2011 XC90 - My car eats batteries for lunch...

[JohnCC]

I have been doing something similar, when I remember. The battery is always showing a good charge state when I shut it down, 12.6 volts or so, and generally shows about 12.3 the next morning. 12.3 indicates significantly under charged, and even if it is not accurate, a drop of 0.3 volts seems significant. I did pull that fuse once, and don't remember the numbers, but I recall I decided it did not fix the problem.

The problem is, I'm so programmed to jump in and start the car that getting consistent, frequent readings is a problem.

[abscate]

Measure the battery voltage after shutdown and 30 seconds of headlights on

You need to deplete the surface charge from the battery before measuring resting voltage

[RickHaleParker]

Use to pick up late 90s Lincoln Continentals dirt cheap because they ate through batteries and alternators. Would take them and redo the grounding straps to the firewall, problem solved.

You might want to check all your main grounds ....

[JohnCC]

Measure the battery voltage after shutdown and 30 seconds of headlights on

I turn the key to position 1 and wait about 30 seconds, until the reading stabilizes. After a long trip it usually settles down around 12.6 and after a short trip more like 12.4.

[oragex]

I have been doing something similar, when I remember. The battery is always showing a good charge state when I shut it down, 12.6 volts or so, and generally shows about 12.3 the next morning. 12.3 indicates significantly under charged, and even if it is not accurate, a drop of 0.3 volts seems significant. I did pull that fuse once, and don't remember the numbers, but I recall I decided it did not fix the problem.

The problem is, I'm so programmed to jump in and start the car that getting consistent, frequent readings is a problem.

0.3v over night means about 30-40% discharge, clearly a parasitic drain somewhere

I'd recommend this in the first place, to disconnect it each night, it will save you the battery for now. Remember to have the key in POS II when reconnecting and make sure trunk and door locks work manually. Charging -discharging a car battery is what is killing them, unlike a phone battery, lead acid ones hate being discharged.

www.youtube.com/watch?v=lMT1RdnkxnY

www.youtube.com/watch?v=jdW0t2FJCfA

.

[JohnCC]

make sure trunk and door locks work manually.

Ay, there's the rub. No way to get in the (locked) tailgate without the battery and no (easy) way to connect the battery without opening the tailgate...

[abscate]

That is such a PITA isn’t it? Happens on my P2 and the E83 Bimmer

You can run a pigtail out of the trunk and hook up a jump battery to open the trunk , BTDT