Battery Not Charging

[mitchlit]

My 540i seems to have difficulty holding a charge. I use it mostly on weekends, so it can sit in a cold garage during the cold months for five days at a time.

On a cold day, it wouldn't start. The door locks and interior lights worked and I could hear the click of the solenoid (?), but there wasn’t enough power for it to turn over. I charged the battery with an electrical charger.


After a full electric charge, I drove it for about 20 minutes, parked, and came back in about half an hour. It started and I drove another few minutes and parked again for about half an hour. This time the car wouldn’t start. I got jump start from another driver, and it turned over right away.


While driving the car, the alternator light does not come on and everything seems to be running okay, including the heat. Do I just need to give it more of a charge? Could the battery not be charging while the car is running from a problem other than the alternator?

[Javier]

it is an extract taken from this link. It tells how to re-vitalize a battery. I did it in mine and got excelent results. Discharged to 10.5 volts using both filaments of a double filament 12 V american bulb (park/stop lamp), and charge to 14.5 V using a 5 amp charger. Alternator wiill not do the job.

http://www.amplepower.com/primer/break-in/index.html

Quote



How To Break-In a Battery

Just like a car engine should be used moderately during the break-in period, so should a battery. High rate discharges and charges should be avoided.

The first step to the break-in process is a good charge, including a short period of overcharge. The overcharge will tend to equalize the specific gravity in all the cells.

Now that the battey is thoroughly charged, turn on enough loads to approximate a discharge of 5% of capacity. That is, for every 100 Amp-hours of capacity in your bank, discharge by 5 Amps. For instance, an 8D would be discharged using about 10 Amps.

Assuming that your batteries have the expected Amp-hour capacity, the break-in discharge(s) will take about 20 hours. Let the discharge continue until the battery voltage reaches 10.5 Volts.

With a now depleted battery, recharge using a current of about 10-20% of Amp-hour capacity. Avoid high rate charging during the break-in period.



How Many Break-In Cycles?

The discharge and charge process should be done at least three times, preferably five times on new batteries. Old batteries can usually be rejuvenated with one or two break-in cycles.

Unquote.

If this doesn't work, it is time for a new battery.

Edit: Forgot to mention, I made 3 cycles and it took me about 3 days.

Javier

[Qsilver7]

Batteries usually don't last 10 years...so I know we can exclude that it's a 1993 540. Have you unlocked your OBC...if yes, then do a TEST #9 to see what your battery voltage is...then start the car and do TEST #9 again, and it will reveal how your whole charging system is doing.

At rest, your battery should show at least 11.5v-up....running, the system should display 12v-14v. If the test reveals your voltage below these numbers...then your battery is starting to fail.

I would have posted instructions on how to unlock the OBC...but the instructions for the e34 & e39 are different. Hopefully the importance of model identification...other than typing 540i...is sinking in...especially when the model number ranges between 2 different 5 series styles.

I'm sure you can find the instructions in the archives, too.

[mitchlit]

I haven't unlocked the OBC, though I would certainly like to test the voltage and charging system.

Thanks.

Batteries usually don't last 10 years...so I know we can exclude that it's a 1993 540. Have you unlocked your OBC...if yes, then do a TEST #9 to see what your battery voltage is...then start the car and do TEST #9 again, and it will reveal how your whole charging system is doing.

At rest, your battery should show at least 11.5v-up....running, the system should display 12v-14v. If the test reveals your voltage below these numbers...then your battery is starting to fail.

I would have posted instructions on how to unlock the OBC...but the instructions for the e34 & e39 are different. Hopefully the importance of model identification...other than typing 540i...is sinking in...especially when the model number ranges between 2 different 5 series styles.

I'm sure you can find the instructions in the archives, too.

[mitchlit]

Once I confirm the starting voltage after a charge, I'll give this technique a try.

it is an extract taken from this link. It tells how to re-vitalize a battery. I did it in mine and got excelent results. Discharged to 10.5 volts using both filaments of a double filament 12 V american bulb (park/stop lamp), and charge to 14.5 V using a 5 amp charger. Alternator wiill not do the job.

http://www.amplepower.com/primer/break-in/index.html

Quote



How To Break-In a Battery

Just like a car engine should be used moderately during the break-in period, so should a battery. High rate discharges and charges should be avoided.

The first step to the break-in process is a good charge, including a short period of overcharge. The overcharge will tend to equalize the specific gravity in all the cells.

Now that the battey is thoroughly charged, turn on enough loads to approximate a discharge of 5% of capacity. That is, for every 100 Amp-hours of capacity in your bank, discharge by 5 Amps. For instance, an 8D would be discharged using about 10 Amps.

Assuming that your batteries have the expected Amp-hour capacity, the break-in discharge(s) will take about 20 hours. Let the discharge continue until the battery voltage reaches 10.5 Volts.

With a now depleted battery, recharge using a current of about 10-20% of Amp-hour capacity. Avoid high rate charging during the break-in period.



How Many Break-In Cycles?

The discharge and charge process should be done at least three times, preferably five times on new batteries. Old batteries can usually be rejuvenated with one or two break-in cycles.

Unquote.

If this doesn't work, it is time for a new battery.

Edit: Forgot to mention, I made 3 cycles and it took me about 3 days.

Javier