Solar Roof trickle charge battery
 

I seem to remember a while ago talk of wiring the Solar roof up to the battery so that it will keep a constant charge well i would like to do this and wandered if anyone has a guide on what to do to make it possible,

i often worry that if i do short journey all the time i will wear down my battery.

any advise, Guides or help would be great +++

I haven't doe this yet, but here is the thread wit some hardware that will help:

http://forum.a8parts.co.uk/showthread.php?t=7631

Sorry Guy, The only references to this that I can find are just questions like yours.
There are remarks about a VW solar panel that new cars are shipped with to the States. These sit on the roof via four suction pads and plug into the cig lighter socket. Keeps the battery charged during transit/storage. But that, I know, is not what you really want.

I recall reading the earlier stuff with vague interest and deciding not to bother.
BUT it was for the D2 which has fairly simple battery circuitry, whereas the D3 is much more complex. :tuttut:

Not sure what voltage solar sunroof panel outputs but you will need some kind of DC-DC charger that can take variable voltage from the solar panel and supply constant voltage to the battery. Example here http://www.powerstream.com/pv-control.htm

Having a switch so that you can choose weather you want battery charged or fan running would be a good idea too.

How about making a little temp based change over ciecuit, I'm sure there must be something like that available from Maplin.

So on vey hot days it switches to cool the cabin on other days just charge the battery

Just buy a solar trickle charger you push in the cigar lighter?

Don't work on a D3, been there and tried it. The solar charger needs direct connection to the battery.

The reason it does not work is the battery controller, it blocks the current flow to the battery with the ignition off. The controller is quiet complex and even with the engine running can stop the alternator from charging the battery when it reaches full charge, its why you must use the correct connections when charging at home with the battery in situ.

I don't think those solar chargers work very well.

I got a AA one with ODB socket and battery socket.
I connected it to a spare battery in the garage and over a week I checked the voltage in the battery.
Day one the battery was as 10 volts. By day 7 it was was 11.5.
The battery is less than 6 months old, so its not the battery.

Guy, You can buy 12v solar charger control units for caravans and such.
I think one of them will work fine connected to the battery correctly.

They are not exactly meant for charging batteries, only to keep it charged. If it provides 0.5 amps on a good bright day then to get 95ah battery from 10-90% charge wold take over 150hrs if it was charging with 100% efficiency. My 3.8A mains charger takes 2.5 days to charge from 25% to 90%.


Edit

Just had a quick look at the AA one and it only provides up to 0.2A and up to 12.7V sit it will probably never get battery charged but should help to keep it charged.