I think it's more important to have the correct charger, rather than the charge rate. My experience with this is I was using a standard automotive, single stage, typical battery charger and my TM batteries weren't lasting as long as I thought they should on the water. After a lot of homework, I learned that deep cycle batteries can benefit from a true marine deep cycle charger. I thought it was wichcraft but I ended up buying a Promariner Prosport marine charger and my batteries have doubled in their capacity. The same, identical batteries; not new ones of the same brand but the same actual bateries that were failing before, now outlast my days on the water with just a change to the correct charger. These chargers use multi-stage charging where the charger fully charges the battery, then automatically ups the voltage to over 14v for a designated time, then back down to a maintain mode. This process cleans sulfate off the plates; exposing more surface area of the plate to generate battery power.