorten battery life).
Having said that, a more permanent solar setup would be better.
Perhaps so; but you really aren't "there" yet. Please understand that I am NOT arguing against Solar, per se; but it is vitally important to approach such a project realistically, and to NOT underestimate what will be required in order to avoid disappointment later.
Two small Solar panels with an inverter set up to charge a deep cycle battery would be all you need.
I seriously doubt that.
I have a system here that charges from two 80 watt panels charging two 6 volt batteries. This system runs the office, computer, phone, answer machine as well as a couple of lights. It also trickle charges via a battery tender from the mains.
You'll pardon me if I remain skeptical. The 'phone and answering machine are relatively trivial in terms of electrical draw. But even a smallish desktop computer with a flat-panel LCD monitor will consume something in the neighborhood of 100+ watts, even when it's not working all that hard. That figure could easily be several times that if it is a high-performance model or has a particularly large display; and Ghod help you if you have a laser printer. "Office lighting" can often be rather subdued; but you're probably still looking at another 50-100 watts there, at minimum. Throw in a few misc. odds & ends, and allow a modest "fudge factor" to cover intangibles and (especially) inverter inefficiencies, and you're probably looking at 250-300 watts total draw, maybe more. Let's be conservative and say 240 watts. That means that even
IF those "80-watt" panels really do consistently put out that much power (which they near-certainly don't), you'd need at least three hours of direct bright sunlight for every two hours you spend in the office, and you have no "safety margin" to cover the occasional extended stay or night-time work session.
You mentioned that your battery bank is ALSO charged off the mains power. I would wager that more of the power you use every day is actually coming from that source, than from the solar panels.
