You don’t need anything but a basic 3 stage charger and if S’s battery is actually still useable, he will need to do some rejuvenating of the battery once he gets home.

These Recovery procedures should only be used once in a while as they can be quite hard on batteries, and note, they should not be used on AGM batteries.

The best and safest way to rejuvenate any type of lead acid battery is to charge it with a small current charger and leave the charger on 12 hours, then rest the battery for 12 hours and repeat the process every night for about a week. And you do this even if you are using the vehicle during the day.

This is a safe process and is very kind to the battery.