The Optima (Exide) and Odessey (Hawker) are basically the same design with a lot of marketing effort and wishful thinking. Unless you really need spill control or have some other issue, a real deep cycle flooded battery will outperform and with proper care outlast theses miracle batteries.

For starters, the PC1200 at 44 A/H capacity is limited in capacity. You need three of these to equal 1 group 31 flooded battery. No cost or weight savings if you really need capacity. Just get a starting battery (65 A/H) and replace it when it dies. These batteries do not withstand multiple complete discharges well and they require special charging curves for recovery after a deep discharge. Not practical for alternator based charging systems. So they claim 400 cycles at 80% depth of discharge, (DOD). A good flooded deep cycle battery will give 1,200-1,500 cycles. 10-12 year design life? if used daily, I see less than 18 months based on 400 cycles.

As for larger alternators, 90 amps is adequate for almost any application in a Vanagon. More A/H does not generally charge batteries faster. battery charging takes time. An 8-10 hour rate is the ideal. While AGM batteries can take a charge faster, they damage more easily doing. Basically, if the battery heats up enough to vent, electrolyte is permanantley lost.

Another problem with high output alternators is that they actually put out less power at low RPM such as idling or in traffic. If you want to charge a house battery by idling the engine, these will make things worse.

Much has been written about batteries and proper charging methods. Check the archives.

I can be of further help if would provide some detail as to what needs to be accomplished.

Dennis