Nice one Slieve, thanks.

I've installed the 100 watts of solar and they're working a treat, even in Cornish rain, of which there is plenty.

I've been running everything i have and the little battery has not dropped below 12.4 volts overnight, and is back up to 13.6 by lunchtime.

So i may not even bother with a bigger battery, time will tell.

I'm not sure if I mentioned my Garmin GPS 76, given to me in 2000.  It runs from the cigarette lighter and uses no appreciable electricity.  Mine shows lights and buoys and I'm sure a more recent one would have a couple more bells and whistles.  Together with a medium scale chart and the appropriate cruising guide you could dispense with your I-pad and maybe just break it out in fog.  Honestly, coastal pilotage is a hugely satisfying and you can quickly check your lat and/or long if you are a little dubious as to what you are looking at.  Why use a computer and take all the fun out of it?  I never switch my VHF on, and see no reason to do so.  I suppose if you are near a busy port you might want to, although if you keep your eyes open you should be able to see what's going on.  Now, we've already got rid of two of your big electricity guzzlers!!

Yes, listening to the radio on your phone works like a charm, as long as either you are in range of FM (the phone's own app) or have a reasonable amount of data (download your favourite station's app)  I have started using the former, but reception is often pretty iffy.

Thanks, interesting and informative replies.

I did something of a test last week; i charged up the battery fully using the mains and smart charger, then ran all my interior lights (48 LEDs overall), charged the iPad and left it running with Navionics open, charged up the handheld VHF.

Over a 48 hour period the battery went from 13.6 volts down to 11.5 volts. The VHF needed to be charged 3 times over the period when left always on, and the iPad worked for only about 7 hours before i needed to plug it in to charge, then, with Navionics open and on screen, it didn't actually charge up, just held station at 20% battery, i.e. if running the thing full time it seems to need 0.9 amps charging full time too (and yes, i do have the special 3 amp cig lighter charging thingy). It does however charge up the battery when the screen is turned off, so i guess while sailing i might let it go into the 'lock' screen and only wake it up every 20 minutes or so, depending on the hazards in the neighbourhood.

Interesting, i think 48 hours of battery life in 'sailing' mode with everything on is bit of a narrow margin, so i'll get another battery, keeping the 60ah one as 'reserve'.

I'm hoping to get away with 100 watts solar. I actually went ahead and ordered the 50 watt panel thinking 'what the hell, i can always buy another' but the seller got back to me saying they were out of stock, and would i like the 100 watt panel for the same price? So i have a 100 watt panel coming this week, and i'll just have to find a way to fit the damn thing on the cabin top.

I like listening to the radio but i don't have one, i use internet radio ( www.tunein.com is my favourite for now). When in a wireless area i use the wifi, but it works just dandy on the phone too using 3G. Doesn't seem to draw too much power or even conume too many of my gigs. Natuarlly it won't work when not connected to either wifi or mobile phone towers.

I also subscribe to a bunch of podcasts, BBC mostly.

Been there, done it, emptied the wallet.

I have a 200 watt solar panel plonked immovably on deck, because I am far too lazy to orient it towards the sun.  I did have a 60 Ah battery.  That was fine in the summer, inadequate in the winter.  I now have a 120 Ah battery, which is supposed to thrive on being charged either by alternator or solar/wind.  I haven't lived through a winter with it, but in the summer it's always fully charged.  (My alternator is not charging at the moment, but it's not a worry.  I'll get round to it!)  I would have bought golf cart batteries, but they were both too big and too tall for my locker.  I now have just the one battery, but can hand start my engine.  In theory.

My requirements: a Tohsiba NB500 with solid state hard drive.  Several hours a day.  A small smart-phone. An e-reader.  Car stereo radio - very greedy on electricity both for radio and CD/USB stick.  Turn it off at the switch as it draws quite a lot even when it's not being used.  4 LED cabin lights.  Digital echo sounder.  Electric autopilot in light winds, motoring and/or sunny conditions.  Masthead nav light (LED).  More Mingming than Footprints.  In the winter I have to be conservative about listening to the radio, which is a pity.

My rule of thumb, to save nervous breakdowns and a flat batteries is: your battery holds half of what it claims; your electrical goodies use twice what they say; the solar panel puts out half of what it says for a maximum of six hours a day.  Follow that and you should be OK!

David, i suspect your requirements are greater than mine, i lean a little more in the Mingming direction...

Cheers, Matt

Yes, well we do like to have our gin and tonics nicely chilled in the evening! I would try and go for the largest solar panel you can fit. IN NZ we can now get a good quality 75w solar panel for around NZ$100 and these panels are not physically large. Try and fit the panel where it is not going to be in shadow even some of the day. A bracket at the stern of the boat seems to be the most effective mounting position as this generally gets the panel clear of most shadow inducing things such as rigging etc. Same with the battery, try and go for the largest you can fit in the space and ensure that it is a suitable deep cycle battery rather than a starting battery. I have had good success for fully sealed absorbed glass matt (AGM) batteries.