My wife had Panamera trouble two nights before yesterday. Driving home from work she got 2 messages, PSM and Start/Stop disabled or deactivated. She stopped by the gas station to fill up some 15 gallons, and left the remaining space for the 100 that I usually mix. (Come to think of it maybe she was running too low on gas and this caused these messages)? So I went to the Pasadena gas station two days ago before sun up and filled up the remainder of the tank with 100. She drives around the next day with no apparent issues then yesterday gets rough engine.. She had difficulty restarting and through Facetime showed me the display where the voltage of the battery was 10.x V. Bingo, bad battery. I'm under the weather, so I grab the LiFePO4 I bought for a 2004 Toyota Sienna, see that the +,- orientation is the same, so I fit it. The +,- harness had to be pulled a little taught to reach the posts but got them not uncomfortably taught. It was a little on the tall side as well, bolted down the battery hold down then that frame on top just mounted the other two bolts finger tight. I grab my Foxwell NT510 Elite and try to program it in. (In a previous software version I saw an option for LiFePO4 but this time I did not see the option. Since the battery spec shows 40Ah + 8 Ah I set it to 75Ah AGM as that is the smallest Ah rating choice.

Usually they have a warning that if the charging voltage drops below 13V that there is a problem with the rectifier to replace it, but I notice that if I fully charge the 12 V with an external charger the car will drop the voltage as low as 12.4 V and drain some. It does not keep the AGM battery full. I'll update on how it goes. I wish I took a picture but I'm afraid I didn't as I'm feeling pretty ill (if I didn't mention it already).

 

Yesterday my wife drove around with it. She's happy with how the car is running. I got in with her to take our cat to the vet for a checkup in the afternoon. I verified the Voltage displayed showed a minimum of 12.9 V which is very close to the minimum required/recommended voltage (13 V) as noted in most of the eBay listings. (I suspect maybe my last battery registration was not successful and set to a regular lead acid battery with 110Ah vs AGM, which was what I fitted. It may be why the system was dropping down voltage as low as 12.4 V because it felt the battery was overcharged. (I do believe AGM has a higher voltage than regular lead acid).

I may yet buy a 100-20 size battery from eBay which should fit exactly like the H8/LN5/49 battery. I noticed some space to the sides of the H8 in the battery bay. I wonder if the next size up actually fits....

 

These cars do not keep the battery fully charged since they wait for coasting or braking opportunities for recharging. Part of the battery management system function. That is why I use a battery maintainer if the car will sit for a few weeks.

 

I thought so too. I am beginning to wonder if the older Foxwell software incorrectly registered the battery as a PbA. I have programmed the new battery as an AGM as I think I mentioned and it has kept the voltage whenever I look at the monitor on the right dash pod 12.9 V (minimum I saw once) and 13.0 V I saw a little bit yesterday, but otherwise above. I drove a short distance from the gas station to a next door shopping complex and my wife waited in the car as I went to order food to go, it was busy so took maybe 10 mins to find a spot. She had the cigarette lighter charger charging her phone with the car off and when I got back in and started her the voltage was still 13.1 (as I saw when I turned her off). I have not seen the 12.x range like I did with the prior battery…

I also think I noted it did not fit as well because it’s narrow and a little taller. I am beginning to wonder if the black ECU like thing on top monitors the battery temperature? It does not sit flush on top of the battery as there are two buttons that are not flush, (one button displays current voltage the other emergency start). Even with the new battery that is coming it may not function properly as the Li does not reach the top of the case as the lead does. I assume the top is just a gap filled with air.

The 100-20 battery is arriving today but my wife is going to work with the car. I’ll swap it out as soon as I can…