Battery Dead - CTEK question

I keep my battery on trickle charge via a CTEK MXS 5.0 as I sadly don't get to drive it very frequently. Woke up to a sunny Sunday last weekend and excitedly jumped in for a spirited drive only to find the battery not able to turn the car over and to add insult to injury I was then deafened by the alarm going off in the garage. I tried a couple of CTEK regenerations on it over the weekend but it keeps tripping out at stage 5 (according to the manual this means the battery won't hold a charge). I have a Bosch S5 010 in the car which is around 5 years old. I know these cars are hard on batteries but it did surprise me a little that the battery has gone this quickly when it's always been kept on trickle charge. I'll buy a replacement but my question is this; could it be the way I'm charging the battery that has led to its unexpectedly short life? Until a year or so ago I used to charge it via the ciggy lighter socket but after a couple of episodes of the CTEK dropping out I figured it might be more reliable to switch to charging via the battery terminals in the front. Easy enough to leave the clips on the terminals permanently and just pop the frunk lid and unplug the extension cable each time I take the car out. The CTEK manual instructs charging via battery + and - terminals and looking at the 996 FAQ on battery issues it seems others also charge this way, but digging around I have found a PH post which says you must use an earthing point rather than the battery negative or you're likely to reduce the life of the battery as you miss out the 'little black box' that provides feedback on the status of the battery to the charging source. Is this true for the CTEK MXS 5.0 does anyone know or is it clever enough to not require this? Could connecting directly to the terminals have contributed to my battery's (relatively) short life?

Personally I reckon 5 years on a battery that's hardly been charged by use is pretty good. :dont know:

Thanks T8. So charging through driving > trickle charging from a battery's perspective? Gives me another good reason to drive it more frequently...

Hello I have no experience with 911's BUT: I have an Audi RS6 ("smart" battery in the boot) and this car must be charged (trickle charged) by terminals in the engine bay, not on the battery terminals. The reason given is the car "monitors" current use and therefore the battery must not be charged etc directly whilst in situ. If your car is similar this may be the likely problem. Does your handbook advise? My previous car was 13 years old when sold still on first battery, my Audi is now 11 years old and the same. I use a CTEK 5 also, but normally only boost charge/condition it sometimes a year. Hope this helps.

Thanks don I have no access to the handbook at the moment but will check it later

40Anni996 - I have experienced very similar problems with a CTEK dropping out of its cycle and showing the error light on my 40th AE - initially it seemed fine but then started to go to about No 4 and then throw a wobbly. Tried it with both the cigarette lighter connection and direct to the battery and same issue. However the more clunky Halfords one is just fine (direct to battery terminals) and does the same smart charge job as far as I can see. The CTEK charger seems to work fine with my other older "classic" cars so don't think it's the CTEK charger itself - maybe there is something in the car circuit that the charger is sensing and throwing a fault. Not aware of any differences electrical wise between the 40th AE and the standard 996 though. Any electronics experts out there can probably advise. Also interested in any answer to the best connection to the negative side if not the terminal itself. Cheers..Ian

No idea... but my battery is at least 5 yrs old, and has been kept on trickle charger through the lighter socket when in the garage and has shown no signs of letting go. Not a CTEK though, its an Airflow. That said, I did have a battery go on a 4S a while ago which I used daily for long trips. Drove 90 mins to work, hopped into it at lunchtime, battery dead.

Thanks Ian, sounds like a very similar experience. I'll order a new battery anyway but think I'll try the CTEK one last time on this battery via an earthing point to see if it still throws a wobbly. I need to find a long term solution to keeping the new battery in good shape!

If your car has a battery management system ie stop/start, if connecting to the battery, only the pos+ should be connected & the neg- should be connected to a body earth ie a screw etc. Without stop/start, + & - are ok If your battery has gone so low as you say you need to use an old fashioned charger to get the volts up as ctek will not bring back a dead battery, then connect ctek & it will then optimise the charge & care. My F type which only did 200miles this year has ctek on constantly & starts on the button. Possibly you have a dead cell then its a new battery.

Like I said, I have been using a Halfords brand "smart" charger (which in principle seems to do pretty much the same as the CTEK type) until a couple of weeks ago - always went through the charge sequence fine and then sat as expected on the top up mode. Just changed recently to the one supplied with a Carcoon as I needed the Halfords one for another vehicle and the Carcoon one had been sitting in the box doing nowt. It seems to be working fine as well - again, it's classed as a "smart" charger so has a sequence of lights then a steady one when its in maintenance mode. Still non the wiser why neither of my CTEK 5 chargers work on the 911 when they are absolutely fine with every other battery/vehicle I have. It's like something on the car circuitry stops it from going through the sequence. Cheers...Ian

You are not alone, I have exactly the same issue with CTEK 5 on my 911, when it is fine on other cars! I would love to figure out why...

Thanks freshy - tis odd indeed. Any joy using another type of ('smart') charger/maintainer? Thinking of pulling the trigger on a cheap Chinese one from Amazon to try instead of the CTEK.

My Lidl £15 one is doing a great job so far...

I use a charger made by Granite Digital in CA. Save-a-battery is the trade name and it does just that.....highly recommended.

I'm in a similar boat, just being more cautious before I buy another charger as thought I was buying the best when I bought the c-tek! I'll update this thread before I buy something, maybe its a 996 MY04 thing? :?: