12V surprise

I too have a 2018 Prime albeit an Advanced trim. Early on I let the 12v drain due to not driving it for 10 days. After searching the threads here I found this is a common issue with cars these days that have Telematics systems. I invested in a battery tender and a BM2 Bluetooth battery monitor. This eventually told me the deep discharge that one time did damage the battery and it never held a charge for more than 7 days before I needed to recharge it via the tender. I replaced the battery 10 weeks ago and the BM2 stats show how much better the new battery holds a charge. I did not loose any settings/presets during the battery install as far as I can tell which was done at my dealership.

 

Yes, if you want to listen to the radio, put the car in ready

 

The batteries in these cars don't last that many years it seems. I used a 9v powered battery memory retainer to keep all the car settings when I replaced my battery. Worked great.


iPhone ? Pro

 

there's a pretty big drain on them when they are off, and charging while in ready does not seem adequate

 

For how long? Best to leave the car fully on (aka Ready) when doing this.

Batteries age. How regular is your use of the vehicle? Infrequent short trips are worst for batteries. Do you frequently sit and listen to radio?

Look up memory savers: you connect before disconnecting the 12 volt for the swap, they supply sufficient juice to avoid memories getting lost.

 

So if I want to swap out my wife's 12-volt in her Prius I can use the memory saver and don't need to visit the dealer for any reprogramming stuff??

 

Yeah they should have something like that.

I’ve found when intentionally disconnecting (say for brake work), it’s no big deal: the clock, trip meters, radio presets. Window auto up/down “may” get screwed up; in my experience it was ok.

I use a jump pack with a special memory saver cord: has cig lighter plug at jump pack end, and OBD plug with just the 12 volt pin at other end. And indicator light to confirm connection.

 

It takes some getting used to with hybrids to realize that there is no point in turning off the car for a short time if someone is still going to be in the car, and they could be using things like the radio or A/C. When we have have a quick grocery trip, I will often run into the store leaving the car "ready" with my wife in the car, mainly for the A/C. Old habits from gasoline engine days die hard.

 

There may be a short circuit or a factory defect! I usually changed the 12 volt battery and that's it! Unforeseen circumstances can always be!

 

2021 Prius prime Ltd purchased Feb 2022. 12 volt battery died and was unable to recharge (online videos did not have same relay box). Bought a new battery from Auto Zone. Checked out the videos to replace. Didn't look like I wanted to take this job ASI would normally do on my 1993 Toyota pick up. Called AAA and this expert ex-Marine was awesome. He backed up my data soil wouldn't lose it and replaced the battery with one he happened to have as the one from Auto Zone was the wrong one! Thank you AAA!

 

amazing they had the right size. i used triple a for my dakota 12v this spring, they were great.

 

You nailed it. Total BS. I replaced our late-2016 battery just a year ago. It was still working fine, but with winter coming, and 6 years old...better now than on a dark and stormy night. I had the practice of giving the battery a full recharge with a good charger a couple of times a year. Maybe that helped extend the life. I also kept the electrolyte topped up to the marks with distilled water as needed. (It looked like the original battery cell caps were designed to be opened with a 100 yen coin...a U.S. quarter held in Vise Grips worked fine.)

Anyway, I simply removed the old battery and dropped in a new ACDelco LN1 AGM battery, $152 shipped, from Summit Racing Equipment. Works fine. Nothing lost but a few things like the clock settings.

 

If you can manage to supply 12 volt during the swap you won’t loose anything. There are devises and cables for this, typically connect to just the 12 volt pins in OBD port.

Still as you say, no big deal.

 

I got a connector that plugs into the OBDII port, pulled the 12v battery out of the garage door opener for the 12v source and hooked it all up when I changed the battery in the other car, and all this was more work than just swapping the battery and resetting a few things. If the nav address book was wiped out, that would be a headache, but it stays good without the 12v, at least for the short time it takes for the battery change.

 

I use a JNC jump pack with a cable that runs from the cig lighter socket on the jump pack, to the obd port. It has just the 12 volt pins at the obd end. has an indicator light too, to verify you've got a solid connection.

This:


Plus:



Lay the jump pack in driver's footwell, plug in cable.

 

Why not just connect a jump pack to the 12V terminals at the battery (but not ON the battery) and disconnect the battery while making sure the jump pack cables stay connected to the terminals? While the battery is out, the jump back should be enough to keep the electronic happy, right?

 

When I disconnected my 12v, I connected a 12v jumpstarter tp the jumpstart connections under the hood.
When I bought a new battery the technician left the car in the ready mode.
Neither time did I lose clock, etc. Settings.
However, when I installed the new battery it took maybe 6 half-hour low speed trips to regain mpg. The highway speed mpg was ok.