Got a free 40W solar panel and need a regulator.
Bearing in mind this will only be used once a year for a short trip.............
I see lots of cheap, say $20 ish - regs on eBay, are they worth it? Surely not when the cheapest Jaycar one is about $65 ............?
And do I need to consider the size of the panel, or will any cheap one run a 20W - 100W panel?
But like I said, if it just gives me 14.5V out and I can take it on and off the car battery as I choose, then I am happy. I have no need for an intelligent charger and automatic on and off for fridge blah blah.
Grab the Jaycar one. The ebay chinese ones are junk, even a small panel like that without a working controller can cook your battery, albeit very slowly. Wire the controller as close to the battery as possible, this will get as much charge into the battery without to much voltage drop. This is opposed to most panels that have the controller secured to the back of the panel...........thats just a dumb idea. Try and get a MPPT one.
Cheers
Sadly the jaycar one is chinese junk too. been there done that. for what you want a cheapo PWM regulator will do the trick just keep an eye on the volts going into the battery once in awhiile like cord says
^^ cheap PWM regs are $20 on eBay....
I wanna know if that gives me nice constant 14V or so.......
Really the guts of the device is the same........
In my experience if you buy cheap you get cheap. spend the extra money and get something that will last.
^^ Redgy like I said it is a free panel that will be used bugger all. In my experience we get ripped in Australia and often there is the exact same thing avail in a different package for 1/10th the price.....
The way I figure, if I can get a battery charger for $20 at Supercheap that will charge my car battery and not blow it up, there must be a simple 21V to 14.5V converter that does just that with a solar panel.
Thats why I am asking.
Cord its a BP Solar, 40W (36W min)
Open circuit voltage 21.8V. Gave me about that on the multimeter when I tested to see if it even works.
Says "Current (Imp) 2.31A" whatever Imp means......
You could just connect the panel to the battery, don't leave it connected for days on end in WA.
Disconnect the panel when the voltage gets to an appropriate voltage, 14.8 or lookup the battery specs on the interweb...
This is for reasonable size 12V lead acid battery BTW, and a little panel 40w, even better with a load like a fridge.
Be a little bit sensible about it though, don't create a situation where it could overcharge, and have the battery in a well ventilated area, camp site should be good...
Don't leave the panel connected at night... :-)
Otherwise a cheap and cheerful solar PWM unit, i.e. that can cope with 3amps, which should be all of them. For you application anything more is a waste of money...
Mark
I got couple of these about a year ago from ebay, $30 or so each.
Rigged up to 12v system in my shed (lights, water pump and a 3000W AC converter for the odd job I want 240v).
They seem to work good, easy to use and install. Couple of nifty features (I don't use) like optional timed on after sunset (so when the panel stops making lectricity the lights come on for a pre-set (and adjustable) period.
Seem quite well made as well in terms of casing and connections.
I also have a panel rigged directly to a 12v battery. I put a panel on an esky with an old spare battery inside to run an electric fence zapper. I move it around to whichever fence I need it on but most of the time it just sits there charging but not being used for anything. I have never had a controller on this (just panel direct to battery) and the battery is good after a couple of years so far (and it was maybe 3 years old when I put it in). I have every intention of adding a controller, I have a spare one as above, but just haven't got round to it, although it hasn't zapped the battery yet.
So I guess its a reasonable risk to run no controller but for $30 and 30 mins to wire it in I'd go with the controller. Batteries cost more than panels these days.
Also the controller above will run fine on that spec panel you have. 21v open circuit is what I have and normal for a panel for a 12v battery. The controller above cuts out at (from memory) 14.8v charge and 10.6v discharge, so you can't overcharge your battery or run it so flat you need to piss about trying to charge it again.
I have the same as "Carantoc" above and it's working on 2 x 100wt panels on the top of my Troll.
It was supplied with the 2 German cells off Flebay
Works a treat and is programmable (which I have never done) Just used the default settings for the last 6 months.
I've had an old 29ltr Engel fridge that pulls lots of power, hanging off the system and it works a treat with lights at night.
The 2 USB outlets have been handy to charge my GoPro batteries when away from home too.
Very simple to wire up and gives you all the info you need as to what power is going where. 
