So my '07 SD 990 has been having some issues as of late, beginning a few weeks ago. My side-stand sensor wiring got sliced and so I replaced it with a bypass switch. After reassembling everything I attempted to start the bike and the battery did not have enough cranking power to start. I trickle charged it for just over an hour or so and it started just fine. Fast forward three weeks; there have been maybe 3 occurrences in which the bike struggled to turn over and the Soft 20 - Dat 100 code would be displayed. Today however the bike just couldn't overcome the weak cranking struggle and was completely dead. I cannot find the listed error code anywhere and basically I would like to know if the issue sounds like needing a new battery, or charging system issue.

The bike as I said is an '07 and I would assume the battery is at least a few years old.

Start with the battery, big chance it's only that if it is a few years old as big V twins need lots of juice to start.