Carpokes Porsche Forum

I have several Battery Tenders lying about from my motorcycling years and am not keen to go buy another Porsche branded item unless its necessary.

My 911 GTS is brand new and I am not keen to burn the thing to the ground, so I thought I would seek the wisdom of the forum. I have always connected the Tender on other vehicles directly to the battery as opposed to utilizing an accessory outlet. If I connect the charger pigtail to the positive battery terminal and then ground the other wire to the frame, can anyone see that as harmful to the electrical system of my beautiful car?

I also thought this setup would allow another method of battery connection should I ever experience a battery failure as, i could secure the battery tender hookup plug below the wipers for outside the car access.

59 Panhead wrote: Mon Jan 30, 2023 2:52 pm I have several Battery Tenders lying about from my motorcycling years and am not keen to go buy another Porsche branded item unless its necessary.

My 911 GTS is brand new and I am not keen to burn the thing to the ground, so I thought I would seek the wisdom of the forum. I have always connected the Tender on other vehicles directly to the battery as opposed to utilizing an accessory outlet. If I connect the charger pigtail to the positive battery terminal and then ground the other wire to the frame, can anyone see that as harmful to the electrical system of my beautiful car?

I also thought this setup would allow another method of battery connection should I ever experience a battery failure as, i could secure the battery tender hookup plug below the wipers for outside the car access.

Before I add my two cents, I'm assuming a regular AGM battery? Or is it a lithium (LiFePO4) battery?

Thank you for your post Tim…
I thought that the lithium batteries were reserved for other “track” oriented cars, but a quick parts number check revealed that mine is indeed a lithium battery!
Well so much for my battery tender!

59 Panhead wrote: Mon Jan 30, 2023 3:51 pm Thank you for your post Tim…
I thought that the lithium batteries were reserved for other “track” oriented cars, but a quick parts number check revealed that mine is indeed a lithium battery!
Well so much for my battery tender!

Glad to help Ron!

I have two Porsche's with LiFePO4 batteries. One gets driven almost every day while the other does not, so I do keep a Lithium-only digital maint charger on it and will occasionally hook it up to the daily driver too.

Don't use regular SLA/AGM charging devices as these can degrade or possibly even ruin an expensive Lithium battery.

Also, don't spend the dough on Porsche's maintainer. It's crap per Porsche. (Honest Porsche svc/parts/sales personnel will tell you that they are problematic. The device was designed and manufactured at Porsche's request to do both regular and lithium batteries. It didn't work out well.)

Rather, check out the links for the CTEK product I've attached below. It's actually the same company that built the one Porsche sells but it's for Lithium only and is far superior. (My dealer's service dept techs have been recommending them to their LiFePO4 customers who are seeking a maintainer since I told them about it over a year ago. So far, all feedback I've been given from the dealership has been 100% positive.)

Also, I love using the accessory outlet in the pass side foot-well. So easy to hook up and safe too. I don't like fooling with pigtails and such.

One note is that if you don't drive the car for a long time, say two or three weeks, Porsche has an onboard UVP - under voltage protection - that will disconnect the CTEK. You can tell by the digital indicators on the CTEK if the power outlet has gone into UVP mode. It's easy to remedy - simply unplug the accessory lead from the foot-well, start the car for a moment (or just turn on the ignition switch), turn it all off and reconnect the accessory outlet plug.

I've attached the pdf owners guide for the CTEK, a pdf fact sheet for LiFePO4 batteries that is not really important but that you might find interesting, and three (3) Amazon links to what I bought.



https://smile.amazon.com/gp/product/B00 ... UTF8&psc=1

https://smile.amazon.com/gp/product/B00 ... UTF8&psc=1

https://smile.amazon.com/gp/product/B00 ... UTF8&psc=1

your post is very helpful to me. thanks for taking the time to thoughtfully reply and attach all the links.

59 Panhead wrote: Mon Jan 30, 2023 5:04 pm your post is very helpful to me. thanks for taking the time to thoughtfully reply and attach all the links.

You are most welcome. Enjoy that fabulous new 911 GTS!!

Regardless of Charger I suggest you consider installing a polarized tap connector at the battery to allow connecting with the frunk lid closed

audi4t wrote: Mon Jan 30, 2023 6:32 pm Regardless of Charger I suggest you consider installing a polarized tap connector at the battery to allow connecting with the frunk lid closed52EADC7F-C4B2-4878-A8F8-37A74965312D.png[attachment=0]310AA3C9-45B9-4CEC-94BC-5A6B329C7CD4.png

That's a great way to hook up if one prefers that over the foot-well outlet. Definitely agree that it's best to have the lid closed if you go that route.

Where did you find your tap?

My car has nothing but problems when I try to use the cigarette lighter sockets. They disconnect themselves by design, and I finally gave up trying. You are supposed to be able to stop that from happening, but nothing I tried would work and they'd shut off after maybe 20 minutes of charging. I just go straight to the battery now when I need to put the 992 on a trickle charger. And totally agree with Tim about the Porsche-branded charger -- ask me how I know....

When I first got my car, my PPF guy inadvertently killed the lithium battery by keeping the key in his pocket and constantly triggering the wake-up mode as he moved around. That resulted in a crash course on lithium battery revivals and trickle chargers, some of which is captured in this very early Carpokes how-to....

https://www.carpokes.com/viewtopic.php? ... dead#p4054

It’s NOCO - available on Amazon

Also if the doors and frunk are locked you can access the battery positive an negative without having to access the fuse box

https://a.co/d/2rjTngi