Battery low

[mark hamster 28]

Washed my car today then moved it to hoover inside. Left keys in after switched off and then noticed it was beeping and then saw an amber pic of the battery on the sat/nav screen. Is it really flat when this comes on or is this an early warning ? will go for an hour drive 2 mo and hope it recharges it back to full ? Strange as my sat nav dont always come on and after eject and re insert it back in to make it work. Did ask bmw derby if maybe the battery was getting low but i was told things like heated seats and heater will stop working when the battery is low ?? just a bit confused.com lol

[535dboy]

They don't like winter!!!

[X5Sport]

My X6 does exactly the same.  If you have the ignition on at 'radio ready' but not running, these cars draw a huge amount of power doing nothing - in my case almost 60A.  That canes a 100Ah battery very quickly.

Richard

[RenoHuskerDu]

Mine has the gel cell battery, probably due to its Webasto option. Voltage was hovering around 12.4v AFTER a long drive. A trickle charger brings it up to 13.4v but then it drops to 12.6v again after an hour of sitting. I like to see at least 13v resting voltage on my vehicle batteries. Call me a perfectionist.

Hating winter as I do, and seeing a strong battery as my first line of defense, I'm having the German dealer put in a new battery today.  Crikey, the gel cell is expensive! I hope Odyssey makes the bugger.

[X5Sport]

6 cells at 2.1V per cell is 12.6V so your battery is fine.  Anything over that usually means you still have stray charges on the plates which need to settle for at least 4 hours.

Charging voltage on an AGM should be around 14.2 - 14.4V, 13.8 on a 'wet battery'

Richard

[RenoHuskerDu]

Yep, but 12.4v after a 30min autobahn drive is too low in my book. Call me a perfectionist, but I think my battery was weak. The PO probably ran the Webasto a lot with the timer and/or remote control. The car came from the frosty NE of Deutschland.

Speaking of auxiliary heating, we just bought a Crafter 9-seater which has an Ebersprächer heater for the rear. I have not been able to figure out the German manual entirely, but it does not seem to drain the battery much if at all. OTOH, it does not warm the engine coolant. It only space heats.

[X5Sport]

You also have to allow for the fact it takes 20 minutes to put the starting charge you used back into the battery, and that the electrical/electronic systems in the car all use power too with the alternator output being a fixed maximum.

Put it all into play and a 30-min drive is unlikely to give you a fully charged battery.  There's being a perfectionist and then there's the rules of physics & chemistry.

Richard

[RenoHuskerDu]

For once I hope you're wrong.  ::)