Size of Battery Charger

[zboss]

Folks,

I need a gut check.

I need to replace my battery charger. I currently have a 270 AMP (90x3) battery bank, the charger, and a 90 AMP alternator.

I want to move up to a 500 AMP battery bank to support our future cruising wants.

When I talked to our local Electronics guy at the marina he advised Lifeline AGM's (4 x GPL-31XT) but also advised that I would need a 100 AMP charger to appropriately charge that battery bank.

Question: is a 100 AMP charger really necessary? If I am going to be hooked into a marina I'll be there at LEAST overnight, so 8 hours with a 30 AMP charger to top up 250 AMPS isn't really a problem. Is there something I am not getting? Am I getting sold on a Bill of Goods?

- z