"I've never ran a Optima 6 volt battery but I seem to recall they require a special charging technique when really ran down. I'd put a charger on it and make sure it's fully charged."
If an Optima battery has been run down, an easy recommended technique is:
- connect a 6V lead-acid battery in parallel
- connect the 6v charger ti gte Optima battery
- if it is an automatic charge, charge until done/fully-charged
Here is Optima Tech Tip(s) on:
"HOW TO RESUSCITATE A DEEPLY DISCHARGED AGM BATTERY"