Not sure if this helps, but it looks like the BMS monitors temperature and will act accordingly.
https://newsroom.porsche.com/en/2023...able%20maximum


I'm looking at getting a Noco Genius 10, which also monitors ambient temperature and adjusts charging cycles.
https://no.co/media/nocodownloads/fo..._8.22.2022.pdf

 

That's an EV battery, and how it's suppose to be done.

 

Never been a problem up here to date. The only concern is the fact that I use Liqui Moly 5-40w and thus I'm restricted to temps above -20F (don't use Ceratek additive)

siberian

 

Sure, but the concept is the same, no? BMS exists in LiFEPO4.

 

There is a BMS, it doesn't have active thermal management. The problem is even if it did, you would need to tell the car to precondition before you start it up and the alternator starts pushing current into the battery.

I don't know if any of you folks are familiar with EV's need to "precondition" the battery, but that is what we are talking about. Getting the battery temp in a safe range for charging.

This isn't some kind of secret. It's called Lithium plating and is a well understood failure mechanism.

 

isn't your car dead? I trust that isn't battery related.

What kind of tests have you performed on the battery to know if it has been degraded? How much have you used the car when the cells were below freezing, and what was the SoC before / after?

 

Had nothing to do with a LiFePO4 or battery issue.

We're 120 or so miles from the arctic circle and I've never had ANY problems with the battery on my 2021 C4S, or AGM on my 2020 Macan S or lead acid battery on my V8 Touareg. These things are tested extensively in Northern Europe and here in Alaska.

siberian

 

>> How much have you used the car when the cells were below freezing,
I spend winters in northern Vermont, never heard of anyone being concerned with this, Li, AGM, or otherwise... 'below freezing' is a fact of life up here. Guessing our friends in Chicago, Minnesota etc have similar non-problems. Is this a 'theory vs practice' discussion?

Winter tires, yes? Winter battery, no.

 

Can you elaborate on that? Which SAE tests specifically?

 

How many people have OEM LFP starting batteries? How many people even know what kind of battery they have period? You can't even get an LFP starting battery at most places people would go to get a replacement battery.

 

I test drove for VW/Audi/Bentley and the tests on AGM (as lithium batteries were not yet implemented) comprised leaving the cars UNPLUGGED (MEANING NO ENGINE BLOCK, BATTERY OR OIL PAN HEATER) OUTSIDE OVERNIGHT and timing the start delay. Never had an issue by -40 and below.

There is a difference between theory and actual tests. I've never in 18 years I've lived up here had any problems with cold on lead, AGM or LiFePO4 batteries. AAMOF, while most cars here need engine block heaters VDub/Audi etc. are guaranteed to -50F with no plug-in.

Getting a lithium battery just requires you to use google to find a dealer or VAR

siberian

 

People live those theories every day with their electric cars and stationary battery installations. So just so I have it straight, you didn't do any testing with LFP? The tests you did do consisted of letting the cars sit for one night?

 

No, we tested AGM batteries throughout the winter season every night from October to March. LiFePO4 batteries are tested recently as well of course. Porsche IIRC goes up to Deadhorse, AK, MB to Whitehorse YT as well as the Nordic countries and back in the day Russia.

If there had been any concern that cold could cause an issue it would have been discovered and addressed. As I stated, I've not had an issue with my lithium battery on my 992 and the car's woes had absolutely nothing to do with the battery.

siberian

 

During that testing did you ever take the battery out of the car and do any kind of testing on it? Were there any kind of specific tests you could speak to that involved bringing the battery to a low SoC and charging it up from that state below freezing temperatures via drive cycles?

 

I honestly can't remember as this was 12 years ago and even if I did I signed an NDA so whatever we did (and the after action reports at times covered pages on our 400 mile 8 hour drives not to mention content of the data loggers) I wouldn't be able to divulge.

I'm explaining to you not in tests, but in real life, living where I do with three cars (and a diesel bobcat) and three different batteries, I've never had an issue due to cold. We've gone into town and out for dinner in my 08 Touareg and returned it was -56F, the car started with no problem. Yes after that I reverse engineered a heated steering wheel. In the 3 years (in April) since I've had the 992 and with temps dipping to -35 and close to 90 in the summer leaving the car outside did not cause any issue and the car started perfectly; no hesitation, no current dip as the starter did its job as it should be. And I'll leave it at that. I have a lot of complaints about the 992, but cold affecting my LiFePO4 is not one of them.

siberian