Battery Tender/Maintainer Malfunction

[930slant]

I have a 2018 Boxter that has run great but if I don't drive it for an extended period, the battery dies. So I have a battery tender/maintainer I plug in to the cigarette lighter to keep the battery charged. Currently, my Porsche maintainer doesn’t continue to charge even though I never take it out of the electric outlet in the wall. When that happens, I have to push the “Mode” button choosing from “small battery”, "normal battery”, and" Li-ion" (used for Porshe lightweight battery Lithium-ion). Without selecting “mode” manually, the car battery will not be being charged. I choose the “normal battery” mode.

This “shutting off" happens irregularly and sometimes the maintainer continues to work for many days and then one day I go out and the power is on from the outlet, but no “mode" is still on. As the manual states, the green power lamp is on meaning that no charging program has been selected or the charger has been disconnected. So I have to select the mode to start it in order to begin charging the car battery..

I read the following on the internet

For 2013-2018 Boxster, Cayman, & 911 Carrera models: Long term storage can put these cars in "Sleep Mode", which will disable the center console plug socket and shut off the battery maintainer. To bypass this, lock the door after setting up the battery maintainer. I have tried this and this process didn’t work for my car.. I even saw another internet statement that I should plug the maintainer into the other 12 V outlet in the car instead of the cigarette plug and that didn’t work.

Even though I have called some dealerships' service departments,I have not gotten a definitive answer from them why this is happening and more importantly to confirm that the Boxster has a “sleep Mode” that causes it to shut off.Because of the shut off, I can’t use a maintainer over 2 weeks unless I am there to check that it is working and if not have to restart it by selecting a “mode”

I had another of the same Porsche maintainer and used it with my Porsche 2009 for over 8 years and it worked. I never had to worry that the maintainer would shut off when I wasn’t there.

The current one I am using was purchased in June 2021 and is the second one I've tried. Yet the problem continues.

I don’t think it is the maintainer since I've tried two new ones, but something in the car that is shutting off the maintainer…and just can’t get an expert to confirm that it is the electronics of the car and give me a process that will work around it, without spending a lot of money.

I just don’t want to have pay an extra $300 dollars for a solution that was quoted by my dealer’s service department( putting a cable on the battery and then have it come into the front truck area. How can I be assured that is the solution and it also means that I have to open my front trunk every time I want to plug in my maintainer vs just putting into my cigarette lighter or other 12V outlet in the car.

[Tremelune]

What a joy it was to be locked out of my Cayman due to a dead battery when it was parked extraordinarily close to a wall, making it impossible to enter via mechanical means.

You could just buy a $25 Battery Tender Jr and attach it to the battery. For another $10, they have a cigarette lighter adapter (but that won't solve your sleep-mode problem). For a car that isn't driven much, it seems pretty trivial to open the frunk.

If you don't give it a good drive every month, bad things will creep in...

[Reiver]

I have a 2018 Cayman...CTek
https://www.amazon.com/dp/B00CD44RQO?psc=1&ref=ppx_yo2_dt_b_product_details

Wired to the battery with the included plug with cap...no issues.