The UK Forum is silent on this matter, so I am reposting here as there are many more XF owners in the USA.

I have a CTEK charger which I have just transferred from my X358 SV8 to my new X260 Portfolio 250PS Estate.

It has an AGM function.

I have wired 'Power' to the battery positive and negative to a convenient body earth.

The handbook says to recharge only off the car.

Any idea why this is? I know it has some 'intelligent' power management function, but I don't understand why this would influence charging.

Voltage levels or spikes from a 'dumb' charger? CTEK charger better?

My car can go for weeks at a time doing short <10 mile journeys once a week then sit for a couple of weeks at a time so I normally hook up the charger when it is not is service. I would like to continue doing this with the X260. Don't worry it gets used for 500-750 mile trips every 6 weeks or so; enough exercise to keep it supple and lithe.

(Yes I have tried searching and failed!)

 

I'm assuming your CTEK is a battery maintainer (trickle charge) and not a charger...... correct? It's designed to provide a low charge to keep a battery healthy when not in use. Don't worry about the "off the car" statement.

 

It is a CTEK MXS 7.0

https://www.ctek.com/products/vehicle/mxs-7-0

They were rebadged by Jaguar, Land Rover and Aston Martin and sold as 'factory' accessories at vastly inflated prices. They may still be - I haven't checked. Mine is simply the CTEK badged type.

Can you cite a source for the 'Don't worry' please, or otherwise elaborate?

 

Your XF, like my XK, will be fitted with BMS (Battery Monitoring System). In order to avoid false calibration or damage to this, the negative connection for the CTEK should be made to a body earth point and not directly to the terminal.

There is no need to remove the battery for maintenance charging with a battery tender. The whole point of the CTEK is rapid and simple connection when the vehicle is garaged. Mine has a CTEK connected whenever it sits in the garage. On the other hand, if you have a flat battery which requires to be fully charged with a battery charger then removal or disconnection from the vehicle is advised.

Graham

 

Always done it that way - even back when the chargers had transformers and probably valves!

I assumed the CTEK was sufficiently intelligent to maintain the AGM battery - it even has a setting for it.

Thought it was worth checking in case some magical new technology had crept in. The periodic table only went up to 103 Lawrencium when I last looked at my undergrad textbooks!

 

Aside from what's been already said: Battery maintainers/tenders are designed to top off batteries that don't get sufficient recharge time or are not used for long periods of time. Ideal wet cell battery state is fully charged and sitting without use will sulfate and slowly reduce their effectiveness until they fail. There's not much specific information on the newly introduced automobile "intelligent" battery management systems but most people believe they have all kinds of algorithms built in to extend battery life. From what I've read, and experienced, it has nothing to do with battery life and everything to do with fuel efficiency. I also contend that some reduce battery life because they keep a certain % of the battery free for charging when decelerating and wet cell batteries don't like that . The 'synching' of new batteries to the system only ensures type (AGM or flooded cell) and size are noted so the system will not overcharge them. In the past with the "old" charging parameters the voltage regulator just shut off current to the battery when it was fully charged but didn't stop the alternator from charging. The current was wasted and the gas required to make it lost (small amount for sure). I'm not an EE but understand basic electricity/electronics and could be wrong on all of this so anyone feel free to contradict my take.

 

Thank you for taking the time to explain all that.

I wired the connector in last week but haven't put it on charge yet. I'm off on a little jaunt to a wedding, then visit in-laws, then offspring then sister-in-law then home, so the battery should be fully charged after that!

I'll put it on charge later this month and let you know if I let any of the Magic Lucas Smoke* out in the process.

*or do cars contain Imps riding CanBus Unicorns these days?

 

Where did you install the connector? My last MB had a terrible battery management system and the car pulled a lot of current when off so I put it on a tender every couple of days. Snaked the tender connector up under the hood by the edge of the cowling for easy access. You can also use that connector to test the battery health without opening a door and drawing current. If you use the start/stop feature and do much around town driving the battery will get quite a good workout. The X260 has a HUGE battery and oversized alternator (IMO) to make up for the stop/start and having one battery (the X250 had a separate stop/start battery). I unplugged that feature anyway because it's annoying and now I don't have to remember to hit the button after starting..

 

I have a CTEK used on my Ford pickup truck stored out of state. I place it on a timer so it is not "on" all of the time. I am not certain this is the "proper" thing to do with this, but I haven't had any difficulties with it to date. As to doing this on a Jaguar I don't know as the electronics are different, but I am of the understanding our chargers self regulate when fully charged.

 

Out of curiosity (devilment?) I emailed CTEK's customer support with the same question.

The chocolate fireguard/teapot (delete as required) I received:

Dear Sir
Thank you for your question.
Regularly there is no reason to disconnect or remove the battery from the vehicle, or open the battery caps, while charging even if you do the recond- program.
CTEK chargers are spark proof and reverse polarity protected and electronic safe. Also when you use RECOND mode, or any other mode your battery requires.

If you have a very special vehicle, please check special recommendations for it, anyway it is always good to read the vehicle manual, what is advised.

Yours, faithfully,
CTEK SUPPORT TEAM

I wonder to which country they have outsourced their on-line customer support.

 

What was that doublespeak?

 

I was performing some CCF adjustments with SDD and was prompted the battery voltage was low, 12.67 volts. This 2015 is a daily so I have never used the CTEK on it. I have an MXS 5.0 and use in on the X150 religiously as it is rarely driven, with no issues and I have a 2013 5 litre supercharged that I use it on occasionally also without any fuss.. All 3 are AGM batteries and this one is less than 3 years old. I attached the leads as usual, positive to the battery terminal and negative to the chassis. CTEK auto detected the fitted AGM battery and started off at step 3.

Perhaps I'm a bit impatient, but 8 hours later the CTEK was still on step 3. Anyone else have similar experience?

 

That's not a low SOC. In fact it shows almost if not fully charged. Did you measure the battery with a DVM to see if the diagnostic tool was correct?

Now this sounds like the battery was actually low. Trickle chargers can charge batteries from a low SOC but that is not their intended use. They are designed to provide a very low current to keep the battery topped up. During the #19 lockdown I measured my battery and the SOC was at 40% which didn't surprise me. My battery tender took 2 1/2 days to bring it up to 12.7 volts.

 

So 12 hours later still at step 3. I measured the voltage across the terminals with a VOM and measured 13.34 volts. I did not measure the voltage prior to attaching the CTEK when SDD said 12.67 volts so I do not have a reference.

 

When measuring SOC you need the battery to normalize by first removing the charge leads then wait at least 15 minutes before making a measurement. As well, any use of electricity (even as simple as opening the door and the foot well lights come on) will give low readings for that 15 minutes. Take measurements immediately after opening the door and at different periods and you'll see how it bounces back. On the X260 there's also about a 10 minute period after opening and closing the door that the LED headlight fans activate so you have to wait after the fans stop to count your time (if you have LED lights).