Battery? :(

[BobA]

So I had the car valeted today (I’m too old for squirming around under the seats and so on). 2 hours into it the guy knocked on the door to say the car was giving a battery warning and he was right - too flat to start. I measured the battery at only 5.8V! So we jumped it and alls well, leaving it running a bit and I’ll put the charger on overnight.

But is the battery on its way out? Surely not - it’s only 3 years old and I did a 30 mile run this morning. Certainly all the doors open and Dashcam on and whatever for a couple of hours but that doesn’t sound much at all for a 100Ah-ish battery???  😞 😞 😞 

Edited September 14, 2022 by BobA

[q96169we]

I don't think it's the battery getting too old as it's only 3 years old. Many possibilities:

1. When detailer clean the interior, the idrive will be on to drain the battery. If he listen to music/raido, the speakers will drain the battery as well. Then, if he touched the air-con control button, it will be turned on to drain the battery.

2. If the detailer put the car into diagnosis mode, the car will be kept on and consume a lot power

3. How your dashcam is wired up? If the dashcam keeps running even when the car is off, the battery will be drained quite quick and you might start the detailing when the battery was already low so that above two points will make it worse.

 

My experience on my G29 is that after parked for two weeks with dashcam running, the fully charged battery will drain to less than 50%. The normal long distant drive (e.g Sheffield to York, 60miles) won't charge it up to 70+%. I have to use the CTEK charger to fill the battery. My G31 has the 48v mild-hybrid so the 12v battery is usually at around 75% charge level. I guess the DC-DC converter use 48v system as CTEK charger to the 12v battery. All these battery charge figures are read by the BimmerLink in case anyone think the data is not accurate.

[Matthew]

On 14/09/2022 at 16:08, BobA said:

So I had the car valeted today (I’m too old for squirming around under the seats and so on). 2 hours into it the guy knocked on the door to say the car was giving a battery warning and he was right - too flat to start. I measured the battery at only 5.8V! So we jumped it and alls well, leaving it running a bit and I’ll put the charger on overnight.

But is the battery on its way out? Surely not - it’s only 3 years old and I did a 30 mile run this morning. Certainly all the doors open and Dashcam on and whatever for a couple of hours but that doesn’t sound much at all for a 100Ah-ish battery???  😞 😞 😞 

A good AGM battery will last well over 8 years so it’s doubtful the battery. As has been said, doors open, radio on, dashcam being triggered for lengthy period of time is probably the cause

[BobA]

On 15/09/2022 at 22:53, Matthew said:

A good AGM battery will last well over 8 years so it’s doubtful the battery. As has been said, doors open, radio on, dashcam being triggered for lengthy period of time is probably the cause

I think it was nearer 3 hours really. I mostly do a fair amount of runs around the 20-30 mile mark with a few to the shops. If I make a guess that the battery was around 50% charged so 40Ah available it would take a steady 12A or so to flatten it in 3 hours (all finger in the air estimates) which seems quite a lot just for a few led lights and a dashcam and whatever else is running when the car is “on”. I suppose depending what he was doing the fuel pump and suspension compressor might kick in a bit too but I’m still quite surprised. I left the charger on overnight and all seems well.

As you say, I’m not expecting a problem after only 3 and a bit years. We’ll wait and see.

Edited September 17, 2022 by BobA

[Mujib]

Do a load test, check it first thing in the morning.