If the engine battery is going down over night, there may be some things still powered up after you stop. With the engine battery fully charged, disconnect the negative terminal of the engine battery. If it is still going down over night, the battery is bad. If the battery is staying charged over night, there are probably some things left on.
If the battery is suspect, take it to a shop and have it load tested.
Always disconnect the negative side first, because if your wrench touches the chassis, it's already grounded and safe. The other side is the positive terminal, and it's hot to chassis ground. Touching there can cause a short circuit with serious arcing, discharging very high current through the tool to ground.
As a side note, be careful out there!
Tom & Jan ---- Westwing43
2005 NEWMAR KSDP 3910 NOW PULLING A 2014 CHEVY CAPTIVA