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bo_duke
Monza


Joined: 27 Jul 2014
Posts: 158



PostPosted: Sat Jan 06, 2018 8:11 pm    Post subject: DIY: Fitting Trickle Charger Pigtails To 981 Cayman/Boxster Reply with quote

The consensus on the interwebs seems to be that 981 Cayman/Boxsters:
- Disconnect the cigarette lighter sockets after a few minutes, unless the car detects they are being used for charging.
- Use an AGM battery (for stop/start), which requires a special trickle charger with a slightly higher output.

However, I tried charging my CGTS with my old accumate charger, and a new CTEK MXS5.0, and the centre armrest socket still disconnected after a few minutes (even if I connected the charger with the ignition on, and locked the car after charging started).

More googling, inc. the following threads, suggests a problem with cars made early in 2016 (mine is March 2016):
- https://rennlist.com/forums/gt4/927287-charging-the-car-battery-via-lighter.html
- https://rennlist.com/forums/987-981-718-forum/947900-battery-charger-connector-question.html

A couple of solutions are suggested:
- Hardwiring charging ‘pigtails’ to the battery.
- Re-coding the car, to stop the sockets disconnecting. This seems to be the preferred solution for early Macans, but I read at least 1 thread where a dealer applied the Macan fix to a 981, and it didn’t work. Plus, shutting everything down to save the battery seems like a good idea, which I didn’t want to disable.

The MXS5.0 comes with pigtails, and instructions to attach them direct to the battery terminals. However, google suggests a few reasons not to attach pigtails direct to the negative terminal (although its OK to use the positive terminal):
- The Porsche manual says not to (and to use a dedicated earth bolt on the wiper mechanism).
- There is a safety risk from a spark near the battery (which gives off gas).
- There is risk of a voltage spike frying the battery sensor.
- Using the negative terminal bypasses the battery sensor, which prevents it optimising charging from the car, and reduces battery life.
- There is a captive nut on the negative terminal, so the only way to attach a pigtail is via a spade connector.

Ive seen threads suggesting that some OPCs fit pigtails direct to the battery terminals anyway, but nothing confirmed for the 981. So I decided to try alternatives. You cant use the earth post shown in the Porsche manual, as its an awkward shape, and only suitable for crocodile clips. The most common suggestion is a painted bolt under a rubber cover near the wing (see http://www.planet-9.com/981-cayman-and-boxster-service-and-tech/99455-ground-connection-trickle-charger.html). However, its too much of a stretch for the standard pigtails, and I wasn’t keen on breaking the paint.

I tried the horn mounting bolt first (see attached picture), but the voltage reading across this was about 0.5V less than a reading directly across the battery terminals. This may only be a poor connection on my car, but it made the charger work harder/think the battery was more depleted than it was (compared to a connection via the cigarette lighter).

Then I inserted an M8 bolt into the empty threaded hole in the strut tower. This gave the same voltage as a direct connection to the battery terminals, so I went with it. The only slight faff was needing to enlarge the hole in the M6 ring connector on the CTEK pigtail (using a dremel), to fit the M8 bolt through it. The standard CTEK pigtails were then long enough to reach the hand recess used for removing the frunk cover panel. The connector wedges in there nicely, and cant be pulled back through once the waterproof cover is in place.

Hope this helps anyone with an early 2016 car.
 



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tim993
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Joined: 22 Aug 2006
Posts: 5125
Location: Hampshire

2016 Porsche Boxster 981

PostPosted: Sat Jan 06, 2018 10:35 pm    Post subject: Reply with quote

Thanks very much for posting this. Mine is a '65 plate which I’d assumed would be the same as the last cars. I'm just surprised they changed anything so late in the life of the 981 🤷‍♂️. Anyhow you have just answered all my questions about how best to attach a CTEK so I am very grateful for your extensive and well researched post👍👍👍

tim
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bo_duke
Monza


Joined: 27 Jul 2014
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PostPosted: Sat Jan 06, 2018 11:11 pm    Post subject: Reply with quote

Thanks Tim!
Ive seen posts confirming the problem in Jan, Feb and March 2016. And posts that imply its fixed by June. Out of interest, when was your car built (assuming you have the disconnecting socket problem)?
 
