Wifes XC90 threw a "Start/Stop Service Required" warning light. As I expected the first thing to check is the aux battery (small 10Ah battery to help with the engine shutting off at lights and restarting). Anyhow, I tried to charge it.. says its charged. Battery tester says its "good".. but light is still on. So.. ordered a new battery (AGM).. cheaper than a trip to the dealer for them to sell us a new battery for $200 plus a $200 install.. not to mention when can they get us in. So anyhow, I'll install the new battery tomorrow and hope for the best.