OK, so how about some practical, meaningful , easy to do real world flooded lead acid battery checking you can do on your boat.
This is going to sound over simplified to some, but alas things do not need to be overly complicated to be useful.
Its easy.
- With the shore power on, assuming it has been on and your batteries are charged, read the voltage. It should be something around 13.25 to 13.5 volts. If its much lower your batteries are not getting a full charge. If its too much higher, your batteries are getting overcharged.
- Turn off your shore power. Leave things running just like if you were on the hook.
- Wait a few hours.
- Assuming you have 6 volt batteries, measure each of them with a voltmeter.
- Compare those numbers with each other. If they are much different, then you have a problem. Time for a replacement.
- Turn back on your battery charger.
- After a few minutes feel for heat. Just touch each connection, and the top of each battery.
- If a connection feels warmer than others, take it apart, clean and re-assemble.
- If a battery feels warm, then you have a problem. Replace it
Other than that, enjoy your boat. Keep your batteries topped off with distilled water and think about the nice sunset, or the fish, or contemplate life on your boat.
Oh, and if you have the inclination, install a battery monitor. I use the Xantrex Link units and love them. Would not have a boat without one.