Overcharged FLA

[metrologist]

I put a dry stored FLA into service on my solar panel a couple months ago and just forgot to reduce the charge voltage from 14.1V to 13.5V for a float charge (I used the default B-3 setting for FLA). I noticed several of the cells have low fluid level, down around 50%.

This got me wondering about service vehicles that run pretty much all day, such as police or mass transit vehicles. I recall these systems typically charge and hold the voltage well over 14V, so are these batteries constantly being overcharged? I've not heard it as a problem, however. If it is not a problem, then I wonder why my battery boiled off so much fluid?

[SeanB]

Most modern car alternators drop the voltage as they heat up, so as to reduce water boil off in the battery. The batteries however still fail after a few years because they are never serviced, just run till dead from lack of water. Your battery probably did not lose too much capacity if you caught it early enough, though the cells definitely lost material dropped off from lack of electrolyte, and you probably took a year off the battery life.

The car alternator will typically start at cold bringing the battery up to 14V0, then it will taper off the charge voltage as the engine warms up, going down to 13V6 when at operating temperature, and if you have heavy loads ( idle engine, AC  and lights on) it will drop down to 13V3 after a while as the alternator is no longer capable of handling the running current so a balance is reached. More modern cars the ECU actually controls the alternator, and does a similar thing to fast replace the energy used in starting, then does a temperature and load compensated maintenance charge on the battery, as it warms up and terminal voltage drops.