solar powered battery charger

[trailertam]

I have a lorry with 24v electrics - 2 x 12 volt batteries connected together - but because i dont use it very frequently, the tacho drains the batteries over a period of time. I was considering fitting a solar powered battery charger to trickle charge the batteries during the non use period, but my problem is, (1) do I connect it to one of the batteries and it will charge both batteries at the same time, or, (2) do i have to connect it to both batteries at the same time, or, do i require a 24 v battery charger to do either (1) or (2) above.
Thanks in advance

[Hymie]

You will need to keep both batteries charged with something like this:-

http://www.maplin.co....solar-suitcase-228539

This device is rated at 13W, you could probably get away with a 5W solar panel (which might be cheaper if you could find one).

[sddsddean]

Are you sure nothing else is on? The tacho on stand by is only a clock, so draws hardly anything. I've left my truck for over 6 weeks and it still had plenty of umph in the batteries...unless your batteries are getting old...they only last about 3 years nowadays.