Battery Inspection and how to change a battery cable
The first thing you need to do is inspect the Lithium Ion battery. Be extremely careful when handling the battery, as water and lithium ion can be a dangerous combination.
Here is a video of Mark discussing both how to inspect a battery for water / water damage, and how to change a battery cable in detail:
To inspect the battery, remove it from the battery bag and unscrew the four Philips screws on the top side of the case. Open the case and look for any water inside. If there is water, dump it out and dispose of the battery at a local hazardous waste facility. Replacement batteries are available at https://www.carttek.com/collections/batteries/products/lithium-ion-batteries.