Body Control Module?

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Originally Posted by Silenceisgolden

It all sounds a bit sus to me. I have no idea what a Body Control Module is for, but my working life was spent designing high tech microprocessor controlled devices, and there is practically nothing that can be intermittent in electronics other than connectors. If a semi-conductor device fails, it stays failed. Likewise most electronic components. Other than a flat battery, I can see no reason why a faulty BCM would allow a jump start but not start from the cranking battery.
Have you a multi-meter to check the voltage of the battery with the engine running, preferably continually while driving?

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If you have a multi meter, check battery arriving home, then first thing in the morning. I would not expect any significant drop in voltage. If there is then you have an issue.
Multi-meter handiest tool in the kit! [thumbsupbig]

I will try the multi-meter approach and report back....

Just get the battery tested at a battery shop - normally free - my battery was playing up a little while back - still producing 13v, cranking amps were sort of still there but was only holding about 30Ah worth of charge not the normal 95Ah - so it would crank and start but if anything went wrong like a cold start it was not up to the job.

It's been on the CTEK charger for 24 hours, and is reading 12.76V tonight. That's around 80% charge for an AGM, I think. Interestingly, the CTEK reckoned it was fully charged and had shifted into float charge. Will see what the voltage is in the morning, and then look at a battery shop.

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Originally Posted by Jpdv

It's been on the CTEK charger for 24 hours, and is reading 12.76V tonight. That's around 80% charge for an AGM, I think. Interestingly, the CTEK reckoned it was fully charged and had shifted into float charge. Will see what the voltage is in the morning, and then look at a battery shop.

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You should test the battery when it is under a little load such as a 55w light globe - a basically dead battery might still show reasonable voltage until loaded when it then goes to nothing.

The combination of only around 12.8V and the charger going to float mode suggests that the battery has a problem unless the charger is set for an SLA battery.

OK, thanks to all for the advice and comments. I got 12.9 last night when I held the multimeter properly(!). This morning, the battery read 12.89/12.9. So it seemed to hold its charge overnight, at somewhere north of 95% charge for an AGM.

However, taking 110RRS's advice, I then checked with the doors open, and all the interior lights on (mine are not LED).
It immediately dropped to 12.56, and stayed there with the doors re-closed and the lights off. That's somewhere around 75-85% charge. I'm not a battery expert, but that 'seems' to me to be quite a loss/drop from powering 3 or 4 globes for about 60 seconds? Grateful for any follow up comments...

All other things being equal, I. think I'll change the battery as a first step. Frustratingly, I don't know when this one went in, but I'm guessing it's the second on a 2015 vehicle, so this would just about fit with a 3 to 4 year life expectancy?

3-4 years is a bonus for a battery I feel, they are a disposable item, and yes a lot of people will say they get 7-8 years which is great for them but I’m happy if I get 18 months, that’s me thou. Get the battery load tested with a proper old school load tester then buy a new one.

Quote:

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Originally Posted by Jpdv

OK, thanks to all for the advice and comments. I got 12.9 last night when I held the multimeter properly(!). This morning, the battery read 12.89/12.9. So it seemed to hold its charge overnight, at somewhere north of 95% charge for an AGM.

However, taking 110RRS's advice, I then checked with the doors open, and all the interior lights on (mine are not LED).
It immediately dropped to 12.56, and stayed there with the doors re-closed and the lights off. That's somewhere around 75-85% charge. I'm not a battery expert, but that 'seems' to me to be quite a loss/drop from powering 3 or 4 globes for about 60 seconds? Grateful for any follow up comments...

All other things being equal, I. think I'll change the battery as a first step. Frustratingly, I don't know when this one went in, but I'm guessing it's the second on a 2015 vehicle, so this would just about fit with a 3 to 4 year life expectancy?

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Opening the doors on a D4 wakes up the ECU train and can pull up to 30amps in my car. That normally pulls it down a bit.

Quick update:

1. It's all settled down after a good weekend's CTEK AGM trickle charge.
2. Lesson learned. The garage's nonsense about BCM was just that: I've run my cheap and cheerful OBD2/android software several times, and the BCM DTCs are all negative. A scanner will earn its cost the first time you need it.
3. No more warning lights. The next step is a Traxide unit, for various reasons, but that should assist in avoiding any low battery issues.
4. OBD is showing a rock steady 14.1 V system voltage when the engine is running - I'm happy.