Battery losing charge

[david.spence47431]

My X350 3 litre V6 loses charge from the battery if left for 2 - 3 days - so much that it will not start. Is there something that could be causing this - alarm, immobiliser, or the like? Or is it simply just needing a new battery? The original battery was swapped for another one that was known to be good with only a slight improvement. I am reluctant to spend money on a new battery if that is not the problem.

[J44EAG]

You need to capacity "drop test" the battery before doing anything else. One has to start from a known good point before a correct diagnosis can be achieved. Anything else is guess work.

A garage could drop test for your or otherwise buy a drop tester from eBay. If you buy one, come back to us again and we can tell you about its use and what you can deduce from the test results.

If you have a volt meter handy, charge the battery and test terminal voltage. Test every twelve hours and see what you find. 12.8v is a fully charged battery. 12.4v is half discharged, 12v is discharged and will only just start the car. Anything less than 12 is useless.

Mike K

[PaulGover]

Probably not relevant, but AFAIK you need to double-lock the doors (so the wing mirrors fold in) to let the car electronics go into their lowest energy state; even then I think it can take about an hour for it to fully shut-down things.

[david.spence47431]

Going for a new battery - should I go for an expensive one or Halfords own brand - Halfords have Yuasa 100Ah 900amp for £143 or their own brand 95Ah 800amp for £113

[J44EAG]

Regret that personally, I`ve nothad much luck with the Halfords own badge batteries. Yuasa are fine but also consider Bosch Silver or Varta Blue which have "silver" technology which makes it a Premium grade battery. Plenty of all on ebay with great prices and next day delivery. I have a Varta unit in my 350 and its not let me down in five years. I`d advise against cheapo batteries which don`t have a reputation for voltage stability. Stability of the battery is badly needed on our cars. Unstable batteries are likely to cause electronic glitches which you can do without. The phenomena gets worse in cold winter conditions. Just what you don`t want! Buy the best and you won`t regret it.

Hope that helps.

Mike

[rosemary]

Just a quick note. Under Park Brake Fault in the XF forum you'll see my saga re Battery. New bought, Bosch S5 100AH Battery from Tanya on line, problem fixed.
Old battery, LION , barely 4 years changed in 2016 after spurious alarms including Park Brake Fault, losing charge as I watch on my Voltmeter from 12.8 (Fully Charged according to my CTEK) to 12.2 in a matter of a minute or so. History of batteries losing strength over 3/4year periods in the car's history. Like Mike says don't buy a cheaper battery.
Dave

[ptjs1]

David,

Be sure you look around for best price. I can find that Yuasa 019 battery at tayna.co.uk for £114 delivered. If you are going to use Halfords, try and find someone who has a Halfords Trade card. With my Halfords card, that battery is £105.

Good luck

Paul

[david.spence47431]

Found battery at tanya.co.uk - extremely annoyed, they will not deliver to my postcode, actually illegal to do this, but doesn't help!!!! Looks like it'll have to be Halfords.

[davidr]

It's worth keeping an eye on Euro Car Parts as they frequently have flash sales.
If I can add my five penneth I'd agree completely with the idea that it is essential to get a top grade battery on these cars. Putting on a cheap one will prove to be the ultimate false economy!

[david.spence47431]

Got a Yuasa for £105 from Halfords with discount card. Strangely enough all warning lights went out just before fitting it. However still all OK with new battery so fingers crossed.