Yellow Top Battery is approx. 5 years old. This morning, I tested my battery with engine off === It shows 11.5V I then tested my battery with the engine on === It shows 14.3V Are 11.5V first thing in the morning too low, is my 12V battery getting weak?
11.5V shows that the battery is not fully charged. Either it is not being charged or is not holding a charge. With 14.3 V available with the engine ON, this should be sufficient to charge the battery given enough time. The manufacturer's website has some good information to review. A load test would be your next best step, but with a 5 year old battery it is may be that the battery is at the end of its useful life. Recommended Battery Voltage- YELLOWTOP®, REDTOP®, BLUETOP® | Support | OPTIMA® Batteries "Fully charged, engine not running, starting batteries (all REDTOP® or BLUETOP® 34M) should measure about 12.6 volts to 12.8 volts. Deep-cycle batteries, including all YELLOWTOP® and dual-purpose BLUETOP batteries, should measure approximately 13.0 to13.2 volts." http://d26maze4pb6to3.cloudfront.net/optimabatteries/1213/4333/7097/Battery_User_Guide.pdf
do you drive much? if not, put a charger/maintainer on it and see how it holds up. otherwise you'll have to drive for a long time to see if the voltage comes up at all. 11.5 is definitely low.
I'm going to put a slow 2amp charge to the battery and see if it improves. Is it OK to charge the 12V from the 'jump points' in the engine bay?
Yes, absolutely. Note that some "smart" chargers need you to connect to the battery BEFORE you plug it into the wall but most models don't care.
