Porsche Battery Tender

[StuW]

Have a battery tender from Porsche. It comes with a connector to the 12 V outlet but as many of you know (and it took me a few tries to figure this out because the Manual doesn't tell you), with the 992, the outlet shuts off 30 minutes after the car is off. So you have to have clamps and connect the tender directly to the battery. I did this and it works for several hours, it goes to full charge, then the on/off power lights start to blink, indicating an issue. The troubleshooting portion of the Manuel doesn't help. Any suggestions?

[Hawk]

Have a battery tender from Porsche. It comes with a connector to the 12 V outlet but as many of you know (and it took me a few tries to figure this out because the Manual doesn't tell you), with the 992, the outlet shuts off 30 minutes after the car is off. So you have to have clamps and connect the tender directly to the battery. I did this and it works for several hours, it goes to full charge, then the on/off power lights start to blink, indicating an issue. The troubleshooting portion of the Manuel doesn't help. Any suggestions?

With my 992 I had no issue with the Porsche Charge-o-mat connected directly to the battery. Make sure you use the grounding point near the battery and not the negative post on the battery for your ground.

You can also try this procedure using the 12 volt outlet in the passenger footwell area:
PORSCHE 992
CHARGE-O-MAT PRO INSTRUCTIONS

1. Unlock Car
2. Plug Charger into Car Auxiliary Outlet
3. Turn Ignition Key to Accessory Position
4. Plug Charger into AC Wall Outlet
5. Select Charge “Mode”
6. Turn Ignition Key to Off
7. Lock Car

[Tom]

I tried and tried and ended up with battery clamps too....

I agree with Hawk about the connection being a possible culprit. Next time it starts to blink, I'd try adjusting the clamps to make sure they have a good bite on the positive battery terminal and the designated ground post; and make sure the cigarette lighter connection joint is secure as those things were never really designed to be used as a power coupler like this....

There's a picture of the ground post in this thread if helpful:

viewtopic.php?f=14&t=60

[audi4t]

I read pages and pages of posts on how to charge the Porsche battery.

We've had auto batteries and chargers since around 1920 - over a hundred years.

Not much has changed (Lithium batteries excluded) in that time and the procedure for keeping a lead acid or AGM battery charged is not rocket science.

My car has the AGM battery and I am using the NOCO Genius trickle charger with pigtails directly connected to the positive battery terminal and a grounded bolt, adjacent to the battery.

The pigtail is accessible by the windshield even when the frunk lid is closed, avoiding the issue of accessing the fuse box if the battery completely dies.

If I had a lithium battery I would use the same procedure.

I have a BMW at my vacation home which is on a trickle charger 9 months of the year and it has started fine using this method for the past 8 years. In fact the trickle charger I use on the BMW is a Harbor Freight $10 "special".

https://www.amazon.com/dp/B07W8KJH44?pd ... 1a2e078054

[StuW]

Thank you for the replies. I assume it was the connection too, particularly to the positive terminal, as the clamps Porsche provide are small and you don't get a nice firm fit around the positive terminal. The ground bolt is easy, you get a firm connection.

[Tom]

I read pages and pages of posts on how to charge the Porsche battery.

We've had auto batteries and chargers since around 1920 - over a hundred years.

Not much has changed (Lithium batteries excluded) in that time and the procedure for keeping a lead acid or AGM battery charged is not rocket science.

My car has the AGM battery and I am using the NOCO Genius trickle charger with pigtails directly connected to the positive battery terminal and a grounded bolt, adjacent to the battery.

The pigtail is accessible by the windshield even when the frunk lid is closed, avoiding the issue of accessing the fuse box if the battery completely dies.

If I had a lithium battery I would use the same procedure.

I have a BMW at my vacation home which is on a trickle charger 9 months of the year and it has started fine using this method for the past 8 years. In fact the trickle charger I use on the BMW is a Harbor Freight $10 "special".

https://www.amazon.com/dp/B07W8KJH44?pd ... 1a2e078054

The issue with the 992 is really the lighter sockets that turn themselves off, not so much the tender or batteries (which, as you say, aren't that different from my old Firebird). I have that same quick-connect plug on my 951 and 450SL and love it -- makes it sooo much easier. I tried to install one on the 992, and couldn't get the wires on without more surgery than I was willing to undertake that day. I can't remember the exact issue, but the nut on the positive terminal was trapped in place if I recall. I'm sure with a little effort that's the way to go however. In the meantime, I've vowed to just drive the car more.

[cassius]

Hello, this is a fairly basic question but I hope it’s on topic.
I have a 2012 991.1 with a battery I replaced in 2018. Daily driver, about 5-6 days/wk.

I just returned from a 16 day vacation, and my car cranked right up when I drove it today. However later in the day, I remembered I had to change the DST settings.
When I turned the key to change the setting, my display showed an error: “Battery Low, please start engine”. I’d never seen that message, so that brings me to the question: do I really need a battery tender for when I won’t be driving for a week or more?

I thought this was a curious error in light of the fact that I had driven the 15 or 20 miles in the morning.

Would appreciate comments and suggestions.

Cassius Smith
Cary, NC

[Tom]

Hello, this is a fairly basic question but I hope it’s on topic.
I have a 2012 991.1 with a battery I replaced in 2018. Daily driver, about 5-6 days/wk.

I just returned from a 16 day vacation, and my car cranked right up when I drove it today. However later in the day, I remembered I had to change the DST settings.
When I turned the key to change the setting, my display showed an error: “Battery Low, please start engine”. I’d never seen that message, so that brings me to the question: do I really need a battery tender for when I won’t be driving for a week or more?

I thought this was a curious error in light of the fact that I had driven the 15 or 20 miles in the morning.

Would appreciate comments and suggestions.

Cassius Smith
Cary, NC

First thing I'd mention is that they just don't make batteries the way they used to. The 'good' ones come with a 3-year warranty. If yours is from 2018, it's getting long in the tooth by modern battery standards. Modern cars tend to have more parasitic drain too. My guess (just a guess) is the your battery was/is indeed low after 16 days, and your drive this morning wasn't enough to fully charge it. Take it out for a long drive and hopefully that message goes away.

The battery will always be better off on a tender if it's not regularly driven -- i.e., it will last longer if you never let the voltage drop. So, if it's going to sit 16 days (or a week here and a week there) a tender is a good idea. You can get a decent one for under $50, so there's no real downside, and it will likely extend the life of your battery.

[cassius]

Tom - you said you had your pigtail such that it can be connected without opening the frunk - that sounds perfect. Question - did the pigtail come with your tender, or is that a separate accessory? THANKS.
Cassius

[Tom]

Tom - you said you had your pigtail such that it can be connected without opening the frunk - that sounds perfect. Question - did the pigtail come with your tender, or is that a separate accessory? THANKS.
Cassius

I think every tender I've purchased came with a battery pig tail. They put ring connectors on the battery side, which may or may not fit any given car. I've installed these on maybe half a dozen cars and think I replaced the ring connectors every time. You can get a variety pack of connectors at any hardware store if needed -- cut off the ones that comes on the pig tail, slip a piece of adhesive-lines heat shrink tubing on the wire, solder on the new eye connector, seal it up (and make it look pretty) with the heat shrink.