The last time out my engine started & ran fine as usual & tach worked perfectly. I was changing lowerunit oil yesterday & went to trim engine up to get a pan under it & nothing as battery was completely dead. Hooked charger up which showed no connection problems or battery bad readings. I checked & no fuses blown & trimmed it to where I wanted & then left charger on until fully charged which I let charge for about 6 hours. Wonder if a switch accidently left on could have caused this ??? I however didn't see one & honestly just reach under cover & pushed switches to make sure that I now had them off for sure. It had been about a month since charged, but was fully charged as soon as I got home from last trip to lake & I always check them when hooking up & after charging right before unhooking. I've never had a single issue with this battery either. Thanks