"On many of the old analog DC Volt Meters there is a small scale that has the % or and/or are colored coded that tell you how fully charged a battery is. "
Thats why the older boats had 2 house sets. , And a start set.
In order to have any measuring value the bat set must "rest" for about 24 hours with no load , no charging.
Then the voltage is a mere approximation of the SOC ,no where near accurate , 'cept to tell you when their mostly dead.
Danforth had a pretty large face expanded scale unit , that has as little value as any volt meter.
A voltage log done with a cheap digital will do far better than any of the historic photo shot V meter methods.
In the "old days" a batt set lasted 3 years of active cruising, today 7 to 11years or more in common with modern monitoring and charging methods,with Trojan or other medium priced batts.
Sams club batts are great for starting to live at anchor , moving up to the Trojans or Surettes , AFTER getting 3 years from the Sams set.
Only a monitoring system can observe the normal decay/decline of the set and allow you to decide when to change them out .
The historic methods work fine today on a Marina >Marina motorist or a dockside cottage , but are pretty useless to figure if the set will be damaged by , "just one more night" before recharging.
And the quick deposit of surface voltage makes them completely useless at deciding when the set is actually recharged fully. NOT fully recharging shortens the sets life and reduces the sets capacity in a short time .
FF
