tna3

What's the process to swap AGM with Antigravity Lithium? Last I had checked 992 wasn't listed as supported.

repcapale

The US batteries must be a sub par version or something.

All Canadian cars have Lithium batteries since 992 production began. My friend has a 2020 with Lithium battery and he has had zero issues.

My car has had zero issues so far, and all that weight savings! Think about it!!

Mike818

Which is hilariously ironic considering how notoriously bad lithium chemistry is at low temps. Sounds like being Canadian opted you into the Porsche Beta test.

jlegelis

>> Which is hilariously ironic considering how notoriously bad lithium chemistry is at low temps. Sounds like being Canadian opted you into the Porsche Beta test.

So, um that's totally backward. Sure they lose some at low temps, but they are much better than lead-acid. Here's even a mention on this from a Canadian publication

Mike818

I'm not talking about capacity.

Since you brought it up though... When you have a BMS that will lock out the battery when it drops below a certain voltage, and a chemistry that changes voltage with temperature..... you might run into some problems.


I am talking about operating temperatures of the cells, and how you can't charge most Lithium chemistry's below freezing without damaging them. Electric cars deal with this by actively managing cell temperature.

jlegelis

>> I am talking about operating temperatures of the cells, and how you can't charge most Lithium chemistry's below freezing without damaging them.

I don't know much (anything) about Li chemistry, but just noting that Porsche (like all car makers) does massive amount of cold weather testing (just ask @siberian ), so wondering if putting Li batteries in *all* CA 992 is some sort of cold weather advantage? In any case, the car is constantly 'charging' the Li battery in all temps, so your statement about 'not being able to charge below freezing' doesn't pass this sniff test at first review. Not arguing - just calling out seemingly conflicting datapoints.

Mike818

Just read a data sheet for any LFP cell. Most aftermarket automotive lithium batteries also come with this warning.

siberian

There are two issues here.

The BMS (a crap piece of software definitely not ready for prime time) and the actual LiFePO4.

There are many issues with these types of batteries like the difficulty of putting out LiFePO4 battery fires (like in a collision) but charging by sub-zero temps is not one of them (living 120 or so miles from the arctic circle).

As to BMS...

siberian

PS Your handle brings a tear to my eyes having owned a 68 Roadrunner high 12s in the 1/4 mile

Mike818

Page 4

https://antigravitybatteries.com/dow...ser-Manual.pdf

" Do not jump-start a frozen battery. Do not charge a frozen battery. Only charge within the range of 0°C to 45°C (33°F to 113°F). "


If anyone has the data sheet for the actual cells used in the Porsche Battery that would be extremely helpful information.

siberian

The battery is constantly being charged by the alternator in sub zero conditions after the car being left outdoors by -40F or below. Porsche et al do cold weather testing up here as well as in the Nordic countries.

siberian

Mike818

Exactly my point.

It's nice that Porsche did "testing" but I tend to believe the published literature and documentation from the actual manufacturers.

siberian

Not sure I understand what you're getting at.

Temperatures below freezing do not prevent a LiFePO4 from charging. While most cars have engine block heaters (as well as battery, remote start and oil pan blankets), the 992 doesn't and in my experience I've not had any issues with it not charging in below freezing temps.

My only limit is the fact that I don't use Mobil1 C40 0w-40 but LiquiMoly which is C40 but 5w-40 so I'm limited to driving when temps are above -20F.

siberian

Mike818

sorry for the confusion, this is not an issue of the battery "accepting" a charge. If you charge a frozen cell it will damage the internals of the battery. I'm not an expert but I believe the term is Lithium Plating.

siberian

OK so several car manufacturers (including the VW/Audi family as well as MB et al) come to do winter testing up here. I personally test drove for VW/Audi/Bentley and cars were left outdoors (we had two shifts with about 400 miles driven per shift) with no auxiliary warming devices. I didn't see or in my case experience battery malfunctions due to "frozen cell(s)" or battery failing due cold and not charging.

I've seen plenty of LiFePO4 failures due to BMS and phantom battery drain issues etc. such as PVTS, memory seats, etc. But that's a coding issue in BMS not a LiFePO4 failure per se.

I will concede that any battery (whether AGM, wet or LiFePO4) if exposed to sufficiently cold temperatures will fail due to cell failure. But unless you live in extreme weather conditions, it's irrelevant.

siberian

Mike818

That sounds like a lot of fun. I don't know how this failure mode commonly manifests, or how long it takes. I also don't know how that stacks up to a Lead Acid variant given a certain climate. If it was a nothingburger though, I don't think OEMs would be investing in / spending on active thermal management for their EVs.

What I do know is that every data sheet I have ever read for an LFP cell carries this stipulation.

Lead acid batteries go bad all the time, that's well understood and accepted. However it is cheap and easy to replace a lead acid battery.