Battery charging ?

[Smoky14]

Is it improper to leave the batt connected while charging if using a trickle charger and monitoring batt voltage, not exceeding 14.5V?
This is an OBD II car. If you can include the science behind your answer I'd appreciate it.
Smoky the confused

 

[brianl703]

Once the battery is fully charged, voltages over about 13.8 volts can cause water loss from the battery.

For that reason, the answer to your question depends on the charger.

I have a battery charger/maintainer (Wal-Mart, $30) that is specifically designed to shut itself off when the battery is charged, and to turn itself back on when it discharges below a certain level. For this reason, it is perfectly OK to leave this charger connected to the battery. I wired a cigarette lighter cord up to it so I can connect it without even lifting the hood.

 

[Donald]

Dump the trickle charger and get a float or also called battery maintainer. It will keep the battery fully charged and can be left on forever.

Some (Battery Minder) have an anti-sulphitation circuit once they go into float mode. I leave one on boat battery all winter after filling cells with water in the fall.

I have a 15/100 Century battery charger that has light that comes on to indicate charge complete. But it appears that while the charge might be complete, it still charges at a small 1-2 amp rate. I had thought it went into float mode.

 

[Smoky14]

I was more concerned about adverse affect/damage to the elect system on the car during charging.
Smoky

 

[brianl703]

The output of the battery charger is likely cleaner than the output of the alternator. For that reason alone I wouldn't worry about it.

 

[eljefino]

As long as the battery has any life at all to it AC ripples and overvoltage problems won't happen with a consumer 10amp charger. The battery's internal resistance will go up as charge nears complete. It's worth making sure the terminals are clean because one hooks the alligator clips to the cables and not the terminals themselves usually. So a poor connection there could cause more ripple to make it into the rest of the car's electrical system. And battery chargers DO have rather dirty output.

I don't even use an automatic charger; a 6 amp walmart $20 special left on overnight will get down to about a 2 amp rate by morning and by then the batteriy is "done" enough to start the car and not overload the alternator.

 

[Smoky14]

Brian: Very logical answer, AC ripple being what it is I'd expect it's rampent during normal operation of an alternator.
Thanks Smoky

 

[MN Driver]

I've done it with the cars around here when they were left in the garage with the dome light on overnight(not by me). I charge until they drop to 2 amps and then they start up and I don't worry about it. I would just make sure the key stays out and the only things that should be able to get power would be the lights when you open the doors and the PCM which should be forgiving enough for a battery charger as long as it operates properly.

I used to have a battery charger that when I would leave a battery on it for over a few hours I would check the voltage and it would indicate 17 volts. I don't use that charger for 12 volt batteries anymore, I bought a better one, and I just use that charger for the 6 volt batteries around here because it has a 6/12 volt switch.