  
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tim993
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Joined: 22 Aug 2006
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2016 Porsche Boxster 981

PostPosted: Sat Jan 06, 2018 11:39 pm    Post subject: Reply with quote

I'd guess it was built mid/late July '15 as it was registered on 1st Sep.

I don’t actually know if it has the problem - in fact I’d simply assumed I’d need to attach some flying leads direct to the battery.

If I can find the lighter socket lead I’ll test it out.

Is the disconnecting socket problem purely one of which version of the software the car was loaded with or something more fundamental ?

Slightly off topic but are you saying there were still 981s coming off the production line in June ‘16??

All the best

tim
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jonttt
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Joined: 20 Aug 2012
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2014 Porsche Boxster 981

PostPosted: Sat Jan 06, 2018 11:40 pm    Post subject: Reply with quote

Interesting post ..... by comparison mine had the pigtails still fitted from the OPC (I assumed they forgot to take them off) and its fitted direct to the battery terminals with the connectors converted to spade connectors ie looks like they have been cut in half. I believe this is because the terminal bolts have to be replaced once removed Question
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bo_duke
Monza


Joined: 27 Jul 2014
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PostPosted: Sat Jan 06, 2018 11:58 pm    Post subject: Reply with quote

tim993 wrote:
I'd guess it was built mid/late July '15 as it was registered on 1st Sep. I don’t actually know if it has the problem - in fact I’d simply assumed I’d need to attach some flying leads direct to the battery.
...
Is the disconnecting socket problem purely one of which version of the software the car was loaded with or something more fundamental ?
Slightly off topic but are you saying there were still 981s coming off the production line in June ‘16??

I'd guess from your build date your car would charge OK through the lighter socket.
I'm not sure what causes the problem, but saw a post suggesting the battery sensor hardware changed over time.
Ive not checked when the last 981s rolled of the production line, but there are posts in my first hyperlink about a GT4 built in June 2016 (which works OK), and another delivered in August. HowManyLeft also implies that cars were still being registered in late 2016.

Last edited by bo_duke on Sun Jan 07, 2018 12:05 am; edited 2 times in total
 
  
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bo_duke
Monza


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PostPosted: Sun Jan 07, 2018 12:02 am    Post subject: Reply with quote

jonttt wrote:
... mine had the pigtails still fitted from the OPC (I assumed they forgot to take them off) and its fitted direct to the battery terminals with the connectors converted to spade connectors ie looks like they have been cut in half. I believe this is because the terminal bolts have to be replaced once removed Question

Yes, the end of the main terminal bolts are deformed, effectively meaning the nuts are captive, and cant be removed to slide ring connectors on. On the positive terminal there is a 2nd bolt, which can be used without issue. However, there is no alternative option on the negative terminal, which is why some people convert the standard ring connectors to spade connectors, and slide them on without removing the nuts.
 
  
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deMort
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PostPosted: Sun Jan 07, 2018 5:30 pm    Post subject: Reply with quote

Excellent thread worship

You cant go direct to the battery with a charger as it would be bypassing the battery manager .. basically if that doesnt see the charge going into the battery then it will act as if its low on charge .

Crocodile clamps can potentially cause a spark so best not used on the jump start terminal.
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bo_duke
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PostPosted: Sun Jan 07, 2018 7:09 pm    Post subject: Reply with quote

Thanks Demort Thumb
It’s good to get confirmation of the battery manager thing - I was a bit sceptical
 
  
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tim993
Zolder


Joined: 22 Aug 2006
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Location: Hampshire

2016 Porsche Boxster 981

PostPosted: Sun Jan 07, 2018 7:13 pm    Post subject: Reply with quote

Hi Demort - don't the pics above effectively show a direct connection to the battery? The one to the chassis is effectively a direct connection to the negative post and the one to the positive is right on the battery Dont know
Just want to make sure i'm not missing something key before i do the same!
all the best
tim
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deMort
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PostPosted: Sun Jan 07, 2018 7:53 pm    Post subject: Reply with quote

I tryed to find a picture of a 981 battery neg terminal but failed Sad

Picture below will give you an idea though .. look at the negative lead and you will see a black box , this is a sensor.



