The recent discussions about EVs in the cold got me wondering. With Lead Acid having a minimum charge temperature of -20C (-4F), will temperatures below this sustained simply drain the 12V battery? I'm assuming the 12V battery is exposed to ambient temps and can't be heated using the car's coolant heater. The manual says not to leave Model S (I have a 2016) in temps below -30C for more than 24 hours. At -25C, the 12V lead acid battery cannot be recharged, so it would presumably deplete itself as it performed normal idle tasks. Does the car forgo these tasks in these conditions to conserve the 12V battery, does it initiate DC-DC charging anyway, or what?
-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
12V DC-DC Charging Below -20C?
- Thread starter randall_s
- Start date
Before going into all your speculation following this, you're going to have to give a citation for this outlandish claim. Cars all around the world in far colder temperatures than that use lead acid batteries.
Battery Charging and Discharging at High and Low Temperatures
Most battery chemistries experience some type of damage when charging outside recommended temperature ranges based on the materials used in the battery.
blog.epectec.com
This reference shows it can be charged at -40C. If that's true, this isn't an issue at all.
Complete Guide On How To Charge A Lead Acid Battery - Power Sonic
Power Sonic's guide on how to charge a lead acid battery includes charging methods, characteristics & how to charge in series and parallel
www.power-sonic.com
Last edited:
@randall_s Hmm. Thanks for the links. That is very odd that they say (but still don't reference why) that all families of all of the vastly different chemistries have EXACTLY the same minimum temperature for discharge. That seems like an insane coincidence. How can lead acid, NiCd, and lithium ion all have that exact same coincidental temperature cutoff point? Those battery chemistries don't behave the same in dozens of other characteristics, and I would like to see a reason why they line up on this.
The second article had something funny. It had this sentence:
"However, lead acid batteries will experience similar discharging problems as charging problems."
And the phrase in the middle, "experience similar discharging problems" was highlighted as a hyperlink. I thought, "Oh, finally, something will tell why this is." Nope. That link...goes back to the top of the page of that very article. Unhelpful.
So this still gets to my original premise. When a statement is disproven by evidence, the statement needs further explanation or justification. Lead acid batteries do operate at temperatures lower than that cutoff point, so why is that still claimed? Is it one of those statements that isn't fully fleshed out, like, "They can be safely operated without damage down to this temperature." I would certainly understand if that were the case, that lead acid batteries can operate colder, but suffer from noticeable damage and short life. Maybe that's what they mean but isn't being stated.
The second article had something funny. It had this sentence:
"However, lead acid batteries will experience similar discharging problems as charging problems."
And the phrase in the middle, "experience similar discharging problems" was highlighted as a hyperlink. I thought, "Oh, finally, something will tell why this is." Nope. That link...goes back to the top of the page of that very article. Unhelpful.
So this still gets to my original premise. When a statement is disproven by evidence, the statement needs further explanation or justification. Lead acid batteries do operate at temperatures lower than that cutoff point, so why is that still claimed? Is it one of those statements that isn't fully fleshed out, like, "They can be safely operated without damage down to this temperature." I would certainly understand if that were the case, that lead acid batteries can operate colder, but suffer from noticeable damage and short life. Maybe that's what they mean but isn't being stated.
I pulled a few spec sheets, but haven't gotten hard numbers on minimum charge temp. Onc says the electrolyte freezes at -60F. It seems that the lead acid battery can freeze if discharged, so it's important to keep it topped up. Maybe charging in -20F or -30F is OK as long as it stays topped up and the charge controller compensates? The -20C/-4F was the first and easiest figure I found. It was logical that Tesla put a 24 hour limit of exposure at -30C if the 12V couldn't charge at that temp, but that was a guess.
I'm just thinking much simpler than that on the discharge side in plain old boring gas cars from the 1980's for example that don't have "charge controllers". Car batteries could start cars below -4 degrees F, so what is with this claim that the batteries just don't work? I get maybe on the recharging side, the batteries generally sat in an engine bay next to the engine, so over time, the engine would get hot, and the battery would warm up, and could eventually get warm enough to a recharging point, but cold starting has always been a thing. That's why they call it cold cranking amps.
I'm addressing charging, not discharging. Most batteries can discharge at much lower temps than they can charge.
Similar threads
