Thread: charging voltage and other things

I have two questions. Having just replaced my alternator on my 300tdi due to blown diodes and wear in shaft I now have a voltage on batteries of 14.2 volts during running. The old alternator put out 13.8 v whilst running. Is the new one too high? At least my fuel gauge now reads correctly.
Second question. I read a lot on here about second battery installations. My local autoelec guy fitted my second unit. All it has is a solenoid coil which parallels the batteries whilst running an isolates them when off charge. Is this a good system ? So far I have not had any problems... but Jim

13.8v is the maximum nominal voltage of a normal lead acid battery, think of it as the voltage you would want to see with just a small sub 1a trickle charger keeping your battery topped up.

14.4v is about the maximum normal charging voltage you want to see, (think alternator)

if you're brute forcing the battery (quick chargers that get max oomph in the battery in the minimal amount of time) you can goto 17v and higher BUT you are not doing the battery any favors the battery will vent gasses and heat up the plates.

depending on how your wired up you might also be reading the charging voltage closer to the alternator than the battery in which case there might be some voltage drop to the battery terminals. I've seen alternators putting out 16v yet still only making 14v at the battery due to a bad earth on the battery.