Battery plugs not removed and not holding charge

[Smint]

LunarOne said:

I have a few cars but do very little mileage since I work from home. None of them get driven more than once or twice a week, and then only for relatively short trips. Because of that I am susceptible to battery issues, so I bought one of these for each of my cars:
https://www.amazon.co.uk/dp/B08VHMJYXY

It's a little voltage datalogger that connects to your car battery and records its voltage over time. You can then display the data in an app on your phone. It will show you instantaneous battery voltage, and measure cranking voltage and also display a graph of how the voltage varies over time. Highly recommended.

Thanks for the tip, bought one of these which has proved a dying battery to be my cold starting issues, low cranking voltage for which it sent me messages otherwise the battery was performing normally, new battery now installed cc voltage back in the green.

[liner33]

Mikey G said:

Seen a battery go bang, was about 30 years ago when a neighbour borrowed my car to jump start his 2CV, he put the leads on his battery and up it went. Was probably faulty anyway. But there is a reason why it is advised that the last connection you make is the earth and you do it to a metal body part or engine away from the battery...

Back in the 70's a guy in my street was charging his battery in his garage , he popped in the garage to check the water level and used his lighter to illuminate the area .....bang .... battery exploded as did the asbestos garage roof

[Mikesalem]

liner33 said:

It needs to be checked for a drain but i suspect you have a faulty alternator

The garage confirmed the alternator is all okay, theres a 1 1/2amp loss in the internal fuse box but they cant find it.

[E-bmw]

Mikesalem said:

liner33 said:

It needs to be checked for a drain but i suspect you have a faulty alternator

The garage confirmed the alternator is all okay, theres a 1 1/2amp loss in the internal fuse box but they cant find it.

1.5 amp loss is massive & should be VERY easy to find, any competent auto electrician will be all over that.

[Mikesalem]

E-bmw said:

1.5 amp loss is massive & should be VERY easy to find, any competent auto electrician will be all over that.

Yes next step is an auto electrician, or a jump starter.

[LunarOne]

Connect ammeter between a battery lead and battery terminal. Do not run A/C blower or try to start engine like this or you'll blow the fuse in the ammeter, which is typically rated for about 10 Amps. You'll then see the drain current. Then pull each fuse one by one until the current shown on the ammeter drops. It's possible that there is more than one current drain, so test all of the fuses even if one early on seems to be a culprit. Once you know which fuses are culprits, you can then work out what's happening on each circuit.

Also bear in mind that some cars continue to draw current for a while after shutting off the engine and closing doors, as the car is awake. You'll probably know if your car sleeps more deeply after a while.

By way of example, I have an old 7-series, that has the ability to keep pumping coolant through the heater matrix so that occupants of the car can stay warm even after the engine is switched off. This never shuts off correctly, so I disabled that feature that I don't care about. Apparently the cause is the HVAC panel in the car, so I just unplugged the control unit/secondary pump in the engine bay and my battery discharging problems vanished. Your car probably also has something that is supposed to shut down, but doesn't. Or you have a short circuit somewhere.

[Mikesalem]

Yes the garage did that with each fuse but couldnt narrow it down, only to the internal fuse box from the one in the engine bay