Ive use a few different set ups over the years and the one that works the best for me, is....
2 Exide Ultra (70 AHR ish each) linked as you have in parrallel -for starter/winch (sat front to backin Rover, side by side in battery box) - and one 85 AHR deep cycle battery (sat across the back of the others) on a split charger for the fridge,flourescent strip light etc - so it cant drain the starter/winch batteries with the ignition off.
As for the Optima, they are pretty expensive, though im sure there vibration resistance is good and they work well, Ive found the Exides to be a good battery and a lot cheaper. (which means I can buy more Tanglefoot......hic!!!)
There are alot more companies that make spiral cell batteries - Exide included, so if yo ugo down this route, check out the competition and pricing.
If you are not running a winch, you could use one larger battery (as youve been doing) for starting and one deep cycle for the fridge on a split charger. Though for me in the boonies, having 2 smaller (starter) batteries is piece of mind if one packs up - the other one is there and I still have the fridge on a separate one.
go along to your local battery specialist,(you wont get a deal in Halfords!) take a tape measure, try a few different sizes into the Rover (remember the battery box in the Defender has different height front to back!) and see if he will cut you a deal on a couple of batteries.
This might sound daft, but also take a volt meter and check the volts on what you are buying - if it reads low (just above 12v) its probably been sat on the shelf for a long time and will have a shorter life in use - pick the ones with the highest voltage (13-14v is nice!) that suit your purpose.
Also, any decent battery shop will give you 5 quid for your old battery under the recycling scheme in the UK - get hold of another (if you buy 2) and blag a tenner from them !!! (throw this in after youve beaten his price down!)
I ended up getting the best deal from 'Motabitz', much to my suprise....
Ive not used them, but try these guys in Eastliegh, if they dont cut you a deal, try somewhere else -theres quite a mark up on batteries:
Eastliegh Auto Electrics
Address: 6 Nightingale Avenue, Eastleigh, Hampshire, SO50 9JA
Last edited by Gipper; 4 Feb 2007 at 15:42.