wei said:
The Optima Red Top is a gell cell battery while the Yellow Top is an AGM battery. Gell cells are not compatible to many battery chargers because they can only handle 10A charge current. Compared to the AGM, which can handle up to 35A.
Just to clarify, the Optima Red Top is an AGM (Absorbed Glass Matt) battery, as is the entire Optima Line. Check out their web site if you need any clarification (
http://www.optimabatteries.com ). For their size they are rated very well. The Oddyssey Line of Batteries appear to be quality batteries, but to me their specifications let them down (Size verses capacity) when compared to the Optima. The PC1200 is the closest in size to say a yellow top Optima, but only carries a 78 min reserve capacity in a similar size/weight package as the Optima who carries a 124 min reserve. To me, reserve capacity is the important number, and a 47 minute advantage in a similar sized battery is a HUGE difference. The PC1700 specs are better, but good luck getting two of them in anywhere, and two Optima Yellow tops in parallel out pace the PC1700?s capacity by a wide margin (248 minutes verses the PC1700?s 142 minutes).
If you are really looking for a high capacity set-up, consider this. I haven?t tried it yet in my ?96 Discovery, but I believe it will fit perfectly. I don?t know much about the Disco II?s space availability though, so this may be a series I solution only. On the original Discoveries, when going to dual batteries, they are generally mounted with one in the factory spot, and one on the opposite side in place of the jack and wheel chock (a bracket has to be fabricated to move the power steering fluid reservoir and the intake trumpet removed from the airbox). Check out Lifeline Batteries (
http://www.lifelinebatteries.com/marine.asp ) model GPL-4C. Lifelines are well respected (in commercial applications) AGM deep cycle batteries. The GPL-4C is approximately the same length and width as an Optima, but slightly less than 2.5? taller (I?m almost certain they will just clear the hood blanket), and is a 6 volt battery. By placing two in series (instead of parallel) you get a 12 volt battery with, are you ready for this, 492 minutes of reserve time (standard 25 amp draw test). That?s roughly the equivalent of four Optima Yellow tops in parallel. Plenty of juice for winching, and would probably run an ARB/Engle fridge for a week! How is that for reserve capacity?