crewzer

This may or may not be OK. Battery voltage drops when a load is applied, and it will drop further as the load is increased (i.e., turning on the seat heater(s)). The drop from 11.8/11.6 to 11.5/11.4 looks OK, but the initial drop to 11.8/11.6 seems a bit high too for an SLI car battery, as they're designed to supply lots of current for a relatively short period of time... this could be a sign that the battery is weakening and/or cold.

~14.6 V is the normal-ish target voltage for charging a "12 V" battery.

Normal-ish "resting" voltage for a "12 V" battery is ~12.65 V, so this also looks OK.

All of this information suggests to me that the car battery is behaving correctly, but the initial voltage drop, if unusual, could suggest a weakening and/or cold battery.

HTH,
Jim / crewzer

Cream Sauce

Thank you Crewzer for your reply, so if we can rule out the battery as a problem what other things can I check so we can see what other conclusions we may come to ?

Xeronix

Yeah, generally on my E60, when the engine has been off all night, the battery voltage tends to be about 12.3-12.4, 11.8 is extremely low with sensitive electronics in mind (I do a lot of RC things), and could easily be your problem. I would first try charging the battery, and see if that helps to charge the battery. When you turn the engine off, and you're at 12.6, that sounds about right (where my car is after the engine is turned off). Tomorrow morning, I'll head out and see what my battery is reading.

Cream Sauce

I have seen a very slight improvement in the range of the keyfob nothing major.

I am going to get my mechanic to charge the battery sometime this week and then report back with my findings.

The car only has 20000 miles on it after nearly 6 years maybe it might be some useful information ?

I don't want to start a new thread for this but however if someone would like to answer this I would apreciate it, my question is in how many years should you change the battery of a car like the E60 my car is a 525D and only has just over 20000 miles (2006 July Model)

crewzer

I've always found it difficult to predict car battery life. My pickup truck is 12 years old, has 125K miles on the odometer, and is on only its second battery, which is doing fine. On the other hand, our 2006 Honda Accord needed a new battery after just three years and ~50K miles.

In the case of your apparently "lightly used" BMW (~3K miles/yr), it may be that the battery is dying a long, slow death. There's no mention of the following issue in my car's owner's manual, but my E61's Service and Warranty Information booklet contains the following statement on page 16:

In the renewable energy world, there's a condition called "deficit recharging" in which a battery bank is regularly discharged, but then not fully recharged. This protocol weakens and eventually kills the battery bank.

There's an easy experiment that you can try. Connect a good battery charger to the car battery for several hours, or perhaps overnight. With the charger still attached, try the remote(s). If all's well, then it's probably the car battery is going. If not, then there may well be a different problem.

HTH,
Jim / crewzer

Cream Sauce

Hello,



I want to bring this thread back to life and say I still have this issue, maybe someone new reading this will come up with some suggestions we can try.

Cream Sauce

Looks like nothing... need to live with this then I guess.

AchtungE60

I read through the 1st page but not the second. Just change out the battery in your key fob yes it can be done.

Cream Sauce

Many many thanks for your reply AchtungE60, however all the threads I am searching are for Comfort Access key fobs, mine does not have comfort access... is there anywhere that still shows how to change the battery even though I do not have comfort access ?

vkhong

A friend of mine discovered that he had low battery charge in both keys by accident. I had just coded his E46 convertible with comfort open and close. He was using a key for comfort open and close, until it would only only open or close partially (key in door lock still works). He switched to his other key and comfort open and close worked fully. Then it stopped working. He charged each key in the car's ignition for about 2 hours, in position 1 (accessories). Both keys work fine now. The comfort operation was draining the key's battery. He used a trickle charger on the car and turned off all accessories during the key charging. The BMW center should also have an inductive charger for the keys.