On the negative lead there is a box and it senses voltage flow , if the charger is connected to the negative battery pole then it bypasses this box ..

If you connect the charger to the chassis ( any bodywork ) the voltage will flow up the negative lead and the box will sense that.

The car will switch on and off different systems depending on what it thinks the voltage of the batery is .. includeing the charge rate so if the Ctek charges at the battery the battery will be fully charged but the battery manager wont know this .

All modern Porsches work this way so Panemera .. Macan 991 etc etc .

It also means that you cant just change a battery .. you have to TELL the system it is a new battery as the system accounts for ageing as well as battery charge state.

The auto stop start will not work if the battery voltage is below 80% .. so now you know the main reason it doesnt always work !!!



Its no longer simples Very Happy
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tim993
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2016 Porsche Boxster 981

PostPosted: Sun Jan 07, 2018 8:07 pm    Post subject: Reply with quote

Hi Demort - Ah, now I understand! Thank you for explaining. I need to move my head on from the simple systems in the old 993... I'm guessing that the captive nut mentioned above is to discourage home-tinkerers from tackling a battery replacement themselves.

all the best

tim
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deMort
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PostPosted: Sun Jan 07, 2018 8:09 pm    Post subject: Reply with quote

Pretty much .. yup .

Stickers on the jump start pole as well to help explain .

Just for info the Cayenne has had a battery manager since 2003/4 but not as advanced as the current ones.

993 Very Happy life is so much easier when working on them when they have a fault .. its the earth lead lol Smile

EDIT

You own my favourite Porsche .. 981 GTS !
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tim993
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2016 Porsche Boxster 981

PostPosted: Sun Jan 07, 2018 8:25 pm    Post subject: Reply with quote

Smile and it's lovely Guards Red too Cloud 9
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bo_duke
Monza


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PostPosted: Sun Jan 07, 2018 9:47 pm    Post subject: Reply with quote

Weird how a CTEK knows how to test/manage a battery 2 secs after it’s been connected, and yet the car loses the plot if it’s not programmed to recognise a new battery, or is kept out of the loop for a few days?
 
  
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deMort
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PostPosted: Mon Jan 08, 2018 7:47 pm    Post subject: Reply with quote

The system is more complicated than how i posted .. i was trying to explain a point without having to rewite War and Peace Smile

I can have a dig around to see what info i can send you on it if you really want a boreing read ..

But to be honest ive probably got far more interesting documents on Porsche systems depending on what you prefer that would make far better reading Very Happy
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fastlowe
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PostPosted: Mon Jan 08, 2018 8:13 pm    Post subject: Reply with quote

I've got my C tek connected direct to the battery on my 2010 gen 2 C2s , do I need to move the negative lead, sorry to jump in but I had a new battery a few weeks back and don't want to ***** it up Smile)
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deMort
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PostPosted: Mon Jan 08, 2018 8:30 pm    Post subject: Reply with quote

fastlowe wrote:
I've got my C tek connected direct to the battery on my 2010 gen 2 C2s , do I need to move the negative lead, sorry to jump in but I had a new battery a few weeks back and don't want to ***** it up Smile)


Thats fine .. 981 / 991 are different systems .
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bo_duke
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PostPosted: Mon Jan 08, 2018 9:06 pm    Post subject: Reply with quote

Demort wrote:
The system is more complicated than how i posted ... I can have a dig around to see what info i can send you on it if you really want a boreing read ... Very Happy

Heh heh, I’m OK for dull reads at the mo ta, still smarting from spending an entire afternoon attaching 2 wires to a battery. I’d be a very skint mechanic worship
 
  
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