While were on the subject of batteries, with a serviceable type battery, it's pretty common to develop a conductive path between the posts on the battery from the battery venting oxygen and hydrogen during the charging and discharging process .
To check for this, place the leads of a multimeter set to the DC volts scale, next to, but not touching the metal posts of the battery, if you have a conductive path, you will show a couple of volts .
Common term for this, is 'leakage' .
It can cause a battery to discharge without any 'load' attached to it .
Cleaning the battery with baking soda will neutralize this conductive deposit .