When starting my 09 XK it initially when cold cranks slowly for the first second or two then cranks normally and starts. However sometimes when hot it cranks over really slowly as if the battery is flat (and slow enough to make me think its not going to start) and then starts this happened earlier today. I drove about 10 miles, turned engine off for about 10 minutes then pressed the starter and it cranked over really slowly and started, i let it run for about 15 seconds then turned off again and it then started normally. I replaced the battery about 10 months ago so I know the battery is OK plus I am not getting not getting any on screen low battery warning messages.
Any feedback will be appreciated and thanks for reading
Chris

 

I would say unless you did a battery check you don't know if the battery is OK. 1st do a voltage check at the battery. 12.6V or better for sitting battery (not running). Then do a load test. If all ok then dig into the starter system.

 

It's (nearly) ALWAYS the battery.

 

Check battery first as Ceejay and Jagtoes suggested.
If battery fine maybe a bad earth on the starter motor?

 

Welcome to the forums Chris,

As other have already said, it's almost always the battery. However, the BMS (Battery Monitoring System) can play strange tricks on a rarely used vehicle.

If the replacement battery is an OE Varta, it's still under guarantee after 10 months. Do you keep the vehicle on a CTEK or equivalent?

Graham

 

Hi Chris, also in Somerset (BoS) if you need to borrow a CTEK for a few days happy to loan you one (have 2). Contactless of course!

Not read many failures of starter motor but have had a few batteries that have failed within a year of purchase which were replaced FoC.

 

Cold winter weather is a battery's enemy. According to AAA's Automotive Research Center, at 0°F, a car's battery loses about 60 percent of its strength and at 32°F it loses 35 percent. During cold temperatures starting an engine can take up to twice as much current as needed under normal conditions.

https://patch.com/virginia/vienna/de...blame-aaa-says

 

What viscosity engine oil do you use? 5W-20 is thicker than 0W-20 when cold, which makes it harder to start.

Find a safe accessory to keep the engine warm when parked overnight. That'll make it easier to start, as the oil won't be as cold. Some vehicles are available with an OEM heater for that purpose.

 

Thank you all for your feedback my gut feeling is it isn’t the battery because it doesn’t always do it for example last night after I posted I thought I would try it out and it started perfectly with no slow cranking at all! I will however check the battery voltage jagtoes said do a load test however I don’t know how to do that so jagtoes can you tell me how to do that please.
when I first got my xk I put it on a 1amp smart trickle charger that I used to use on a BMW 645 but all it did was discharge the battery so I stopped using it and put a new battery in - any ideas why that was happening.

 

Thanks for the offer I will probably get myself a Ctek which model would you recommend

 

As I mentioned just 1st check the voltage . Go out first thing in the morning and put a volt meter on it and see what you get. You should see at least 12.6 volts. If is less then get a battery CHARGER and not a Ctek battery maintainer. As far as a load test you would need to either go to a dealer or an auto parts store to get it checked.

 

The MXS 5.0 is an excellent choice.

 

THIS is a battery charger.



https://www.bargain-junction.com/pro...gn=sag_organic

 

Bill's recommendation is the one I have.

As a matter of interest, since your battery is so new you'll have the receipt for it, in with your service stuff, so share the specs.

I've never used anything as hefty as the charger CJ recommends and have never had a failed battery in 39yrs of car ownership. Just a shop bought one as in the link below:

https://www.halfords.com/motoring/ba...2l-329109.html

If it is your battery consider the bosch S5 type 019 with 5yr guarantee on amazon for £115 delivered.

In my case It helps to have some extra oomph as have heated seats/screen/wheel, plus a dashcam, ashtray display unit and tracker fitted!

As to temps it's currently 11c/52f in my part of Somerset at 1.30am, I think we've seen frost 6 times so far this winter, so it's hardly what you'd call arctic.

 

One reason (other than I use battery chargers quite frequently, as many vehicles, many projects and lots of other stuff) is that it has the 40-Amp capability, which is required for using SDD.
I'd not need the charger I had if no SDD, and also no shop, no vehicle hobby cars, RVs and all that nonsense. A typical homeowner has no need for it, but danged if I'd want to live without it!

 

I have one and and i'm a typical home owner I think. LOL

 

This morning I went out to start my XKR which has a new battery (about 2 months old), and as normal I unlocked the doors with the fob, mirrors folded out like usual, and then I got in, tried to start and nothing...no weak cranking, no ticking, nothing except 'kEY NOT RECOGNIZED" WARNING followed by insert into the slot. When I tried inserting several times it didn't recognize the key, and I figured this was caused by a low battery. I hadn't driven the car in a few days and sparingly before that as I had some surgery last week. Fortunately, there was enough juice to open the trunk to get to the battery. I exposed the battery and put my (regular homeowner) battery charger on a 10amp charge for a couple of hours, and went out to start it and voila! everything back to normal. When Cee Jay talks, "people listen." It's always the battery.

 

Quick update before a business trip - checked this morning battery was at 12.5v started ok (very slight slow crank for a second) went for a 6 mile drive parked stop and then restarted all ok drove back home tested voltage and was 12.4v. I have a silver Bosch battery

 

I don't recall the measurement number but I think that 12.4 V is about 80% charge value. 12.6 or above is 100% charged. Also what is the voltage at idle.

 

Congratulations on buying a new battery soon!

Cold weather is often fingered as the culprit when car batteries die, but actually warm temperatures do the most damage to them. High temperatures quicken corrosion of internal plates and vaporize the electrolyte faster. But car batteries usually go dead in cold weather mostly because damage done during the summer doesn’t show up until the battery is more taxed. A cold battery has reduced cranking power, and cold temperatures thicken motor oil, making it harder to turn the engine over. Modern electrical and fuel systems can mask a weak battery by starting an engine with a minimum of cranking, but when a weak battery is further compromised by cold conditions, it’s more likely to fail.
https://www.consumerreports.org/cro/...engine%20over.