X-type battery discharge
 

Hello everyone,
I have a 2009 (facelift) X-type estate 2.0d SE – lovely motor and generally very pleased with it. However, I just want to ask owners about battery drain.
If I'm listening to the football on the radio when washing the car (ignition on, no more than 2hrs tops) or, like yesterday when doing a bit of work inside (feet sticking out door, so interior light on), the battery seems to drain pretty quickly, to the point where it needs a recharge (drops to 10.6V). In other, normal, day-to-day use, there's no such problems and it starts fine every time.
It's a pretty chunky and new Bosch battery, and I would have expected to be able to listen to the radio for more than an hour without the battery draining.
Is this normal? Any ideas?
Thanks for any help you can give.
Andy

Andy, I play with batteries of multiple sizes (some capable of powering a small town). This is what I would tell you, time using a battery is not what you really need to be looking at. What you need to look at is the amp-hour total. A battery is going to drop by the same amount of voltage if you pull 10 amps out of it for 1 hour or 1 amp out of it for 10 hours. Either way, you used up 10 amp-hours of power. Most batteries for our cars have an 80 amp-hour reserve (ie, source of power). Does that mean at 80 amp-hours it will still crank the car over. By no means. I find after about 10 amp-hours of discharge, the battery is weak enough that it is going to struggle to crank over the engine. So, things like the volume that you have the radio at will affect how much power you are pulling out. Having the door open turns on a bunch of lights which is a power draw. This all affects how long you can do things and still start the car.

with this being said, there is a benefit to doing a discharge like this periodically (say 1-2 times a year). Some batteries undergo what is called mossing and by doing a discharge like this, you kill off that moss inside the battery and it will help the battery survive longer before it gives up the ghost.

Terrific - thank you. I'll have a good look at the battery's exact specification (should've done so before posting). And I'll bring the tranny out to listen to the footy next time I wash the motor!