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Contact mark @928 International and get a nice used factory one that already has the bends in it or run down to Tractor supply,they usually have them in different lengths. Lost a ground strap on my Jag while on a road trip, picked up a braided cable type for 9 bucks,but it was a short one.
I would not buy a used Porsche cable in this application - they deteriorate with age and can become intermittent before total failure. An aftermarket (slightly longer) cable with a heat shrink sheath sealed with adhesive at the battery end is the best bet. Personally I used a clear adhesive heat shrink sheath (‘clearly’ not stock) - it allows monitoring of the health of the woven strap - which is normally hidden anyway. This also allows for a battery switch in the ground line located behind the tool panel at the ground point.
NOTE I would suggest that you dont add a ground cutoff switch,
as it will create more issues with the charging system.
NOTE of the 928s that I have fixed 6 of them all had either loose or corroded or broken cut off switches, wire connections.
2 of these caused the car to be disabled while it was being driven.
Or better yet wait till you find one of these devices thats filled with water from a leaking hatch seal
That data point given,
it is more common than you might think to have a loose or dirty battery connection.
Using the ground strap and wingnut gives the operator the chance to inspect this connection every time its connected.
NOTE in every case I removed the cutoff switch and restored the system to stock configuration.
I would not buy a used Porsche cable in this application - they deteriorate with age and can become intermittent before total failure. An aftermarket (slightly longer) cable with a heat shrink sheath sealed with adhesive at the battery end is the best bet. Personally I used a clear adhesive heat shrink sheath (‘clearly’ not stock) - it allows monitoring of the health of the woven strap - which is normally hidden anyway. This also allows for a battery switch in the ground line located behind the tool panel at the ground point.
Alan
Alan, if not concerned about originality, why not use a woven bare metal strap? Why the need to sheath? These woven ground straps can be ordered to length, are easy to find, and were used for decades on American cars.
Good to know. Thank you for the been there done that life experience.
So maybe the battery tender in the garage is the smarter solution to the "Porsche Battery Drain".
I'm looking forward to having my battery and spare tire tucked away. The jump post might be the best option for the tender.
Good to know. Thank you for the been there done that life experience.
So maybe the battery tender in the garage is the smarter solution to the "Porsche Battery Drain".
I'm looking forward to having my battery and spare tire tucked away. The jump post might be the best option for the tender.
Alan, if not concerned about originality, why not use a woven bare metal strap? Why the need to sheath? These woven ground straps can be ordered to length, are easy to find, and were used for decades on American cars.
Battery outgassing (acidic fumes) corrodes the strap - thats why a sheath and sealing the sheath to the battery lug (which Porsche does not do) is so important. You should also vent the battery outside the battery box to avoid such corrosion - including of the box itself.
The 928 battery is much more enclosed than a typical american car...
NOTE I would suggest that you dont add a ground cutoff switch,
as it will create more issues with the charging system.
NOTE of the 928s that I have fixed 6 of them all had either loose or corroded or broken cut off switches, wire connections.
2 of these caused the car to be disabled while it was being driven.
Or better yet wait till you find one of these devices thats filled with water from a leaking hatch seal
That data point given,
it is more common than you might think to have a loose or dirty battery connection.
Using the ground strap and wingnut gives the operator the chance to inspect this connection every time its connected.
NOTE in every case I removed the cutoff switch and restored the system to stock configuration.
I agree its possible to do a crappy job of installing a battery switch and many switches are crappy even if installed well. However if done well using a high quality switch I don't see any major downsides. Its not easy to install (tight quarters there) and you really need an alternative battery ground strap. I would not recommend using a battery switch to mitigate parasitic current issues - its use is for maintenance, fast charging the battery and emergency battery cut off (not while running - that won't work). There are enough unfused circuits on a 928 that I think this is a worthwhile additional safety method - especially because getting to the battery is so awkward, and even unbolting the ground strap takes too long.
Switches I'd recommend are Blue Sea Systems (likely too large for this location) and genuine Hella >500A (warning there are huge numbers of cheap & nasty copies). You'd need to fabricate a bracket to bolt the switch to the ground point and make the ground connection. If you aren't confident you can do it well - best not to do it at all for the reasons Stan noted.
Here is a picture of the end of the Porsche supplied ground strap and my own aftermarket strap.
The problem with the Porsche strap is the first 3" of BOTH ends are solid with solder. This makes the strap rigid and not conform to the bends required to fit a 928 battery in a 928 battery box. https://928srus.com/products/copy-of...-strap-porsche - if you do not want to make your own ours are $39.95
The aftermarket strap flexs right from the joint both ends.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
My solution:
I bought a longer and a shorter ground wire, insulated them with glue-infused heatshrink, mounted the switch in the corner beside the sparewheel. Easy access and works great. The red switchtop is removable when switched off...
@Alan, I've never seen a battery cutoff switch (shown in Post #9) configured in such a way before. When I was having a current drain problem with my '89 S4, I was looking for a battery cutoff switch and only saw the ones like you'd use for marine applications. In contrast, this one looked slick and well made. Would this one have the same potential problems as described by @Mrmerlin in Post#18? Don't know...I went the battery maintainer route.
What you described in Post #24 is a good plan for a cutoff switch design if you get the right components. However, the battery maintainer still seems a cheaper alternative (if you can't find/fix the current drain).
If you have a current drain doesn’t it make sense to remove the battery from the circuit or would you rather put it on trickle charge so you now have two power sources feeding a draw ?
you might have missed the point of a battery cut off adding more connections to remove power will increase the possibility of a failure of one of these connections
I have seen this happen more than a few times
IMHO the best thing you can do is keep the system as simple as possible Isolate the battery by disconnecting the ground strap
Charge the battery every few months with a 6 amp battery charger.
this should give your charging system and the starting relays a long life
You just have to be smarter than your ground strap
04-06-2024, 06:02 AM
George Layton March 2014
