Put my 2020 911 on a lithium Ctek charger and left it for two months. Locked the car which I've been told shut down the system and didn't allow the battery to be charged. (Not sure if that is a fact.) Couldn't get into the car when I returned. After opening the door and attaching a power source to the proper station in the left footwell I was able to open the frunk. And with the power source started the engine. Ran the car for about 50 miles and then put it on the Ctek (with the car unlocked), for about 5 days. The battery shows 13.3 volts but the PCM shows "VEHICLE BATTERY CHARGE IS LOW. SYSTEM WILL BE SHUT DOWN". The car starts but I'm not happy with the message. The battery shows 13,3 volts but I don't know the amperage available. I don't have a drain on the battery. My car is 18 months old and has 7000+ miles. I drive it in winter. Kendall of Bend won't help me. They told me to call 1-800-PORSCHE.

 

Where do you read 13.3V? Through the PCM or directly on the charger or test on battery? 13.3V is a charging voltage as Li battery should not go above 12.6V fully charged. My battery shows 12.4V fully charged but still on Ctek trickle charger.

 

I’ve never seen my Li battery voltage (measure in the car by both the instrument display and voltage reading on my radar detector) to drop below 13.2v. Normally bounces between 13.4-13.5v.

 

Same place you read the oil tem/pressure/turbo pressure/etc

 

I just customized that display to add the "on board power" and it shows 12.4V. I am not understanding how you can see much more as Lithium battery cells don't get you beyond 12.6V (or I need to relearn what I know about lithium cells)..maybe when car is on and you see charging voltage from alternator?

 

I am screwed then, as I have had liPo batteries on at least one of my cars the last 10 years (not porsche) but including my 2020 992 C4S (which I had 2 years before I just got my 2022 992 Targa) - I had all of them hooked directly to the pos and negative posts. I have never had a problem. Though it shouldn't matter - I could not keep the charger active with it on the ground post on the 992 for whatever reason.

 

Hey Bill, a few points
- 13.4v is perfectly fine for your lithium to be sitting at, and you say the car is starting fine so it looks all good for now. The BMS can't be said to be bad if your car is starting and it appears to be sitting at a fine voltage. Perhaps the Car's Intelligent Battery Sensor (IBS) is just reading the voltage wrong and giving you a flag. Becuase if your car is starting and the voltage is a 13.4v everything is working on the battery side just fine. That is just where you want to see a lithium battery when it just sitting at resting voltage. Its nominal/resting voltage is 13.2 so 13.4 is right in the pocket.

- Abosoltly NEVER give into Porsche claiming its not covered under Warranty... that is the biggest money making scheme in the Auto Industry.... tell them buzz off , this battery is warrantied for 4 years (if it does ever become the battery) and replace it or your willing to take them to court. The reason I say this is because they tried to burn me like this after buying my GT3 RS.... they try to deny basic Warranty claims I had. Just fight them, they will say OK we'll cover it . Additionally they CANNOT put any statement of having to drive your car any distance as part of a warranty on a battery! Tell them to buzz off and that your Lithium Battery is on a Charger so you don't NEED to drive to keep it perfectly charged and conditioned. 6000 miles of driving have nothing to do with your battery. You can drive 2 miles a year and you battery won't know the difference as long as it is kept charged. Porsche Dealer are not your friends... yes they can be nice as pie, and smile and ask about your kids when they see you again... but they are just there to make money.... and if they lie about a warranty oh well they will do it while acting like your friend.

- You may drain the battery if you don't keep it charged... but sounds like you did keep it charged and its working fine except for a warning you got. Keep in mind that warning could easily come simply because the battery was a little over discharged and then on the start attempt it went down into the 9 or 10v range for a few seconds which will cause the Porsche system to report low voltage or a flag. All I can say is don't worry until you actually see a functional reason to worry because these Porsche Systems are very sensative to the slightest discharge... but they flag sometimes when the battery isn't continously low but just low for a few seconds of time.

 

Not sure, but I read the same voltage of ~ 13.4v on the battery (no engine running) on both the Porsche instrument panel and the readoff from the radar detector plugged into the car’s cigarette lighter/outlet. Been this way since I got the car. In fact, when I turn on (not starting engine) and watch the voltage over a minute or two, I see NO drop in the voltage.

That said, I found this on a car battery web site:

”A 12-volt lead-acid battery that is fully charged often provides a voltage of about 12.7V. If the lead-acid battery only has 20% left, it will only deliver 11.6V. A fully charged lithium battery delivers 13.6V but delivers 12.9V at 20%.”

I have seen as high as 13.6v, and never in the 12v range. Maybe the 12.6 v you are seeing tells you something, per the comment above, “…delivers 12.9v at 20%”?

 

Mhm, Ctek says its all charged and green....but voltage on display never goes higher than 12.7V even with charger still on but engine off. I guess another detail for Porsche to figure out. I never see a resting Voltage of 13.6V and I am puzzled by that. I thought LiFePo4 batteries deliver 3.2V per cell aka 12.8V max (not charging voltage). Mhm.

 

All this complexity of battery management makes my head hurt. After delving into these threads and learning, it does appear there is only ONE correct way to do all this, and anything other than that correct way can lead to issues.

Somedays I think I want to return to the analog car days of the 60's and 70's. Then I go drive one of those ancients and ....ahhh..no...Modern is better. lol

 

I found this for LiFePO4 battery:

https://diysolarforum.com/threads/li...ge-chart.3156/

13.6v - 14.4v is considered to be 100% charged {I assume Porsche limits the charge so it doesn’t reach higher than 13.6v}?
13.4v (which is what I normally see) is considered to be 99% charged
.
.
12.8v is considered to be 17% charged
12.5v is considered to be 14% charged

 

Well, I will let Porsche figure that out. My Ctek shows green, fully charged...

 

Just curious…where have you connected the black lead of the ctek…the negative terminal on the battery, or the grounding post?

 

To chassis ground but not the post they show in the manual as the leads are not long enough of the quick connect. I used a post on the other side closer to battery.

 

The following is from my service department manager. He was responding to my email that after charging, the ONLY light on the ctek that was lit, was the green power light. It was charging, as seen by the various yellow charging status lights, but when I left the charger and came back in a few hours. None of the status lights were lit, and only the green power button was lit. That was wrong…so i asked him what was up? His response worked and fixed my problem after i moved the negative terminal from the negative post on the battery, the the grounding post. No idea if this will fix your problem, but it might if you connected the ctek to the battery? Give it a try, and see if it helps? Start the trickle charge all over again.

“The negative lead on the charger is to be connected to the negative jump post, and not on the battery. Connecting at the battery can short the battery sensor. I’m not sure if doing this will interrupt the charge-o-mat pro, but it’s certainly possible. The negative jump post is located here on a 992”