Trick for dead 12v battery

The cooling/heating, i.e. the heat pump, runs off the traction battery rather than the 12V battery. So if the traction battery is online, the hybrid system must be online, too. But to get the hybrid system online, the computers have to be powered by the 12V battery.

Maybe this trick puts a lighter load on the 12V battery than a normal startup does.

 

I agree with @EdPalmer42

I can't see it works but admittedly, I have never tried. Maybe works if the battery is very weak but not completely drained. I would think, if the 12v battery is so dead that it will not start the car, how can it wake up the computer and the hybrid system to use the remote AC function?

 

Does the remote AC function cycle the brake booster... or illuminate the stop lamps? If not, then the act of switching the car from dormant-to-ready involves less 12v discharge.

Could be that an intermediate method is to enter the car without opening the driver's door...

 

No booster. Yes, I can see that it is less demanding than a normal start-up. But if the 12v is so dead, then it would not have enough power to even receive the remote signal, wouldn't it? In most cases of a dead 12v battery in a PP I have read about, the SKS stops working.

 

If the key fob can somehow activate the DC-DC converter; that should supply the juice to close the relays. But as Sal stated, it's a matter of degrees - how dead is dead. At what voltage will the SKS stop working???? If you don't have enough voltage/amps to close the relays; but your car door still unlocks - the trick above will probably work. If you have to use your backup key to get into the car - this trick will not work.

IMHO: Someone from each scenario need to try this and report back.

 

yes, if it were that dead.

The redditor in question is probably in Miracle Max territory.

 

Trick to that might be unlocking the car without the remote ... and only the driver's door having a mechanical lock cylinder.

 

I've had the situation where the door unlocked normally when I grabbed the handle. I pushed the start button, the displays lit up, but then flickered and the display said that the 12V battery was low. I forget what the actual wording was. In order to display that message, the computers have to be functioning correctly. That suggests that some relatively heavy load has to be applied to the battery to test it before the system will start up. My battery was apparently too low to pass that test.

This was one of my cold weather battery charging experiments. I intentionally let the battery fade down until it wouldn't start the car.

 

Hey if we're this deep in the hypothetical, why couldn't the battery have died from having left one of the other doors open? You'd still have a reason to avoid opening the driver's door.

Anyway, it's just a theory that doing a remote start for climatization can transition from dormant-to-ready with fewer watt-hours consumed than opening the door, sitting in the car, stepping on the brake pedal and pushing the button. I'm in no position to prove it; no remote start of any kind on mine.

 

no... not possible... just like you can be at a charging station in a PRIME all night and your power inverter to the 12v is powering multiple laptops all night while you fall asleep. You will wake up with dead 12v and need someone to give you a jump to start the car... even with full charged PRIME/PLUGIN battery.

 

I started carrying one of these:

Amazon.com: NOCO Boost Plus GB40 1000 Amp 12-Volt UltraSafe Lithium Jump Starter Box, Car Battery Booster Pack, Portable Power Bank Charger, and Jumper Cables for up to 6-Liter Gasoline and 3-Liter Diesel Engines : Automotive

The DC-DC converter doesn't charge the 12V consistently when driving like in a conventional vehicle. I can see it on my dashcam videos. It will run at >14V for a while, then drop to 12.8 while driving, and may be only 60-80% charged when you're not driving. I asked a dealer about this soon after getting the car, and they said it was normal. They tested it there and the 12V showed 60% charged and good condition.

Had multiple issues where the wife or I had parked somewhere, shut off the car, then waited for a while before opening the driver door. The DRL headlights don't turn off until the driver door is opened and would drain the battery. I also use a dashcam, which combined with the headlights issue, wore the OEM battery down over about 2 years to where it needed to be replaced. If the 12V battery is too low, say 9-11V, there won't be enough power to finish pressurizing the brakes when you open the driver door, and it will start clicking consistently, making the issue worse. It won't enter ready mode and won't stop trying to run the pump.

I've not tried the A/C trick mentioned, but once you've opened the driver door and it won't pressurize the brakes, I'm sure it's too late. By then it's dropped down to like 7-8V with the pump trying to run. The high-volt wall charger won't start a charging session. The only solution I've found is a jump start, the sooner the better.

The portable jump starters (Noco or similar) work instantly. I also switched to a 12V lithium replacement from OhmMu and have not had a single issue since. Lead-acid batteries like to stay at 100% full to avoid degradation, but the lithium 12V doesn't have this problem.

 

You should probably check the options settings on your Prime. My 2021 DRL turns off immediately whenever I shut down the car (OFF button). I don't have to open a door for them to turn off.
It's nice you bought a lithium battery; so it'll probably take 4 years instead of only 2 to wear that battery out. Due to the nature of a lithium battery. Your battery recharge circumstances hasn't changed; so unless your hooking up to a battery tender - you'll eventually kill the lithium one too.