Putting your foot down.
Mechanics, seems like just about any place a Soldier puts his big feet can cause you problems. The latest spot is inside the troop compartment of the Stryker.
The W4 cable that screws into the side of the battery box sits right under the squad leader's seat. It would be really easy for a Soldier's heel to hit the W4 cable and either damage it or slowly unscrew it.
A damaged or loosened cable won't allow the vehicle's batteries to charge. You can spend a lot of time and lose a lot of sleep trying to troubleshoot this problem. So make it one of your first checks.