Battery health. High reading? - Page 1 - Boxster/Cayman - PistonHeads UK

Hi all On a 3 hour run back tonight, mostly with lights on, the charging level for the battery has been a constant 14.9. Is this high, low, normal etc? The battery is about 6 months old. Any comments…..? Thanks

In Sport mode, absolutely normal.

Sadly…..and in non sport mode?…..it was mega busy on the motorways

^ In my experience that’d be unusual. With ignition on and engine off, do you get a full 12.8ish volts?

Nope! 11.8 only

Normal in my book. My GT4 regularly runs at that voltage. I queried it and its something to do with these new alternators that can vary the rate of charge.

11.8V before you fire it up is on the low side if you're using the car regularly. If the battery is getting on a bit you might want to consider replacing - I always hope they'll hold at least 12V on relatively light load without the alternator. But if it starts easily with that voltage showing, does it really matter? 14.9V while in use always seems on the high side to me, but both my Caymans (981 and 718) seem to be up around there when I bother to look. Having said all that, I thought my 981 probably needed a battery pretty soon when I bought it in 2018. Gets a CTEK attached if I'm not using it for much more than a fortnight, and run the reconditioning mode every few months. It has been good as gold for well over 4 years now. Liam

Thanks to all Car in question is a 981 GT4. Battery is about 6 months old. I had an Apple Car play upgrade about a month before that, new circuit board in the head unit. Works brilliantly, but stopped suddenly. Blank screen and apparently dead PCM. It was diagnosed as a battery issue, which is why I changed the battery. All perfect until yesterday when mid way through a 3 hour motorway run, restating the car after a quick coffee, same again. Dead PCM. I’m struggling to believ that is the battery, hence my queries. Any thoughts……apart from “ditch the car play upgrade!” Thanks

Did you get the new battery coded when it was fitted? Out of interest what make was the PCM upgrade?

Normal behaviour from my experience. Charging voltage varies depending on ambient temperature. Colder weather sees a higher charging voltage, 15v+. Warmer weather (ie not brass monkey weather) drops to 14v or so. (2014 CGTS here, battery OK) Can’t find a Porsche reference but a number of articles that detail temp vs charging voltage. Eg… https://shop.pkys.com/assets/images/Lifeline-charg... HTH

Hi there No I had the battery fitted by Halfords, they didn’t seem to know about coding. Will that cause an issue? Apple Car play supplied and fitted by Daniel @ smart tune. No issues with either Daniel or the system. Very good guy and eager to help . Check them out at www.smart-tuning.co.uk

The plot thickens! Car Play now working Battery shows 12.8 at rest and 14.4 or 14.5 when running What impact does battery coding have? I’m at a loss!

Are you using the car enough to keep the battery in a healthy state of charge? If the battery is low (11.8v) then the alternator would be running hard and maybe the low voltage means the CarPlay unit has insufficient juice to run. Your long journey has recharged the battery and now CarPlay has enough power.

Rogere said: The plot thickens! Car Play now working Battery shows 12.8 at rest and 14.4 or 14.5 when running What impact does battery coding have? I’m at a loss! Coding the new battery to the car supposedly allows for the optimal charging routine depending on type and frequency of use - you’ll need someone with a code reader that can deal with Porsche codes to do this. Unfortunately like many things on a modern car, battery technology has moved on a lot to support lighter weight, more environmentally friendly alternatives without much explanation to the consumer. One consequence is that the new battery types e.g. AGM or EF don’t like being left unused or allowed to go flat. I would advise investing in a decent trickle charger/ maintainer if you situation allows to prolong the life of your new battery, especially if the car is not used frequently.

Hi all The car is a daily driver and does a load of miles. But I take on board all the comments. I suspect that it is battery condition that is causing problems with Car play, as opposed to a troublesome Car play unit. I’ll get the battery coded at Fearnsport. Matt knows what he is doing!

elisered said: One consequence is that the new battery types e.g. AGM or EF don’t like being left unused or allowed to go flat. I would advise investing in a decent trickle charger/ maintainer if you situation allows to prolong the life of your new battery, especially if the car is not used frequently. Knowing Roger from these forums as the Daily Driver 'tester' of Porsche GT products, the term 'not used frequently' is not in his lexicon. As a 981GT4 owner I'm keen to follow Roger's exploits and hopefully 100k+ miles in his.

Well, I have to admit it’s a joy to drive. …..so that’s what happens! No doubt my desire to break records for GT4 mileage will cost a fortune in depreciation, but hey, it was bought to be driven. And driven it will be. Comfortable, quick, looks the dogs xxxx and with car play, when needed, very relaxing!

Thanks to all Car in question is a 981 GT4. Battery is about 6 months old. I had an Apple Car play upgrade about a month before that, new circuit board in the head unit. Works brilliantly, but stopped suddenly. Blank screen and apparently dead PCM. It was diagnosed as a battery issue, which is why I changed the battery. All perfect until yesterday when mid way through a 3 hour motorway run, restating the car after a quick coffee, same again. Dead PCM. I’m struggling to believ that is the battery, hence my queries. Any thoughts……apart from “ditch the car play upgrade!” Thanks

My 2016 CGTS had a new OPC battery 3 months ago. Seems to regularly show 15.1v-15.3v even on a run in the cold weather. Apart from the high readings all seems to be fine, so who knows. Its got a Porsche warranty, so not too bothered at the mo. Funny things these new AGM batteries.

Rogere said: I suspect that it is battery condition that is causing problems with Car play, as opposed to a troublesome Car play unit. I doubt that very much - if the alternator was charging at a silly rate it could start to affect things but the battery would smooth most of it out anyway. A battery reading 11.8v at rest is not something to be concerned about, if you checked it when you pull up and again after a couple of hours it would read differently anyway. I wouldn't get too bogged down with the numbers, the weather can change most of them easily when it is this cold. Battery voltage will drop when cranking, more so when very cold as it is harder crank/start in the cold, thicker oil etc and batteries don't like a drop in temp it alters the way they release power. A car will start at 10v+ anyway, a lot of systems are disabled whilst the starter is cranking to prioritise starting over heating your seats etc. Coding the battery tells the charging system what the capacity it has, which alters the charge rates in different conditions, the make of battery (as opposed to type) makes no difference, only the Ah rating. Halfwits is not a great place to get anything done to a car, let alone anything vaguely technical. I would forget the car and focus on the PCM mod, if we had done it I would be changing the board and putting it on the shelf to be used (or not used) at a later time when your issues have been identified. It could be something simple like a ribbon cable not pushed all the way in. All IMHO.