My battery reading is around 12.4 when I get going, but then rapidly drops and the water trickles within a miniute. I then have to run the van to get through the job as my van batt charges the system batt. My battery has been tested and is fine - only changed it about a year ago, but I am being told that it's not holding its charge. Anyone know how I deal with this? I have an Interloc System bought from WCW.