platinum997

So instead of enjoying another beautiful day racheting through the gears, I was frustrated when I tried to go to lunch and click, click.. no start. I know it's getting colder but if I don't keep this baby juiced up on a tender, she gets snippy with me.

On 2nd Battery in ~5yrs or so. my question is why? It's the only car I have had that needs a tender even for shorter stents. I get the hibernation/winter but a couple days/weeks.. uugh.

Do AGM or Lithium have the save issue?

user 729082021

That sounds like a problem. My battery is 5 years old and I can leave my car for 3 weeks and it will still start, albeit slowly. A new battery is still towards the top of my list on things to do. I am considering a Lithium (antigravity) because I do go so long between starts (the weight savings is attractive too).

slips2

Experienced similar. Battery tender was necessary if 997.1 was not driven for more than about a week. Recently noticed a "failing bearing noise" at idle. Initially thought it was the water pump, but it turned-out to be a failing alternator over-run clutch diagnosed with a mechanics stethoscope. So I replaced the complete alternator with a new Bosch unit. Ever since the replacement my battery has never needed the tender during periods of no use as long as 3 weeks. Plus, the starts are more robust and the cabin lights are noticeably brighter. Bottom line, I believe the original 17 year-old alternator was no longer providing adequate charging.

ADias

Measure the current current drain while the car is parked in your garage. It should be about 40/45mA. If higher check for a cause. If on that range it's normal and your battery does not hold a charge.

The sitting drain (40/45mA) is approximately 1Ah of battery capacity lost per day. So, if the car sits 15 days, that is 15Ah which is about 20% of a fully charged 80Ah battery. Many batteries do not like to be drained below the 80% capacity.

4Driver4

Locking or unlocked?
Locking is important to conservation in parked cars.

ADias

Check locked.

kellen

Put a yellow top optima in and no issues a year out.

rileyracing1

Yep this is about right on my car ...Haven't driven mine for two weeks and I have one of those battery monitors on my AGM battery and i am at 82% .

Our cars need "really good" batteries with at least 800cca ..I am not saying your average interstate battery won't go the distance but in experience with my last Bosch OEM battery, it started exhibiting symptoms as described in yr 3 and I swapped it out for an Odyssey AGM and cranking and battery longevity from non use has been perfect and without any issue. I put the old Bosch battery in my winter ML500 and it has been working flawlessly since but not when it was in my 4S.

Conventional batteries in our cars tend to experience a drop in performance after a few years this may be due to the high demands on them when in use and prolonged periods of storage and climate where used,

Optima batteries use to be my go to battery of choice , unfortunately quality started to lack with their batteries as many others have also confirmed, so since I have switched to Odyssey AGM and they have been bullet proof for me.

Scalp_em

I just keep my CTEK plugged in my cig lighter with the comfort indicator adaptor when not driving my car, no problems or issues...I can go from a couple of days to a couple of weeks depending on weather, business travel etc and since its a weekend car I just got in the habit of plugging it in as soon as I pull into the garage.

Antigravity

Hey Platinum, I'll give you some facts and at least you'll be armed with info about Batteries Lead and Lithium.

- In general a modern lead acid battery gets form 2-5 years and that is because as they say "they don't make em' like they used too..." THey use thinner lead plates and the interconnectors are thinner and can break easier and most often they are not using 100% pure lead anymore. This is also done intentionally for a recurring revenue stream. Big Lead companies do not want your battery lasting 8-10 years anymore. Sounds cynical but it true.

- If you ever over-discharge a lead below 50% its state of charge it damages the battery, and if it goes deeper into is state of charge and stays there for a while then the damage is greater. This does not mean that after one over-discharge your battery will go immediately bad it just means the life is shortened and after a few deep discharges your battery will not be good anymore. Meaning it will not hold it charge well and drain quicker, it will not have it starting power, and it will not hold a stable voltage under a load. That is why Porsches will often get flags when the battery is starting to fail.

- Batteries lifespans are based on what is called Cycles.... while this isn't really spoken about much, it is generally the lifespan of a battery using the term Cycles, which means how many times a battery can be discharged and fully recharged. Not how many starts it can get, but how many full discharges and recharges it can take. Lead/Acid Batteries and there relatives such as AGM and Gel Batteries are rated at roughly 1000 Cycles when using the best materials, like a high quality brand would.

-Lead Acid Batteries also suffer from Self-Discharge which is just the chemical reaction between the two materials that leads to battery discharge even if not connected to anything. So in long storage times couples with a cars parastic draw you can get a flat battery relatively quick, but this will depend on how much parastic draw or accessories you might have connected to your car.

So in the end there are several factors on why a Lead/Battery can drain, and be damaged if Over-Discharged, which is the number one reason for a Battery going bad. The second most common reason is just the quality level of current lead acid batteries is lower than it used to be so they fail earlier.

