OK. Thanks Mr S
got a brand new Toyota wish with a lot of electronic stuff like screens in the back and whatever and after 4 days the battery is flat as well… I don’t know why, they are off when the car is locked and can’t be turned on till ignition is turned on
Almost bought one of these when I was in the UK this past “summer”.
http://www.maplin.co.uk/12v-2w-solar-briefcase-348075
Wish I had now. Neat, and only 10 quid, (500NT approx) but I had a lot of stuff to carry.
The ones I’ve seen available in Taiwan are’nt quite so neat and are about twice as expensive. Might still be worth it though.
Average power output would probably be significantly higher than in the UK (I’d guess the nominal output assumes “ideal” insolation, which certainly wasn’t happening in Scotland last summer) and there’s probably a lot less chance here of someone smashing a window to knick it.
First I would check for parasitic drain and isolate the circuit responsible. After that check the circuit for poor connections, or incorrect fitment. Sometimes with media systems an incorrectly chosen earth or power lead can cause power drain. I can’t be more specific than that without seeing the vehicle for myself. It may also be possible in an extreme situation that whilst running your systems are using too much power which can reduce the effect of charging on the battery, but I do stipulate that this is an extreme condition and not likely.
Found a couple of solar-powered signs on the school scrap pile and unscrewed the power bits. They’ve each got a small (motorcycle size) 6V lead-acid battery in them, so I guessed the output of each panel would be a bit above 6V, and if they’re regulated (I assume so. There’s a “black box” attached that I havn’t opened yet) they’ll be set likewise.
Under the office flourescents the panels themselves seem to be putting out about 7V, 120ma (assuming I’m reading my Chinese-instruction-leaflet meter correctly). Havn’t had a chance to try them in sunlight yet.
I assume its OK to connect the photovoltaic panels themseles in series, so I can get enough voltage to charge a 12V battery?
I’m less sure that I’ll be able to make any use of the (assumed) existing 6V regulators, so I might need to get or make my own.
I’d be interested in any informed comments/advice.
EDIT: Here’s a charge regulator designed by E-hippy tree huggers. (Suits you, sir.)
motherearthnews.com/do-it-yo … spx?page=4
Course making that will probably cost more than buying a complete unit. ENDEDIT.
I know a solar charger needs a diode to stop the battery discharging back through the panel at night.
It’ll probably also need regulated to stop overcharging the battery, though the degree of necessity for that will depend on its maximum output, which I don’t know yet.
Car alarms can drain juice from your battery.
Heard this in Australia. Havn’t tried it myself, but I thought it quite elegant, in an Australian kind of way.
Tune your radio off-station and then work your way down the wire, pressing on it. A short will spark and generate a radio signal, which’ll make your radio crackle.
[quote=“Ducked”]Heard this in Australia. Havn’t tried it myself, but I thought it quite elegant, in an Australian kind of way.
Tune your radio off-station and then work your way down the wire, pressing on it. A short will spark and generate a radio signal, which’ll make your radio crackle.[/quote]
That’s interesting. I have noticed of course that you can cause the speakers to kick when working on wiring at times. I hadn’t realized that this might be used as a tool though. Perhaps it’s because I have a multimeter though.
[quote=“sulavaca”][quote=“Ducked”]Heard this in Australia. Havn’t tried it myself, but I thought it quite elegant, in an Australian kind of way.
Tune your radio off-station and then work your way down the wire, pressing on it. A short will spark and generate a radio signal, which’ll make your radio crackle.[/quote]
That’s interesting. I have noticed of course that you can cause the speakers to kick when working on wiring at times. I hadn’t realized that this might be used as a tool though. Perhaps it’s because I have a multimeter though.[/quote]
I have the same one, but not always to hand, and there’s the worry about frying it, though the risk should be low unless I do something stupid.
Ah…
So did you ever get your solar charger working, Ducked?
If you’re getting 120mA I(sc) out of those panels indoors, they must be quite substantial ones (1m2?). Nice find. Can’t believe your school think it’s OK to just chuck these things away.
Designing an efficient regulator for PV panels isn’t easy, but if you just want something that gets you working, a diode and an LM317 (set to about 13.8V) will do the job.
Nah. I’m all talk. Thought I might just buy one when I was in Australia, but they were quite a bit more expensive than I’d seen them in the UK, and I was too stingy. No time now but I might have a go later.
Can you connect 2 6V-ish panels in series to get 12V-ish, or does that risk damaging them?
I’d guess they’re about 0.9 sq m each and were pretty firmly connected to hefty stainless steel lamposts with a lump of concrete on the bottom, so actually quite difficult to chuck away.
They may have usable regulators in the little black boxes that came with them. I took them off as well, but unsurprisingly I didn’t really know what I was looking at when I opened them up.
Yes, if they have built-in bypass diodes (most do - inside the terminal box). If not, fit one yourself. The purpose of the diode is to prevent damage if one panel is inadvertently shaded.
Depending on the open-circuit voltage you may or may not be able to charge a battery directly. The output voltage of a PV cell falls as the load increases; the maximum power point is (more-or-less) at a constant voltage slightly below the open-circuit voltage, which is why you would normally use a switching converter to actually charge the battery. Otherwise, the charge state of the battery will determine the charge current, which isn’t really what you want.
If you’re lucky, the MPP voltage will be >13V. If it’s in the range 13-14V, you can just use a series diode to charge you battery (use a Schottky type if possible). If it’s significantly higher, you can then use a standard linear regulator (eg., LM317) which gives you the added advantage of a built-in current limit (at 1.5A). If the panel voltage is too low to use a regulator (it has to drop about 1.3V in order to work properly) make sure you use a BIG diode, because the battery will pull a lot of current if deeply discharged. A panel that size will probably have an Isc of 5A or more.
This arrangement isn’t a very good solution, but it’s cheap and easy, and it will work.
Thanks. IIRC that hippy circuit referred to above dumps excess current (defined by a battery voltage threshold, I’d guess) through a resistor.
I thought of substituting a water electrolysis cell for the resistor, and using the HOH as a choke substitute for starting (I currently use butane).
Probably not worth it, and I’m very unlikely to get around to trying it, but it might be amusing.