Does an alternator charge a battery to 100%

[matt12 Junior Member Find all posts View Profile Close matt12]

Found a table with temperature adjusted 100% SoC voltages.

The adjustment is about 0.01 for 5 degrees, so the 12.84V at 25 degrees = 12.83V at 20 degrees.

Also adding the 0.02V open circuit adjustment to my readings, equates to:
12.72V alternator
12.77V 240 DC charger

[dBC Member Find all posts View Profile Close dBC]

I have a new PC1400 arriving soon as an aux battery, so i will be able to test with that too

I'd definitely be keeping your voltage booster diode in place for charging that one, since it'll be seeing deeper cycles than your cranking battery. That graph on p14 is pretty telling: you'll get much better battery longevity with a decent charging voltage. Or as they summarise it:

The message to be taken from this graph is clear – in deep
cycling applications it is important to have the charge
voltage set at 14.4 – 15.0V. A nominal setting of 14.7V
is a good choice, as shown by the test results.