You also asked if Lithium does that so here are some facts about lithium batteries also. But I will be talking about Antigravity Lithium Batteries specifically because we do not know the exact build quality of the other brands selling Lithium, and most do not have the features we do.


- Lithium Batteries also can be drained by a Cars Accessories or Parasitic Drain from the Cars computer system, but the benefit to Lithium here is that the Antigravity Lithium Battery has what is called a Battery Management System in it (BMS) that is a circuit board inside the battery that has multiple protections to prevent the battery from being damaged. So the Lithium Battery cannot be damaged by and over-discharge, over-charge, short circuiting, over voltage or other issues because the BMS protects the battery from that. For example the battery will go into a SLEEP mode just before going completely dead. So in essense the battery cannot be damaged by outside issues like a lead/acid battery can be.

- An Antigravity Lithium Battery offer 3000 Cycles compared to Lead/Acid Batteries having 1000 Cycles. So that is 3x the Cycles lifespan... but you also have a BMS inside the Battery so that adds to the lifespan since it will not allow the battery to be damaged accidentally by over-discharge as a Lead/Acid Battery would be. So it giving much more life than the 3000 cycles alone, it protecting the battery from damages that would hurt the battery's Lithium cells inside.

- Lithium has a much lower self-discharge rate than a Lead/Acid Battery. So if you do not have parasitic drains and all things being equal a lithium battery can hold a charge without self- discharging about two times longer than lead/acid batteries. So that is a big advantage during storage.

- Lithium offer about 2x the Cranking Power of a Lead/Acid Battery... it spins the motor faster.

- Lithium Con- If you leave your car out consistently for a week on end in below freezing temperatures Lead is a better option. THat will be rare with a Sports Car, and we are talking more for work Trucks in below freezing weather. Lead is a better option in that use.

-Lithium Con- Lithium Batteries can cost from 2x to 3x the cost at Purchase than Lead/Acid Batteries. But I will state that this is recouped due to the much longer lifespan, and the built in protections, so over the cost of ownership the Lithium will be a significantly better value.

Last word on the Antigravity Lithium Battery. Much higher initial cost than a Lead/Acid Battery.... but I did not mention that our battery also has Built-In WIRELESS JUMP-STARTING. So that means you will never again but stuck and not being able to start your car because of a dead battery. Our battery comes with two Wireless Keyfobs, and in the event you left your lights on, or the stereo on and are now locked out of your frunk and can't start the car...... you simply press the Wireless Keyfob, the battery comes back to life using its reserve battery capacity and starts the car and you drive away. So the Antigravity Lithium Battery is actually and Intelligent battery that puts itself to sleep if over discharged and never leaves you stranded, or locked out of your frunk.

You can see the Battery that fits all 911s here at this link and we did a video on them if you want to see that....

https://antigravitybatteries.com/pro...tive/ag-h6-rs/

platinum997

All good info.. thanks for the reply's.

My battery is draining at 43.3 mA so I guess that is normal for these cars? Having only 15 days of battery before an issue if the numbers above are correct is crazy to me. I have some cars I don't start for months and go over winter with no tenders and fire right up.

The alternator is measuring 15.2 volts when at 2,000rpm so that seems good to me.

Why would having the car locked make a difference? I don't lock mine so can try it that.

NOTE: when i use the tender, no issues... works as expected. Just annoying during non hibernation to drag a cord into the car when i get out.

This may have persuaded me to go lithium.. but Jesus, 1,000 for a battery. That's a hard sell for being lazy with the tender.

Wayne Smith

Locking the car allows it to go into sleep mode after a period of time to conserve the battery. There is also a way to turn off the internal motion sensing.

Note that once the car goes into sleep mode the remote unlock will not work. Use the key to unlock the door but beware that if you don't start the car soon thereafter the alarm will go off. I have found on my 997.2 I can unlock the door and then lock it and then the remote unlock works without triggering the alarm.

ADias

To turn off the internal motion sensing lock the car with 2 (rapid) clicks. The flashers will light solid for about 3 seconds .

That only happens after 7 days of locking. The procedure is: unlock the door with the physical key, and quickly click the lock/unlock FOB button (or insert the key in the ignition; there is no need to rotate the key). Relays will click and the system will reboot.

ADias

Your car electrical current stats are good. You have a bad battery or your driving pattern is such that does not keep the battery charged.

Li is your choice and all the rage now. Li has its downfalls some not mentioned above. I suggest a good deep-cycle AGM battery and if your use pattern demands it the use of a CTek maintainer.

Keeping the car locked (as explained above) minimizes the dormant current drain.

groovzilla

3 of my 997's never had any battery drain after sitting for over a month.
My 1st 2005 997S had battery drain after only a few days and culprit was the front trunk light wire being shorted out. Check your trunk light wire to make sure it's not making contact on metal surface.