jpoint

I don't own a 992 but thought I'd share a recent experience reviving a friends car that appeared completely non responsive. That means nothing from the remote fob, no dash lights, no frunk latch access, nothing. I'm posting this because - assuming the car is locked - you won't have access to the owners' manual that explains any of what follows - like how to get into the car to get the owners' manual. The first step of using the emergency access key inside the remote fob to open the door was pretty straight forward. There's not much room to insert the key under the driver's side handle so you have to fully extend the handle to get the key inserted. You can unlock and get the door open but if you close it - remember the retracting window won't function so you'll bang the window against the weather stripping. Since the frunk release is electronic you'll need to get power to the car to get anything to open. Following the owner's manual - you pull a cover panel above the driver's side foot rest to reveal a fuse panel that has a red jumper plug that extends out of the panel when you pull it gently. It will subtly click when fully extended. Using this plug you can attache a jumper box or battery to provide enough power to open the frunk. The plug accepts the positive side of the jumping source - you can use the door hing for the ground. When properly connected - the tail lights blinked. This set up will NOT provide enough power to start the car ONLY open the frunk. Here's the odd part - on this car the frunk would not open when jumped using the switch on the door threshold. We ended up having to use the key fob button for the frunk. This might be the method for all cars - I don't recall what the manual says. Also - on some jumper boxes (digital) the box may give a message that the battery is protected. If so - disconnect the jumper box and reconnect it.

Even at this point the car still appeared to be completely dead - except for the blinking tail lights. However, when the jumper box was attached to the battery the car came alive and was able to start - even without the jumper box. SOOOO - what happened. I'm not sure but I think the battery tender that was on the car caused the lithium ion smart battery to go into protection mode - essentially shutting down the car. Once awakened - the battery actually had a full charge. In all of this - the only part that wasn't clear was the need to use the key fob to open the frunk instead of the frunk switch on the door threshold. I don't know if that was because the fob was too far from the car when we tried the threshold switch or if I missed something in the manual that said use the fob button NOT the switch. Maybe no one else will ever need this but we were about to have Porsche service come and pick up the car. The reason I persisted is because - without power to the car - you also can't get it into neutral to roll it onto a flatbed.

I also suspect that I'd be pretty frustrated if my new 992 went into full sleep mode with what should be a fully charged battery. It also appears these cars need a battery tender that is switchable to Lithium Ion mode. Really neat cars with LOTS of tech to understand. . . . and maybe a bit of "mind of its own".

py0413

My friend and I were trying to do the same thing to revive his 992 which hasn’t really been driven during the winter months. We couldn’t make it work but since we didn’t have a battery or regular jump starter kit, we used both a power bank size jump start kit and the battery tender that came with the car, no luck. Probably will need to call porsche roadside assistance tomorrow to figure it out. That’s quite a frustrating experience to revive a dead car battery compared to everything else we had to deal in the past.

jpoint

The jumper box I used is pretty small - about the size of a cell phone - but an inch thick. The first day we tried - we got nothing. Then I tried it with the fob and bingo. I also charge the jumper box to 100%. I think the fob needs to be very close to or in the car. Otherwise I suspect the car(?) suspects a theft attempt. Funny to speculate on what the car thinks is going on.

detansinn

If you’re not driving your car for weeks at a time, you should have it on a battery maintainer.

Owners of 992s with Lithium batteries should be particularly diligent with this, because if you let the battery discharge too far, you will have to replace it and that will set you back a few grand. No joke.

Carlo_Carrera

I think the key takeaway from all of this is to use a trickle charger. Don't let the battery die.

py0413

Good to know, I believe we have the similar jumper kit. I’ve used that same jump start kit reviving some other cars for other friends in the past. Maybe we should give it another try before calling the roadside help.

py0413

In my own garage I have battery tenders mounting on the walls of each side, whenever I’m going on a trip more than 2 weeks, I’d connect them just in case.

In my friend’s case, his car is in the underground parking of his condo and the nearest power outlet is at about 70ft away from his parking stall and would require strata permission to use the port. That’s makes it difficult to have the battery tender connected especially that’s sort of a public space too. I guess the solution would be drive more.

Cheshi143

The 12V Lithium Ion batter does not really die, but has an internal disconnect that will activate if the battery senses too much current draw over a period of time. A trickle charger will help avoid this.

If the battery disconnects, you just need to connect a jump box to it for a few minutes and the battery will reconnect itself. The jump box may be also needed to ensure there is enough amperage for the vehicle electronics to start the car.

jpoint

In this case the car was connected to a battery tender but it did not have a specific Li-on setting. It appears the battery shut down in response to the traditional AGM battery tender.

Brad911

Great post jpoint, could have used this three weeks ago! And I have been religious with my CTEK Li-ion charger this past winter.

Bluehighways

Just an FYI. Although many people use the terms "Trickle Charger" and Battery Maintainer" interchangeably, they are very, Very VERY different. Please do NOT ever use a "Trickle Charger" on a car or motorcycle battery. Strike that phrase from your vocabulary. Left unattended a "Trickle Charger" can result in a battery that will explode with the force of several sticks of dynamite. A "Battery Maintainer" will not cause this sort of an accident to occur. A "Battery Maintainer" can be left unattended without the risk of a similar incident.

ipse dixit

I think the takeaway is to drive the car more.

Carlo_Carrera

A completely ridiculous statement.

Battery Maintainers are trickle chargers.

jpoint

Just to add information - the car was on a very high quality battery maintainer, stored during the time that 911's aren't generally the best option on the streets in terms of weather. For me - the reason for the post was simply to add some 992 user information to the issue that has puzzled us for years since access to Porsche batteries got difficult when the battery fails (the frunk release has been electric since the 996). During our conversations with Porsche service personnel we did not get the impression that using the fob to open the frunk would work when the door threshold switch did not. So for me that's the take away - try both the fob and the switch before giving up. We still don't know why the battery went into the mode that made a fully charged Li-on battery appear stone dead. One last point. We had accessed the car less than a week before and it seemed to be functioning normally. No judgements of right or wrong intended here. Just wanted to share.

Antigravity

We, Antigravity Batteries make aftermarket lightweight Lithium Batteries for Porsches and all other Cars too, so I'll add some information to this excellent post about what is going on with a Lithium Battery if over-discharged and they go into Protection/Sleep mode and shut down. I'll add a few things about Chargers too.

A high quality Modern Automotive Lithium Battery, like Porsches latest Lithium Battery, or Antigravity's Lithium Batteries have what is called a Battery Management System (BMS) inside the Battery. It is basically a Circuit Board that has settings programmed to put the battery into a Protection Mode if Over-Discharged, Over-Charged, Short-Circuited and other potential issues that could damage the Battery. For an Over-Discharge scenario (the most common issue) the battery usually goes into what we will call a SLEEP MODE where it basically shuts itself down so that any load or parasitic draw on the battery cannot continue to drain the battery. The reason the Lithium Battery does this is because it protects the battery's Lithium Cells from being damaged. The fact is ANY type of Battery be it Lead/Acid, or Lithium is damaged by being over discharged below a certain voltage usually in the 8-9v range, but being conservative the Lithium Batteries are usually set to go to Sleep//Protection Mode in the 11v~12v range since that is basically safely away from being damaged yet still has some power left within the battery.

So when the BMS goes into Sleep/Protection Mode and shuts down the battery due to being Over-Discharged, it will need to be awakened by seeing sufficient Voltage and Current to know it can WAKE-UP to be operative and accept a charge again. So in effect the Battery's BMS needs to see a certain voltage to awaken and then begin charging. It is usually about 12.5v or above, so connecting a battery source that has that is 12.5v or above to your Lithium battery for a few seconds will usually will awaken it. But keep in mind a Modern Charger will in most all circumstances NOT awaken your Lithium Battery because if the Charger does not see Voltage at its clamps then it will not put out any Charging Voltage/Current. So simply Connecting most Modern chargers will NOT work because these modern chargers have a safety feature that does not allow them to put out energy UNLESS they see some voltage at their clamps to recognize they are connected to a battery. Additionally Modern Chargers start at a very low voltage then ramp up to higher voltage and current... so they are not starting at 12.5v which is needed to awaken the BMS. The same is true for many of the small Lithium Jump Starters because they have built in protections at the clamps..., so they also will not send energy to the clamps unless they see some voltage from a battery. But some of these new Lithium Jump Starter such as our Antigravity MICRO-START models do have a bypass button to press that will allow voltage to the clamps and in most cases can awaken the Lithium Battery. Also note that SOME Charger companies are now putting a BMS RE-SET button on their Chargers that will send the appropriate PULSE of energy to awaken the BMS on a Lithium Automobile Battery. In fact we developed this with Optimate Chargers because we wanted a Charger that could do this on the fly.... meaning you simply press a specific "BMS RESET" button located on the Charger and it provide a PULSE of energy to the Battery to specifically awaken the Battery's BMS from it's SLEEP/PROTECTION mode... the Optimate unit is called the TM-271 that has this feature.

So I just wanted to explain that to awaken a BMS on most Lithium Batteries requires Voltage to be applied to the terminals that is usually above the 12.5v range to wake it up, and just putting a charger on it won't do it because of the Chargers safety features.

Now to toot our own horn a bit.... at Antigravity Batteries we have incorporated a much more user friendly system to awaken our batteries. You can do it Wirelessly with the Keyfob that comes with our Battery, or use the Button that is located directly on our Battery to wake it up manually. So with our Lithium battery you never would be locked out of the Frunk or have to use the Fuse box area since you can wake up it up with our Wireless Keyfob. And last our battery has a RESERVE that allows you to start the Car even after its fully discharged which Porsche Battery can't do. Unfortunately the new Porsches using their new Lithium Battery have a LIN BUS system that plugs into the Car itself to transmit voltage data and information so you cannot use aftermarket Batteries as a replacement yet.