I have a 100w 3amp? solar panel battery charger/maintainer. Its about 3yrs old and I don't think it is charging properly meaning in over a week the battery is not fully charged. The battery is a deep cycle battery. My question is there some way to test the output with a meter? First off just because I have a meter I don't know how to use it properly, so any explanations should be in KISS for dummies "where to set the dial and what should the reading be"? My next step is to bring the battery in to have a load test put on it, when I put the battery on a battery charger it charges 100%. TIA Chip