On 3 September 2014 07:26, Luis Moreira wrote: > The solar panel doesn't really appeal to me. The van is high enough and i= n > the UK what size panel do I really need to have? > mp suffix =3D when operating at maximum power point =3D full sun, optimum alignment and loading. so Vmp =3D volts at PV panel maximum power point. Also Wmp, Imp Wmp is specified at 25 C and will be lower when panel is hot. SSH =3D sunshine-hour =3D 1 kW/m^2 for 1 hour. _____________ London England has 4+ "sunshine hours"/day (kWh/m^2/day) average in summer and about 0.5 SSH/day in December - January See http://www.gaisma.com/en/location/london.html A "12V" PV panel diode connected to a battery will give about Wmp/18 x SSH Ah/day if optimumly aligned and about half that if mounted flat and not shadowed. So say Wmp/40 x SSH So a 100W panel would give about 100/40 x 4+ =3D 10Ah/day average in Summer and 100/40 x 0.5 =3D~ 1.25 Ah/day in mid winter (if not snow covered :-) ). Note: Output at low light may not meet expectations (very overcast all day) but as a 12V panel is 18V at Vmp it operates close to Isc as close to a current source in most reasonable light conditions. If battery needs equalising panel output may be too low in mid-Winter to give enough current. ______________ Larger (100W+) silicon crystalline PV panels are available here for about $NZ1 per Wmp on national auction site from a range of suppliers. (Astounding) Not tried yet, but I have a 30 Vmp, 250 Watt panel which I intend to mount flat on a caravan roof for use this summer. I should [tm] be able to charge eg laptops directly from that (with suitable converter) directly over a fair part of a NZ summer day. Russell --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .