Causes of flat batteries on BMWs explained - Great guide!!

If you own an older BMW, no doubt you will have experienced your battery suddenly starting to go dead for no apparent reason. All modern BMWs have a ‘shut-down’ procedure after the ignition is turned off, things can be heard whirring and humming even after you’ve locked the car and this is the most common cause of your battery going dead over night with no warning, but there are others too...

Below is a great guide from Vlad at MCA Blog explaining the reasons BMW batteries go flat over night and where to check. It also details that bane of the BMW battery's life, the 'IBS' or Intelligent Battery Sensor fitted from the '90s on. 

https://mca.electricmura.ro/en/blog-bmw-what-causes-dead-battery/

• Plugged in external devices
• Plugged in OBD-II scanner
• BMW Intelligent Battery Sensor
• The infamous ”hedgehog” (from the climate control panel)
• One of the electronics on your car drains too much power or does not go into sleep mode
• Faulty alternator
• Old battery

E46 318i Touring: Back on the road with new battery!

Despite paying road-tax and insurance on the E46 Touring it's been laid up for 6 months and with an improvement in the weather it's high time I put it back on the road. All it really needed was some air in the tyres and the brakes beating up. The battery was totally dead, however. The previous owner had put an AGM [automated glass-mat] battery design for vehicles with Start/Stop technology on it, which was great but clearly the 19 year old alternator and charging setup on the E46 was not up to the job of charging it properly. Ah well, it has lasted for over twelve months... 

I've always sworn by Bosch batteries, but the £100+ price tag these days, yes even with a Euro Car Parts discount code, is a bit too expensive for this car. ECP, as well as the parts dept. at work can offer a budget Lion battery for a little over £50, but I have been warned by everyone willing to give their fifty pence that these don't last five minutes and I should avoid like the plague. Ultra-budget batteries can be found on eBay for as little as £27, but who knows anything about their quality.

At this point I have to hand it to the parts dept. at work here, who loaded me up a Yuasa 3110 series battery [760Ah] for just £60 all in! Yuasa get a good write up, in fact I am told they beat Bosch in tests and are currently one of the best on the market. ECP could offer me a Yuasa for £67, but it was a tiny little square battery and this just goes to show how useful working or knowing someone in the motor-trade can be...

F10 530d: Water in Battery well / Bootwell / Trunkwell - where is it leaking?

I lifted the boot/trunk floor to jump-start a friends car and noticed that my battery well / spare-wheel well is full of dirty water.... oh dear. I’ve got a leak... but where? Boot seal? Bottom of the rear windscreen? There was a second aerial / antenna fitted in the roof that I removed, so figured it might be leaking through there and running down the C-pillar into the boot, but no water marks in the headlining or signs of ingress... Think I will have a proper look this weekend and try get to the bottom of it!