If I have a 85ah deep cycle battery, that had been run down to say 35ah, would I be right in thinking it would take a 2amp charger 25 hours to charge it? ALso would a solar panel charger be able to charge it (12v 2watt panel)
current draw varies with load, but the voltage is what will diminish as the battery is drained. the charging rate will depend on the type of battery charger you're using, since not all of them are 100% duty cycle. the solar panel chargers help to maintain a charge on batteries, but really don't supply enough current to do much more than that.